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.