Standardized extract of Lactuca sativa Linn. and its fractions abrogates scopolamine-induced amnesia in mice: A possible cholinergic and antioxidant mechanism.

OBJECTIVES: The present study was designed to evaluate the efficacy of Lactuca sativa (LS) Linn. (Asteraceae) against scopolamine-induced amnesia and to validate its traditional claim as memory enhancer.

METHODS: Ethanol extract of fresh LS leaves (LSEE), standardized on the basis of quercetin content, was successively partitioned using various solvents viz., hexane, ethyl acetate, and n-butanol in increasing order of polarity. LSEE (50, 100, and 200 mg/kg) and its various fractions (at a dose equivalent to dose of LSEE exhibiting maximum activity), administered orally for 14 days, were evaluated for their memory enhancing effect against scopolamine-induced (1 mg/kg, i.p.) amnesia in 3-4 months old male Laca mice (n = 6 in each group). The memory enhancing effect was evaluated using behavioural (elevated plus maze, novel object recognition and Morris water maze tests) and biochemical parameters (acetylcholinesterase activity, malonaldehyde, superoxide dismutase, nitrite, catalase, and reduced gultathione content). The results of the test substances were compared with both scopolamine and donepezil that was used as a standard memory enhancer and acetylcholinesterase inhibitor.

RESULTS: Scopolamine elicit marked deterioration of memory and alteration in biochemical parameters in comparison to the control group. LSEE and its n-butanol and aqueous fractions significantly (P < 0.05) attenuated the scopolamine-induced amnesia that was evident in all the behavioural and biochemical test parameters. LSEE (200 mg/kg) and n-butanol fraction (15 mg/kg) exhibited maximum anti-amnesic effect among various tested dose levels.

DISCUSSION: The results exhibited that LS prophylaxis attenuated scopolamine-induced memory impairment through its acetylcholinesterase inhibitory and antioxidant activity validating its traditional claim.