PRELIMINARY IDENTIFICATION OF THE CONSTITUENT SECONDARY METABOLITES OF A FRESHWATER WEED (Nymphaea lotus) AND TOXICITY TO SHRIMP LARVAE

Abstract

This study investigated the bio-active constituents and toxic threat of excessive population of Nymphae lotus in aquaculture pond through extraction, phyto-screening and shrimp-lethality. The phyto-chemical analysis of the ethanolic leaf-extract revealed the presence of alkaloids, anthraquininone, cardiac glycoside, steroid, tannins, and triterpenes. Saponins and flavonoids were absent in the crude leaf-extract. Brine shrimp lethality bioassay involved a completely randomized design (CRD) which accommodated four (4) concentrations (0.0µg/mL, 10.0µg/mL, 100.0µg/mL and 1000.0µg/mL. A static non-renewal method was employed and each treatment accommodated 30 larvae and was replicated thrice.. Lc50s of 1000.0µg/mL and 11.4µg/mL were obtained at 24 and 48- hour of exposures, respectively. Presence of metabolites in the leaf-extract of N. lotus indicated its
medicinal and toxic potentials. A reduction in LC50 value, as the time of exposure of shrimp-larvae to leaf-extract increased, is a warning to aqua-culturists and other static water managers to disallow accumulation of die-offs for a long period of time.