Effects of aqueous and ethanolic leaf extracts from drumstick tree (Moringa oleifera) on gilthead seabream (Sparus aurata L.) leucocytes, and their cytotoxic, antitumor, bactericidal and antioxidant activities

Aqueous and ethanolic extracts of drumstick, Moringa oleifera, leaves were evaluated in vitro to ascertain their principal active components and determine their immunostimulant, cytotoxic, antitumoral, bactericidal and antioxidant activities. Phytochemical screening of M. oleifera leaf extracts showed a greater abundance of phenolic and cyanogenic glycosides in aqueous than in ethanolic extracts, characterized by several flavonoids, condensed tannins and saponins. No significant effects on gilthead seabream (Sparus aurata) head-kidney leucocyte activities (phagocytic ability and capacity, respiratory burst and peroxidase) were detected after incubation for 24 h with different concentrations (0.001/1 mg mL^-1) of either extract. In addition, the aqueous extract showed a marked cytotoxic effect on both SAF-1 (at doses above 0.01 mg mL^-1) and PLHC-1 (at doses above 0.25 mg mL^-1) cell lines. The ethanolic extract improved the viability of SAF-1 cells and decreased the viability of PLHC-1 cells when used at higher concentrations. Both the ethanolic and, particularly, the aqueous extracts showed significant bactericidal activity on pathogenic Vibrio anguillarum and Photobacterium damselae strains. The antiradical activity of M. oleifera, as determined by the ABTS assay, increased in a linear dose-response with increasing extract concentrations. The results as a whole for the cytotoxic, bactericidal and antioxidant activities of M. oleifera leaf extracts point to their possible use as additives in functional diets for farmed fish.

Keywords: Antioxidant; Aquaculture; Bactericidal activity; Cellular immunity; Cytotoxicity; Gilthead seabream (Sparus aurata); Moringa oleifera extracts.