Terpenoids from the Marine-Derived Fungus Aspergillus sp. RR-YLW-12, Associated with the Red Alga Rhodomela confervoides .

Two new meroterpenoids, aspermeroterpenes D and E ( 1 and 2 ), two new ophiobolin-type sesterterpenoids, the C-18 epimers of 18,19-dihydro-18-methoxy-19-hydroxyophiobolin P ( 6 and 7 ), and two new drimane-type sesquiterpenoids, 3 S -hydroxystrobilactone A ( 8 ) and 6- epi -strobilactone A ( 9 ), along with 11 known terpenoids ( 3 - 5 and 10 - 17 ) were isolated from the cultures of the algicolous fungus Aspergillus sp. RR-YLW-12, derived from the red alga Rhodomela confervoides . The structures and relative configurations of new compounds were established by detailed spectroscopic analysis of NMR and HRMS experiments, and the absolute configurations were assigned by X-ray diffraction experiments and comparison of their experimental and calculated ECD spectra. Compound 1 features a rare 6/6/6/6/5 pentacyclic system with a meroterpenoid skeleton, and the structure of terretonin E ( 3 ) was revised in this study. Compound 4 showed significant inhibitory activities against three microalgae, Prorocentrum donghaiense , Heterosigma akashiwo , and Chattonella marina , with IC ₅₀ values of 10.5, 5.2, and 3.1 μg/mL, respectively.