ETHNOPHARMACOLOGICAL RELEVANCE: Evening primrose (Oenothera biennis L., Onagraceae) is a wild medicinal plant of Central American origin that is now one of the most widely used herbal medicines in different parts of the world. Oil extracted from it seeds is traditionally used in the treatment of eczema, asthma, rheumatoid arthritis, breast problem, premenstrual and menopausal syndrome, all they have an inflammatory component. The present study demonstrates the in vitro anti-inflammatory effect of long-chain fatty alcohols, minor compounds isolated from Evening primrose oil (EPO).
MATERIAL AND METHODS: A mixture of long chain fatty alcohols (LCFAs) was isolated from the non-triacylglycerol fraction of the EPO. Hexacosanol (C26OH: 38.65%), tetracosanol (C24OH: 31.59%), docosanol (C22OH: 11.36%) and octocosanol (C28OH: 7.64%), were the major constituents, identified and quantified by GC and GC-MS. LCFA was tested with LPS stimulated murine peritoneal macrophage. This fraction, significantly and dose-dependently decreased nitric oxide production induced by LPS (P<0.001) and the inhibitory effect seems to be consequence of an action at the level of the inducible nitric-oxide synthethase (iNOS) gene enzyme expression rather than to a direct inhibitory action on enzyme activity. The release of PLA2 and TXB2 also was significantly inhibited by LCFAs (P<0.001) although LCFAs did not affect to PGE2 generation, however the western blot assay showed that LCFAs reduced cyclooxygenase-2 enzyme gene expression at all doses assayed. In the same way, the secretion of inflammatory cytokines interleukin 1β (IL-1β) and tumour necrosis factor α (TNF-α) from LPS-stimulated murine macrophage, were also significantly reduced (P<0.001).
CONCLUSION: These results demonstrates the anti-inflammatory activity of LCFAs, providing an additional value about the role of bioactive minor compounds in the beneficial effect of EPO and supports its traditional uses in inflammatory processes management.