A comparative study in rodents of standardized extracts of Bacopa monniera and Ginkgo biloba: anticholinesterase and cognitive enhancing activities.

Bacopa monniera and Ginkgo biloba are well-known cognitive enhancers in Indian and Chinese traditional medicine systems. Standardized extracts of B. monniera and G. biloba were used to evaluate the antidementic and anticholinesterase activities in adult male Swiss mice. Antidementic activity was tested against scopolamine (3 mg/kg ip)-induced deficits in passive avoidance test. Three different extracts of B. monniera (30 mg/kg) and extract of G. biloba (15, 30 and 60 mg/kg) were administered postoperatively, daily for 7 days and 60 min after the last dose, i.e., on Day 7, first trial was conducted. In passive avoidance test, increased transfer latency time (TLT) and no transfer response (NTR) were taken as criteria for learning. TLT and NTR were significantly increased and decreased in second trial, 24 h after the first trial in control group and scopolamine-dementia group, respectively. The B. monniera- and G. biloba-treated groups produced significant increase in TLT and NTR on second trial (40-80%) after scopolamine treatment, thus, attenuating its antidementic effect. Both the extracts showed a dose (10-1000 microg)-dependent inhibitory effect on acetylcholinesterase (AChE) activity (in vitro), performed spectrophotometrically. IC(50) of G. biloba was 268.33 microg, whereas none of the extracts of B. monniera showed more than 50% inhibition. At a dose concentration of 30 and 60 mg/kg, extracts of G. biloba showed a cognitive enhancing property and, at the same time, a significant decrease in AChE-specific activity in both per se and scopolamine-dementia groups. These extracts possess a significant anticholinesterase and antidementic properties, which may be useful in the treatment of dementia.