Leonurus cardiaca L. herb extracts and their constituents promote lactoperoxidase activity

Besides other applications, motherwort (Leonurus cardiaca L., Ph. Eur.) is used in traditional medicine as an anti-inflammatory remedy. In order to gain more insights into the underlying mechanisms in this study we prepared different Leonurus extracts, which were characterized by determining their polyphenolic contents using RP-HPLC separation and quantification. Afterwards the extracts as well as ten of their phenolic components and five Laminaceae-typical caffeic acid derivatives were tested for their ability to regenerate the pseudo-halogenating activity of lactoperoxidase (LPO). During this enzymatic activity the bactericidal product hypothiocyanite is formed which contributes to the humoral immune defence against pathogens. Moreover, hypothiocyanite production may contribute to the regulation of inflammatory reactions. In fact, phenolic Leonurus components with a 3,4-dihydroxyphenylic partial structure (e.g. caffeic acid derivatives or phenylethanoids) emerged as efficient LPO activity regenerators. This is also reflected by results obtained from the LCH whole extracts, where especially the ethanol extract, which is rich in such compounds, showed the strongest effects. These results may explain the anti-inflammatory properties of motherwort.