Hydroxydiorygmone A, a New Guaiane-Sesquiterpene from the Cultured Lichen Mycobiont of <i>Diorygma</i> sp

Objective: Cultured mycobiont of the Vietnamese crustose-lichen Diorygma sp. has been chemically investigated. Biological activities including cytotoxicity against HepG2 cell line, α-glucosidase inhibition, and nitric oxide inhibitory activity were evaluated. Methods: Extensive spectroscopic methods (NMR and ECD) and HRESI mass data were employed for structural elucidation. These isolates were evaluated for their cytotoxicity against HepG2 cell line, α-glucosidase inhibition, and inhibitory activity toward nitric oxide production in LPS-stimulated RAW 264.7 cells. Results: Four compounds (1–4), including a new guaiane-sesquiterpene, hydroxydiorygmone A (1), along with three known analogues, diorygmones A and B (2 and 3) and pruinosone (4), were isolated and characterized. Compound 1 showed moderate α-glucosidase inhibition with an IC 50 value of 160 ± 2.2 µM and significant inhibitory activity toward nitric oxide production in LPS-stimulated RAW 264.7 cells with an IC 50 value of 8.11 ± 0.21 µM. Others were inactive in α-glucosidase inhibitory and nitric oxide inhibitory tests. Conclusion: A new guaiane-sesquiterpene, hydroxydiorygmone A (1) was isolated and showed moderate α-glucosidase inhibition with an IC 50 value of 160 ± 2.2 µM and significant inhibitory activity toward nitric oxide production in LPS-stimulated RAW 264.7 cells with an IC 50 value of 8.11 ± 0.21 µM.