Topical anti-inflammatory activity of Plantago major L. leaves

The leaves of Plantago major L. (Plantaginaceae) are traditionally used for the topical treatment of skin inflammations, infections and wounds [1]. Their constituents, such as terpenoids, phenols and iridoids, possess immunostimulant activity and/or inhibit enzymes involved in inflammation [2, 3]. Although the main therapeutic use of P. major is in cutaneous inflammatory diseases, their topical antiphlogistic properties were not yet investigated. Therefore, P. major leaves were studied for their topical anti-inflammatory activity.

P. major leaves were sequentially extracted with n-hexane, chloroform and methanol and the relevant extracts were evaluated for their ability to inhibit the Croton oil-induced ear dermatitis in mice [4]. 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 drug indomethacin: their ID₅₀ (dose giving 50% edema inhibition) values were 177 and 93µg/cm², respectively. By column chromatography, the extract was separated in four fractions (I-IV), concentrating its activity into fraction III, a mixture of ursolic acid and oleanolic acid, in the ratio 1:2. Each compound induced a dose-dependent edema inhibition, being ursolic acid (ID₅₀=56µg/cm²) more active than oleanolic acid (ID₅₀=132µg/cm²) and indomethacin. The antimicrobial activity of the plant is under investigation, in order to identify possible active compounds, different from the well known aucubin.

References: 1. Samuelsen, A.B. (2000), J. Ethnopharmacol. 71: 1–21. 2. Chiang, L.C. et al. (2003), Planta Med. 69: 600–604. 3. Ringbom T. et al. (1998), J. Nat. Prod. 61: 1212–1215. 4. Tubaro, A. et al. (1985) Agents Actions 17: 347–349.