11,12-seco-Abietane-type diterpene lactones with potential antiplatelet activity from Salvia prattii

Phlecarinatones H-N: Abietane-type diterpenoids from Phlegmariurus carinatus with proliferative inhibitory effect on U251 glioblastoma cells

Thirteen abietane-type diterpenoids, including seven previously undescribed compounds and six known analogs, were isolated from the root and aerial parts of Phlegmariurus carinatus. Their structures were elucidated by comprehensive spectroscopic data analysis (UV, IR, NMR, and HRESIMS) and quantum chemical calculations (calculated ECD or 13C NMR). Notably, these compounds exhibited high structural diversity. Compounds 1-8 possessed six distinct fused ring systems. Phlecarinatones I (2) and J (3) were identified as rare 6,7-seco-abietane diterpenoids featuring a five-membered lactone ring B. Compounds (1-12) were evaluated for their anti-proliferative activities in the U251 cell line. In particular, phlecarinatone I (2) exhibited potential inhibitory effects on U251 cell proliferation, with an IC50 value of 13.88 ± 1.82 μM. To elucidate the underlying molecular mechanism, p53 signal pathway was enriched from our RNA-seq data. Further investigations using western blot and immunofluorescence assays confirmed that p53 expression was up-regulated in a concentration-independent manner. Additionally, molecular docking studies suggested 2 likely binds to the MDM2-p53 binding region. Finally, an shRNA-mediated MDM2 knockdown experiment provided definitive evidence that 2 acts as a potent inhibitor of glioma proliferation, operating via the modulation of the MDM2-p53 pathway. These findings suggest that 2 might be a valuable of lead compound with anti-proliferative activity.

Unprecedented nor-seco-diterpene lactones inhibited osteogenic differentiation of valve interstitial cells

The first examples of ent-atisane and ent-isopimarane diterpene lactones with an unusual 2,3-seco-2-nor-tetrahydro-2H-pyran-2-one nucleus, eufislactones A (1) and B (2), were isolated from the roots of Euphorbia fischeriana, together with a new (3) and fifteen known biosynthetic congeners (4-18). Their structures incorporating absolute configurations were elucidated via the comprehensive spectroscopic analyses, electronic circular dichroism (ECD) calculation, and single-crystal X-ray diffraction analyses. Biogenetically, compounds 1 and 2 were constructed by the plausible monomeric precursors, ent-atis-16-ene-3,14-dione (6) and ent-isopimara-8(14),15-dien-3-one (17), respectively, via key Baeyer-Villiger oxidation, decarboxylation, and semi-acetalization reactions to create a unique 2,3-seco-2-nor-tetrahydro-2H-pyran-2-one core. Our bioassays have revealed that eufislactone A (EFA, 1) displayed significant inhibitory effect on the osteogenic differentiation of human valvular interstitial cells (VICs), highlighting its potential as a preventive agent against the progression of human calcific aortic valve disease (CAVD).

Discovery and Bioinspired Synthesis of Salpratone A

Salpratone A (1), a novel abietane diterpenoid containing a unique cis-fused A/B ring, was isolated from Salvia prattii. Bioactivity studies showed that 1 has potent activity in inhibiting platelet aggregation induced by multiple agonists as well as antithrombotic efficacy in the FeCl3-induced rat in vivo thrombosis model. Furthermore, a bioinspired synthesis of 1 from the abundant natural product ferruginol was achieved in 6 steps with a 22% overall yield. The key steps include a stereoselective allyl oxidation and a subsequent regioselective Meinwald rearrangement.