Meroterpenoids with divers' rings systems from Phyllosticta capitalensis and their anti-inflammatory activity.

Four undescribed sesquiterpene-shikimates (1 – 4), eight undescribed monoterpene-shikimates (5 – 12), together with two known ones were isolated and identified from the 95% ethanol extract of the plant endophytic fungus Phyllosticta capitalensis cultured in rice medium. Capitalensis A (1) was identified as the first sesquiterpene-shikimate-conjugated spirocyclic meroterpenoid degradation product, while capitalensis B (2) is a sesquiterpene-shikimate-conjugated spirocyclic meroterpenoid with a unique D-ring formed by a C-2– O –C-9′ connection. The structures of these previously undescribed compounds were elucidated by multiple techniques, including IR, HR-ESI-MS, and NMR analysis. Furthermore, their absolute configurations were established through the comprehensive approach that involved the calculations of ECD spectra, optical rotation values, and single-crystal X-ray analysis. Moreover, the anti-inflammatory activity of all isolated compounds was evaluated using a lipopolysaccharide (LPS)-induced inflammation model in BV2 microglial cells. Meanwhile, these compounds exhibited activity in inhibiting NO production. Four compounds, capitalensis C (3), capitalensis D (4), 15-hydroxyl tricycloalternarene 5b (13) and guignarenone A (14) showed strong inhibitory effects with IC 50 values of 21.6 ± 1.33, 12.2 ± 1.08, 18.6 ± 1.27, and 15.8 ± 1.20 μ M, respectively. In addition, the structure-activity relationship of the anti-inflammatory activity of the compounds was discussed. 12 undescribed meroterpenoids compounds were isolated from Phyllosticta capitalensis , compounds 1 – 2 are rare sesquiterpene–shikimate-conjugated spirocyclic meroterpenoids containing a 5/6/5/6/5 ring system, while compound 8 contains a 5/7/6/5 tetracyclic skeleton. Two of the compounds showed potential inhibitory activity in LPS-induced BV2 microglial cells. [Display omitted] • 12 undescribed meroterpenoids were isolated from the secondary metabolite of Phyllosticta capitalensis. • The unprecedented 13′-nor-sesquiterpene-shikimate-conjugated spirocyclic meroterpenoid skeleton was found. • An undescribed compound characterized by the linkage of the first example C-2– O –C-9′ in 5/6/5/6/5 ring system. • Meroterpenoid-shikimate derivatives exhibited significant anti-inflammatory activity. [ABSTRACT FROM AUTHOR]