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Heritiera fomes is a mangrove tree which is widely distributed in the Sundarbans mangrove forest, Bangladesh. In this study, the EtOH extract of stem bark from H. fomes was shown to be rich in procyanidins. Trimeric, pentameric and hexameric procyanidins were identified in addition to highly polymeric material (average degree of polymerization 18-24). Bioactivity studies showed high DPPH radical scavenging and 15-lipoxygenase (15-LO) inhibiting activities of the bark extracts (EC 50 = 19.4 ± 1.7 and IC 50 = 22 ± 1 μg/mL, respectively) which could be ascribed to its high content of procyanidins. The procyanidins were also assayed as DPPH scavengers and 15-LO inhibitors, with EC 50 and IC 50 values in the range of 8-15 and 10-15 μg/mL, respectively. The bark extracts showed antibacterial activities against K. rhizophilia, S. aureus, B. subtilis and P. aeruginosa, as well. No toxicity was observed in the brine shrimp assay.

Sarcolobus globosus is a medicinal plant growing in mangrove forests in Asia. No constituents from this plant have been reported previously. From the diethyl ether extract of S. globosus a new rotenoid sarcolobin and a new isoflavone sarcolobone, as well as the previously known rotenoids tephrosin, 12aalpha-hydroxydeguelin, 11-hydroxytephrosin, 12a-hydroxyrotenone, 12aalpha-hydroxyrotenone, 6aalpha,12aalpha-12a-hydroxyelliptone, 6a,12a-dehydrodeguelin, 13- homo-13-oxa-6a,12a-dehydrodeguelin, the isoflavone barbigerone and a chromone 6,7-dimethoxy-2,3-dihydrochromone were identified. 6,7-Dimethoxy-2,3-dihydrochromone has not previously been reported as a natural product.

Procyanidins and catechins were found in high amounts in the methanol extract of the bark of the mangrove tree Xylocarpus granatum. The procyanidins showed a consistent structural pattern with catechin as the starter and epicatechin as the extender units. Four limonoids with a tetranortriterpenoid structure, previously identified in X. granatum, were isolated as well. Catechins, procyanidins, limonoids and plant extracts were evaluated for DPPH radical scavenging and 15-lipoxygenase (15-LO) inhibiting effects. Catechins and procyanidins demonstrated high activity, and the procyanidin of the pentamer type was found to be most potent (IC 50 ; DPPH: 3.3 ± 0.3 μM, 15-LO: 9 ± 1 μM). Extracts were also found to have antibacterial activity.