Antibacterial and Anticancer Properties of Sapogenols from Streptomyces globisporus LL096, an Endophyte in Leucaena leucocephala (Lam.) de Wit.

Thongchai Taechowisan, Thanaporn Chuen-Im and Waya Phutdhawong

Background and Objective: Endophytic Streptomyces globisporus LL096, a bacterial strain isolated from the roots of Leucaena leucocephala (Lam.) de Wit, has been the subject of limited research, highlighting a significant knowledge gap regarding its potential applications in secondary metabolite production. The primary objectives of this study were to isolate and characterize the major bioactive compounds produced by S. globisporus LL096 and to evaluate their antibacterial and anticancer activities. Materials and Methods: The bioactive compounds produced by S. globisporus LL096 were isolated and purified using a combination of chromatographic techniques, including column chromatography and thin-layer chromatography (TLC). The chemical structures of the isolated compounds were elucidated by Nuclear Magnetic Resonance (NMR) spectroscopy and mass spectrometry (MS). The purified compounds were identified as soyasapogenol A (compound 1) and soyasapogenol B (compound 2). Subsequently, the antibacterial and anticancer activities of soyasapogenol A and soyasapogenol B were evaluated. Treatment effects were analyzed using one-way ANOVA with Tukey’s post hoc test, considering p<0.05 as statistically significant. Results: Soyasapogenol A and B exhibited antibacterial activity against Gram-positive bacteria, including Staphylococcus aureus TISTR885, Staphylococcus epidermidis TISTR518, Bacillus cereus TISTR687 and Bacillus subtilis TISTR008. The minimum inhibitory concentrations (MICs) of the compounds against these bacterial strains ranged from 128 to 256 μg/mL. The compounds demonstrated significant cytotoxicity against these cancer cell lines, with IC₅₀ values ranging from 321.90 to 369.90 μg/mL for HeLa, 434.03 to 475.42 μg/mL for HepG2 and 282.96 to 362.17 μg/mL for MDA-MB-231 cells. However, moderate cytotoxicity against the non-cancerous Vero cell line was also observed, with IC₅₀ values ranging from 729.81 to 811.14 μg/mL. Conclusion: This study demonstrates that Streptomyces globisporus strain LL096 produces bioactive compounds, including soyasapogenol A and B, which exhibit antibacterial activity against Gram-positive bacteria and demonstrate cytotoxic effects against various human cancer cell lines.

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