Abstract

Myrtucommulone (MC) and semimyrtucommulone (S-MC) are unique oligomeric, nonprenylated acylphloroglucinols contained in the leaves of myrtle (Myrtus communis). Although extracts of myrtle have been traditionally used in folk medicine for the treatment of various disorders, studies addressing select cellular or molecular pharmacological properties of these extracts or specific ingredients thereof are rare. Here, we show for the first time that MC and S-MC potently suppress the biosynthesis of eicosanoids by direct inhibiting cyclooxygenase-1 and 5-lipoxygenase in vitro and in vivo at IC₅₀ values in the range of 1.8 to 29 μM. Moreover, we show that MC and S-MC prevent the mobilization of Ca²⁺ in polymorphonuclear leukocytes, mediated by G protein signaling pathways at IC₅₀ values of 0.55 and 4.5 μM, respectively, and suppress the formation of reactive oxygen species and the release of elastase at comparable concentrations. The isobutyrophenone core of MC as well as S-MC was much less potent or even not active at all. In addition, MC or S-MC only partially inhibited peroxide formation or failed to block Ca²⁺ mobilization and elastase release when polymorphonuclear leukocytes were challenged with ionomycin that circumvents G protein signaling for cell activation. We conclude that, in view of their ability to suppress typical proinflammatory cellular responses, the unique acylphloroglucinols MC and S-MC from myrtle may possess an anti-inflammatory potential, suggesting their therapeutic use for the treatment of diseases related to inflammation and allergy.