ENHANCEMENT OF TOTAL PHENOLIC, L-DOPA AND PROLINE CONTENTS IN GERMINATING FAVA BEAN (VICIA FABA) IN RESPONSE TO BACTERIAL ELICITORS

Abstract

Fava beans are important legumes of the Mediterranean diets that potentially contain higher total phenolics and associated antioxidant activity compared to many other legumes. Further, fava beans with high L-dihydroxy phenylalanine (L-DOPA) are known to have anti-Parkinson's effect. In this study, we investigated the stimulation of L-DOPA, total phenolics and related antioxidant activity in dark germinated seeds by food grade elicitors, gellan gum, a polysaccharide from Pseudomonas elodea and xanthangum from Xanthomonas campestris. The objective of this study was to investigate the role of glucose-6-phosphate dehydrogenase (G6PDH), the first rate-limiting enzyme of the pentose phosphate pathway leading to the synthesis of phenolic acid, L-DOPA and the activity of guaiacol peroxidase (GPX). We also investigated the potential link between proline metabolism and G6PDH activity in dark germinated fava bean over a period of 8 days. Total phenolics, L-DOPA, proline and antioxidant activity were determined. L-DOPA was measured spectrophotometrically and by HPLC. Results indicate that gellan gum stimulated a 9-fold increase in total phenolic compared to the control and this may be regulated via the pentose-phosphate pathway. The corresponding L-DOPA and antioxidant activity did not vary significantly between gellan gum and control treatments. The L-DOPA content was higher in the hypocotyl compared to cotyledon. This novel approach to stimulate the levels of phenolic metabolites provides a mechanism to improve their nutraceutical functionality and enhance their potential for the treatment of Parkinson's disease with enhanced phenolic content.