Occurrence of Secondary Metabolites and Free Radical Scavenging Ability towards Better Adaptability of Some Mangrove Species in Elevated Salinity of Indian Sundarbans

Abstract

Mangrove, a specialized group of plant communities, provide immense ecological and protective benefits to the coastal areas of the tropical and subtropical world where they thrive. Demographic obligation and climatic hostilities have massively altered their vegetation pattern and, even ruined some key species to large extent. The present study aims to consider Reactive Oxygen Species (ROS) scavenging skills in some degrading mangrove taxa of Indian Sundarbans (Xylocarpus granatum and Heritiera fomes) compared with some opulently growing ones (Excoecaria agallocha, Bruguiera gymnorrhiza and Phoenix paludosa) in increasing salinity gradient, in relation to their sustainability. Non-enzymatic antioxidants (secondary metabolites) Proanthocyanidin and Tannin were estimated and Free radical scavenging ability was evaluated by Singlet Oxygen Scavenging Activity Assay, Reducing power assay, effects on Peroxynitrite, Nitric Oxide Radical Scavenging, Hydrogen Peroxide Scavenging Activity Assay, Reaction with Hypochlorous Acid, Superoxide Radical Scavenging Activity Assay and Hydroxyl Radical Scavenging Activity. Relatively higher occurrence of secondary metabolites and improved antioxidant ability were recorded in E. agallocha, B. gymnorrhiza and P. paludosa; than the other two plants X. granatum and H. fomes; where the trend showed a decline in the ROS scavenging after a certain increase in salinity. Strong positive correlation of both secondary metabolites and radical scavenging ability with salinity pose the three stable taxa more viable in the higher salty environment of the Indian Sundarbans. But relatively less ROS scavenging ability in more saline zones, may be the potential reason for the unfavorable existence of the two red listed plants, which would ultimately lead to gradual natural extinction of them from the Indian Sundarbans.