In vitro έλεγχος αντιοξειδωτικών, αντιμικροβιακών και αντι-υπερτασικών ιδιοτήτων μελανοϊδινών κουμανδαρίας

Abstract

Commandaria is an amber-coloured dessert wine produced in Cyprus since 4000 years ago, being considered a protected designation of origin (PDO) product. It is exclusively produced through the fermenting process of must obtained from sun-dried grapes of two indigenous grape cultivars, namely ‘Xynisteri’ and ‘Mavro’. In general, a direct exposure to sunlight results to a significant water loss in the grape berry and several changes in its chemical composition. Among them, the formation of brown-colored melanoidins via Maillard reaction is carried out. The aim of the present study was to isolate and characterisize melanoidins from Commandaria wine. In addition, functional properties such as in vitro antioxidant (DPPH and FRAP assays), antimicrobial (Listeria monocytogenes ATCC23074, Salmonella enterica subsp. enterica serovar Enteritidis NCTC 5188 and Escherichia coli ATCC 11775) and anti-hypertensive properties were evaluated. Commandaria wines were dialyzed using three types of cellulose dialysis tubing that retain melanoidins bigger than 3.5 kDa, 7 kDa and 12-14 kDa, respectively. The chemical characterization of isolated melanoidins was performed by spectroscopic analysis as well as the determination of total sugars and total phenolic content. Results showed that their molecular weight was mostly bigger than 12-14 kDa; whereas sugars mainly compose the skeleton of melanoidins. In addition, significant amounts of phenolic compounds are attached to the skeleton; total phenolic content ranges from 47.1 to 165.2 mg gallic acid equivalents per g melanoidin. Results also highlights a great impact of wine aging on the structure of melanoidins. In a next step, the in vitro antioxidant potential of melanoidins were evaluated. The antioxidant activity of Commandaria melanoidins ranged between 85 and 216 μmol ascorbic acid equivalents per g melanoidins and 49 to 130 μmol ascorbic acid equivalents per g melanoidins for FRAP assay, respectively. Regarding to the antimicrobial capacity, melanoidins had higher potency agianst gram-positive bacteria than gram-negative; whereas the minimum inhibitory concentrations (MIC) values of melanoidins was between 5 and 20 mg mL-1. Finally, the angiotensin-converting enzyme (ACE) assay was used to determine the anti-hypertensive capacity of melanoidins. Results showed that the ACE-inhibitory activity of Commandaria melanoids reached up to 66 %.