Bioactivity potential and chemical profile of endophytic Stutzerimonas stutzeri strain D2 isolated from Myristica fatua Houtt

Abstract

Endophytic bacteria isolated from medicinal plants are recognized as a source of valuable secondary metabolites. The present study aimed to isolate and evaluate the potential antibacterial, antioxidant, and cytotoxic properties of endophytic bacteria associated with Myristica fatua Houtt, along with molecular identification and chemical composition analysis of the most potential isolate. A total of 25 isolates were obtained from the root, leaf, and stem bark of M. fatua. 16 isolates (64%) exhibited antibacterial activity against at least one target strain. Preliminary screening showed that the D2 isolate displayed remarkable antibacterial activity against four targeted strains. D2- derived metabolite extract possessed moderate antibacterial activity with minimum inhibitory concentration (MIC) of 1,875 μg/mL for E. coli, P. aeruginosa, and S. aureus, and 3,750 μg/mL for B. subtilis, and minimum bactericidal concentration (MBC) of > 3,750 μg/mL. Furthermore, D2 extract exhibited weak antioxidant activity against DPPH (IC50: 242.61±3.2 μg/mL) and ABTS (IC₅₀: 317.32±9.3 μg/mL). In the concentration of 100 μg/mL, the extract was able to decrease the viability of MCF-7 and HepG2 cells, with inhibition percentages of 52.6±9.7 and 41.5±9.36%, respectively. 16S rRNA-based identification confirmed D2 isolate was very similar (99.92%) to Stutzerimonas stutzeri strain SM12. The total phenolic content (TPC) and total flavonoid content (TFC) of the D2 extract were 21.11±2.3 mg GAE/g extract and 8.12±1.2 mg QE/g extract, respectively. At least fifteen volatile compounds were found in the D2 extract, as identified using GC-MS analysis. Four out of 15 compounds are well known responsible for antimicrobial, antioxidant, and cytotoxic properties, such as 2,4-di-tert-butyl phenol, pyrrolo[1,2-a] pyrazine-1,4-dione, hexahydro-3-(2-methylpropyl), and bis(2-ethylhexyl) phthalate. The present study suggests that endophytic S. stutzeri strain D2 isolated from M. fatua Houtt could be a good source of active compounds valuable for pharmaceutical purposes.