Eleven previously undescribed 3,4-seco-spiromeroterpenoids, penicitrinoids A–K (1–11), one revised analogue (12), and three known compounds (13–15) were isolated under HPLC-UV guidance from the marine-derived fungus Penicillium citrinum F5025. Their structures and absolute configurations were unequivocally determined through HR-ESIMS, extensive 1D and 2D NMR analysis, ECD calculations, and a single-crystal X-ray diffraction study. Notably, Penicitrinoid A (1) represents the first example of a 3,4-seco-spiromeroterpenoid incorporating a tetrahydrofuran ring. Moreover, the previously reported structure of fusariumin B was revised and corresponds to compound 12. In antiviral assays, compounds 8 and 14 exhibited activity against influenza virus (strain ZX1109) with EC50 values of 6.41 and 10.91 μM, respectively. Compound 8 also showed activity against Ross River virus (RRV) (EC50 = 51.92 μM), while compound 10 was active against dengue virus (DENV-2) (EC50 = 51.91 μM). Mechanistic studies indicated that the antiviral effects of compounds 8 and 10 against RRV and DENV-2 are primarily mediated through interference with viral RNA replication. This study not only expands the structural diversity of 3,4-seco-spiromeroterpenoids but also provides a foundation for their development as potential antiviral agents.
The essential oil of the underground parts of Doronicum austriacum subsp. giganteum (Griseb.) Stoj. & Stef. (Asteraceae) was studied here for the first time. Based on GC-FID peak-area normalization, neryl isobutyrate (44.2%) and neryl 2-methylbutyrate (28.8%) were the two most abundant identified constituents. Targeted chromatographic fractionation guided by GC–MS revealed a series of oxygenated acyclic monoterpene diesters that proved difficult to identify by conventional means. By combining the synthesis of authentic reference compounds with high-field NMR spectroscopy (HSQC, HMBC, NOESY) and diagnostic 13C–1H coupling constants, nine previously undescribed natural products were identified, including 8- and 9-acyloxyneryl isobutyrates and the corresponding 2-methylbutyrate analogues. Systematic relationships between structure and linear retention indices on nonpolar and polar stationary phases provided transferable criteria for distinguishing C-8 vs C-9 oxygenation and neryl (Z) vs geranyl (E) geometry, and enabled estimation of chromatographic behavior for related, not-yet observed congeners. A re-evaluation of reported NMR patterns further suggests that a subset of literature “acyloxyneryl/geranyl” assignments may correspond to C-10-acylated isomers. Collectively, these findings expand the phytochemical space of acylated monoterpenes in Asteraceae roots and provide a validated spectral and retention-index reference framework for future studies of closely related metabolites.
Ten undescribed dammarane-type triterpenoid saponins (1‒10), along with six known analogues (11‒16) were isolated from the dry leaves of Gynostemma pentaphyllum (Thunb.) Makino, collected from Guilin City in Guangxi, China. Their diverse structures were elucidated on the basis of comprehensive spectroscopic analysis of 1D and 2D NMR, HR-MS, and acid hydrolysis. Among the isolates, three compounds (5, 12, and 16) significantly increased intracellular ATP levels in C2C12 myotubes, reaching 153.2%, 154.7%, and 134.9%, respectively. Further investigation revealed that these regulatory effects were mediated through the modulation of mitochondrial function, among which compound 12 exhibited the strongest agonist activity on the mitochondrial ATP production, elevating it by 25.45%. These findings deepen the insight into dammarane-type saponins and underscore the potential of G. pentaphyllum in anti-fatigue applications.
