Purification and Characterization of Bioactive Metabolite from Streptomyces monomycini RVE129 Derived from the Rift Valley Soil of Hawassa, Ethiopia

Abstract

Streptomyces species have produced a variety of bioactive secondary metabolites with intriguing antimicrobial and anticancer properties. In this study, the bioactive compound obtained from the potent strain RVE129 was purified and characterized. Its bioactivity against various pathogens and its cytotoxicity toward the human cervical cancer (HeLa) cell were also examined. The strain was previously isolated from unexplored areas of the rift valley soil of Hawassa (Ethiopia) and identified by phenotypic characteristics and complete sequencing of the 16S rRNA gene and found to be closely related to Streptomyces monomycini strain NRRL B-24309 (99.65%); accession no. (ON786620). The active fraction undergoes bioassay-guided purification using the TLC method after being extracted by ethyl acetate. Then, it was subjected to physicochemical and structural characteristics using UV–Vis, FTIR, and NMR spectroscopic methods. A minimum inhibitory concentration of the purified antibiotic was achieved by the broth microdilution method. The cytotoxicity of HeLa cells was determined using the 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The acquired data from spectroscopic studies was compared with that of the reported natural compounds in data bases and found to be the known antibiotic, setamycin. The antibiotic (RVE-02) showed a broad spectrum of bioactivity against both Gram-positive and Gram-negative bacteria, with MIC values that ranged from 1.97 to 125 μg/ml. The bioactivity results also demonstrated antiproliferation and morphological change in HeLa cells with an $\text{I}{\text{C}}_{50}$ value of 24.30μg/ml of antibiotic. The antibiotic, obtained from S. monomycini RVE129, could be a potential candidate to combat pathogens including drug-resistant S. aureus. Further, the effect on HeLa cells suggests that it could be a prominent cancer chemotherapeutic agent.