Anti-inflammatory activity of diterpenes from Croton stellatopilosus on LPS-induced RAW264.7 cells
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An acyclic diterpene (plaunotol; 1) and two furanoditerpenes (plaunolide, 2 and plaunol E, 3), were isolated from Croton stellatopilosus leaves, and assessed for their inhibitory activity on nitric oxide (NO) production by lipopolysaccharide (LPS)-induced RAW264.7 cells. Plaunotol, plaunolide and plaunol E exhibited inhibitory activity with IC50 values of 3.41, 17.09 and 2.79 μM, respectively. Cytotoxic effects were observed at concentrations of ≥100 μM for plaunotol and ≥10 μM for plaunol E. In order to understand the mechanism of this anti-inflammatory activity, transcription profiles of the COX-1, COX-2 and iNOS genes were measured using a quantitative RT-PCR technique. The level of gene expression was expressed as a relative quantitation according to the comparative C T method. The results indicated that plaunotol stimulated the COX-1 and COX-2 genes, and suppressed expression of the iNOS gene. Treatment of cells with plaunolide caused a downregulation of the expressions of the COX-1, COX-2 and iNOS genes. In contrast, plaunol E inhibited the expression of the COX-2, stimulated COX-1 and iNOS expressions. In summary, the present study shows that different diterpenes from C. stellatopilosus leaves exhibit anti-inflammatory activity towards LPS-activated RAW264.7 cells by different mechanisms. Our results provide data to support further investigations into the possibility that these diterpenes could be alternatives to act as anti-inflammatory agents.
KeywordsCroton stellatopilosus Plaunotol Plaunolide Plaunol E RAW264.7 cells MTT assay
We thank Mr. Anan Chaikitwattana from Tipco Foods (Thailand) Public Co., Ltd., for providing Plaunoi leaf powder and Assistant Prof. Dr. Boonchoo Sritularak for his guidance on optical rotation measurement. Grants from the Prince of Songkla University (no. 530220S) and the Graduate School are also acknowledged. We would like to thank Dr. Brian Hodgson for assistance with the English.
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