ANXIOLYTIC ACTIVITY OF GINKGOLIC ACID CONJUGATES FROM INDIAN GINKGO-BILOBA

Ginkgolic acid conjugates (GAC) (6-alkylsalicylates, namely n-tridecyl -, n-pentadecyl-, n-heptadecyl-, n-pentadecenyl- and n-heptadecenylsal icylates) isolated from the leaves of Indian Ginkgo biloba Linn., (IGb ) were tested for their putative role in anxiety in rats. Elevated plu s maze, open-field behaviour, novelty-induced feeding latency and soci al interaction were the rodent behavioural models used in this study. GAC (0.3 and 0.6 mg/kg, each, PO) on single acute administration, show ed dose-related changes in the behaviour. GAC (0.6 mg/kg) and DZ augme nted open arm entries, the open arm/closed arm entries ratio and incre ased time spent in the open arm on the elevated plus maze. In the open field, GAC (0.6 mg/kg) and DZ significantly increased ambulation and reduced the immobility time. EGb 761 showed a similar profile. GAC (0. 6 mg/kg) and DZ significantly attenuated the increased latency to feed in novel environment. By contrast, EGb 761 and Ginkocer further augme nted feeding latency. None of the drugs tested showed any significant effect in the social interaction test. GAC showed consistent and signi ficant anxiolytic activity in all the variables investigated. By contr ast, EGb 761 and Ginkocer, which are devoid of GAC, did not evoke sign ificant activity. However, increased rearing and decreased immobility time only in open field behaviour shown by EGb 761 may be due to some antianxiety activity of a lesser degree. Our observations suggest that GAC may be the active constituents of Ginkgo biloba responsible for t he anxiolytic activity.