Rosmarinus officinalis L. (Labiatae) is a common, evergreen shrub spontaneous in the Mediterranean area. The leaves of the plant are commonly used as a spice, but also for several inflammatory-based disorders, as well as for their wound healing properties. Most of the pharmacological studies on the plant were carried out considering the essential oil or some pure components. However, the component(s) responsible for the anti-phlogistic activity of this species are not clearly defined. Since in the therapeutically related drug Salvia officinalis L. non volatile constituents, such as ursolic acid, were identified as the main anti-inflammatory principles (1), a study on the topical anti-inflammatory activity of a rosemary commercial sample was carried out.
To this aim, the sample was extracted with increasing polarity solvents, obtaining hexane, chloroform and methanol extracts, which were subsequently evaluated for their ability to inhibit the Croton oil-induced oedema in the mouse ear (2). The activity was compared to that of the non-steroidal anti-inflammatory drug indomethacin.
The pharmacological assay revealed a strong dose-dependent anti-inflammatory activity for the hexane and the chloroform extracts whereas the methanol one was almost inactive. The chloroform extract was more potent than the hexane one: their ID50 (dose giving 50% oedema inhibition) correspond to 83 and 265 µg/cm2, respectively. As reference, the ID50 of indomethacin was 93 µg/cm2, indicating that the chloroformic extract was more active. Considering the extraction yields, the chloroformic extract was also quantitatively prevalent and gave the highest contribution to the activity of rosemary.
Preliminary TLC analysis of the extracts revealed the presence of a chromatographic band corresponding to that of ursolic acid. Other phytochemical investigations are in progress in order to characterise the constituents of the two most active extracts and to determine their role in the topical anti-inflammatory activity of rosemary.
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