Grapes are rich in primary and secondary metabolites. Among the secondary metabolites, polyphenolic compounds are the most abundant in grape berries. Besides their important impacts on grape and wine quality, this class of compounds has beneficial effects on human health. Due to their antioxidant activity, polyphenols and phenolic acids can act as anti-inflammatory and anticancerogenic agents, and can modulate the immune system. In grape berries, polyphenols and phenolic acids can be located in the pericarp and seeds, but distribution differs considerably among these tissues. Although some classes of polyphenols and phenolic acids are under strict genetic control, the final content is highly influenced by environmental factors, such as climate, soil, vineyard, and management. This review aims to present the main classes of polyphenolic compounds and phenolic acids in different berry tissues and grape varieties and special emphasis on their beneficial effect on human health.

The aim of this study was to assess the influence of the application of mycorrhizal fungal inoculum on “Cabernet Sauvignon” (Vitis vinifera L.) leaf gas exchange, yield parameters, as well as grape berry composition, especially regarding phenolic compounds. The experiment was conducted over two years under natural vineyard conditions of the Zagreb wine-growing area, the continental region of Croatia. “Cabernet Sauvignon” grapevines were grafted on SO₄ rootstock, both being commonly used in all wine production areas in Croatia. Results obtained demonstrated that symbiotic grapevines, in general, expressed improved leaf gas exchange parameters and higher yield parameters, especially regarding the number of clusters per vine. It should be emphasized that mycorrhizal fungi affected higher total flavan-3-ols, total anthocyanins, and total polyphenols in berry skin in both experimental years. Despite variation in some yield parameters, generally, it is possible to obtain higher yields together with the improved phenolic composition of grapes.

A survey of recently discovered vitiviruses was performed on 113 Croatian autochthonous grapevine cultivars from the national collection “Jazbina” using one-step RT-PCR. The presence of grapevine virus H (GVH) was confirmed in nine (7.9%) cultivars and grapevine virus G in eight (7.1%), while the presence of grapevine viruses I and J were not detected. GVH was transmitted by the vine mealybug (Planococcus ficus) from a source plant to grapevine seedlings with a 10.5% transmission rate using a combination of 10 first and second instars per plant with 48 and 72 h of acquisition and inoculation access period, respectively. Transmission correlated with the presence of grapevine leafroll-associated virus 3 (GLRaV-3) in the GVH-source plant and recipient seedlings. No alternative GVH host was identified. A comparison of 356 nt fragments of the RdRP and CP coding regions showed nucleotide identity between the Croatian GVH isolates in the range of 95.5–99.2% and 97.5–99.4% and amino acid identity between 95.8 and 100% and between 98.3 and 100%, respectively. Comparison with foreign isolates revealed nucleotide sequence similarity in the RdRP and CP between 94 and 100% and between 97.7–100%, respectively. To the best of our knowledge, this is the first report of GVH in Croatia and the first identification of the vine mealybug as a vector of GVH.

Dalmatian vineyards host many autochthonous varieties. The phenolic profile, defined by the relative proportions of different phenolic compounds, is specific for each grape variety. The aim of this study was to determine and analyze the flavonoid compounds of twenty rare red grape varieties. Nineteen phenolic compounds, represented by anthocyanins, flavanols, and flavonols, were detected and quantified using HPLC in three consecutive vintages. The content of grape skin anthocyanins (10414.06 (Plavac mali crni)-19.58 (Trišnjavac) mg kg⁻¹ d.w. of grape skin), flavonols (1742.08 (Pošip crni)-215.56 (Crljenak viški) mg kg⁻¹ d.w. of grape skin), and flavan-3-ols (448.04 (Pošip crni)-87.88 (Glavinuša) mg kg⁻¹ d.w. of grape skin) showed significant differences in investigated varieties. According to the investigated phenolic compounds, Pošip crni, Ljutun, Zadarka, Dobričić, Plavac mali crni, and Trnjak differed from other investigated varieties. These local varieties can be perceived as an alternative to widespread varieties in Dalmatia. This was shown by one of the first studies on phenolic profiles of (mostly) rare autochthonous varieties.

The Croatian native, Vitis vinifera L. cv. Grk, is one of only a few wine cultivars with a female flower, resulting in two types of berries in the cluster: fully developed seeded (~3.5 g) and undersized seedless (~0.7 g), both ripe at harvest. This study investigated the intravarietal variability of Grk and the impact of the different proportion of seedless berries on grape yield and quality of Grk clones. Significant differences in cluster proportions of seedless berries among Grk clone candidates were determined. A high positive correlation was found between the seedless berry proportion and single berry weight, must tartaric acid content, and free volatile terpenes. These results indicate that it is possible to select clones with a higher proportion of seedless berries, which can then be used to improve the wine quality of Grk.

Research background. Coastal region of Croatia is rich in autochthonous grape varieties. Many of them have been almost abandoned, such as the autochthonous varieties of Kastav (Croatia), used for the production of the Kastavska Belica wine. Therefore, the rationale of the presented study is to characterize autochthonous grape varieties Verdić, Mejsko belo, Jarbola, Divjaka and Brajkovac. In addition, we performed a molecular characterization of the corresponding Belica wines. Experimental approach. Firstly, the genetic origin and ampelographic and economic characteristics of five autochthonous grape varieties were determined. Standard physicochemical profiles and phenolic components of 12 wines from different producers were determined by liquid chromatography coupled to triple quadrupole mass spectrometer (LC-QQQ-MS). Fourier-transform infrared spectroscopy (FTIR) was used for determination of standard physicochemical parameters. Results and conclusions. Ampelographic analysis, which includes the data on producing characteristics and cluster and berry composition of the varieties, revealed significant differences between the analysed grape varieties. Results of the physicochemical analysis of the Belica wine showed that all wines met the requirements needed for the production of quality and top quality wines labelled with protected designation of origin (PDO) in Croatian coastal region. The LC-QQQ-MS analysis confirmed the presence of different phenolic components in the Belica wines, where the most prominent phenols were flavonoids from the flavan-3-ol group. Overall, these results showed that autochthonous grapes from the Kastav region can be used for production of wines with added market value due to a growing demand for autochthonous products on the global market. Novelty and scientific contribution. The presented results give scientific insight and a basis for further determination of the optimal cultivation technology aimed to take advantage of the best characteristics of each variety for production of a wine with desirable features.