Effects of extraction temperature on phytoconstituents of leaf extracts of Azadirachta indica and its antiparasitic efficacy against Argulus sp.

Aim: To understand the effect of extraction temperatures on the phytoconstituents of dried and fresh neem (Azadirachta indica) leaf extracts and its antiparasitic efficacy (AE %) against Argulus sp., an ectoparasite of fish. Methodology: Extracts of fresh and dried neem leaf were prepared using water at three different temperatures viz. room temperature (26 °C) for 24 hr, cold extraction (4 °C) for 24 hr and hot extraction (60°C) for 15 min, respectively. The preliminary qualitative and high-performance thin liquid chromatography analysis was conducted to estimate the phytoconstituents of each extract. The antiparasitic efficacy and 6 hr median effective concentration (EC50) of each extract was estimated against Argulus sp. Results: The qualitative test revealed all the estimated phytoconstituents in aqueous dried and fresh leaf extract prepared at 26 °C. Whereas the hot extract of dried leaf lacked alkaloids, and similarly among the fresh leaf extract, the absence of saponin in the cold, and hot extract lacked terpenoids and tannin. Further, thin layer chromatography analysis revealed more phytoconstituents in dried leaf than fresh neem leaf extracts at all extraction temperatures. Significantly higher 6 hr antiparasitic efficacy of 100 % and 61 % with an estimated median effective concentration (EC50) of 2.75 and 3.24 were found for dried and fresh neem leaf extracts, respectively, extracted at 26 °C in 3.5 g l-1 compared to cold and hot extracts. Interpretation: The present study recommends room temperature as the best condition for extracting active phytoconstituents from neem leaf extracts, additionally dried neem leaf extract could be a potent argulocidal agent in the aquaculture industry Key words: Antiparasitic efficacy, Argulus sp., Azadirachta indica, Extraction temperature, Phytoconstituents