Endophytic actinomycetes from mangrove plant \(\textit{Avicennia marina}\) in Quang Ninh province, Vietnam: distribution, cytotoxicity, and antioxidant activities

Mangrove endophytes have recently gained considerable attention due to their diversity and abundance of novel bioactive secondary metabolites. Despite the fact that Streptomyces species are producers more than 75% commercialized antibiotics, associated with extremely widespread mangrove plant Avicennia marina remain poorly characterized. In this study, nine actinomycetes were isolated from A. growing in a forest, as yet unexplored, Quang Ninh province, Vietnam. Phylogenetic analysis actinomycetes-specific 16S rRNA sequences indicated they subjected five including cacaoi, californicus, enissocaesillis, coelicoflavus, variabilis, which not been previously reported plants. Among them, S. cacaoi AM1 showed strong inhibition effects against six tested pathogenic bacteria inhibitory zones ranging 7.5−22.3 mm. Using standard 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, 100 µg/mL ethyl acetate extract potent cytotoxicity breast cancer MCF-7 lung A549 cell lines viability 16.5 ± 1.28% 17.69 2.3%, respectively. As for antioxidant activities, exhibited activities 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical (92.4 0.004%) superoxide anion (42.4 0.019%), positively correlated high polyphenol (84.3 3.4 µg GAE/g FW) flavonoid (34.9 4.8 QE/g contents. These findings could be promising reservoir antibacterial, anticancer, agents. This is first report endophytic derived marina.