Evaluating the efficacy of Boerhavia diffusa L against hexavalent chromium induced toxicity in Ctenopharyngodon idellus cuvier and valenciennes

Abstract

The recuperative impact of ethanolic extract of Boerhavia diffusa leaves on the toxic effect of chronic exposure of hexavalent chromium was evaluated on Ctenopharyngodon idellus, utilising multiple biomarkers including behaviour, bioaccumulation, histopathology, biochemical, genotoxicity and transcriptional profiling. The plant extract was found to be high in total phenolic and flavonoid content possessing antioxidant and metal chelating activity. RP-HPLC analysis indicated the presence of rutin, caffeic acid and quercetin. The short term exposure of Cr(VI) resulted in initiation of defence mechanism to resist the oxidative stress induced, corroborated with increased activity of endogenous enzymatic antioxidants (SOD, CAT and GST), while the incessant treatment with the metal led to enhanced MDA, and declined GSH levels along with reduced antioxidant activity, signifying the inability of fish to endure the chronic stress. Among the different tissues investigated for bioaccumulation and histopathology, kidney was most affected by Cr(VI) followed by liver and gills, as demonstrated by the semiquantitative histopathological analysis, and substantiated by oxidative stress biomarkers and ultrastructural studies. DNA damage induced with the metal was also witnessed which led to initiation of apoptosis studied through transcriptional profiling of anti- and pro-apoptotic genes. The oral supplementation of the plant extract with Cr(VI) exposure provided exogenous antioxidants and metal chelating property which helped in combating oxidative damage and pathological lesion by improving the antioxidant levels and activity, and decreasing MDA. The genotoxicity assessed through micronucleus and comet assay also exhibited less micronucleus frequency and percentage tail DNA, which ultimately prevented the commencement of apoptotic pathway newline