[Phenolic constituents from lichen Usnea longissima]

Abstract

Sixteen compounds were isolated from lichen Usnea longissima using of various chromatographic techniques including silica gel, Sephadex LH-20, ODS, and semi-preparative HPLC. By spectroscopic data analyses, their structures were identified by as useanol(1), lecanorin(2), 3-hydroxy-5-methylphenyl 2-hydroxy-4-methoxy-6-methylbenzoate(3), lecanorin E(4), 3'-methylevernic acid(5), evernic acid(6), barbatinic acid(7), 3,7-dihydroxy-1,9-dimethyldibenzofuran(8), orcinol(9), O-methylorcinol(10), methyl orsellinate(11), methyl everninate(12), 2,5-dimethyl-1,3-benzenediol(13), 2-hydroxy-4-methoxy-3,6-dimethyl benzoic acid(14), ethyl everninate(15), and ethyl 2,4-dihydroxy-6-methylbenzoate(16). Compound 1 was obtained as a natural product for the first time, and 3,4, 8,10,12, and 13 were isolated from Usneaceae family for the first time. Compound 1, 8, and 13 showed significant anti-inflammatory activity against NO production in RAW 267.4 cells with IC₅₀ values of 6.8, 3.9 and 4.8 μmol•L⁻¹, respectively, compared with the positive controls curcumin(IC₅₀ 15.3 μmol•L⁻¹) and indomethacin(IC₅₀ 42.9 μmol•L⁻¹).

Keywords: Usnea longissimia; anti-inflammatory activity; chemical constituents; phenolic; useanol.