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

Abstract

Rhizophora is a genus of tropical mangrove plants belonging to the family Rhizophoraceae and is generally grown in intertidal zones. The genus Rhizophora comprises about seven species in the world (www.theplantlist.org) and three species in Viet Nam. Among them, Rhizophora apiculata is the most widely distributed in Viet Nam (UNEP, 2008). Phytochemical investigations on R. apiculata have resulted in the isolation of various compounds, including alkaloids, flavonoids, aliphatic alcohols, phenolic derivatives, and terpenoids (Kokpol et al., 1993, Gao et al., 2011, Selvaraj et al., 2016). These compounds exhibit valuable pharmacological properties, e.g. antimicrobial, anticancer, antidiabetic, and antioxidant activities (Prabhu and Guruvayoorappan, 2012, Gao and Xiao, 2012, Ramalingam and Rajaram, 2018).

The mangrove ecosystem is on the interface of terrestrial forests and aquatic marine ecosystems and is characterized by highly variable environmental factors, e.g. salinity, nutrients, temperature, sedimentation, and tidal currents (Kathiresan and Bingham, 2001). The mangrove plants that grow under such the diverse environmental conditions provide ecological niches for a wide variety of microorganisms (Thatoi et al., 2013). Along with their plant hosts, mangrove-associated microorganisms have also been well-proven to be rich sources of structurally diverse secondary metabolites with promising biological properties (Kui-Wu et al., 2014, Ancheeva et al., 2018, Xu et al., 2014). Of these, many compounds have potent bioactivities and may be considered lead compounds for further drug developments.

Bacillus species are omnipresent in nature and recovered from all niches in the environment, including soil, marine and plant rhizosphere. Members of Bacillus are widely applied in agricultural, pharmaceutical, and industrial fields (Saxena et al., 2020). The phytochemical and biological investigations of the genus Bacillus have indicated that these species are promising bioactive compound producers (Mondol et al., 2013, Kaspar et al., 2019, Chaabouni et al., 2012, Caulier et al., 2019). These species produce structurally versatile secondary metabolites, including major classes such as macrolactones, lipopeptides, polypeptides, polyketides, lipoamides, isocoumarins, and fatty acids. These structurally diverse compounds exhibit a wide range of pharmacological activities, such as anticancer, antimicrobial, antialgal, and antiperonosporomycetal (Kaspar et al., 2019, Chaabouni et al., 2012, Caulier et al., 2019).

In the present study, we reported the isolation of five metabolites (1–5) from the ethyl acetate extract of the endophytic bacterium Bacillus sp. RAR_M1_45 with the mangrove plant Rhizophora apiculata and their biological activities. Additionally, molecular docking simulation and QSARIS-based calculation were utilized to suggest an inhibitory mechanism for -amylase and -glucosidase inhibition.