Actinomycetes are known to produce numerous secondary bioactive metabolites of pharmaceutical interest. The purpose of this study was to isolate, characterize, and investigate the antibacterial, antifungal, and anticancer activities of metabolites produced by Actinobacteria isolated from the rhizosphere of Paullinia cupana. The Actinobacteria was identified as Streptomyces hygroscopicus ACTMS-9H. Based on a bioguided study, the methanolic biomass extract obtained from submerged cultivation had the most potent antibacterial, antifungal, and cytotoxic activities. This extract was partitioned with n-hexane, ethyl acetate, and 2-butanol. Elaiophylin was isolated from the methanolic biomass extract, and its molecular formula was determined (C54H88O18) based on 1H and 13C NMR, IR and MS analyses. The 2-butanol phase was fractionated into four fractions (EB1, EB2A, EB2B, and EB3M). Chemical prospecting indicated the presence of alkaloids, saponins, and reducing sugars in the methanolic extract and 2-butanol phase. The elaiophylin displayed anticancer activity in HEp-2 and HL-60 cells with an IC50 of 1 μg/mL. The EB1 fraction was selectively toxic to HL-60 cells with IC50 of 9 ng/mL. Bioautography showed that the EB1 fraction contained an alkaloid with antibacterial and antifungal activities (MIC values ≤1.9 and <3.9 μg/mL, respectively). In conclusion, the EB1 fraction and elaiophylin of S. hygroscopicus have potent antimicrobial, antifungal, and anticancer activities.
Keywords: Actinobacteria; Bioautography; Elaiophylin; Fermentation.