Abstract Cultivated lichen mycobionts represent a valuable resource for obtaining unique natural compounds. Mycobionts of Astrothelium straminicolor and Nigrovothelium inspersotropicum, collected in Vietnam, were isolated, cultivated, and subjected to chemical investigation. Consequently, three new compounds, straminones A – B (A1 and A2) and chlorosemivioxanthin (N1), along with five known compounds, 3S,4R-(+)-4-hydroxymellein (A3), 6-methoxymellein (A4), vioxanthin (N2), pigmentosin A (N3), and semivioxanthin (N4), were isolated and structurally elucidated. Straminones A and B represent the first examples of 3-methylhexahydrocyclopentacpyran-1(3H)-one skeletons found in nature. The relative configuration of A1 was confirmed by DFT calculation. Compounds A3 and N4 demonstrated weak alpha-glucosidase inhibitory activity, with IC50 values of 314 and 366 µM, respectively. The other compounds showed no inhibition in the tested assay. Notably, compounds N1–N3 showed significant inhibitory effects on NO production, with IC50 values ranging from 14 to 25 µM, compared with the positive control L-NMMA (IC50 = 49 µM). Further molecular docking clarified the inhibitory mechanism of the active compounds.
Le et al. (Tue,) studied this question.