A new depside from Usnea aciculifera growing in Vietnam

From Usnea aciculifera, a new depside aciculiferin A (1) was isolated, together with eleven known compounds, (+)-(12R)-usnic acid (2), methyl haematommate (3), methyl beta-orsellinate (4), methyl orsellinate (5), atranol (6), 7-hydroxy-5-methoxy-6-methylphthalide (7), norstictic acid (8), stictic acid (9), atranorin (10), barbatinic acid (11) and diffractaic acid (12). Their chemical structures were elucidated by 1D and 2D NMR spectroscopic as well as HR-ESI-MS analysis. Usnic acid (2) and depside diffractaic acid (12) presented in high yield of around 1.5% of the dried material. Some lichen substances inhibited the growth of some cancer cell lines. Three depsides, 1, 11 and 12, were evaluated for their cytotoxic activity against HeLa (human epithelial carcinoma), NCI-H460 (human lung cancer) and MCF-7 (human breast cancer) cell lines at the concentration of 100 microg/mL. Depside 1 showed good and depside 12 strong cytotoxic activity against three surveyed cancer cell lines.