The aim of this work was to improve the knowledge about the potential of Douro region (North of Portugal) to produce table grapes of superior quality. Skin, pulp, and seeds of four table grapes ‘Alphonse Lavallée’, ‘Cardinal’, ‘Dona Maria’ and ‘Muscat Hamburgo’ produced in Dour region, collected at commercial maturity stage, were evaluated. Phenolic compounds, organic acids and sugars were determined in each cultivar and in the different parts of the grape by HPLC-DAD, while the antioxidant properties were evaluated by DPPH, Cuprac and lipid peroxidation assays. Phenolics from different classes were found: four anthocyanins (delphynidin, cyanidin, petunidin and malvidin), two hydroxibenzoic acids (gallic acid and protocatechuic acid), three hydroxycinnamic acids (caffeic, chlorogenic and coumaric acids), one flavonol (rutin), three flavan-3-ols ((+)-catechin, (-)-epicatechin, and (-)-epicagallocatechin)), one oligomer (procyanidin B2) and one stilbene (resveratrol). In addition, three organic acids (tartaric, malic and citric acids) and two types of sugars (glucose and fructose) were detected in all samples. Differences were found between cultivars (p<0.001) and sample material type (p<0.001). Skins presented the higher content in anthocyanins, seeds in flavan-3-ols and pulps in phenolic acids, organic acids and free-sugars. The cultivar ‘Cardinal’ showed the highest content in phytochemicals, while ‘Dona Maria’ was the cultivar with the lowest content. Nonetheless, the content of flavan-3-ols and organic acids in ‘Dona Maria’, associated with its higher antioxidant capacity, makes it an interesting choice as table grape from healthier point of view. According to our results, Douro region have proper environmental conditions to produce these table grapes.

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Some Portuguese minor grapevine varieties may reveal a good oenological potential for diversifying the wine market. Therefore, it is important to characterize them. This work has been carried out in the Douro Region and compared the Touriga Nacional variety with three Portuguese minor grapevine varieties (Preto Martinho, Malvasia Preta and Cornifesto). During 2016, 2017 and 2018 several parameters related to canopy, production and grape quality were determined. Radial visualization revealed eight relevant parameters for characterizing the differences among these varieties, showing that pruning weight was the main feature for Touriga Nacional, clusters weight for Malvasia Preta, must total soluble solids for Cornifesto and must tannins for Preto Martinho. According to the parameters analysed, Malvasia Preta showed the highest number of shoots and yield, Cornifesto stood out by the total soluble solids content. Preto Martinho exhibited the greatest richness in phenolic compounds (total polyphenols, tannins and total anthocyanins). In this study, Preto Martinho exhibited higher concentrations in total soluble solids, tannins, anthocyanins and polyphenols than Touriga Nacional, it might be the minor grapevine variety with the best profile for diversifying the wine market in the Douro Region.