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Open AccessArticle

Effects of Defoliation on Phenolic Concentrations, Antioxidant and Antibacterial Activity of Grape Skin Extracts of the Varieties Blaufränkisch and Merlot (Vitis vinifera L.)

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Department of Biology, Josip Juraj Strossmayer University of Osijek, Cara Hadrijana 8/A, 31000 Osijek, Croatia
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Faculty of Agrobiotechnical Sciences Osijek, Josip Juraj Strossmayer University of Osijek, Vladimira Preloga 1, 31000 Osijek, Croatia
3
Julius Kühn-Institut, Federal Research Centre of Cultivated Plants, Institute for Grapevine Breeding Geilweilerhof, 76833 Siebeldingen, Germany
*
Author to whom correspondence should be addressed.
Academic Editors: Margarida Castell Escuer and Mariona Camps-Bossacoma
Molecules 2019, 24(13), 2444; https://doi.org/10.3390/molecules24132444
Received: 31 May 2019 / Revised: 27 June 2019 / Accepted: 3 July 2019 / Published: 3 July 2019
(This article belongs to the Special Issue Natural Polyphenols and Health)
Vitis vinifera L. has been highlighted by its many positive effects on human health, including antibacterial, anti-inflammatory and antioxidant activity due to its rich phytochemical content. Removing six basal leaves has great potential to influence the production of phytochemicals. The purpose of this study was to determine the impact of different terms of defoliation on the antioxidant and antibacterial activity of grape skin extracts of the Blaufränkisch and Merlot varieties. The total phenolic concentration, total and individual anthocyanin concentration, antioxidant activity and antibacterial activity on gram-positive and gram-negative human pathogens have been determined. The study was conducted on three treatments (control treatment without defoliation, defoliation immediately after bloom and defoliation before the start of the véraison phase). The results showed statistically significant enhancement of the total phenolic concentration as well as the antioxidant and antibacterial activity in both studied cultivars. Defoliation just after blooming was the preferable defoliation term in the Merlot variety for achieving the highest total anthocyanin concentration, antioxidant activity and significant increase of antibacterial activity against all four investigated bacteria. Defoliation before the start of the véraison phase was the preferable defoliation term for achieving the highest total anthocyanin concentration in the Blaufränkisch variety. In general, treatment of defoliation immediately after bloom was more beneficial compared with the defoliation before the start of the véraison phase. View Full-Text
Keywords: defoliation; Blaufränkisch; Merlot; phenols; antioxidant activity; antibacterial activity defoliation; Blaufränkisch; Merlot; phenols; antioxidant activity; antibacterial activity
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Pavić, V.; Kujundžić, T.; Kopić, M.; Jukić, V.; Braun, U.; Schwander, F.; Drenjančević, M. Effects of Defoliation on Phenolic Concentrations, Antioxidant and Antibacterial Activity of Grape Skin Extracts of the Varieties Blaufränkisch and Merlot (Vitis vinifera L.). Molecules 2019, 24, 2444.

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