In vitro antiproliferative evaluation of onopordopicrin isolated from leaves of Arctium lappa L.

Because of the need for new anti-cancer drugs, many compounds have been evaluated for treatment of the disease [1]. We assessed the crude extract (CE), ethyl acetate fraction (EAF), and onopordopicrin compound isolated from leaves of Arctium lappa L. CE was obtained by 50% hydro-alcohol extraction (Ultra-Turrax), and was partitioned with ethyl acetate to obtain the EAF. EAF was subjected to sequential column chromatography with Merck ® silica gel (0.063–0.200mm), and Merck ® silica gel (0.040–0.063mm), thus obtaining onopordopicrin, which was identified by spectroscopic methods (NMR, MS) and by comparison with the literature. The in vitro antiproliferative test was performed on human tumor cell line Caco-2. The activities of the fractions and compound against Caco-2 cells were determined by sulforhodamine assay, as described by Skehan et al. [2]. The cells were seeded in 96-well tissue plates at a density of 8×10⁵ cells/mL for 24h in the CO₂ incubator. The compounds were dissolved in dimethyl sulfoxide and added to the medium at various concentrations. After incubation for 48h, the cell monolayers were fixed with trichloroacetic acid and stained for 30min with 0.4% sulforhodamine B. The protein-bound dye was extracted with 10 mM unbuffered Tris base for determination of optical density in a computer-interfaced, microtiter plate reader (Power Wave XS, BIO-TEK®). The results of CC₅₀ in Caco-2 cells were 347.6±26.9 (RSD%=7.7) 24.7±3.0 (RSD%=12.2), and 19.8±3.7 (RSD%=18.5)µg/mL for EC, EAF, and onopordopicrin, respectively. These results showed that onopordopicrin may be a promising anti-cancer drug.

Acknowledgements: CAPES, CNPq, INCT_if.

References: 1. Aggarwal BB. et al. (2008) Planta Med. 74: 1560–69.

2. Skehan P. et al. (1990)J. Natl. Cancer Inst. 82: 1107–12.