Stimulation of Phenolics

Stimulation of phenolics, antioxidant and antimicrobial activities in dark germinated mung bean sprouts in response to peptide and phytochemical elicitors.

By: Randhir, Reena; Lin, Yuan-Tong; Shetty, Kalidas.

Process Biochemistry,

Jan 2004, Vol. 39 Issue 5, p637, 10p;



The phenyl propanoid pathway (PPP) was stimulated in mung beansprouts through the pentose phosphate and shikimate pathways, by natural elicitors such as fish protein hydrolysates (FPH), lactoferrin (LF) and oregano extract (OE). Elicitation significantly improved the phenolic, antioxidant and antimicrobial properties of mung beansprouts. The optimal elicitor concentrations were 1 ml/l FPH, 250 ppm LF and 1 ml/l OE for the highest phenolic content that was approximately 20, 35 and 18% higher than control, respectively, on day 1 of dark germination. The antioxidant activity estimated by β-carotene assay in mung beansprouts was highest on day 1 of germination for all treatments and control. In general, higher antioxidant activity was observed in the elicited sprouts compared with control. In the case of 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay the antioxidant activity for all treatments and control was highest on day 2. Among the different elicitor treatments, OE elicited mung beansprouts showed the highest antioxidant activity of 49% DPPH inhibition on day 2. This increased activity correlates with high guaiacol peroxidase (GPX) activity indicating that the polymerizing phenolics required during lignification with growth have antioxidant function. For all elicitor treatments a higher glucose-6-phosphate dehydrogenase (G6PDH) activity was observed during early germination following the high phenolic content. This is due to the general mobilization of carbohydrates to the growing sprouts in response to elicitation. In general the GPX activity steadily increased with germination for treatments and control. The higher phenolics produced on day 1 was utilized for GPX-mediated polymerization to form polymeric phenolics and lignin required during germination. The late stage polymerization linked to GPX activity preceded stimulation of G6PDH. This indicated that as phenolics were polymerized by GPX in late stages, G6PDH linked precursors such as ...