LAUSR

Abstract Endophytic fungi have been a focus of attention for producing diverse classes of bioactive metabolites but little is known about endophytic fungi Aureobasidium pullulan, isolated from the bark of frankincense producing tree (Boswellia sacra). Extensive chromatographic methods resulted in the isolation of two known diketopeprazin (1 and 2) along with three fatty acids derivatives (3–5) from the ethyl acetate fraction of Aureobasidium pollulan BSS6. The structures of mentioned compounds were characterized by advanced 1D and 2D spectroscopic techniques such as, ultraviolet–visible (UV), infrared (IR), electrospray ionization mass spectrometry (ESI-MS) 1H NMR, 13C NMR, heteronuclear multiple bond correlation (HMBC), heteronuclear multiple-quantum coherence (HMQC) and correlation spectroscopy (COSY). The resulted compounds were evaluated for α-glucosidase inhibition potential to know their hyperglycemic effect in type 2 diabetes mellitus. Compound 3 showed significant inhibition having an IC50 value of 23.3 µM. To know the binding energy and pharmacophore of compound 3 with in active site of enzyme, the molecular docking was performed. Compound 3 has shown π-alkyl type of interactions with Asp214 and Glu276, key amino acid residues in the catalytic triad of α-glucosidase. In conclusion, the current study reports novel sources of anti-diabetic constituent's from Aureobasidium sp. for the first time.