Carolina Henríquez

Determination of Antioxidant Capacity, Total Phenolic Content and Mineral Composition of Different Fruit Tissue of Five Apple Cultivars Grown in Chile

Apples (Malus domestica Borkh.) have been identified as one of the main dietary sources of antioxidants, mainly phenolic compounds. These compounds vary in their composition and concentration, among cultivars and fruit tissues. In this research, the total phenolic content (Folin-Ciocalteau assay), antioxidant capacity (Ferric Reducing Antioxidant Power, FRAP assay) and mineral composition in three fruit tissues (peel, pulp and whole fruit), of apple cultivars commonly used for dried apple production in Chile, were studied. In addition, the physical-chemical characteristics (dry weight, pH, titratable acidity, soluble solids content and color) were also evaluated. The results indicated that the total phenolic content, the antioxidant capacity, and the mineral composition, of peel were substantially higher than those of whole fruit, and pulp for all the cultivars studied. Among cultivars, �Red Delicious� apple peels have a significantly much higher content of total phenolic (11.6 mg gallic acid equivalents [GAE] g-1 FW) and a higher FRAP (209.9 µmol Fe+2 g-1 FW). Additionally, a high correlation between total phenolic content and antioxidant capacity was found in all the cultivars and fruit tissues analyzed, except in the apple pulp. On the other hand, the physical and chemical composition differed among cultivars and fruit tissues. In conclusion, our results demonstrated that the total phenolic content, antioxidant capacity, mineral composition, and physical and chemical characteristics vary considerably depending on the apple cultivars and fruit tissues analyzed.

Phenolics and antioxidant capacity of table grape (Vitis vinifera L.) cultivars grown in Chile.

UNLABELLED Grapes (Vitis vinifera L.) possess health-promoting effects attributed to their supply of a wide variety of bioactive phenolics. Juice and skin fractions of 4 varieties of table grapes: Red Globe, Crimson Seedless, Autumn Royal, and Ribier were prepared to determine and compare their total phenolics content, antioxidant capacity (DPPH, FRAP, and ORAC), anthocyanins, and specific phenolics (caffeic acid, gallic acid, resveratrol, and catechin) content, since a series of positive health benefits are expected from the intake of any of these fractions. Higher amounts of total phenolics and antioxidant capacity were observed in the skin fractions (P < 0.05). Blue grapes (Autumn Royal and Ribier) exhibited higher phenolics content and antioxidant capacity (P < 0.05) than red grapes. The most abundant phenolic compound observed was catechin (P < 0.05). Significant correlations between the antioxidant capacity and total phenolics were observed in grape juice and skin fractions. Autumn Royal juice provides a very high amount of phenolics, anthocyanins, and exhibits the highest antioxidant capacity, offering the best health promoting properties compared with the other grape varieties studied. PRACTICAL APPLICATION Grapes possess health-promoting effects attributed to their supply of a wide variety of bioactive phenolics. Grape juice made with blue grapes (Autumn Royal, Ribier) exhibit higher phenolics content and antioxidant capacity than juice elaborated with red grapes (Red Globe, Crimson Seedless). The skin is a good source of phenolics and has a high antioxidant capacity. Specific health-promoting phenolics are more abundant in blue grapes, mainly in their skin fraction, which should not be discarded.

Phenolic content and antioxidant capacity in fresh and dry fruits and vegetables grown in Chile

The study evaluated the impact of dehydration on the total phenolic content (TPC) and antioxidant capacity (AC) of fruits and vegetables (F&V). Fresh small fruits (berries) had the highest TPC, anthocyanin contents, and AC (2,2-diphenyl-1-picrylhydrazyl (DPPH) and oxygen radical absorbance capacity (ORAC)). The lowest TPC were observed in carrot and tomato and the lowest anthocyanins were observed in fresh sweet peppers (green and red), red apple, carrot, and tomato. Dehydrated blackberry and eggplant exhibited the highest TPC and anthocyanins. The retention of phenolics after drying ranged from 38.5% (spinach) to 92.1% (red apple). TPC increased in dehydrated tomato and green apple. The lowest DPPH and ORAC were obtained in dried carrot and tomato. DPPH retention ranged from 16.4% (tomato) to 64.7% (blackberry). Dehydrated small fruits and sweet peppers presented lower AC (ORAC) retention, while most dehydrated F&V increased ORAC, ranging from 9.5% (carrot) to 52.9% (eggplant). Dehydrated F&V represent good quality functional foods or ingredients.

Bioavailability of phenolic compounds in grape juice cv. Autumn Royal

The bioavailability of major phenolics in Autumn Royal grape juice was measured in 16 subjects distributed into two groups: the experimental group (n = 8 receiving 300 mL of juice) and the placebo group (n = 8 receiving 300 mL of artificial beverage). Blood was obtained before and after 30, 90, 180, and 300 min after juice or placebo intake and 24-h urine was collected. At 30 min, catechin and gallic acid levels were 3.18 ± 0.06 and 0.33 ± 0.06 nmol/mL plasma (p < 0.01), respectively. The maximal plasma levels of catechin and gallic acid observed at 180 min were 7.11 ± 0.53 and 1.56 ± 0.07 nmol/mL, respectively. After 300 min, gallic acid was not detected and only two subjects exhibited measurable levels of catechin. After juice intake, urinary catechin and gallic acid contents were significantly higher than the basal values (p < 0.001). After a regular serving of grape juice, catechin and gallic acid are bioavailable and thus potentially capable of exerting their expected biological effects.

Phenolics content and antioxidant capacity of Chilean grapes cv. País and Cabernet Sauvignon

Grapes (Vitis vinifera L.) are a source of phenolics and exhibit a high antioxidant capacity. In this study, the total phenolics content and the antioxidant capacity of ground grapes, juice, and skin fractions of two varieties of red grapes widely produced in Chile (Cabernet Sauvignon and País) were analyzed and specific phenolics (caffeic acid, gallic acid, resveratrol and catechin) were determined. The total phenolics content and antioxidant capacity were higher in Cabernet Sauvignon grapes vs. País, mainly in the skin fraction. The predominant phenolic species in all grape fractions was catechin, except in the skin of Cabernet Sauvignon, where resveratrol prevailed. Phenolic acids were not detected in grape juices, probably due to the absence of skin. Significant high correlations between specific phenolics, total phenolics content and antioxidant capacity were observed. The study presents practical data on some relevant chemical characteristics of grape fractions that are associated to potential health benefits.