Antioxidant, cytotoxic properties, and chemical constituents of soil Streptomyces spp. isolated from Muna Islands, Southeast Sulawesi, Indonesia

Abstract

Soil Streptomyces are filamentous Gram-positive bacteria which were the biggest producer of remarkable bioactive compounds with multiple biological roles. This study aimed to assess the antioxidant and cytotoxic activities of crude extract derived from 3 soil Streptomyces strains, namely APM-7, APM-11, and APM-21, which was isolated from Muna Islands, Southeast Sulawesi as well as profiling its compounds using gas chromatography and mass spectrometry (GC-MS). The results indicated that the ethyl acetate extract of APM-7 strain showed the most antioxidant potential with an IC50 value for both 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2’-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) of 31.61 and 57.91 μg/mL, respectively. Interestingly, this corresponding extract exhibited the highest total phenolic content (TPC) and total flavonoid content (TFC) values of 41.74 mg GAE/g extract and 32.51 mg QE/g extract. The cytotoxic effect of APM-7 extract (100 μg/mL) against human breast carcinoma cells (MCF-7) was found as having the best with the inhibition value of 81.31%. GC-MS analysis of APM-7 extract revealed 12 peaks which included some dominant compounds, including isophorone and Bis (2-ethylhexyl) phthalate which might be responsible for the antioxidant and cytotoxic properties. Our results indicate that the Streptomyces sp. strain APM-7 could be developed as medically useful compounds.