We elucidated the pharmacological and biological effects of Oenothera laciniata extracts on the production of inflammatory mediators in macrophages. The CH2Cl2 fraction of O. laciniata extract effectively inhibited UPS-induced NO, PGE(2), and proinflammatory cytokine production in RAW264.7 cells. These inhibitory effects of the CH2Cl2 fraction of O. laciniata were accompanied by decreases in the expression of iNOS and COX-2 proteins and MOS, COX-2, TNF-alpha, IL-1 beta, and IL-6 mRNA. Asiatic acid and quercetin were present in the HPLC fingerprint of the O. laciniata extract. We tested the potential application of O. laciniata extract as a cosmetic material by performing primary skin irritation tests. In New Zealand white rabbits, primary irritation tests revealed that application of O. laciniata extracts (1%) did not induce erythema or edema formation. Human skin primary irritation tests were performed on the normal skin (upper back) of 30 volunteers to determine if any material in O. laciniata extracts had irritation or sensitization potential. In these assays, O. laciniata extracts did not induce any adverse reactions. Based on these results, we suggest that O. laciniata extracts be considered possible anti-inflammatory candidates for topical application. (c) 2009, The Society for Biotechnology, Japan. All rights reserved.