In vitro and in vivo characterisations of Centella asiatica extract against Vibrio alginolyticus infection in whiteleg shrimp, Penaeus vannamei

Methanolic leaf extracts of the medicinal herb Centella asiatica (Asiatic pennywort) were screened for in vitro and in vivo antimicrobial activities against Vibrio alginolyticus isolated from whiteleg shrimp, Penaeus vannamei. Phytochemical analyses were positive for tannins, saponins, steroids, and cardiac glycosides. Antioxidant test revealed antioxidant activity nearly as potent as that of 0.8 mg/mL ascorbic acid. Minimum inhibitory and bactericidal concentrations against V. alginolyticus were determined to be 0.79 and 12.50 mg/mL respectively. Scanning electron microscopy demonstrated disruptions of treated bacterial cells. 30 mg/kg extract supplementation achieved 85% survival of juvenile shrimp in a feeding trial. Histopathology showed increasingly fewer alterations in hepatopancreas from 10, 20 to 30 mg/kg supplementation, where 30 mg/kg preserved the tissues most with relatively complete structure including the star-shaped tubule lumen and various cell types. The present findings suggest the potential of C. asiatica as an alternative antimicrobial agent against V. alginolyticus as well as other Vibrio spp. and gram-negative bacteria in aquaculture.