Phytochemical screening of leaves and flower extracts of Sesbania grandiflora (L.) Pers. and its antimicrobial activity against fish pathogens

Antibiotic-resistant fish pathogens have emerged as a serious concern in the field of aquafarming. As commonly employed antibiotics are becoming increasingly ineffective, conventional medicinal herbs have been identified as a potential drug source that can combat microbial antibiotic resistance. The current work aims to scrutinize the antibacterial potential of a nutritional and conventional medicinal herb i.e., S. grandiflora extracts against predominant fish pathogens. The leaves and flowers were extracted consecutively by solvents of different polarities (hexane, chloroform, ethyl acetate, and methanol) and the presence of potential phytoconstituents was examined qualitatively. Alkaloids, flavonoids, and steroids were identified in both leaves and flower extracts whereas saponins and phenols were present only in flower and leaves, respectively. Agar well diffusion method was employed for determining the antimicrobial activities of different extracts. The hexane, chloroform, ethyl acetate, and methanolic fractions of both leaves and flowers showed an acceptable inhibition for all the fish pathogens except V. harveyi. The methanolic flower extract shows a maximum inhibitory activity against V. alginolyticus (33 mm). In conclusion, the extracts of S. grandiflora contain potential secondary metabolites, that can be used as antimicrobial agents for predominant fish pathogens and also the flower extracts possess higher inhibitory activity compared to that of the leaves.