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A new drimane-type sesquiterpene with an isocitric acid moiety, cryptoporic acid S (1), together with six known compounds, cryptoporic acid D (2), β-sitosterol (3), β-daucosterol (4), stigmast-4-en-3-one (5), ergosterol (6), and (22E,24R)-ergosta-7,22-diene-3β,5α,6β-triol (7), was isolated from the fruiting bodies of Cryptoporus volvatus. The structures of these compounds were established on the basis of UV, IR, MS, 1D and 2D NMR analysis. In the meanwhile, compounds 1 and 2 were evaluated for antioxidant activity using the methods of 2,2-diphenyl-1-picrylhydrazyl free radical scavenging activity (DPPH-RSA) and ferric reducing antioxidant power (FRAP) assay, and they exhibited moderate antioxidant activities.

Natural daphnane diterpenoids, mainly distributed in plants of the Thymelaeaceae and Euphorbiaceae families, usually include a 5/7/6-tricyclic ring system with poly-hydroxyl groups located at C-3, C-4, C-5, C-9, C-13, C-14, or C-20, while some special types have a characteristic orthoester motif triaxially connectedat C-9, C-13, and C-14. The daphnane-type diterpenoids can be classified into five types: 6-epoxy daphnane diterpenoids, resiniferonoids, genkwanines, 1-alkyldaphnanes and rediocides, based on the oxygen-containing functions at rings B and C, as well as the substitution pattern of ring A. Up to now, nearly 200 daphnane-type diterpenoids have been isolated and elucidated from the Thymelaeaceae and Euphorbiaceae families. In-vitro and in-vivo experiments of these compounds have shown that they possess a wide range of biological activities, including anti-HIV, anti-cancer, anti-leukemic, neurotrophic, pesticidal and cytotoxic effects. A comprehensive account of the structural diversity is given in this review, along with the cytotoxic activities of daphnane-type diterpenoids, up to April 2019. [ABSTRACT FROM AUTHOR]