Grape Phytochemicals and Associated Health Benefits

The phytochemicals present in fruits and vegetables may play an important role in deceasing chronic disease risk. Grapes, one of the most popular and widely cultivated and consumed fruits in the world, are rich in phytochemicals. Epidemiological evidence has linked the consumption of grapes with reduced risk of chronic diseases, including certain types of cancer and cardiovascular disease. In vitro and in vivo studies have shown that grapes have strong antioxidant activity, inhibiting cancer cell proliferation and suppressing platelet aggregation, while also lowering cholesterol. Grapes contain a variety of phytochemicals, like phenolic acids, stilbenes, anthocyanins, and proanthocyanidins, all of which are strong antioxidants. The phytochemical composition of grapes, however, varies greatly among different varieties. While extensive research exists, a literature review of the health benefits of grapes and their phytochemicals has not been compiled to summarize this work. The aim of this paper is to critically review the most recent literature regarding the concentrations, biological activities, and mechanisms of grape phytochemicals.     

Phenols,Flavonoids, and Antioxidant and Antibacterial Activity of Leaves and Stem Bark of Morus Species

Leaves and stem bark composition from Morus species (M. alba var. alba, M. alba var. rosa and M. rubra) was evaluated for its antioxidant and antimicrobial activities in order to enhance its therapeutic uses. Total phenolics and flavonoids contents were estimated in hydromethanolic and aqueous extracts. Results showed highest content in M. rubra leaves aqueous extract (1129 mg gallic acid equivalent/100 g dry weight and 816 mg gallic acid equivalent/100 g dry weight, respectively). Using 2,2-diphenyl-1-picrylhydrazyl assay, the highest antioxidant activity was obtained in aqueous stem barks extracts. M. alba var. alba has an IC₅₀ of 2.84 mg/ml and the IC₅₀ value of M. rubra was the highest (4.78 mg/ml). ABTS^.+ (2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid)) method and reducing power assay were used to confirm the results from the 2,2-diphenyl-1-picrylhydrazyl test. All extracts expressed considerable free radical-scavenging properties. Hydromethanolic and aqueous extracts were tested against Staphylococcus aureus, Enterococcus feacalis, Staphylococcus epidermis, Escherichia coli, and Salmonella Typhimurium bacteria. Hydromethanolic stem bark extracts have the highest antimicrobial activities, and it may be a good antimicrobial agent for human gastrointestinal infections. This plant could be used as an additive to foods and also as a possible source to obtain new and effective herbal medicines to treat infections of multi-drug resistant strains of microorganisms.     

Pomegranate peel phenolics: Microencapsulation,storage stability and potential ingredient for functional food development

In this study, we investigated the effects of microencapsulation conditions on product quality of pomegranate peel phenolics. Our results indicate an optimum air inlet temperature of 160 °C and 1/1 (w/w) or 1/3 (w/w) for phenolics/maltodextrin ratio. No differences were observed amongst the maltodextrins used for coatings. There were also no statistically significant differences in phenolic content of microcapsules for the storage periods of 90 days at 4 °C (p > 0.05). We also evaluated the resultant microencapsulated phenolics for enrichment of the functional properties of regular ice cream used as model food in our studies. Addition of pomegranate peel phenolics at 0.5 and 1.0% (w/w) showed significant improvement of the antioxidant and α-glucosidase inhibitory activities of the enriched ice creams compared with control sample. Antioxidant activity as EC₅₀ and α-glucosidase inhibitory as IC₅₀ of 1.0% phenolic enriched ice creams were 133.3 and 22.9 μg/mL, respectively. More than 75% of the panellists accepted the phenolic enriched ice creams in sensory evaluation, which lends supports to such products for commercial introduction to the general public with the potential as functional foods.     

Mass Transfer during Osmotic Dehydration in a Multicomponent Solution Rich in Grape Phenolics with Antioxidant Activity

Osmotic dehydration has been assessed as an operation for obtaining solid foodstuffs supplemented with grape phenolics. However, mass transfer in multicomponent osmotic solutions during OD needs to be described appropriately if the infusion of target solutes, in this case phenolics with antioxidant activity, is to be better controlled. The effective diffusion coefficients of moisture, total phenolics, and the major individual phenolics of low-molecular-weight (caftaric acid, coutaric acid, caffeic acid, coumaric acid, ferulic acid, and rutin) were evaluated during the OD of a model food with a concentrated red grape must. An increase in the concentration of soluble solids above 50° Brix decreased the level of penetration of phenolics in the model food.     

Phenolic composition of Merlot and Cabernet-Sauvignon grapes from Bordeaux vineyard for the 2009-vintage: Comparison to 2006, 2007 and 2008 vintages

Cabernet-Sauvignon and Merlot skin and seed extracts from Bordeaux grapes were investigated to determine both grape variety and vintage effect on phenolic composition. The total content of polyphenols and tannins in Merlot seeds was higher than that of Cabernet-Sauvignon allowing to discriminate the varieties. HPLC analyses underlined significant differences in the absolute concentration of proanthocyanidins amongst the two varieties and in their composition: mean degree of polymerisation (mDP) and percentage of galloylation of seed extracts were good indicators of grape variety. The vintage effect on the phenolic composition was confirmed for 2009 in comparison to previous vintages. Low values of mDP and concentrations of proanthocyanidins and anthocyanins were found in 2009 seeds and skins. The climatic conditions of 2009 (high rainfall before flowering followed by a strong hydric stress during berries development until ripening) let us hypothesise a lower activation of flavonoid pathway.     

Effects of Fining Agents on Antioxidant Capacity of Red Wines

The antioxidant capacity of wine depends not only on the grape variety but also on the wine processing steps. The aim of this study was to determine the effects of different fining agents, used at different concentrations, on the antioxidant status of fined wines. The results demonstrated that the use of a combination of gelatin and Kieselsol led to the highest total phenol value (3,491 mg/L GAE) and antioxidant activities (29%) among the tested fining agents. Wines were mostly negatively affected by the use of egg white as an agent and led to the lowest value of total phenol (3,038 mg/L GAE) and the lowest rate of antioxidant activity (26%). Significant differences (p<0.05) were determined between gelatin, egg white, and the control groups. The results of the grouping of analyzed parameters in n‐dimensional space, with different fining agents at different concentrations, demonstrated the importance of a low concentration of fining agents for high antioxidant activity and total phenols.     

A generalist herbivore in a specialist mode Metabolic,sequestrative, and defensive consequences

Adults of a generalist herbivore, the lubber grasshopper,Romalea guttata, can be converted to functional specialists by feeding them exclusively on catnip,Nepeta cataria. No obvious adverse effects on adult development resulted from this enforced monophagy. Notwithstanding the fact thatR. guttata has had no coevolutionary relationship with this Eurasian mint, it readily sequesters compounds that are identical to or derived from the terpenoid lactones that are characteristic ofN. cataria. R. guttata appears to both biomagnify minor allelochemicals and to sequester metabolites of theNepeta terpenes in its paired defensive glands. The levels of autogenously produced phenolics are not affected by feeding onN. cataria and the defensive secretions of catnip-fed grasshoppers are more repellent to ants than those of wild-fed acridids. Metabolites of theN. cataria monoterpenes are sequestered in the defensive glands when catnip is added to the natural diet ofR. guttata. The ability of a generalist,R. guttata, to facilely bioaccumulate a potpourri of foreign allelochemicals when feeding in a specialist mode is analyzed in terms of its biochemical, physiological, and functional significance. Sequestration is examined as a response to the enteric effronteries represented by the phytochemicals that can be characteristic of the overload in a monophagous diet.     

Antioxidant activity of red wine phenolic extracts towards oxidation of corn oil

The antioxidant activity of Xinomavro red wine phenolic extracts in corn oil stripped of tocopherols was evaluated. One wine extract, at 100 mg/L total phenolics, rich in phenolic acids and flavonols, inhibited the oxidation of corn oil stripped of tocopherols to a greater extent than butylated hydroxyanisole, at 200 mg/L. Moreover, another extract, at 100 mg/L total phenolics, rich in flavanols, flavonols and tyrosol, also exhibited high inhibitory action. The present results indicate that some red wine phenolics – such as phenolic acids, flavonols or flavanols – may be strong antioxidants in corn oil.