Allelopathy Journal

The influence of aqueous extracts of alfalfa (Medicago sativa) tops, roots, seeds and isolated total saponins (SAP) from alfalfa roots on the growth and biological activity of Trametes versicolor was examined. Results indicate that saponins from roots of a Medicago sativa strain are very good inductors of extracellular laccase (LAC). This strain was cultivated on liquid, mineral medium for 30 days. A 10-fold increase in the LAC activity was observed after the addition of saponins. Both crude saponin extracts and highly refined saponins were examined. The kinetic data were calculated for crude LAC prepared from the liquid growth medium of T. versicolor. These data were obtained with three different substrates: 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonate) (ABTS), 2,6-dimethoxyphenol (DMP)and o-methoxyphenol (o-MP) in the presence of SAP. Using ABTS as substrate, the quantity of SAP did not make any difference for the Km and Vmax. The same results were obtained using DMP as substrate in the presence of 0.1 and 1 mg of SAP and the lowest results were obtained with o-MP as substrate. The results of the present study suggest that saponins may be used as natural inductors of fungal LAC and this would obviate the need to use toxic xenobiotics.