ELICITATION OF THE PROLINE-LINKED PENTOSE PHOSPHATE PATHWAY METABOLITES AND ANTIOXIDANT ENZYME RESPONSE BY ASCORBIC ACID IN DARK GERMINATED FAVA BEAN SPROUTS

Abstract

ABSTRACT Elicitation by ascorbic acid stimulated higher phenolic content in late stages of germination and higher antioxidant activity during early and late germination in fava bean sprouts. The high free radical scavenging-linked antioxidant activity on day 1 coincided with high levo-dihydroxy phenylalanine and total phenolics. A positive correlation between the stimulation of phenolic synthesis and glucose-6-phosphate dehydrogenase (G6PDH) activity was also observed, indicating its likely role in carbohydrate mobilization. Improved guaiacol peroxidase (GPX) activity in response to elicitation indicated the likely polymerization of soluble phenolics. Higher GPX, superoxide dismutase and catalase linked antioxidant enzyme response correlated to increase in proline and phenolics. A proline-linked stimulation likely provided nicotinamide adenine dinucleotidephosphate from pentose phosphate pathway (PPP) as indicated by an increase in G6PDH, the first committed step of PPP, which then supported phenolic synthesis and antioxidant enzyme response. PRACTICAL APPLICATIONS This research indicates that ascorbic acid is an effective elicitor of the pentose phosphate pathway (PPP) in dark germinated fava bean sprouts. It increases synthesis of health-relevant phenolics and levo-dihydroxy phenylalanine relevant to Parkinson's disease management. The stimulation of PPPwas linked to accumulation of free proline thereby supporting the proline-linked pentose phosphate pathway model. It provides an understanding of the role of phenolic antioxidants on redox modulation in the cell by being effective free radical scavengers and also by inducing the antioxidant enzyme responses through providing the reducing equivalents required for their activity. This knowledge can be used as a biochemical strategy to design seed sprouts for functional food applications.