Resorcinol derivatives with α-glucosidase inhibitory activities from Syzygium samarangense.

Nine resorcinol derivatives including two new ones, 5-[(8Z,11Z,14Z)-nonadeca-8,11,14-trienyl] resorcinol (1) and 5-[(8Z,11Z,14E)-heptadeca-8,11,14-trienyl] resorcinol (2), were isolated from the leaves of Syzygium samarangense. The new structures were elucidated by means of extensive spectroscopic techniques including interpretation of 1D and 2D NMR spectra. Among them, compounds 3, 4, 6 and 7 exhibited significant α-glucosidase inhibitory activities with IC50 of 3.16, 3.16, 2.34 and 0.99 µM, respectively. This finding provides evidence that resorcinol derivatives with long aliphatic chain function as new promising antidiabetic alternatives.