α-Amylase inhibition of xanthones from Garcinia mangostana pericarps and their possible use for the treatment of diabetes with molecular docking studies.

Chromatographic separation of the methanol extract of Garcinia mangostana (mangosteen, Guttiferae) dried pericarps led to the isolation and structural characterization of a new xanthone, namely garcimangostin A (5), together with garcixanthone A (1), gartanin (2), normangostin (3), and garcinone C (4). Their structural characterization was achieved using various NMR spectroscopic tools as well as HRMS. Their α-amylase inhibitory (AAI) potential was assessed. It is noteworthy that 5 had the most potent inhibitory effect with % inhibition 94.1 compared to acarbose (96.7%). Moreover, the molecular modeling studies were estimated. The observed scoring results correlated to those results of the AAI assay. Interestingly, 5 was completely fitting with acarbose structure and a superimposition of acarbose complexed structure with 5 in the enzyme binding site was observed. The AAI activity of 5 could be attributed to the xanthone moiety insertion in the active site of the enzyme via H-bonds network and pi-pi interactions. PRACTICAL APPLICATIONS: Garcinia mangostana is a widely consumed fruit for its unique pleasant aroma and sweet taste. Also, it contains valuable nutritious compounds that are advantageous for human body. It is used as various traditional medicines for treating several ailments such as skin infection, hyperkeratosis, eczema, wounds, psoriasis, amebic dysentery, cholera, diarrhea, and suppuration. The findings of this work can demonstrate the significant AAI potential of G. mangostana xanthones. Therefore, mangosteen as a functional food could help in lowering the postprandial glucose absorption and identifying lead compounds from α-amylase inhibition for the treatment and/or prevention of diabetes and obesity.