Anti-inflammatory activities of several diterpenoids isolated from Hemionitis albofusca

Hemionitis albofusca (Baker) Christenh is a plant that grows in various regions of China. Although it is not recognized as a traditional medicine, it is often mistakenly labelled and used as Aleuritopteris argentea (S. G. Gmél.) Fée to alleviate menstruation-related issues. Recently, several diterpenoids such as ent-16-oxo-17-norkauran-19-oic acid (Compound A), 14-oxy-7β,20-dihydroxycyath-12,18-diene (Compound B), ent-8(14),15-pimaradiene-2β,19-diol (Compound C), ent-kaurane-16-ene-2β,18α-diol (Compound D), ent-kaurane-2β,16α,18α-triol (Compound E), and onychiol B have been extracted from H. albofusca. In this study, we investigated the anti-inflammatory activity of these diterpenes. We confirmed that compounds A ~ D suppressed the amount of cellular NO production by inhibiting the expression and transcription of iNOS protein. They also significantly inhibited the expression and transcription of inflammatory factors TNF-α and IL-6. Additionally, Compounds A and C suppressed the activation of the NF-κB signaling pathway and inhibited the phosphorylation level of p38, ultimately down-regulating inflammation. Compound B suppressed the activation of the NF-κB signaling pathway, while Compound D inhibited the phosphorylation level of p38 and down-regulated the activation of the p38 MAPK signaling pathway. In a word, our investigation supports the potential application of natural diterpenes as lead compounds for developing anti-inflammatory agents.