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From the chloroform extract of the lichen Ramalina peruvianaAch. (Ramalinaceae), collected at Cau Dat farm, Lam Dong province, Vietnam, eight organic compounds had been isolated: nonadecan‐1‐ol (1); nonadecenoic acid (2); (+)‐(12R)‐usnic acid (3); three monophenolic compounds‐ rhizonic acid (4), divarinolmonomethylether (5) and divaricatinic acid (6); and two depsides‐ decarboxy‐2'‐O‐methyldivaricatic acid (7) and sekikaic acid (8). The chemical structure of these compounds was elucidated by spectroscopic analysis as well as high resolution ESI–MS analysis and comparison with those reported in the literature. Among these compounds, (1), (2), (4), (5) and (7) were the first time known in the Ramalinagenus. Although compound (7) was detected in the lichen Neofuscelia depsidellaby chromatographic comparisons with authentic material that was synthesized by condensation of the benzoic acid and 3‐methoxyl‐5‐propylphenol but it is isolated in the nature for the first time. The results of determining the α‐glucosidase inhibitory activity of four isolated compounds show that the α‐glucosidase inhibitory effect of (8) was the best with IC50values in 136.62 μg/mL (compared with the control acarbose IC5093.63 μg/mL).

Six new compounds, globunones A–F (1–6), and two new flavonoids (7and 8) together with nine known compounds (9–17) were isolated from the stems of Knema globularia.The chemical structures of 1–8were elucidated by an analysis of their NMR and high-resolution electrospray ionization mass spectrometry data as well as by comparison with literature values. The absolute configurations were determined using time-dependent density functional theory electronic circular dichroism (TD-DFT-ECD). Globunones A–E (1–5) represent the initial combined structures of a flavan-3-ol core and a 1,4-benzoquinone core. Globunone F (6) is the first flavanone-type compound bearing a 2-(2,4-dihydroxyphenyl)-2-oxoethyl group found to date in Nature. Compounds 1–3and 6–17were tested for their yeast α-glucosidase inhibitory activity. All compounds tested (except for 13and 14) showed potent inhibition toward α-glucosidase with IC50values in the range 0.4–26.6 μM. Calodenin A (15) was the most active compound with an IC50value of 0.4 μM (the positive control, acarbose, IC5093.6 μM). A kinetic analysis of 15revealed that it is a noncompetitive inhibitor with a Kivalue of 3.4 μM.