Six new highly oxygenated polycyclic cyathane-xylosides, named striatoids A-F (1-6), were isolated from the cultures of the basidiomycete Cyathus striatus. Their structures were established by comprehensive spectroscopic analysis including 2D NMR (HMBC, HSQC, ROESY, (1)H-(1)H-COSY) and HRESIMS experiments. Compounds 2 and 3 possess an unusual 15,4'-ether ring system. The isolated compounds dose-dependently enhanced nerve growth factor (NGF)-mediated neurite outgrowth in rat pheochromocytoma (PC-12) cells.

Cyathane diterpenoids, occurring exclusively in higher basidiomycete (mushrooms), represent a structurally diverse class of natural products based on a characteristic 5-6-7 tricyclic carbon scaffold, including 105 members reported to date. These compounds show a diverse range of biological activities, such as antimicrobial, anti-MRSA, agonistic toward the kappa-opioid receptor, antiinflammatory, anti-proliferative and nerve growth factor (NGF)-like properties. The present review focuses on the structure diversity, structure elucidation and biological studies of these compounds, including mechanisms of actions and structure-activity relationships (SARs). In addition, new progress in chemical synthesis of cyathane diterpenoids is discussed.

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Hericium erinaceus is a culinary-medicinal mushroom used traditionally in Eastern Asia to improve memory. In this work, we investigated the neuroprotective and neuritogenic effects of the secondary metabolites isolated from the MeOH extract of cultured mycelium of H. erinaceus and the primary mechanisms involved. One new dihydropyridine compound (6) and one new natural product (2) together with five known compounds (1,3–5,7) were obtained and their structures were elucidated by spectroscopic analysis, including 2D NMR and HRMS. The cell-based screening for bioactivity showed that 4-chloro-3,5-dimethoxybenzoic methyl ester (1) and a cyathane diterpenoid, erincine A (3), not only potentiated NGF-induced neurite outgrowth but also protected neuronally-differentiated cells against deprivation of NGF in PC12 pheochromocytoma cells. Additionally, compound 3 induced neuritogenesis in primary rat cortex neurons. Furthermore, our results revealed that TrkA-mediated and Erk1/2-dependant pathways could be involved in 1 and 3-promoted NGF-induced neurite outgrowth in PC12 cells.

Five new sesquiterpene polyol esters with a dihydro-β-agarofuran skeleton, designated as wightianines A-E (1-5), besides two known compounds, were isolated from the methanolic extract of the whole plant of the traditional herbal medicine Parnassia wightiana Wall. The structures of the isolated compounds were elucidated on the basis of spectroscopic analyses, including two-dimensional nuclear magnetic resonance techniques (correlation spectroscopy, heteronuclear multiple-quantum coherence, nuclear Overhauser effect spectrometry, and heteronuclear multiple-bond correlation) and electronic circular dichroism studies. The antifungal and insecticidal activities of five compounds were evaluated against several plant pathogenic fungi and armyworm larvae (Mythimna separata Walker). Among the test metabolites, compounds 2 and 7 both exhibited potent antifungal activity against the phytopathogenic fungus Cytospora sp. with minimum inhibitory concentration values of 0.78 μg/mL, which are equal to the two positive controls, hymexazol and carbendazim. However, no insecticidal activity of the test compounds was observed in the present study. Compounds 2 and 7 could be promising leads for developing new fungicides against agriculturally important fungus Cytospora sp.

Abstract:Two picrotoxane sesquiterpene lactone glycosides, nepalactones A (1) and B (2), and one new coumarin, nepalarin (3), were isolated from the root barks of the poisonous plant Coriaria nepalensis. Their structures were elucidated via HRESIMS and 1D and 2D NMR spectroscopic analyses, and further verified via transformation methods. In addition, compounds 1-3 and five semisynthetic congeners (1a-e) were assayed for the activity to induce neurite outgrowth in rat pheochromocytoma (PC12) cells. As a result, nepalactone A derivative 1c and nepalarin (3) significantly enhanced nerve growth factor (NGF)-mediated neurite outgrowth in PC12 cells.

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