Sivaramakrishnan, T.; Swain, S.; Saravanan, K.; Rajendran, K.S., and Dam Roy, S., 2019. In vitro antioxidant, free radical scavenging activity and chemometric approach to reveal variability in different solvent extracts from selected mangroves of Andaman and Nicobar Islands, India. In: Jithendran, K.P.; Saraswathy, R.; Balasubramanian, C.P.; Kumaraguru Vasagam, K.P.; Jayasankar, V.; Raghavan, R.; Alavandi, S.V., and Vijayan, K.K. (eds.), BRAQCON 2019: World Brackishwater Aquaculture Conference. Journal of Coastal Research, Special Issue No. 86, pp. 263–269. Coconut Creek (Florida), ISSN 0749-0208.

Presence of various secondary metabolites is helpful for mangroves to tolerate biotic and abiotic stressors. In the recent years, the quest for more natural possibilities has led researchers to focus on secondary metabolites produced by plants such as alkaloids, phenolic compounds, terpenoids, flavonoids, glycosides, saponins, tannins, etc. which are reported to possess anti-oxidative, anti-microbial, anti-viral and anti-cancer properties. The present study was aimed to determine the antioxidant activity of mangrove leaf extracts obtained from two species, Rhizophora apiculata and R. mucronata. Four different solvent extracts, methanol, acetone, chloroform and aqueous of two different mangrove species, R. apiculata and R. mucronata were evaluated for their total phenol, flavonoid and antioxidant content such as total antioxidant activity (TAA), DPPH (1, 1-diphenyl-2-picrylhydrazyl) radical scavenging activity, ABTS (2, 2-azinobiz-3-ethylbenthiazoline-6-sulfonic acid) radical cation scavenging activity and reducing power (RP). Results revealed that the methanolic extract of R. apiculata exhibited the maximum phenol (168.1±0.96 mg GAE/g) and flavonoid content (117.92±0.51 mg RE/g). Higher total antioxidant activity (103.22±4.17 mg ascorbic acid/g), DPPH (90.16±0.44%), ABTS (99.45±0.14%), radical scavenging activity and reducing power (36.51±0.33 mg/g) were observed in the methanolic extract of R. apiculata. Overall, the methanolic extract of R. apiculata showed better results among the two species, revealing higher antioxidant activity of R. apiculate, and also unravelling the strength of methanol in extracting the active compound.