A SPECTROPHOTOMETRIC ASSAY FOR QUANTITATIVE-ANALYSIS OF THE OXIDATION OF 4-HYDROXYSTILBENE BY PEROXIDASE-H2O2 SYSTEMS

A new and sensitive spectrophotometric assay has been developed to study and to characterize kinetically the oxidation of 4-hydroxystilbene (an analogue of the putative viniferin precursor, trans-resveratrol, directly involved in the resistance mechanism of the grapevine to fungal diseases) by peroxidase-H2O2 systems. The technique measures the overall increase in absorbance at 248 nm in the reaction media, probably due to the formation of a phenoxy radical of the 4-hrdroxystilbene (4-HS). This technique was developed by using the purified isoenzyme C of horseradish peroxidase and all the validity criteria (sensitivity and reproducibility) were checked. The results show that it is especially suitable for low activity measurements. It was finally applied to the determknation of the oxidation rate of 4-HS by peroxidases isolated from the media of suspension-cultured grapevine cells, at two different developmental stages. © 1990.