PHASE III

Stage III had as its goal:

-the monitoring of the antioxidant principles in terms of content and antioxidant efficiency of FNIV3 and CSIIV1 wines (red wines with the highest improvement in antioxidant activity and produced in the previous stage), to understand how melatonin might regulate the metabolism of polyphenols;

- integration of the results obtained in order to understand how melatonin might regulate polyphenol metabolism due positive synergistic effects of melatonin treatment.

For the first time, melatonin treatment was used in the winemaking of Feteasca Neagra and Cabernet Sauvignon red wines, which allowed polyphenolic compounds to be obtained via phenylpropanoid metabolism, and an increase in the concentrations of antioxidant compounds was found to be directly proportional to the concentration of melatonin used. Furthermore, melatonin was found to stimulate the activity of the enzymes PAL (phenylalanine ammonia lyase) and C4H (cinnamic acid 4-hydroxylase) and to significantly alter the expression of specific genes for anthocyanin biosynthesis, in particular UDP-D-glucose flavonoid 3-O-glycosyltransferase. It can be concluded that significantly higher concentrations of resveratrol (50%), quercetin (36%) or cyanidin-3-glucoside (77%) in red wines can be achieved by applying melatonin in the preliminary stage of wine production. It can also be used to produce red wines with increased antioxidant activity (almost 14%).

The reproducibility of the technology for obtaining improved wines and the positive synergistic effects of melatonin on the polyphenolic profile and antioxidant capacity were demonstrated.

Tabel 1. The phenolic acids, flavanols, flavonols, stilbenes, anthocyanidins, anthocyanins and melatonin values obtained by the HPLC methods, the trans-resveratrol values obtained by amperometric method, total phenolic content and the results obtained from DPPH/ABTS assay from red wines, after 3 and respectively 6 months of ageing.