New triterpene sulfates from Vietnamese red alga Tricleocarpa fragilis and their α-glucosidase inhibitory activity

Three new compounds (methyl-3β,25-dihydroxycycloart-23-en-29-oate 3-sulfate (1), methyl-3β-hydroxy-25-methoxycycloart-23-en-29-oate 3-sulfate (2) and 3β-hydroxy-25-methoxycycloart-23-ene 3-sulfate (3)) and a known one (3β-hydroxycycloart-24-en-23-one 3-sulfate (4)) were isolated from Vietnamese red alga Tricleocarpa fragilis. All isolated compounds 1-4 showed potent inhibitory activity against yeast α-glucosidase with IC50 values of 16.62 ± 2.80, 36.34 ± 4.04, 30.19 ± 5.01 and 6.52 ± 0.17 µM, respectively. The docking data showed that the substitutions at C-3 and the differences in the side chain of cycloartane-skeleton could influence the interaction of molecule with enzyme, which was consistent with the experimental findings.