Bioactive Naphthoquinone and Phenazine Analogs from the Endophytic Streptomyces sp. PH9030 as α-Glucosidase Inhibitors

A talented endophytic sp. PH9030 is derived from the medicinal plant (Lem.) A.C. Smith. The undescribed naphthoquinone naphthgeranine G ( ) and seven previously identified compounds, - , were obtained from sp. PH9030. The structure of was identified by comprehensive examination of its HRESIMS, 1D NMR, 2D NMR and ECD data. The inhibitory activities of all the compounds toward α-glucosidase and their antibacterial properties were investigated. The α-glucosidase inhibitory activities of , , and were reported for the first time, with IC values ranging from 66.4 ± 6.7 to 185.9 ± 0.2 μM, as compared with acarbose (IC = 671.5 ± 0.2 μM). The molecular docking and molecular dynamics analysis of with α-glucosidase further indicated that it may have a good binding ability with α-glucosidase. Both and exhibited moderate antibacterial activity against methicillin-resistant , with minimum inhibitory concentration (MIC) values of 16 μg/mL. These results indicate that , together with the naphthoquinone scaffold, has the potential to be further developed as a possible inhibitor of α-glucosidase.