The study on biological activity and molecular docking of secondary metabolites from Bacillus sp. isolated from the mangrove plant Rhizophora apiculata Blume

Five known secondary metabolites, namely 2-(2-heptenyl)-3-methyl-4-quinolinone (1), 3-methyl-2-(2-nonenyl)-4-quinolinone (2), 2-phenylacetic acid (3), 4-hydroxybenzoic acid (4), and (-)-jasmonic acid (5) were isolated and identified from the crude extract of an endophytic bacterium Bacillus sp. RAR_M1_45 from the mangrove plant Rhizophora apiculata Blume. Cytotoxic assays showed that compounds 1 and 2 exhibited cytotoxicity against the tested cancer cell lines A549 (human lung carcinoma), MCF7 (human breast carcinoma) and KB (human mouth epidermal carcinoma) with IC50 values from 65.09 ± 2.06 to 97.88 ±4.16μg/mL, whereas antimicrobial assays showed that compounds 1–3 exhibited selective antimicrobial activity against plant pathogens with MICs of 16–64 μg/mL. Additionally, compounds 1–5 exhibited α-amylase and α-glucosidase inhibitory effects with IC50 values from 63.87 ± 4.23 to 649.9 ±17.5μg/mL and from 163.3 ± 10.66 to 960.4 ±8.62μg/mL, respectively. Experimental bioassays also revealed that the α-amylase and α-glucosidase inhibitory activities of the isolated compounds were consistent with computational docking results. Regarding ligand-7TAA systems, the potential stability of the complexes by molecular docking simulation was high consistence on the order of α-amylase inhibitory assays: 5 (DS -11.9 kcal.mol−1) > 4 (DS -11.3 kcal.mol−1) > 3 (DS -10.7 kcal.mol−1) > 2 (DS -9.9 kcal.mol−1) > 1 (DS -9.0 kcal.mol−1). Regarding ligand-3W37 systems, the potential stability of the complexes by molecular docking simulation was high consistence on the order of α-glucosidase inhibitory assays: 5 (DS -12.8 kcal.mol−1) > 4 (DS -12.1 kcal.mol−1) > 3 (DS -11.7 kcal.mol−1) > 2 (DS -10.0 kcal.mol−1) > 1 (DS -9.8 kcal.mol−1).