Kolaviron, a mixture of C-3/C-8 linked biflavonoids obtained from Garcinia kola produces significant hypoglycaemic effects when administered intraperitoneally to normal and alloxan diabetic rabbits at a dose of 100 mg kg-1. The fasting blood sugar in normoglycaemic rabbits was reduced from 115 mg/100 mL to 65 mg/100 mL after 4 h. In alloxan diabetic rabbits, the blood sugar was lowered from 506 mg/100 mL to 285 mg/100 mL at 12 h. The hypoglycaemic effects have been compared with those of tolbutamide. Kolaviron inhibited rat lens aldose reductase (RLAR) activity, with an IC50 value of 5.4 x 10(-6). The significance of these findings in the potential use of kolaviron as an antidiabetic agent is discussed.

Garcinia kola Heckel (Guttiferae), known in commerce as "bitter kola", is used extensively in African traditional medicine for the treatment of various diseases. In our investigations, the most common usage was found to be for the treatment of coughs and mouth infections. The plant is also used for the treatment of liver disorders. It is served in Nigerian homes to guests as an adjunct to the true kola nut. Garcinia species have been reported to be used BS an aphrodisiac (1) and for the treatment of diarrhea and dysentery (2).Earlier work on the phytochemistry of Garcinia species resulted in the isolation of triterpenes (3), xanthones (4) , and biflavonoids (5,6) from various species.As part of a continuing project to study the constituents of plants used in Nigerian ethnomedicine, we have investigated the flavonoids of G. kola seeds.Simple flavonoids: apigenin-5,7,4'-trimethylether (500 mg), apigenin -4'methylether (150 mg), and fisetin (3',4',7-trihydroxyflavonol) (280 mg) were isolated together with the biflavonoids: amentoflavone (5',8"--biapigenin) (500 mg), kolaflavanone 1-3'-11-3-14'-114'-1-5-11-5-1-7-11-7~ctahydroxy-11-3'-methoxy-3/8"-biflavanone (350 mg) and GBI 11-3-14'-114'-1-5-11-5-1-7-11-7-heptahydroxy-3/8"-biflavanone (120 mg).Although apigenin was not isolated in this work, flavonoids based on apigenin represent 60% of the total flavonoids present in the diethylether fraction of G. kola seeds. The bifIavonoids isolated belong to both the GB-kolavanone and the amentoflavone series, both types have been isolated previously from the Guttiferae.The use of the plant in the treatment of liver disorders could be attributed to the presence of biilavonoids in G. kola since complex flavonoids such as silybin are known antihepatotoxic agents. The isolated compounds are the major seed flavonoids of this plant, minor constituents are yet to be characterized and the constituents of the other fractions have not been investigated. EXPERIMENTAL PLANT ~~mm.-Seeds of G. kola were bought from the local market a t Nsukka and authenticated by our Department of Botany. A voucher specimen (UN/PHARM 080-OA) has been deposited in the Pharmacy Herbarium, University of Nigeria Nsukka. EXTRACTION AND IsommoN.-Air dried and peeled seeds of G. kola were milled to a coarse powder after removal of the soft brown testa. Seed powder (3.5 kg) was defatted with petrcleum ether (bp W 0 ) and later extracted with acetone. The concentrated extract was digested successively with benzene (8 hrs.), diethylether (10 hrs.), and ethyl acetate (a0 hrs.).The benzene and ethyl acetate fractiops were set aside for further analysis. The diethylether fraction was chromatographed on a silica gel column; benzene, benzene-ethanol (various ratios) and ethanol were the eluants. The compounds were purified by preparative tlc (silica gel and cellulose) with n-butanol-water-acetic acid-acetone (7:1:1:2); toluene-ethyl acetate-formic acid (5:4:1) and 15% aqueous acetic acid as the solvent systems. IDENTIFICATION OF mvoNoms.-The flavonoid 5,7, dihydroxy-l'-rn...

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Kolaviron, a mixture of Garcinia biflavonoids GB-1 (ll-3-I-4'-ll-4"-I-5-II-5-I-7-II-7-heptahydroxy-3,8"-biflavanone), GB-2 (1I-3-11-3'-1-4'-11-4"-1-5-11-5-1-7-1I-7-octahydroxy-3,8"-b~avanone) and kolaflavanone (11-3-11-3'-1I-4-I-5-11-5-1-7-11-7-heptahydro~-3,8-biflavanone) obtained from Garcinia kola, protected rats against the toxic effects of thioacetamide in uiuo. The biflavonoid mixture at a dose of 100mg/kg i.p. reduced the thiopental-induced sleep in thioacetamide-poisoned rats, both in the chronic and acute test models. The microsomal enzyme levels in the serum of rats poisoned with thioacetamide were also significantly altered by treatment with kolaviron.