Salazinic Acid-Derived Depsidones and Diphenylethers with α-Glucosidase Inhibitory Activity from the Lichen Parmotrema dilatatum

Three new depsidones, parmosidones F - G (1 - 2), and 8 '-O-methylsalazinic acid (3), and 3 new diphenylethers, parmetherines A - C (4 - 6), together with 2 known congeners were isolated from the whole thalli ofParmotrema dilatatum, a foliose chlorolichen. Their structures were unambiguously determined by extensive spectroscopic analyses and comparison with literature data. The isolated polyphenolics were assayed for their alpha-glucosidase inhibitory activities. Newly reported benzylated depsidones1and2in particular inhibited alpha-glucosidase with IC(50)values of 2.2 and 4.3 mu M, respectively, and are thus more potent than the positive control, acarbose.