Anti-inflammatory and antioxidative effects of six pentacyclic triterpenes isolated from the Mexican copal resin of Bursera copallifera

BACKGROUND: Bursera copallifera (Burseraceae) releases a resin known as “copal ancho” which has been used, since pre-Colombian times, as ceremonially burned incense and to treat tooth ache, tumors, arthritis, cold, cough, and various inflammatory conditions; however, its anti-inflammatory potential is poorly studied. The aim of the present study was to isolate, quantify, and to investigate the anti-inflammatory activity of triterpene compounds isolated from the copal resin of B. copallifera. METHODS: The constituents present in the total resin of B. copallifera were obtained by successive chromatographic procedures, and quantitative analysis was performed by High Performance Liquid Chromatography (HPLC). Anti-inflammatory effects of the isolated triterpenes were investigated to determine their inhibitory effects on phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced edema in mice, viability and nitric oxide (NO) production inhibition on lipopolysaccharide (LPS)-activated RAW 264.7 macrophages, and inhibition of cyclooxygenase (COX)-1, COX-2 and secretory Phospholipase A(2) (sPLA(2)) activities in vitro. RESULTS: Quantitative phytochemical analysis of the copal resin showed the presence of six pentacyclic triterpenes of which, 3-epilupeol (59.75 % yield) and α-amyrin (21.1 % yield) are the most abundant. Among the isolated triterpenes, 3-epilupeol formiate (Inhibitory Concentration 50 % (IC(50)) = 0.96 μmol), α.amyrin acetate (IC(50) = 1.17 μmol), lupenone (IC(50) = 1.05 μmol), and 3-epilupeol (IC(50) = 0.83 μmol) showed marked inhibition of the edema induced by TPA in mice. α-amyrin acetate and 3-epilupeol acetate, at 70 μM, also inhibited the activity of COX-2 by 62.85 and 73.28 % respectively, while α-amyrin and 3-epilupeol were the best inhibitors of the production of NO in LPS-activated RAW 264.7 cells with IC(50) values of 15.5 and 8.98 μM respectively, and did not affected its viability. All compounds moderately inhibited the activity of PLA(2). CONCLUSIONS: This work supports the folk use of B. copallifera and provides the basis for future investigations about the therapeutic use of this resin in treating inflammation.