Topical anti-inflammatory activity of Plantago lanceolata L. leaves: the relevance of triterpenic acids

Abstract

The leaves of Plantago lanceolata L. (Plantaginaceae) are used in traditional medicine for the topical treatment of skin inflammatory affections [1]. Although P. lanceolata leaf extracts and some of their constituents have been shown to inhibit in vitro enzymes involved in inflammation [1, 2], the in vivo topical anti-inflammatory properties of the leaves have not been investigated. Therefore, P. lanceolata leaves have been studied for their topical anti-inflammatory activity by the Croton oil-induced ear dermatitis assay in mice [3]. P. lanceolata leaves were sequentially extracted with n-hexane, chloroform and methanol and the relevant extracts were evaluated for their ability to inhibit the mouse ear edema induced by Croton oil. Each extract (300µg/cm2) provoked a significant edema reduction, the chloroform one being the most active. Its potency was only two fold lower than that of the reference non steroidal anti-inflammatory drug indomethacin: their ID50 (dose inducing 50% edema inhibition) values were 186 and 97µg/cm2, respectively. By column chromatography, the chloroform extract was separated in five fractions (A-E), concentrating its activity into fraction C, which was constituted mainly by ursolic acid (44%) and oleanolic acid (27%). These compounds induced a dose-dependent edema inhibition, and ursolic acid (ID50=56µg/cm2) was more active than oleanolic acid (ID50=132µg/cm2) and indomethacin. The two triterpenes, which give a significant contribution to the anti-inflammatory activity of the parent extract, can be proposed as parameters in the quality control of P. lanceolata leaf preparations for the topical use against skin inflammations.