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Abstract:We investigated the effect of oral administration of hydroalcoholic extract of Brazilian red propolis (HERP) on DMBA-induced oral squamous cell carcinomas (OSCC) in rodents. The chemical components of the HERP were assessed by high-performance liquid chromatography (HPLC). Carcinogenesis was topically induced in the lower lip of 25 rats using 9,10-dimethyl-1,2-benzanthracene (DMBA); the tumour was treated with saline (TUM1) and Tween 80 (TUM2) as well as HERP at 10, 50 and 100 mg/kg (HERP10, HERP50 and HERP100, respectively) for 20 weeks. Topical application of saline and oral administration of 100 mg/kg HERP was used in five rats as a control group (CTR). After 26 weeks, the histological malignancy grading and immunohistochemical expression of INK4A were assessed in the tumours/tissue samples. The compounds identified were propyl gallate, daidzein, catechin, epicatechin, formononetin and biochanin A. Formononetin, daidzein and biochanin A showed concentration of 23.29, 0.38 and 0.67 mg/g of HERP, respectively. HERP at doses of 50 and 100 mg/ kg inhibited 40% of OSCC growth and promoted a 3-week delay in development of clinically detectable tumours. Epithelial dysplasia was observed in all samples with no clinical tumour, except in CTR. No significant difference in the immunoexpression of INK4A was observed between HERP-treated and saline/Tween 80-treated groups (p > 0.05). Our results suggest that HERP exerts chemopreventive activity on the progression of DMBA-induced epithelial dysplasia to OSCC in an experimental model of labial carcinogenesis; however, this effect is not associated with Ki-67 and p16INK4A immunoexpression.Propolis is a natural, resinous hive product that honeybees manufacture by mixing their own waxes and salivary secretions with resins collected from cracks in tree barks and leaf buds [1]. Propolis samples from different regions of Brazil display different colours and chemical compositions, depending on the local flora at the site of collection [2]. Brazilian green propolis, derived from Baccharis dracunculifolia (Asteraceae) [3], is the most popular and well-studied Brazilian propolis.In the last few years, a red variety of Brazilian propolis has been described and characterized by various authors [4][5][6], demonstrating that the botanical origin influences directly its chemical composition. Isoflavones are chemical constituents usually identified in ethanolic extracts of red propolis, being formononetin, daidzein and biochanin A more often found [5,7].Brazilian

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