Zhenwen Zhang

The ameliorative effects of exogenous melatonin on grape cuttings under water-deficient stress: antioxidant metabolites, leaf anatomy, and chloroplast morphology

Grapes are an important economic crop and are widely cultivated around the world. Most grapes are grown in arid or semi‐arid regions, and droughts take a heavy toll in grape and wine production areas. Developing effective drought‐resistant cultivation measures is a priority for viticulture. Melatonin, an indoleamine, mediates many physiological processes in plants. Herein, we examined whether exogenously applied melatonin could improve the resistance of wine grape seedlings grown from cuttings to polyethylene glycol‐induced water‐deficient stress. The application of 10% polyethylene glycol (PEG) markedly inhibited the growth of cuttings, caused oxidative stress and damage from H2O2 and O2∙− , and reduced the potential efficiency of Photosystem II and the amount of chlorophyll. Application of melatonin partially alleviated the oxidative injury to cuttings, slowed the decline in the potential efficiency of Photosystem II, and limited the effects on leaf thickness, spongy tissue, and stoma size after application of PEG. Melatonin treatment also helped preserve the internal lamellar system of chloroplasts and alleviated the ultrastructural damage induced by drought stress. This ameliorating effect may be ascribed to the enhanced activity of antioxidant enzymes, increased levels of nonenzymatic antioxidants, and increased amount of osmoprotectants (free proline). We conclude that the application of melatonin to wine grapes is effective in reducing drought stress.

Varietal differences among the phenolic profiles and antioxidant properties of four cultivars of spine grape (Vitis davidii Foex) in Chongyi County (China).

Spine grape (Vitis davidii Foex) is an important wild plant species in South China. To provide sufficient experimental evidence for the strong antioxidant activity of spine grapes, four cultivars from Chongyi County, China, including three red varieties (Junzi #1, Junzi #2, and Liantang) and one white variety (Baiyu) were evaluated. The Junzi #1 had the highest phenolic content (total phenolic, flavonoids, flavanols, and anthocyanins) and the strongest antioxidant capacity (DPPH radical-scavenging capacity, cupric-reducing capacity and hydroxyl radical-scavenging activity) among the four varieties. HPLC analysis of spine grapes revealed that the (+)-catechin was the most abundant phenolics and the hydroxycinnamic acids were the major phenolic acids in the four varieties. Hierarchical cluster analysis showed that the Junzi #1 belongs to the group with high phenolic content and strong antioxidant power. The results suggest the Junzi #1 has the best health promoting properties, and the higher utilization value and potential for development.

Regulating the secondary metabolism in grape berry using exogenous 24-epibrassinolide for enhanced phenolics content and antioxidant capacity

The objective of this study is to investigate the influence of application of exogenous 24-epibrassinolide (EBR) on the antioxidant capacity, anthocyanins and phenolics content of Vitis vinifera grape berry (cvs. Yan 73 and Cabernet Sauvignon). The grapevine clusters were sprayed with 0 (control), 0.10, 0.40, or 0.80 mg/l of 24-epibrassinolide during veraison, respectively. The EBR application increased the activities of phenylalanine ammonia-lyase (PAL) and UDP-glucose: flavonoid 3-O-glucosyltransferase (UFGT), the content of total phenolics, tannins, flavonoids and anthocyanins, individual anthocyanins and the antioxidant capacity of matured grape skins in both varieties. The application also increased the content of flavonoids and anthocyanins in Yan73 pulp. Compared to the other treatments, the treatment of EBR at 0.40 mg/l had significantly higher level than the control in all above assays. Our results indicated that the exogenous EBR treatment can significantly promote grape ripening and enhance anthocyanins and other phenolics contents and antioxidant capacity in the grape skin.

Predicting the anthocyanin content of wine grapes by NIR hyperspectral imaging

The aim of this study was to demonstrate the capability of hyperspectral imaging in predicting anthocyanin content changes in wine grapes during ripening. One hundred twenty groups of Cabernet Sauvignon grapes were collected periodically after veraison. The hyperspectral images were recorded by a hyperspectral imaging system with a spectral range from 900 to 1700 nm. The anthocyanin content was measured by the pH differential method. A quantitative model was developed using partial least squares regression (PLSR) or support vector regression (SVR) for calculating the anthocyanin content. The best model was obtained using SVR, yielding a coefficient of validation (P-R(2)) of 0.9414 and a root mean square error of prediction (RMSEP) of 0.0046, higher than the PLSR model, which had a P-R(2) of 0.8407 and a RMSEP of 0.0129. Therefore, hyperspectral imaging can be a fast and non-destructive method for predicting the anthocyanin content of wine grapes during ripening.

Comparison on phenolic compounds and antioxidant properties of cabernet sauvignon and merlot wines from four wine grape-growing regions in China.

The antioxidant activities in the Cabernet Sauvignon and Merlot wines from four wine grape-growing regions in China were measured by different analytical assays: 2,2-diphenyl-1-picrylhydrazyl (DPPH·), cupric reducing antioxidant capacity (CUPRAC), superoxide radical-scavenging activity (SRSA) and the contents of total phenols, total flavonoids, total flavanols and total anthocyanins were determined. The results showed that the contents of phenolic compounds and the levels of antioxidant activity in the wine samples greatly varied with cultivar and environmental factors of vine growth. The contents of phenolic compounds and antioxidant activities in Cabernet Sauvignon and Merlot wines from the Yuquanying region of Ningxia were significantly higher than other three regions, followed by the wines from Shacheng region of Hebei, and these parameters were the lowest in Cabernet Sauvignon and Merlot wines from the Changli regions of Hebei and Xiangning region of Shanxi. Taken together, a close relationship between phenolic subclasses and antioxidant activity was observed for the wine samples. Moreover, there were significant discrepancies in the individual phenolic composition and content of four regional Cabernet Sauvignon and Merlot wines, among which the individual phenolic compounds (catechin, epicatechin, cinnamic acid, quercetin-3-O-glucuronide, quercetin-3-O-glucoside, laricitrin-3-O-glucoside and isorhamnetin-3-O-glucoside) revealed a significant correlation (p < 0.05) with the antioxidant capacity in present study, especially for catechin and epicatechin.

Free-radical scavenging properties and reducing power of grape cane extracts from 11 selected grape cultivars widely grown in China.

Total phenolic contents (TPC), total flavonoid contents (TFC), related antioxidative and antiradical capabilities of grape cane extracts from 11 varieties (five V. vinifera cultivars and six Chinese wild grapes) widely grown in China were evaluated. Antioxidant properties were determined as DPPH and ABTS radical-scavenging abilities, superoxide anion and hydroxyl radical and hydrogen peroxide scavenging assays, as well as reducing power. Phenolic profiles of the extracts were characterized by using high-performance liquid chromatography (HPLC) techniques. All extracts exhibited strong antioxidant and effective free radical inhibition activities (EC50 values), which generally correlated negatively with TPC (r = −0.804 to −0.918) and TFC (r = −0.749 to −0.888). In comparison with gallic acid, Trolox and tert-butylhydroquinone (positive controls), most grape cane extracts showed more efficient scavenging effects toward different reactive oxygen species. HPLC analysis revealed the presence of (+)-catechin, (−)-epicatechin, and trans-resveratrol as major phenolic components in the extracts. These results suggest that grape cane extracts may serve as a potential source of natural antioxidant for food and pharmaceutical application.

Simultaneous Determination of 14 Phenolic Compounds in Grape Canes by HPLC-DAD-UV Using Wavelength Switching Detection

The paper described a novel chromatographic method for the simultaneous determination of phenolic compounds such as gallic, protocatechuic, vanillic, caffeic, syringic, p-coumaric and salicylic acid, (+)-catechin, (‒)-epicatechin, rutin, morin, quercetin, coumarin and trans-resveratrol at their maximum absorbance wavelengths (MAW) employing reverse-phase high performance liquid chromatography combined with DAD and UV detection via detection wavelength switching. The method was based on MAW acquisition by DAD and quantification by UV. The separation process was performed on a Shim-Pack VP-ODS C18 column (250 mm × 4.6 mm, 5 μm) held at 30 °C, utilizing 3.0% acetic acid and acetonitrile as mobile phase at a flow rate of 0.8 mL/min in the gradient elution mode. The method was fully validated in terms of linearity (r2 > 0.9990, 10‒350 mg/L), precision (both intra-day and inter-day RSD < 4.22%), accuracy (97.31%‒104.66%), specificity, robustness (0.59% < RSD < 2.86%), limit of detection and quantification. The switching method significantly improved the sensitivities of most phenolics studied in comparison with the standard constant wavelength detection (280 nm). The proposed method has been successfully applied to the determination of 14 phenolic compounds in 89 varieties of one-year-old Chinese grape one-year-canes. Grape canes contain many phenolics, especially trans-resveratrol, (‒)-epicatechin, and (+)-catechin.

Occurrence and estimation of trans-resveratrol in one-year-old canes from seven major Chinese grape producing regions.

The concentration of trans-resveratrol in 165 grape cane samples from three major grape production regions and four large distribution centers of Chinese wild Vitis species were determined by reversed-phase high-performance liquid chromatography (HPLC). Among the different genotype groups and purpose of uses, cultivars of V. vinifera had much higher amounts of trans-resveratrol than did the cultivars of both V. labrusca or V. labrusca and V. vinifera hybrids, and within the V. vinifera species, significantly higher amounts of trans-resveratrol were found in wine grapes compared to table ones. No significant differences were observed between V. labrusca and its hybrids from crosses with V. vinifera, and between red cultivars and white ones (P < 0.05 or P < 0.01). The contents of trans-resveratrol, as a normal constituent occurring in grape canes, in Chinese wild species of V. amurensis, V. pentagona, and V. davidii from their native habitats were also relatively high.

Effect of Rain-Shelter Cultivation of Vitis vinifera cv. Cabernet Gernischet on the Phenolic Profile of Berry Skins and the Incidence of Grape Diseases

Rain-shelter cultivation is an effective cultural method to prevent rainfall damage during grape harvest and widely applied in the Chinese rainy regions. In this study we investigated the effect of rain-shelter cultivation on grape diseases and phenolic composition in the skins of Vitis vinifera cv. Cabernet Gernischet grape berries through the comparison with open-field cultivation at two vintages (2010 and 2011). The results showed that rain-shelter cultivation reduced the incidence of grape diseases significantly and delayed the maturation of Cabernet Gernischet fruits. With regards to most of the phenolic compounds identified in this study, their content in grape samples under rain-shelter cultivation was decreased compared to those under open-field cultivation. However, rain-shelter cultivation stimulated the accumulation of dihydroquercetin-3-O-rhamnoside in grape skins during grape maturation. These were related with micrometeorological alterations in vineyards by using plastic covering under rain-shelter cultivation. It suggests the rain-shelter cultivation makes possible the cultivation of “Cabernet Gernischet” grapes in an organic production system, for providing a decrease in the incidence of diseases and the dependence on chemical pesticides in the grape and wine industry.

Brassinosteroids Regulate Anthocyanin Biosynthesis in the Ripening of Grape Berries

Anthocyanins are important components in the skins of grapes and in the development of wine colour. Various environmental factors cause poor coloration in some areas, even for the same cultivars planted in different production areas. The objective of this study was to evaluate the effect of exogenous brassinosteroids (BR) on the accumulation of anthocyanins and gene expression of anthocyanin biosynthesis in wine grape berry skins. The results show that total anthocyanin content in BR-treated grapes was higher than that in the control (CT) grapes, and that 0.4 mg/L was the most effective treatment concentration. The effect of BR on downstream genes was more effective than that on upstream genes. Full coloration of BR-treated grapes was achieved seven days earlier than in the case of CT. Moreover, BR enhanced the transcript level of the downstream genes of anthocyanin biosynthesis, which caused the total anthocyanin content to increase. The induction of structural and regulatory genes of the flavonoid pathway suggests that the interrelationships between developmental and environmental signalling pathways were magnified by BR treatment, which actively promoted fruit coloration, namely anthocyanin biosynthesis.