Anti-tumor activity of Rosmarinus officinalis (a medicinal plant) on chemical-induced skin carcinogenesis

Over the past decade, interest in evaluation oriental medical herbs and edible phytoproducts for use in cancer preventing strategies is emerging as an acceptable approach for controlling the cancer incidence in many developing as well as developed countries.The present investigation was undertaken to explore anti-tumor promoting activity of Rosmarinus officinalis L. (Rosemary) leaves extract with two different doses (500 mg and 1000 mg/kg b. wt.) on two-stage skin tumorigenesis, induced by a single topical application of 7, 12-dimethylbenz(a)anthracene (DMBA), and promoted by croton oil treatment for 15 weeks in Swiss albino mice. Rosemary administration at different phases (pre- peri- & post- initiation phase) reduced the rate of tumor incidence as compared to control. Furthermore, Rosemary extract when given at a dose of 1000 mg/kg b. wt./ animal, was found to be more effective than 500 mg/ kg b. wt. of plant extract during tumor inhibition studies. The results also indicate that R. officinalis could prolong the average latent period (i.e., time lag between the application of the promoter and the appearance of 50% of tumor occurrence). The effect of this treatment was found to be enhanced in all the Rosemary-treated groups. The protective effect of Rosemary is reflected in a fall in the values of cumulative number of papillomas, tumor burden, tumor yield and an increase in the average latent period. The major proposal for its action and efficacy seems to be the effectiveness of the plant extract to intercept the free radicals and protect cellular molecules from oxidative damage.