Antioxidants in mangrove plants and endophytic fungal associations

The manner in which fungal endophytes activate host stress response systems is unknown; the occurrence of additional mechanisms involved in symbiotically-conferred stress tolerance in mangrove plants (the primary producers of estuarine food chain) is also an unresolved issue. Here, we report antioxidant potentials of four different mangroves and their endophytic fungi. We elucidated the possible roles of antioxidants in symbiotic association between mangroves and their endophytic fungi. Four different mangrove species and the predominant endophytic fungus Aspergillus flavus were analyzed using various in vitro assay systems (such as iron chelating capacity, reducing power, and hydroxyl radicals/hydrogen peroxide/1-diphenyl-2-picrylhydrazyl radical scavenging and inhibition of lipid peroxidation using the beta-carotene-linoleate model system). In vitro models clearly established the antioxidant potency of extracts of mangrove plants and their respective endophytic fungi, which aids in understanding the mutualistic associations of plant and endophyte against various biotic and abiotic stresses. Re-infection analysis of endophytic A. flavus in tobacco plants confirmed the endophytic status of the fungus and its enhancement effect on plant growth.