The effect of Annona squamosa, Lawsonia inermis and their combination with other herbal molluscicides were studied on different enzyme activity in the nervous tissue of Lymnaea acuminata. Twenty-Four hour in vivo exposure to 40% and 80% of 24 h LC50 of plant derived molluscicides and their combination with other molluscicides such as Cedrus deodara, Azadirachta indica oil, Allium sativum, Polianthes tuberosa bulb and oleoresin of Zingiber officinale and acetogenins caused a significant reduction in the activity of acetylcholinesterase, cytochrome oxidase and Na+/K+ ATPase in the nervous tissue of L. acuminata. Combination of C. deodara with A. squamosa or L. inermis inhibited the acetylcholinesterase activity in the nervous tissue up to 60% and 58.70% of control, respectively. Acetogenin was more effective against Na+/K+ ATPase and cytochrome oxidase. Inhibition of these enzymes even at lower concentrations of plant derived molluscicides present in binary mixture with respect to their single treatment inhibit the enzyme activity nearly up to same level.