Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/23/2009
Publication Date: 11/4/2009
Citation: Huang, N., Hauck, C., Yum, M., Rizshsky, L., Widrlechner, M.P., Mccoy, J., Murphy, P.A., Dixon, P.M., Nikolau, B.J., Birt, D.F. 2009. Rosmarinic Acid in Prunella vulgaris Ethanol Extract Inhibits LPS-induced Prostaglandin E2 and Nitric Oxide in RAW264.7 Mouse Macrophages. Journal of Agricultural and Food Chemistry. p. 10579-10589. Interpretive Summary: Self-heal (Prunella vulgaris) is an herb that has been used in traditional medicine to treat inflammation-related conditions for centuries. However, careful scientific studies of its anti-inflammatory activity are lacking. In this study, we applied water and ethanol extracts of four self-heal populations, obtained from the USDA-ARS North Central Regional Plant Introduction Station, Ames, Iowa, to RAW264.7 mouse macrophage cells to determine how these extracts would affect two measures of cellular inflammation: lipopolysaccharide (LPS)-stimulated prostaglandin E2 (PGE2) and nitric oxide (NO) production. The ethanol extracts significantly inhibited both LPS-stimulated prostaglandin E2 (PGE2) and NO production without damaging the mouse cells. Inhibition was dose-dependent, with significant effects seen at concentrations as low as 10 micrograms per milliliter. Results from selected self-heal populations were compared statistically to identify the one with the greatest activity. The ethanol extract from the most active population was fractionated, and two of its fractions were found to contribute to the overall activity. A known anti-inflammatory compound, rosmarinic acid, is found in self-heal, and we confirmed that it independently inhibited inflammatory responses, but it only partially explained the extracts' activity. These results begin to shed light on how self-heal reduces inflammation and may lead to the more effective use of self-heal by practitioners of both conventional and alternative medicine.
Technical Abstract: Prunella vulgaris has been used therapeutically for inflammation related conditions for centuries, but systematic studies of its anti-inflammatory activity are lacking and no specific active components have been identified. In this study, water and ethanol extracts of four P. vulgaris accessions were applied to RAW264.7 mouse macrophages and the ethanol extracts significantly inhibited lipopolysaccharide (LPS)-stimulated prostaglandin E2 (PGE2) and nitric oxide (NO) production at 30µg/mL without affecting cell viability. Extracts from different accessions of P. vulgaris were screened for anti-inflammatory activity to identify accessions with the greatest activity. The inhibition of PGE2 and NO production by selected extracts was dose-dependent, with significant effects seen at concentrations as low as 10 µg/mL. Fractionation of ethanol extracts from the active accession, Ames 27664, suggested fractions 3 and 5 as possible major contributors to the overall activity. Rosmarinic acid (RA) content in P. vulgaris was found to independently inhibit inflammatory response, but it only partially explained the extracts' activity. LPS-induced cyclooxyginase-2 (COX-2) and nitric oxide synthase (iNOS) protein expression were both attenuated by P. vulgaris ethanol extracts, while RA only inhibited COX-2 expression.