The α-Glucosidase Inhibition Activities of Phaeochromycins D and E Isolated from Marine Streptomyces sp. FJ0218

Marine <i>Streptomyces</i> are an important source of naturally occurring active compounds. Out of 23 marine <i>Streptomyces</i> strains, 1 strain of <i>Streptomyces</i> sp. FJ0218 was selected for its high activity in inhibiting α-glucosidase. Two polyketides, phaeochromycins D (<b>2</b>) and E (<b>1</b>), were isolated from the fermentation broth of this strain using bioactivity-guided column chromatography over RP-18, Sephadex LH-20, and silica gel. Their structures were determined using NMR data, HR-EI-MS, and single-crystal X-ray crystallography. Phaeochromycins D (<b>2</b>) and E (<b>1</b>) exhibited inhibitory activity against α-glucosidase, with IC₅₀ values of 10 mM and 25 mM, respectively. Lineweaver-Burk plots revealed that phaeochromycin E (<b>1</b>) acts as an uncompetitive inhibitor, while phaeochromycin D (<b>2</b>) acts as a non-competitive inhibitor. These findings suggest that there is potential for the pharmacological regulation of glucose levels through the use of polyketide phaeochromycins, emphasizing their significant impact on glucose management.