In Vitro and In Vivo Antifilarial Activity of Standardized Extract of Calotropis procera Flowers against Brugia malayi

Background: Lymphatic filariasis (LF) is a parasitic disease that causes permanent disability (elephantiasis). Currently used antifilarial drugs are failing to control LF and there is resurgence in some areas. Looking for new antifilarial leads, we found that Calotropis procera plant parts have been used in traditional medicine for alleviating elephantiasis but the antifilarial activity is not known. Objective: In the present study, the antifilarial activity of ethanolic extract (A001) and its hexane fraction (F001) of C. procera flowers was investigated using the human filarial parasite Brugia malayi. Methods: A001 and F001 were tested for antifilarial activity using motility and 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide (MTT) assays (in vitro) and in the rodent models B. malayi- Meriones unguiculatus and B. malayi-Mastomys coucha. In the rodent models, A001 and F001 were administered orally for 5 consecutive days, and the adult worm burden and course of microfilaraemia were determined. Results: Both A001 and F001 showed microfilaricidal and macrofilaricidal activity in vitro. In animal models, A001 killed similar to 49-54% adult worms. In M coucha model, F001 killed 12-60% adult worms in a dose (125-500 mg/kg) dependent manner; A001 and F001 suppressed microfilaraemia till days 91 and 35 post initiation of treatment, respectively. HPTLC revealed 0.61% lupeol, 0.50% beta-sitosterol and 1.50% triacontanol in F001. Conclusion: Flowers of C. procera have definite microfilaricidal and macrofilaricidal activities. Whether this activity is due to lupeo1, beta-sitosterol and triacontanol found in the hexane fraction remains to be investigated. This is the first report on the antifilarial efficacy of flowers of the plant C. procera.