CRANBERRY PHENOLICS-MEDIATED ELICITATION OF ANTIOXIDANT ENZYME RESPONSE IN FAVA BEAN (VICIA FABA) SPROUTS

Abstract

The antioxidant response mechanism by which phenolic phytochemicals show their positive benefits in plants and animals is not very well understood. The ability of cranberry juice powder (CP), ellagic acid (EA), rosmarinic acid (RA) and their synergies to elicit a phenolic response in germinating fava bean was investigated. Results indicated that elicitation with CP, EA, RA and their synergies resulted in increased endogenous phenolic synthesis linked to the stimulation of pentose phosphate pathway (PPP). Further, the stimulation of PPP was linked to the accumulation of free proline, suggesting a possible coupling of proline biosynthesis with PPP. Elicitation also resulted in the stimulation of guaiaicol peroxidase, suggesting a possible involvement in modulating structural development of the germinating sprout. Exogenous phenolic elicitation also resulted in the formation of malondialdehyde, which was gradually reduced because of the activation of antioxidant enzyme systems superoxide dismutase and catalase. The results indicate that the possible mode of action of exogenous phenolic phytochemicals in dark germinating fava bean could be by stimulating the PPP linked to proline biosynthesis and by the activation of the antioxidant enzyme system. The results also suggest that pure exogenous phenolics, EA and RA appeared to be effective when they were present in a cranberry phenolic background, suggesting a possible synergistic mode of action between EA, RA and cranberry phenolics in generating an endogenous fava bean antioxidant enzyme response.