Title:
METHOD OF TREATING OBESITY
United States Patent 3764692
Abstract:
The inhibition of fatty acid synthesis is obtained in biological systems by utilizing a specific stereoisomer of hydroxycitric acid and derivatives thereof such as esters or lactones and the non-toxic salts of these compounds. It is believed that the present method involves the inhibition of citrate cleavage enzyme. Inhibition of fatty acid synthesis by the present method is useful in the treatment of obesity.
Application Number:
05/077042
Publication Date:
10/09/1973
Filing Date:
09/30/1970
View Patent Images:
Export Citation:
Assignee:
Hoffmann-La Roche Inc. (Nutley, NJ)
Primary Class:
Other Classes:
514/533, 514/909, 514/547, 514/574
International Classes:
C07C59/245; C07C59/00; A61K27/00
Field of Search:
424/317,279,313
Other References:
Chemical Abstracts 60: 13800 b .
Chemical Abstracts 63: 16775 g .
Chemical Abstracts 65: 9373 a .
Chemical Abstracts 67: 69394 G .
Chemical Abstracts 70: 105772 b .
Merck Manual, 11th Edition, 1966 pp. 307-311.
Primary Examiner:
Meyers, Albert T.
Assistant Examiner:
Drezin, Norman A.
Parent Case Data:
RELATED APPLICATIONS
This application is a continuation-in-part of applicant's copending U.S. Pat. application Ser. No. 872,413 filed Oct. 29, 1969, now abandoned.
Claims:
I claim
1. A method for treating obesity which comprises administering to a mammal in need of such treatment an effective amount of a compound selected from the group consisting of garcinia acid, garcinia acid lactone, mono-, di- and tri- lower alkyl, phenyl and benzyl esters of garcinia acid, mono- and di-lower alkyl, phenyl and benzyl esters of garcinia acid lactone, wherein lower alkyl is from one to seven carbon atoms, and non-toxic pharmaceutically acceptable basic salts thereof.
2. The method of claim 1 wherein garcinia acid is administered.
3. The method of claim 1 wherein garcinia acid lactone is administered.
4. The method of claim 1 wherein an ester of garcinia acid or garcinia lactone is administered.
5. The method of claim 4 wherein said ester is a lower alkyl ester.
6. The method of claim 1 wherein the compound is administered in the range of from about 1 to about 25 mg/kg per day.
7. A pharmaceutical composition for the treatment of obesity comprising a pharmaceutical carrier and an effective amount of a compound selected from the group consisting of garcinia acid, garcinia acid lactone, mono-, di- and tri-lower alkyl, phenyl and benzyl esters of garcinia acid, mono- and di-lower alkyl, phenyl and benzyl esters of garcinia acid lactone, wherein lower alkyl is from one to seven carbon atoms, and non-toxic pharmaceutically acceptable basic salts thereof.
8. The composition of claim 7 wherein said compound is garcinia acid.
9. The composition of claim 7 wherein said compound is garcinia acid lactone.
10. The composition of claim 8 wherein said compound is an ester of garcinia acid or garcinia acid lactone.
11. The composition of claim 10 wherein said ester is a lower alkyl ester.
12. The composition of claim 7 wherein said compound is present in the range of from about 15 to 600 mg.
1. A method for treating obesity which comprises administering to a mammal in need of such treatment an effective amount of a compound selected from the group consisting of garcinia acid, garcinia acid lactone, mono-, di- and tri- lower alkyl, phenyl and benzyl esters of garcinia acid, mono- and di-lower alkyl, phenyl and benzyl esters of garcinia acid lactone, wherein lower alkyl is from one to seven carbon atoms, and non-toxic pharmaceutically acceptable basic salts thereof.
2. The method of claim 1 wherein garcinia acid is administered.
3. The method of claim 1 wherein garcinia acid lactone is administered.
4. The method of claim 1 wherein an ester of garcinia acid or garcinia lactone is administered.
5. The method of claim 4 wherein said ester is a lower alkyl ester.
6. The method of claim 1 wherein the compound is administered in the range of from about 1 to about 25 mg/kg per day.
7. A pharmaceutical composition for the treatment of obesity comprising a pharmaceutical carrier and an effective amount of a compound selected from the group consisting of garcinia acid, garcinia acid lactone, mono-, di- and tri-lower alkyl, phenyl and benzyl esters of garcinia acid, mono- and di-lower alkyl, phenyl and benzyl esters of garcinia acid lactone, wherein lower alkyl is from one to seven carbon atoms, and non-toxic pharmaceutically acceptable basic salts thereof.
8. The composition of claim 7 wherein said compound is garcinia acid.
9. The composition of claim 7 wherein said compound is garcinia acid lactone.
10. The composition of claim 8 wherein said compound is an ester of garcinia acid or garcinia acid lactone.
11. The composition of claim 10 wherein said ester is a lower alkyl ester.
12. The composition of claim 7 wherein said compound is present in the range of from about 15 to 600 mg.
Description:
BRIEF DESCRIPTION OF THE INVENTION
This invention relates to a method of inhibiting fatty acid synthesis in biological systems by introducing into such systems a specific stereoisomer of hydroxycitric acid or derivatives thereof. The biological systems in which the method of the present invention may be practiced include cell free enzyme preparations containing citrate cleavage enzyme (also identified as ATP:citrate oxaloacetate lyase), citrate, coenzyme A, ATP (or systems generating ATP), TPNH (or systems generating TPNH), and tissue homogenates, tissue slices, perfused organs, and intact mammals, particularly non-ruminating mammals.
The stereoisomers of hydroxycitric acid and its derivatives are related structurally to citric acid wherein a hydroxy group is substituted for one of the four methylene hydrogens of citric acid. Thus, there are four possible stereoisomers of hydroxycitric acid. Of these four stereoisomers one has been found to inhibit substantially fatty acid synthesis in biological systems. This particular isomer is (-)hydroxycitric acid hereinafter called garcinia acid. It is obtainable by isolation from the fruit of Garcinia cambogia using known procedures. For example, this isolation may be accomplished following the procedure described by Lewis in "Methods in Enzymology" (J. M. Lowenstein, ed.), Vol. 13, page 613 (Academic Press, New York, 1969).
Garcinia acid is usually isolated in the form of its lactone. The free acid may be conveniently obtained from the lactone by base hydrolysis, e.g., sodium hydroxide or potassium hydroxide preferably with heating followed by acidification in a manner known per se.
The term "derivatives" as used herein in conjunction with garcinia acid is meant to include garcinia acid lactone, derivatives of one or more carboxyl groups of garcinia acid, e.g., mono, di or tri esters of garcinia acid or mono or di esters of its lactone and non-toxic pharmaceutically acceptable basic salts of garcinia acid or the lactone or esters thereof.
Ester derivatives of garcinia acid which are useful in the practice of the present invention include the lower alkyl, aryl and aryl-lower alkyl esters. Included within the lower alkyl esters of the present invention are branched or straight chain lower alkyl radicals having from one to seven carbon atoms. Preferred lower alkyl esters of garcinia acid include the methyl, ethyl, isopropyl and butyl esters. Examples of aryl esters include the phenyl and substituted phenyl esters, e.g., phenyl substituted with halogen, lower alkyl, lower alkoxy or nitro. Benzyl represents a preferred aryl alkyl ester. The aforesaid esters may be prepared by esterification of garcinia acid with a desired alcohol in the presence of excess mineral acid such as sulfuric acid, hydrobromic acid, or the like. Suitable alcohols include lower alkanols, phenol and benzyl alcohol, for example. Conventional esterification conditions may be employed. Additionally, alkyl or aralkyl esters may be prepared by reaction with diazoalkylenes or diazoarylalkylenes, e.g., diazomethane, diazoethane or phenyldiazomethane in a manner known per se.
The garcinia acid may also be utilized in the form of its pharmaceutically acceptable non-toxic basic salt. Preferred salts for this purpose include the alkali metals, e.g., sodium or potassium; the alkaline earth metals, e.g., calcium; or complex salts such as ammonium or substituted ammonium salts such as a mono-, di- or tri-alkylammonium salt or a mono-, di- or tri-hydroxyalkylammonium salt.
The inhibition of fatty acid synthesis in biological systems by the use of garcinia acid or its derivatives is believed to arise from the inhibition by such compounds of citrate cleavage enzyme contained in such systems. The cleavage of citrate is catalyzed by citrate cleavage enzyme according to the stoichiometry: citrate + CoA + ATP ➝ acetyl-CoA + oxaloacetate + ADP + P i
In the conversion of carbohydrate and various amino acids to fat by non-ruminant mammals, citrate is the major source of the acetyl group of acetyl coenzyme A which is utilized for the synthesis of fatty acid. Citrate is formed in the mitochondria by the citrate synthase reaction. It is then metabolized via the citric acid cycle. Under conditions when energy intake exceeds energy demand, some citrate is diverted to the extramitochondrial space of the cell where it is used for fatty acid synthesis, that is to say for energy storage.
Garcinia acid and its derivatives are useful in the treatment of obesity. These compounds can be made up in the form of conventional pharmaceutical preparations; for example, the aforesaid compounds can be mixed with conventional organic or inorganic inert pharmaceutical carriers suitable for parenteral or enteral administration such as, for example, water, gelatin, lactose, starch, magnesium stearate, talc, vegetable oil, gums or the like. They can be administered in conventional pharmaceutical forms, e.g., solid forms, for example, tablets, dragees, capsules, suppositories or the like; or in liquid forms, for example, suspensions or emulsions. Moreover, the pharmaceutical compositions containing compounds of this invention can be subjected to conventional pharmaceutical expedients such as sterilization, and can contain conventional pharmaceutical excipients such as preservatives, stabilizing agents, emulsifying agents, salts for the adjustment of osmotic pressure or buffers. The composition can also contain other therapeutically active materials.
A suitable pharmaceutical dosage unit can contain from about 15 to 600 mg. of garcinia acid or its derivatives. Suitable parenteral dosage regimens in mammals comprise from 1 mg/kg to about 25 mg/kg per day. However, for any particular subject, the specific dosage regimen should be adjusted according to individual need and the professional judgment of the person administering or supervising the administration of the aforesaid compounds. It is to be understood that the dosages set forth herein are exemplary only and that they do not, to any extent, limit the scope or practice of this invention.
The present invention may be more clearly illustrated by the following examples. All temperatures are in degrees centrigrade.
EXAMPLE 1
Citrate cleavage enzyme was isolated from the liver of rats which had been starved for two days and which were then fed a diet high in glucose for three days. The purification was carried out using the procedure of Inoue et al., J. Biochem. (Japan) 60, 543 (1966). These steps involved ammonium sulfate precipitation between 0-30 percent saturation and DEAE-column chromatography.
The enzyme activity was measured as follows. The reaction mixture contained 20 mM citrate, 20 mM magnesium chloride, 70 mM Tris-HCl buffer (pH 8.0), 200 mM hydroxylamine, 10 mM dithiothreitol, 10 mM ATP, 0.6 mM CoA and citrate cleavage enzyme. The final volume was 1.0 ml. and the temperature was 37° C. The reaction was started by adding the ATP. It was stopped after 20 minutes and the hydroxamate color was developed as described by Inoue et al. cited above. Hydroxamate formation was linear with time for at least 30 minutes.
The above assay procedure was used for a series of tricarboxylic acids which were added to the reaction mixture in the amounts indicated in Table I which follows. The reaction mixture also contained 65 micrograms of protein. A millimolar extinction coefficient of 0.8 at 520 millimicrons was used to calculate the amounts of hydroxamate formed.
TABLE I
Citrate concentration (mM) Substance added 0 1 10 Hydroxamate formed (mumoles/mg/min.) None 0 210 405 Homocitrate, 25 mM 6 52 310 Homoisocitrate, 25 mM 12 190 401 Homoaconitate, 25 mM 12 198 385 Garcinia acid, 1 mM 0 2 101
table I indicates that garcinia acid is a strong inhibitor of citrate cleavage enzyme as evidenced by a lower rate of hydroxamate formation in the presence of this compound. The other analogs of citric acid which were tested produced much less inhibition even though they were used at twenty-five times the level of garcinia acid.
EXAMPLE 2
This example demonstrates the stereo-specific nature of the citrate cleavage enzyme inhibition exhibited by garcinia acid. In this experiment the assay method described in Example 1 was utilized with the exception that garcinia acid and its stereoisomer (+)-allo-hydroxycitric acid were added in the amounts indicated below in Table 2.
TABLE 2
Citrate concentration (mM) Substance added 0.5 10 Citrate cleaved (mumoles/min.) None 69 165 Garcinia acid 10 μM 25 144 100 μM 6 96 (+)-Allohydroxy citric acid 100 μM 68 162 1000 μM 33 140
as seen from the results summarized in Table 2, garcinia acid is a more potent inhibitor of citrate cleavage enzyme than its structurally related stereoisomer (+)-allohydroxy citric acid.
EXAMPLE 3
This example demonstrates the inhibition of lipogenesis effected by treatment with garcinia acid in isolated rat liver slices. In these experiments Charles River female rats 150-175 gm. were fasted for two days and refed ad libitum for three days on a diet containing 70 percent dextrose, 25 percent casein and 5 Phillips and Hart salt mixture.
The rats were killed by decapitation. Their livers were excised quickly, placed directly on ice for 30 seconds and 100-500 mg. slices were cut using a modified Staty Riggs tissue slicer on ice. The serosal slices were discarded. Slices were transferred to 50 ml. beakers in ice containing 10 times the tissue-volume of Hanks solutes dissolved in 5 mM Tris. buffer pH 7.4- 7.6. Fatty acid precursor in the form of alanine was included along with the transaminase acceptor α-keto glutaric acid in molar ratio 2:3 at pH 7.4-7.6. Synthetic garcinia acid was added either in the lactone or free acid form in the final concentration indicated below. Incubations were carried out at 37° C. under an atmosphere of 100 percent oxygen in an Eberbach water bath shaker, usually for 60 minutes unless otherwise indicated. The incubation period began with the addition of 14 C-alanine (specific activity = 107.2 mc/mM) to a final concentration of 10 μc/gm tissue. Two milliliters of 5N NaOH were added to "0" time control samples before 14 C-alanine and appropriate corrections made with the experimental samples.
Slices were removed with forceps, chilled directly on ice, added to 10 ml. glass homogenizing tubes with 2 ml. of water and homogenized with 5 strokes of a teflon pestle. Homogenates were transferred to tubes containing 2 ml. 5N NaOH, and saponification was carried out for 3 hours at 90° C. Samples were acidified with 2.5 ml. 5N H 2 SO 4 and extracted twice with 5 ml. petroleum ether (boiling point 40°-60° C.). Supernatants were added directly to glass counting vials, evaporated to dryness and 10 ml. of toluene-PPO-POPOP scintillation fluid was added. Samples were analyzed for radioactivity in a Packard Tri-Carb scintillation counter. Data was expressed as mμM of 14 C-alanine incorporated/gram of tissue/60minutes.
In the first group of experiments liver slices were incubated for 60 minutes with 10 mM 14 C-alanine and 15 mM α-ketoglutarate. Table 3 illustrates the inhibition of lipogenesis by garcinia acid under these conditions.
TABLE 3
Sample Additions mμmoles/gm/60" % Inhibition 1 Control 167.5 2 5 μM Garcinia Acid* 159.2 5.0 3 50 μM Garcinia Acid* 118.9 29.0 4 500 μM Garcinia Acid* 80.9 51.7 *neutralized to pH 7.4
table 4 demonstrates the inhibition by both garcinia acid and garcinia acid lactone in liver slices incubated for 60 minutes with 5 mM 14 C-alanine and 7.5 mM α-ketoglutaric acid. From these data the physiological, apparent inhibition constant (K i ) of garcinia acid was 350 μM and the K i of garcinia acid lactone was 30 μM.
TABLE 4
Sample Additions mμmoles/gm/60" % Inhi- bition 1 Control 144.1 2 4 μM Garcinia Acid* 128.8 10.6 3 50 μM Garcinia Acid* 109.9 23.7 4 500 μM Garcinia Acid* 52.0 63.9 5 5000 μM Garcinia Acid* 76.5 46.9 6 5 μM Garcinia Acid Lactone 89.0 38.2 7 50 μM Garcinia Acid Lactone 57.9 59.8 8 500 μM Garcinia Acid Lactone 62.7 56.5 9 5000 μM Garcinia Acid Lactone 39.5 72.6 *neutralized to pH 7.4
table 5 demonstrates the time kinetics of inhibition by garcinia acid under the same experimental conditions observed in Table 4.
Table 5
Time (in mμmoles/ % Sample Additions minutes) gm/t Inhi- bition 1 Control 60 110.3 2 500 μM Garcinia Acid* 60 83.7 24.1 3 Control 90 239.6 4 500 μM Garcinia Acid* 90 137.4 42.6 5 Control 120 737.4 6 500 μM Garcinia Acid* 120 248.1 66.3 *neutralized to pH 7.4
EXAMPLE 4
This example demonstrates the in vivo activity of synthetic garcinia acid and its lactone. Individual groups of Charles River female rats 150-175 gm. were fasted for two days and "meal" fed from 9-12 a.m. using the diet containing 70 percent dextrose, 25 percent casein and 5 percent Philipps and Hart salt mixture.
On the last day of refeeding, approximately 5 hours after feeding, the animals were lightly anesthetized with Penthrane and injected (using a 27 G needle) in the tail vein with the following composition: 12.6 mg. alanine as fatty acid precursor, 30.6 mg. α-ketoglutarate as transaminase acceptor and 5 μc 14 C-alanine (specific activity = 156 mc/mM) dissolved in a total volume of 0.25 ml. saline pH 7.4-7.6. Synthetic garcinia acid either in the free acid or lactone form was dissolved in a total volume of 0.25 ml. saline at pH 7.4-7.6.
The rats were killed by decapitation after 30 minutes. Livers were excised rapidly, weighed, placed in 30 ml. beakers with 15 ml. water and crudely minced. They were transferred to glass homogenizing tubes and homogenized with 5 strokes of a teflon pestle. Three milliliter aliquots of liver homogenates in duplicate were added to tubes containing 2.1 ml. 5N NaOH and saponified with 2.6 ml. 5N H 2 SO 4 and extracted twice with 5 ml. of petroleum ether (boiling point 40°-60° C.). Supernatants were added directly to glass counting vials, evaporated to dryness and 10 ml. of toluene-PPO-POPOP scintillation fluid added. Samples were analyzed for absolute activity in a Packard Tri-Carb scintillation counter. Resulting data was expressed as mumoles of 14 C-alanine incorporated/gram of tissue/30 minutes.
Fourteen rats were fasted for 2 days and "meal" fed as above for 3 days. On the last day of refeeding one group received 10 mg. of synthetic garcinia acid in the lactone form dissolved in a total volume of 0.25 ml. saline, pH 7.4-7.6 by tail vein injections 60 minutes prior to 14 C-alanine. An additional 5 mg. of garcinia acid lactone was given with the 14 C-alanine. Control animals received only the 14 C-alanine injection. Inhitibion of lipogenesis by garcinia acid lactone is illustrated in Table 6 below. In this table rats numbers 1-7 represent controls while rats numbers 8-14 received garcinia acid lactone.
TABLE 6
RAT No. (Controls) mμmoles/gm/30" 1 218.1 2 445.0 3 187.3 4 228.7 5 388.8 6 180.7 7 729.7 339.8 S.E.M. ± 75.7 8 (Garcinia Acid 83.5 Lactone) 9 63.4 10 104.8 11 34.9 12 65.4 13 49.2 14 66.5 66.8 S.E.M. ± 8.5 Inhibition = 80%
Another group of rats were "meal" fed from 9-12 a.m. on Purina lab chow for 10 days, fasted for 2 days and meal fed the high dextrose diet for 5 days. On the last day of refeeding, 4 rats received 10 mg. of garcinia acid lactone 60 minutes prior to 14 C-alanine and an additional 4.6 mg. of garcinia acid lactone was injected with the 14 C-alanine. Table 7 indicates inhibition of the garcinia acid lactone treated animals numbers 5-8 compared with the controls numbers 1-4.
TABLE 7
Rat No. (Controls) mμmoles/gm/30" 1 1018.9 2 1554.4 3 836.2 4 782.4 1048 S.E.M. ± 176.3 5 (Garcinia Acid Lactone) 386.1 6 249.1 7 290.9 8 257.8 296 S.E.M. ± 31.4 Inhibition = 72%
EXAMPLE 5
A solution of (+)-garcinia acid lactone (10 g.) in tetrahydrofuran (100 ml.) was treated with a solution of diazomethane in ether until the yellow color persisted. The solution was allowed to stand at room temperature for one hour then the solvent was removed in vacuo and the residue crystallized from ether haxane to give 8.0 g. of (+)-garcinia acid lactone dimethyl ester, m.p. 70°-72°. A second crop (2.4 g.; m.p. 65°-70°) was obtained from the mother liquors. Crystallization from ether furnished the analytical sample, m.p. 72°-73°; [α] D 25 25 + 85.65° (c, 1.0, CHCl 3 ); ir (CHCl 3 ) 3550, 1810 and 1755 cm -1 ; nmr CDCl 3 ) δ 4.91 (singlet, 1H, CH), 4.14 (singlet, 1H, OH), 4.91 (singlet, 3H, -OCH 3 ), 3.78 (singlet, 3H, -OCH 3 ) and 2.99 (quartet, 2H, jCH 2 ).
Anal. Calcd for C 8 H 10 O 7 : C, 44.04; H, 4.62. Found: C, 44.35; H, 4.87.
EXAMPLE 6
(+)-Garcinia acid lactone (1.0 g.) was added to dry liquid ammonia (10 ml.) and the mixture was stirred until the solids dissolved. The ammonia was then allowed to evaporate and the residue was dissolved in water (5 ml.) and passed through a column of cation exchange resin (Amberlite IR 120; 10 ml.). The acidic eluent was evaporated to dryness to give a colorless solid. Crystallization from methanol-ethanol afforded 800 mg. of (+)-garcinia acid lactone mono ammonium salt, m.p. 231° (decomposition); [α] 25 D +92.9° (c, 1.0, H 2 O); ir (KBr) 3,460-2,500 (broad), 1,800, 1,770 and 1,625 (broad) cm - 1 ; nmr (DMSO) δ 2.71 (quartet, 2H, CH 2 ) and 4.60 (singlet, 1H, CH).
Neutralization equivalent: 207
Anal. Calcd for C 6 H 9 NO 7 : C, 34.79; H, 4.38; N, 6.76
Found: C, 34.65; H, 4.48; N, 6.72.
EXAMPLE 7
Acetyl chloride (3.0 ml.) was added to aboslute ethanol (50 ml.), then after several minutes (+)-garcinia acid lactone (5.0 g.) was added and the solution heated under reflux for three hours. Molecular sieve -3A in a Sohxlet apparatus was used as a water scavenger. The solvent was removed in vacuo to give 7.5 g. of a pale yellow oil which was purified by reduced pressure distillation to give 5.2 g. of a water-white viscous liquid, b.p. 136°-140°0.1- 0.15 mm; ir (CHCl 3 ) - 3,600, 1,810 and 1,745 cm -1 . Nmr analysis indicated that it was a 2:1 mixture of (+)-garcinia acid lactone diethyl ester and garcinia acid triethyl ester.
The triester was converted to the diester lactone upon repeated distillation and pure diester lactone can be obtained in this manner.
EXAMPLE 8
Capsule Formulation
Per Capsule Garcinia acid lactone 10 mg Lactose, U.S.P. 165 mg Corn Starch, U.S.P. 30 mg Talc, U.S.P. 5 mg Total Weight 210 mg
Procedure
1. Garcinia acid lactone, lactose and corn starch were mixed in a suitable mixer.
2. The mixture was further blended by passing through a Fitzpatrick Comminuting Machine with a -1A screen with knives forward.
3. The blended powder was returned to the mixer, the talc added and blended thoroughly.
4. The mixture was filled into -4 hard shell gelatin capsules on a Parke Davis capsulating machine. (Any similar type capsulating machine may be used).
EXAMPLE 9
Capsule Formulation
Per Capsule Garcinia acid lactone 50 mg Lactose, U.S.P. 125 mg Corn Starch, U.S.P. 30 mg Talc, U.S.P. 5 mg Total Weight 210 mg
Procedure
1. Garcinia acid lactone was mixed with lactose and corn starch in a suitable mixer.
2. The mixture was further blended by passing through a Fitzpatrick Comminuting Machine with a -1A screen with knives forward.
3. The blended powder was returned to the mixer, the talc added and blended thoroughly.
4. The mixture was filled into -4 hard shell gelatin capsules on a Parke Davis capsulating machine.
EXAMPLE 10
Tablet Formulation
Per Tablet Garcinia acid lactone 25.00 mg Dicalcium Phosphate Dihydrate, Unmilled 175.00 mg Corn Starch 24.00 mg Magnesium Stearate 1.00 mg Total Weight 225.00 mg
Procedure
1. Garcinia acid lactone and corn starch were mixed together and passed through an -00 screen in Model "J" Fitzmill with hammers foward.
2. This premix was then mixed with dicalcium phosphate and one-half of the magnesium stearate, passed through a -1A screen in Model "J" Fitzmill with knives forward, and slugged.
3. The slugs were passed through a -2A plate in a Model "D" Fitzmill at slow speed with knives forward, and the remaining magnesium stearate was added.
4. The mixture was mixed and compressed.
EXAMPLE 11
Tablet Formulation
Per Tablet Garcinia acid lactone 100 mg Lactose, U.S.P. 202 mg Corn Starch, U.S.P. 80 mg Amijel BOll* 20 mg Calcium Stearate 8 mg Total Weight 410 mg A prehydrolyzed food grade corn starch. Any similar prehydrolyzed corn starch may be used.
Procedure
1. Garcinia acid lactone, lactose, corn starch, and Amijel B011 were blended in a suitable mixer.
2. The mixture was granulated to a heavy paste with water and the moist mass was passed through a -12 screen. It was then dried overnight at 110° F.
3. The dried granules were passed through a -16 screen and transferred to a suitable mixer. The calcium stearate was added and mixed until uniform.
4. The mixture was compressed at a tablet weight of 410 mg. using tablet punches having a diameter of approximately three-eight inch. (Tablets may be either flat or biconvex and may be scored if desired.)
This invention relates to a method of inhibiting fatty acid synthesis in biological systems by introducing into such systems a specific stereoisomer of hydroxycitric acid or derivatives thereof. The biological systems in which the method of the present invention may be practiced include cell free enzyme preparations containing citrate cleavage enzyme (also identified as ATP:citrate oxaloacetate lyase), citrate, coenzyme A, ATP (or systems generating ATP), TPNH (or systems generating TPNH), and tissue homogenates, tissue slices, perfused organs, and intact mammals, particularly non-ruminating mammals.
The stereoisomers of hydroxycitric acid and its derivatives are related structurally to citric acid wherein a hydroxy group is substituted for one of the four methylene hydrogens of citric acid. Thus, there are four possible stereoisomers of hydroxycitric acid. Of these four stereoisomers one has been found to inhibit substantially fatty acid synthesis in biological systems. This particular isomer is (-)hydroxycitric acid hereinafter called garcinia acid. It is obtainable by isolation from the fruit of Garcinia cambogia using known procedures. For example, this isolation may be accomplished following the procedure described by Lewis in "Methods in Enzymology" (J. M. Lowenstein, ed.), Vol. 13, page 613 (Academic Press, New York, 1969).
Garcinia acid is usually isolated in the form of its lactone. The free acid may be conveniently obtained from the lactone by base hydrolysis, e.g., sodium hydroxide or potassium hydroxide preferably with heating followed by acidification in a manner known per se.
The term "derivatives" as used herein in conjunction with garcinia acid is meant to include garcinia acid lactone, derivatives of one or more carboxyl groups of garcinia acid, e.g., mono, di or tri esters of garcinia acid or mono or di esters of its lactone and non-toxic pharmaceutically acceptable basic salts of garcinia acid or the lactone or esters thereof.
Ester derivatives of garcinia acid which are useful in the practice of the present invention include the lower alkyl, aryl and aryl-lower alkyl esters. Included within the lower alkyl esters of the present invention are branched or straight chain lower alkyl radicals having from one to seven carbon atoms. Preferred lower alkyl esters of garcinia acid include the methyl, ethyl, isopropyl and butyl esters. Examples of aryl esters include the phenyl and substituted phenyl esters, e.g., phenyl substituted with halogen, lower alkyl, lower alkoxy or nitro. Benzyl represents a preferred aryl alkyl ester. The aforesaid esters may be prepared by esterification of garcinia acid with a desired alcohol in the presence of excess mineral acid such as sulfuric acid, hydrobromic acid, or the like. Suitable alcohols include lower alkanols, phenol and benzyl alcohol, for example. Conventional esterification conditions may be employed. Additionally, alkyl or aralkyl esters may be prepared by reaction with diazoalkylenes or diazoarylalkylenes, e.g., diazomethane, diazoethane or phenyldiazomethane in a manner known per se.
The garcinia acid may also be utilized in the form of its pharmaceutically acceptable non-toxic basic salt. Preferred salts for this purpose include the alkali metals, e.g., sodium or potassium; the alkaline earth metals, e.g., calcium; or complex salts such as ammonium or substituted ammonium salts such as a mono-, di- or tri-alkylammonium salt or a mono-, di- or tri-hydroxyalkylammonium salt.
The inhibition of fatty acid synthesis in biological systems by the use of garcinia acid or its derivatives is believed to arise from the inhibition by such compounds of citrate cleavage enzyme contained in such systems. The cleavage of citrate is catalyzed by citrate cleavage enzyme according to the stoichiometry: citrate + CoA + ATP ➝ acetyl-CoA + oxaloacetate + ADP + P i
In the conversion of carbohydrate and various amino acids to fat by non-ruminant mammals, citrate is the major source of the acetyl group of acetyl coenzyme A which is utilized for the synthesis of fatty acid. Citrate is formed in the mitochondria by the citrate synthase reaction. It is then metabolized via the citric acid cycle. Under conditions when energy intake exceeds energy demand, some citrate is diverted to the extramitochondrial space of the cell where it is used for fatty acid synthesis, that is to say for energy storage.
Garcinia acid and its derivatives are useful in the treatment of obesity. These compounds can be made up in the form of conventional pharmaceutical preparations; for example, the aforesaid compounds can be mixed with conventional organic or inorganic inert pharmaceutical carriers suitable for parenteral or enteral administration such as, for example, water, gelatin, lactose, starch, magnesium stearate, talc, vegetable oil, gums or the like. They can be administered in conventional pharmaceutical forms, e.g., solid forms, for example, tablets, dragees, capsules, suppositories or the like; or in liquid forms, for example, suspensions or emulsions. Moreover, the pharmaceutical compositions containing compounds of this invention can be subjected to conventional pharmaceutical expedients such as sterilization, and can contain conventional pharmaceutical excipients such as preservatives, stabilizing agents, emulsifying agents, salts for the adjustment of osmotic pressure or buffers. The composition can also contain other therapeutically active materials.
A suitable pharmaceutical dosage unit can contain from about 15 to 600 mg. of garcinia acid or its derivatives. Suitable parenteral dosage regimens in mammals comprise from 1 mg/kg to about 25 mg/kg per day. However, for any particular subject, the specific dosage regimen should be adjusted according to individual need and the professional judgment of the person administering or supervising the administration of the aforesaid compounds. It is to be understood that the dosages set forth herein are exemplary only and that they do not, to any extent, limit the scope or practice of this invention.
The present invention may be more clearly illustrated by the following examples. All temperatures are in degrees centrigrade.
EXAMPLE 1
Citrate cleavage enzyme was isolated from the liver of rats which had been starved for two days and which were then fed a diet high in glucose for three days. The purification was carried out using the procedure of Inoue et al., J. Biochem. (Japan) 60, 543 (1966). These steps involved ammonium sulfate precipitation between 0-30 percent saturation and DEAE-column chromatography.
The enzyme activity was measured as follows. The reaction mixture contained 20 mM citrate, 20 mM magnesium chloride, 70 mM Tris-HCl buffer (pH 8.0), 200 mM hydroxylamine, 10 mM dithiothreitol, 10 mM ATP, 0.6 mM CoA and citrate cleavage enzyme. The final volume was 1.0 ml. and the temperature was 37° C. The reaction was started by adding the ATP. It was stopped after 20 minutes and the hydroxamate color was developed as described by Inoue et al. cited above. Hydroxamate formation was linear with time for at least 30 minutes.
The above assay procedure was used for a series of tricarboxylic acids which were added to the reaction mixture in the amounts indicated in Table I which follows. The reaction mixture also contained 65 micrograms of protein. A millimolar extinction coefficient of 0.8 at 520 millimicrons was used to calculate the amounts of hydroxamate formed.
TABLE I
Citrate concentration (mM) Substance added 0 1 10 Hydroxamate formed (mumoles/mg/min.) None 0 210 405 Homocitrate, 25 mM 6 52 310 Homoisocitrate, 25 mM 12 190 401 Homoaconitate, 25 mM 12 198 385 Garcinia acid, 1 mM 0 2 101
table I indicates that garcinia acid is a strong inhibitor of citrate cleavage enzyme as evidenced by a lower rate of hydroxamate formation in the presence of this compound. The other analogs of citric acid which were tested produced much less inhibition even though they were used at twenty-five times the level of garcinia acid.
EXAMPLE 2
This example demonstrates the stereo-specific nature of the citrate cleavage enzyme inhibition exhibited by garcinia acid. In this experiment the assay method described in Example 1 was utilized with the exception that garcinia acid and its stereoisomer (+)-allo-hydroxycitric acid were added in the amounts indicated below in Table 2.
TABLE 2
Citrate concentration (mM) Substance added 0.5 10 Citrate cleaved (mumoles/min.) None 69 165 Garcinia acid 10 μM 25 144 100 μM 6 96 (+)-Allohydroxy citric acid 100 μM 68 162 1000 μM 33 140
as seen from the results summarized in Table 2, garcinia acid is a more potent inhibitor of citrate cleavage enzyme than its structurally related stereoisomer (+)-allohydroxy citric acid.
EXAMPLE 3
This example demonstrates the inhibition of lipogenesis effected by treatment with garcinia acid in isolated rat liver slices. In these experiments Charles River female rats 150-175 gm. were fasted for two days and refed ad libitum for three days on a diet containing 70 percent dextrose, 25 percent casein and 5 Phillips and Hart salt mixture.
The rats were killed by decapitation. Their livers were excised quickly, placed directly on ice for 30 seconds and 100-500 mg. slices were cut using a modified Staty Riggs tissue slicer on ice. The serosal slices were discarded. Slices were transferred to 50 ml. beakers in ice containing 10 times the tissue-volume of Hanks solutes dissolved in 5 mM Tris. buffer pH 7.4- 7.6. Fatty acid precursor in the form of alanine was included along with the transaminase acceptor α-keto glutaric acid in molar ratio 2:3 at pH 7.4-7.6. Synthetic garcinia acid was added either in the lactone or free acid form in the final concentration indicated below. Incubations were carried out at 37° C. under an atmosphere of 100 percent oxygen in an Eberbach water bath shaker, usually for 60 minutes unless otherwise indicated. The incubation period began with the addition of 14 C-alanine (specific activity = 107.2 mc/mM) to a final concentration of 10 μc/gm tissue. Two milliliters of 5N NaOH were added to "0" time control samples before 14 C-alanine and appropriate corrections made with the experimental samples.
Slices were removed with forceps, chilled directly on ice, added to 10 ml. glass homogenizing tubes with 2 ml. of water and homogenized with 5 strokes of a teflon pestle. Homogenates were transferred to tubes containing 2 ml. 5N NaOH, and saponification was carried out for 3 hours at 90° C. Samples were acidified with 2.5 ml. 5N H 2 SO 4 and extracted twice with 5 ml. petroleum ether (boiling point 40°-60° C.). Supernatants were added directly to glass counting vials, evaporated to dryness and 10 ml. of toluene-PPO-POPOP scintillation fluid was added. Samples were analyzed for radioactivity in a Packard Tri-Carb scintillation counter. Data was expressed as mμM of 14 C-alanine incorporated/gram of tissue/60minutes.
In the first group of experiments liver slices were incubated for 60 minutes with 10 mM 14 C-alanine and 15 mM α-ketoglutarate. Table 3 illustrates the inhibition of lipogenesis by garcinia acid under these conditions.
TABLE 3
Sample Additions mμmoles/gm/60" % Inhibition 1 Control 167.5 2 5 μM Garcinia Acid* 159.2 5.0 3 50 μM Garcinia Acid* 118.9 29.0 4 500 μM Garcinia Acid* 80.9 51.7 *neutralized to pH 7.4
table 4 demonstrates the inhibition by both garcinia acid and garcinia acid lactone in liver slices incubated for 60 minutes with 5 mM 14 C-alanine and 7.5 mM α-ketoglutaric acid. From these data the physiological, apparent inhibition constant (K i ) of garcinia acid was 350 μM and the K i of garcinia acid lactone was 30 μM.
TABLE 4
Sample Additions mμmoles/gm/60" % Inhi- bition 1 Control 144.1 2 4 μM Garcinia Acid* 128.8 10.6 3 50 μM Garcinia Acid* 109.9 23.7 4 500 μM Garcinia Acid* 52.0 63.9 5 5000 μM Garcinia Acid* 76.5 46.9 6 5 μM Garcinia Acid Lactone 89.0 38.2 7 50 μM Garcinia Acid Lactone 57.9 59.8 8 500 μM Garcinia Acid Lactone 62.7 56.5 9 5000 μM Garcinia Acid Lactone 39.5 72.6 *neutralized to pH 7.4
table 5 demonstrates the time kinetics of inhibition by garcinia acid under the same experimental conditions observed in Table 4.
Table 5
Time (in mμmoles/ % Sample Additions minutes) gm/t Inhi- bition 1 Control 60 110.3 2 500 μM Garcinia Acid* 60 83.7 24.1 3 Control 90 239.6 4 500 μM Garcinia Acid* 90 137.4 42.6 5 Control 120 737.4 6 500 μM Garcinia Acid* 120 248.1 66.3 *neutralized to pH 7.4
EXAMPLE 4
This example demonstrates the in vivo activity of synthetic garcinia acid and its lactone. Individual groups of Charles River female rats 150-175 gm. were fasted for two days and "meal" fed from 9-12 a.m. using the diet containing 70 percent dextrose, 25 percent casein and 5 percent Philipps and Hart salt mixture.
On the last day of refeeding, approximately 5 hours after feeding, the animals were lightly anesthetized with Penthrane and injected (using a 27 G needle) in the tail vein with the following composition: 12.6 mg. alanine as fatty acid precursor, 30.6 mg. α-ketoglutarate as transaminase acceptor and 5 μc 14 C-alanine (specific activity = 156 mc/mM) dissolved in a total volume of 0.25 ml. saline pH 7.4-7.6. Synthetic garcinia acid either in the free acid or lactone form was dissolved in a total volume of 0.25 ml. saline at pH 7.4-7.6.
The rats were killed by decapitation after 30 minutes. Livers were excised rapidly, weighed, placed in 30 ml. beakers with 15 ml. water and crudely minced. They were transferred to glass homogenizing tubes and homogenized with 5 strokes of a teflon pestle. Three milliliter aliquots of liver homogenates in duplicate were added to tubes containing 2.1 ml. 5N NaOH and saponified with 2.6 ml. 5N H 2 SO 4 and extracted twice with 5 ml. of petroleum ether (boiling point 40°-60° C.). Supernatants were added directly to glass counting vials, evaporated to dryness and 10 ml. of toluene-PPO-POPOP scintillation fluid added. Samples were analyzed for absolute activity in a Packard Tri-Carb scintillation counter. Resulting data was expressed as mumoles of 14 C-alanine incorporated/gram of tissue/30 minutes.
Fourteen rats were fasted for 2 days and "meal" fed as above for 3 days. On the last day of refeeding one group received 10 mg. of synthetic garcinia acid in the lactone form dissolved in a total volume of 0.25 ml. saline, pH 7.4-7.6 by tail vein injections 60 minutes prior to 14 C-alanine. An additional 5 mg. of garcinia acid lactone was given with the 14 C-alanine. Control animals received only the 14 C-alanine injection. Inhitibion of lipogenesis by garcinia acid lactone is illustrated in Table 6 below. In this table rats numbers 1-7 represent controls while rats numbers 8-14 received garcinia acid lactone.
TABLE 6
RAT No. (Controls) mμmoles/gm/30" 1 218.1 2 445.0 3 187.3 4 228.7 5 388.8 6 180.7 7 729.7 339.8 S.E.M. ± 75.7 8 (Garcinia Acid 83.5 Lactone) 9 63.4 10 104.8 11 34.9 12 65.4 13 49.2 14 66.5 66.8 S.E.M. ± 8.5 Inhibition = 80%
Another group of rats were "meal" fed from 9-12 a.m. on Purina lab chow for 10 days, fasted for 2 days and meal fed the high dextrose diet for 5 days. On the last day of refeeding, 4 rats received 10 mg. of garcinia acid lactone 60 minutes prior to 14 C-alanine and an additional 4.6 mg. of garcinia acid lactone was injected with the 14 C-alanine. Table 7 indicates inhibition of the garcinia acid lactone treated animals numbers 5-8 compared with the controls numbers 1-4.
TABLE 7
Rat No. (Controls) mμmoles/gm/30" 1 1018.9 2 1554.4 3 836.2 4 782.4 1048 S.E.M. ± 176.3 5 (Garcinia Acid Lactone) 386.1 6 249.1 7 290.9 8 257.8 296 S.E.M. ± 31.4 Inhibition = 72%
EXAMPLE 5
A solution of (+)-garcinia acid lactone (10 g.) in tetrahydrofuran (100 ml.) was treated with a solution of diazomethane in ether until the yellow color persisted. The solution was allowed to stand at room temperature for one hour then the solvent was removed in vacuo and the residue crystallized from ether haxane to give 8.0 g. of (+)-garcinia acid lactone dimethyl ester, m.p. 70°-72°. A second crop (2.4 g.; m.p. 65°-70°) was obtained from the mother liquors. Crystallization from ether furnished the analytical sample, m.p. 72°-73°; [α] D 25 25 + 85.65° (c, 1.0, CHCl 3 ); ir (CHCl 3 ) 3550, 1810 and 1755 cm -1 ; nmr CDCl 3 ) δ 4.91 (singlet, 1H, CH), 4.14 (singlet, 1H, OH), 4.91 (singlet, 3H, -OCH 3 ), 3.78 (singlet, 3H, -OCH 3 ) and 2.99 (quartet, 2H, jCH 2 ).
Anal. Calcd for C 8 H 10 O 7 : C, 44.04; H, 4.62. Found: C, 44.35; H, 4.87.
EXAMPLE 6
(+)-Garcinia acid lactone (1.0 g.) was added to dry liquid ammonia (10 ml.) and the mixture was stirred until the solids dissolved. The ammonia was then allowed to evaporate and the residue was dissolved in water (5 ml.) and passed through a column of cation exchange resin (Amberlite IR 120; 10 ml.). The acidic eluent was evaporated to dryness to give a colorless solid. Crystallization from methanol-ethanol afforded 800 mg. of (+)-garcinia acid lactone mono ammonium salt, m.p. 231° (decomposition); [α] 25 D +92.9° (c, 1.0, H 2 O); ir (KBr) 3,460-2,500 (broad), 1,800, 1,770 and 1,625 (broad) cm - 1 ; nmr (DMSO) δ 2.71 (quartet, 2H, CH 2 ) and 4.60 (singlet, 1H, CH).
Neutralization equivalent: 207
Anal. Calcd for C 6 H 9 NO 7 : C, 34.79; H, 4.38; N, 6.76
Found: C, 34.65; H, 4.48; N, 6.72.
EXAMPLE 7
Acetyl chloride (3.0 ml.) was added to aboslute ethanol (50 ml.), then after several minutes (+)-garcinia acid lactone (5.0 g.) was added and the solution heated under reflux for three hours. Molecular sieve -3A in a Sohxlet apparatus was used as a water scavenger. The solvent was removed in vacuo to give 7.5 g. of a pale yellow oil which was purified by reduced pressure distillation to give 5.2 g. of a water-white viscous liquid, b.p. 136°-140°0.1- 0.15 mm; ir (CHCl 3 ) - 3,600, 1,810 and 1,745 cm -1 . Nmr analysis indicated that it was a 2:1 mixture of (+)-garcinia acid lactone diethyl ester and garcinia acid triethyl ester.
The triester was converted to the diester lactone upon repeated distillation and pure diester lactone can be obtained in this manner.
EXAMPLE 8
Capsule Formulation
Per Capsule Garcinia acid lactone 10 mg Lactose, U.S.P. 165 mg Corn Starch, U.S.P. 30 mg Talc, U.S.P. 5 mg Total Weight 210 mg
Procedure
1. Garcinia acid lactone, lactose and corn starch were mixed in a suitable mixer.
2. The mixture was further blended by passing through a Fitzpatrick Comminuting Machine with a -1A screen with knives forward.
3. The blended powder was returned to the mixer, the talc added and blended thoroughly.
4. The mixture was filled into -4 hard shell gelatin capsules on a Parke Davis capsulating machine. (Any similar type capsulating machine may be used).
EXAMPLE 9
Capsule Formulation
Per Capsule Garcinia acid lactone 50 mg Lactose, U.S.P. 125 mg Corn Starch, U.S.P. 30 mg Talc, U.S.P. 5 mg Total Weight 210 mg
Procedure
1. Garcinia acid lactone was mixed with lactose and corn starch in a suitable mixer.
2. The mixture was further blended by passing through a Fitzpatrick Comminuting Machine with a -1A screen with knives forward.
3. The blended powder was returned to the mixer, the talc added and blended thoroughly.
4. The mixture was filled into -4 hard shell gelatin capsules on a Parke Davis capsulating machine.
EXAMPLE 10
Tablet Formulation
Per Tablet Garcinia acid lactone 25.00 mg Dicalcium Phosphate Dihydrate, Unmilled 175.00 mg Corn Starch 24.00 mg Magnesium Stearate 1.00 mg Total Weight 225.00 mg
Procedure
1. Garcinia acid lactone and corn starch were mixed together and passed through an -00 screen in Model "J" Fitzmill with hammers foward.
2. This premix was then mixed with dicalcium phosphate and one-half of the magnesium stearate, passed through a -1A screen in Model "J" Fitzmill with knives forward, and slugged.
3. The slugs were passed through a -2A plate in a Model "D" Fitzmill at slow speed with knives forward, and the remaining magnesium stearate was added.
4. The mixture was mixed and compressed.
EXAMPLE 11
Tablet Formulation
Per Tablet Garcinia acid lactone 100 mg Lactose, U.S.P. 202 mg Corn Starch, U.S.P. 80 mg Amijel BOll* 20 mg Calcium Stearate 8 mg Total Weight 410 mg A prehydrolyzed food grade corn starch. Any similar prehydrolyzed corn starch may be used.
Procedure
1. Garcinia acid lactone, lactose, corn starch, and Amijel B011 were blended in a suitable mixer.
2. The mixture was granulated to a heavy paste with water and the moist mass was passed through a -12 screen. It was then dried overnight at 110° F.
3. The dried granules were passed through a -16 screen and transferred to a suitable mixer. The calcium stearate was added and mixed until uniform.
4. The mixture was compressed at a tablet weight of 410 mg. using tablet punches having a diameter of approximately three-eight inch. (Tablets may be either flat or biconvex and may be scored if desired.)