Influence of potent antioxidant leguminosae family plant extracts on growth and antioxidant defense system of Hep2 cancer cell line.

Legumes are considered to be a very good source of polyphenolic compounds that may act as chemopreventive agents, especially by their antioxidant properties. However, many of the chemopreventive properties may depend on the concentrations of the phytochemical compounds because potent antioxidant polyphenolic compounds may have pro-oxidant properties and negatively affect cell growth and viability. Thus, the aim of the present study was to assess the possible effect of two potent antioxidant Greek Leguminosae family plant extracts on the growth of a specific cancer cell line and its antioxidant defense cell system. Aqueous extracts of aerial parts of Lathyrus laxiflorus and Phaseolus vulgaris plants were initially examined for their cytotoxicity on the Hep2 cancer cell line at concentrations that possess potent antioxidant properties (100, 400, and 800 microg/mL). After a 24-hour incubation with the extracts, only L. laxiflorus plant extract exhibited the ability to inhibit the cell growth at 400 and 800 microg/mL by 57% and 74%, respectively, whereas P. vulgaris extract had no effect on cell growth at any of the tested concentrations. Noncytotoxic concentrations, 100 microg/mL L. laxiflorus and 800 microg/mL P. vulgaris extract, were used for 2-, 12-, and 24-hour incubation of the cells. The influence of the extracts on the antioxidant defense system of the cells was assessed by measuring the total antioxidant capacity (TAC) of the cells, the catalase (CAT) activity, and the concentrations of reduced glutathione, the oxidized form of glutathione, and thiobarbituric-reactive substances (TBARS) in all times of incubation with the cells. From the results obtained, it seems that only L. laxiflorus extract induces oxidative stress in the cells by reducing TAC and CAT activity and by inducing TBARS, especially with 2 and 12 hours of incubation. P. vulgaris extract reduced only TAC at 2 hours of incubation, indicating also a mild induction of oxidative stress. These results imply that potent antioxidant extracts, beyond a critical concentration, may induce oxidative stress even with no apparent cytotoxicity in cells.