Antiproliferative and chemopreventive activity of Citrullus colocynthis Schrad extracts

Citrullus colocynthis Schrad. is an endemic and wild native plant growing in arid areas in the south of Tunisia. This cucurbitaceae is widely used in Tunisian folk medicine for treating many diseases such as disorders related to the presence of free radicals (i.e. inflammatory disorders, rheumatism, hypertension). In fact, recent studies show that aqueous and acetone extracts of different parts of this plant possess free radical scavenging and antioxidant properties. The aim of the present study was to evaluate the antiproliferative and chemoprotective activity towards DNA oxidative damage of different extract types (aqueous, petroleum ether, chloroform, ethyl acetate, acetone, methanol) of different plant parts (seeds, roots, stems, leaves and fruits) at different concentrations (5÷500µg/ml). We also analyzed the major fraction and three pure products derived from chromatographic separation of seeds and fruits chloroform extracts. MTS and alkaline Comet Assay were performed on different kind of human tumor and normal cell lines (HT29, colon cancer; A549 lung adenocarcinoma; HFL1, fetal lung fibroblast). On HT29 cells, the chloroform extracts proved to be the more interesting ones (GI50 values were lower with respect to the other compounds) and, in particular, the leaves extract with a GI50 of 140µg/ml. This antiproliferative activity, at the highest concentration tested (500µg/ml) seems to be related to a cytotoxic effect (Trypan Blue method) and preliminary data obtained with the Tunel assay suggests the apoptosis pathway involvement. The antiproliferative activity of leaves chloroform extract was detected also on lung cell lines. In particular we have found that the chloroform extracts of seeds, stem and fruits lead a higher antiproliferative activity on tumoral A549 cells with respect to normal HFL1. Regarding the major fraction and the pure products, only the product P1 exert an antiproliferative activity (GI50: 160µg/ml) but only on HT29. DNA migration analysis of HT29 treated for 24h with leaves chloroform extract or the P1 product (0.5÷50µg/ml) didn’t show any induced DNA damage. The treatment of HT29 with H2O2 (100µM) as a known oxidative agent, 5 minutes at 0° after 24h of trea tment with leaves chloroform extract (5µg/ml), showed an antioxidative activity comparable to that of vitamin C (1µM) as demonstrated by the significant reduction in the detected DNA migration. Our results strongly support the pharmacological use of C. colocynthis Schrad.