Antiproliferative effect on human cancer cells and antioxidant activity of Tunisian Citrullus colocynthis Schrad. immature fruit and seed organic extracts.

Citrullus colocynthis Schrad., traditional Tunisian medicinal plant, showed beneficial effects against oxidative stress mediated diseases, namely its fruits and seeds which contain several compounds with biological activity. The present study reports the antioxidant and the antiproliferative properties of different seed and fruit organic extracts. Antioxidant activity was assessed by the ability to quench the free DPPH and the superoxide anion radicals and inhibit the ABTS cation. Methanol extracts presented the highest DPPH scavenging (seeds IC50 = 0.178 mg/ml; fruit IC50 = 0.223 mg/ml) and superoxide scavenging (seeds IC50 = 28.102 µg/ml; fruits IC50 = 30.793 µg/ml) activities. All extracts inhibited the ABTS radical formation. The most interesting TEAC values were registered with methanol extracts (seeds = 1.225 and fruits = 1.120). Petroleum ether seed extract showed the lower antioxidant action. Seed and fruit organic extracts were also tested for their antiproliferative activity on HT-29 human cell line. All extracts induced a concentration dependent growth inhibition. Petroleum ether seed extract exhibited the higher growth inhibition activity (IC50 = 321 µg/ml), while methanol fruit extract showed the less antiproliferative efficiency (IC50 >500 µg/ml). Data obtained indicate that seeds and fruits constitute an excellent source of effective natural antioxidants and chemopreventive agents.