A new furanonapthoquinone from the stems of Thunbergia laurifolia .

α-Glucosidase inhibitory assay-guided purification of Thunbergia laurifolia L. stems yielded a new compound named 5-acetoxyfuranonapthoquinone ( 1 ) along with nineteen known compounds ( 2 - 20 ). The structures of the isolated compounds were elucidated by the analysis of multiple spectroscopic data. The isolated compounds were evaluated for α-glucosidase inhibition. Syringaresinol ( 7 ), rosmarinic acid ( 11 ), 1,2,8-trihydroxyxanthone ( 16 ), and isojacareubin ( 18 ) showed the most potent inhibitory activity among isolated compounds. Kinetic study indicated that syringaresinol ( 7 ), 1,2,8-trihydroxyxanthone ( 16 ) and isojacareubin ( 18 ) could inhibit maltase and sucrase function by non-competitive manner, and rosmarinic acid ( 11 ) was identified as a non-competitive inhibitor against maltase and a mixed-manner inhibitor against sucrase.