Role of Secondary Metabolites and Radical Scavenging Aptitude for Better Adaptability of Mangroves in Varying Salinity of Sundarbans, India

Abstract

Comparative adaptability in five halophytes (Bruguiera gymnorrhiza, Excoecaria agallocha, Heritiera fomes, Phoenix paludosa and Xylocarpus granatum, of which, H. fomes and X. granatum presently are stressed in Sundarbans area) were evaluated with respect to occurrence of total phenol, flavonoids, and radical scavenging ability following ABTS [2, 2′-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid)], DPPH (1, 1-diphenyl-2-picrylhydrazyl) assay and Fe2+ chelating ability. Amount of total phenol (TP) and flavonoids (TF) were much higher in all taxa grown in Sundarbans than those of mesophytic one. TP and TF were significantly augmented as the substrate salinity increased in B. gymnorrhiza, E. agallocha and P. paludosa but disordered in H. fomes and X. granatum, where increment occurred only up to a certain salinity level. Percent of free radical scavenging of extractants by DPPH and ABTS radical perceived significant correlation with salinity in former three but differ in H. fomes and X. granatum. Ferrous ion chelating ability also showed the similar trend. Owing to polyphenols occurrence and ROS scavengers, the present work clearly indicates the better adaptability of B. gymnorrhiza, E. agallocha and P. paludosa in elevated substrate salinity than those of the other two. Lower ROS scavenging ability of H. fomes and X. granatum also points to their perilous occurrence in elevated saline zones.