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  • Author or Editor: Shiow Wang x
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The effects of preharvest methyl jasmonate (MJ) application on fruit quality, flavonoid content and antioxidant capacity (ORAC) in black raspberry cv. Jewel (Rubus occidentalis L) were studied under field conditions. Raspberries treated with 0.1 mm methyl jasmonate had 20% higher soluble solids content, 20% higher total sugars, 16% higher fructose, 34% higher glucose and 30% lower titratable acids, 31% lower malic acid and 17% lower citric acid than untreated fruit. El-lagic acid, quercetin 3-glucoside, kaempferol 3-glucoside, kaempferol 3-glucuronide, cyanidin 3-glucoside and cyaniding 3-rutinoside were found in raspberry fruit extract. Cyanidin 3-rutinoside was the most dominant anthocyanin and was the major contributor to antioxidant activity in Jewel raspberries. MJ treatments significantly enhanced the content of anthocyanins by 92%, total phenolics by 53%, flavonoids by 98% and the antioxidant capacities by 74% in the fruit. The ORAC value was positively correlated with anthocyanins and total phenolics. In this study, the correlation coefficient for ORAC (y) vs anthocyanins (x) was 0.977 (y = 0.056x + 27.874), and that for ORAC (y) vs. total phenolics (x) was 0.988.

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Lingonberries have been shown to contain high antioxidant activity. Fruit from different cultivars of lingonberry (Vacciniumvitis-idaea L) were evaluated for fruit quality, antioxidant activity, anthocyanin and phenolic contents. The fruit soluble solids content (SSC), titratable acids (TA), antioxidant capacity, anthocyanin and phenolic contents varied with cultivars. The SSC ranged from 12.9% to 16.9%, the TA ranged from 0.31% to 0.41% and the ratios of SSC/TA ranged from 35.37 to 51.21. Lingonberries contain potent free radical scavenging activities for DPPH·, ROO·, ·OH and O .- 2 radicals. The oxygen radical absorbance capacity (ORAC) values from acetone extraction of lingonberries ranged from 58.5–223.6 μmol of Trolox equivalents (TE)/g fresh berries. The ED50 values for DPPH-radical scavenging ranged from 5.91–11.77 mg fresh weight. The DPPH-radical scavenging activity correlated with ORAC values with a R 2 of 0.8009. ESR spectrum showed that 50 mg·mL-1 of lingonberry extract decreased ·OH radicals by 83% and O .- 2 radicals by 99%. Cyanidin 3-galactoside was the most dominant anthocyanin and contributed the most antioxidant activity in lingonberries. The antioxidant properties of lingonberries may play an important role in protecting cells against the oxidative damage caused by free radicals.

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Fruit and leaves from different cultivars of thornless blackberry (Rubus sp.), red raspberry (Rubus idaeus L.), black raspberry (Rubus occidentalis L.), and strawberry (Fragaria × ananassa D.) plants were analyzed for total antioxidant capacity (oxygen radical absorbance capacity, ORAC) and total phenolic content. In addition, fruit were analyzed for total anthocyanin content. Compared to fruit, leaves were found to have higher ORAC values. In fruit, ORAC values ranged from 7.8 to 33.7 μmol Trolox equivalents (TE)/g of fresh berries, while in leaves, ORAC values ranged from 20.8 to 45.6 μmol TE/g of fresh leaves. Fruit harvested at different stages of maturity were analyzed in blackberries, raspberries, and strawberries. Blackberries and strawberries had their highest ORAC values during the green stages, while raspberries generally had the highest ORAC activity at the ripe stage (with exception of cv. Jewel, a black raspberry). Total anthocyanin content increased with maturity for all three fruit. There was a linear correlation existed between total phenolic content and ORAC activity for fruit and leaves. For ripe berries, there was also a linear relationship between ORAC values and anthocyanin content. Of the ripe fruit and leaves tested, raspberry plants appeared to be the richest source for antioxidants.

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The effect of blackberries (Rubus sp.) genotypes on antioxidant activities against superoxide radicals (O2 ), hydrogen peroxide (H2O2), hydroxyl radicals (OH), and singlet oxygen (O,), was evaluated. The results were expressed as percent inhibition of active oxygen species production in the presence of fruit juice. The active oxygen radical absorbance capacity (ORAC) value referred to the net protection in the presence of fruit juice, and was expressed as micromoles of α-tocopherol, ascorbate, α-tocopherol, and β-carotene equivalents per 10 g of fresh weight for O2 , H2O2, OH, and O2, respectively. Among the different cultivars, juice of Hull' blackberry had the highest oxygen species, superoxide radicals (O2 ), hydrogen peroxide (H2O2), hydroxyl radicals (OH), and singlet oxygen (O2,) scavenging capacity. Different antioxidants have their functional scavenging capacity against active oxygen species. There were interesting and marked differences among the different antioxidants in their abilities to inhibit the different active oxygen species. β-carotene had by far the highest scavenging activity against O2 but had absolutely no effect on H2O2. Ascorbic acid was the best at inhibiting H2O2 free radical activity. For OH, there was a wide range of scavenging capacities with α-tocopherol the highest and ascorbic acid the lowest. Glutathione had higher O2 scavenging capacity compared to the other antioxidants.

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The activity of ascorbic acid oxidase (AAO) was studied in apple (Malus domestica Borkh.) buds during dormancy and thidiazuron-induced budbreak. In dormant buds, activity of AAO was low compared with buds that were treated with thidiazuron and had resumed growth. An increase in AAO activity began at the time of metabolic transition from dormancy to budbreak. The highest level of activity was reached 10 days after thidiazuron induction during the expansion growth phase. In vitro AAO activity of apple bud extract was increased by addition of Cu (CuSO) and inhibited by Cu-chelating agents, diethyldithiocarbamate (DDC), sodium azide (NaN), and 8-hydroxyquinoiine (8-OH-Q). In vivo treatment of apple buds with Cu-chelating agents inhibited AAO activity and bud growth but not budbreak. Chemical name used: N- phenyl -N' -1,2,3-thidiazol-5-ylurea (thidiazuron).

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The effect of silicon (Si) foliar applications on metabolic changes and powdery mildew infection in strawberry plants were determined. Silicon was used in the forms of potassium (K) and sodium (Na) salts. Foliar sprays containing 0, 250, 500, 750, and 1000 ppm of Si were applied. Strawberry plants showed no difference in response to the K or Na salts of Si during the seven weeks of experimental period. Plants treated with potassium and sodium silicate showed reduced severity of powdery mildew, increased chlorophyll content, and increased plant growth. Potassium and sodium silicate treatments also induced metabolic changes such as an increase in citric acid and malic acid levels, and a decrease in fructose, glucose, sucrose, and myoinositol content. The treated tissues also had higher ratios of (18:2 + 18:3)/18:1 in glycolipids and phospholipids and elevated amounts of membrane lipids in leaves and petioles. These results suggest that Si has beneficial effects on strawberry plants and may serve as an alternative to fungicides for controlling powdery mildew.

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Fruit of the cultivated strawberry (Fragaria ×ananassa Duchesne ex Rozier) are a good source of natural antioxidants, which play an important role in protecting human health. Antioxidant levels vary considerably among strawberry genotypes. The cultivated strawberry is a hybrid of two very different wild progenitor species: F. virginiana Mill. and F. chiloensis (L.) Mill. The progenitor species are valued by strawberry breeders as sources of novel traits, but have not been evaluated for antioxidant capacity or levels of antioxidant compounds. The objectives of this study are 1) to evaluate the antioxidant contents and antioxidant activities in representatives of F. virginiana and F. chiloensis in comparison with representatives of the cultivated strawberry species (F. ×ananassa), 2) to determine which strawberry compounds are most closely correlated with antioxidant capacity among these three species, and 3) to identify wild strawberry genotypes with high antioxidant activity and bioactive compounds for use in cultivar development. Fruit of 19 accessions from each of the three species, cultivated strawberry plus the two progenitor species (F. ×ananassa, F. virginiana, and F. chiloensis), were evaluated for levels of antioxidant capacity (oxygen radical absorbance capacity), total phenolics, total anthocyanins, ellagic acid, quercetin 3-glucoside plus quercetin 3-glucuronide, kaempferol 3-glucoside, kaempferol 3-rutinoside, p-coumaryl–glucose, pelargonidin 3-glucoside, pelargonidin 3-glucoside–succinate, cyanidin 3-glucoside, and cyanidin 3-glucoside–succinate. Fruit of the 13 accessions tested from the wild progenitor species F. virginiana had significantly higher antioxidant capacity, total phenolics, and total anthocyanins than did the fruit of three accessions tested from the cultivated strawberry F. ×ananassa, or the three accessions tested from the other wild progenitor species (F. chiloensis), and will be valuable as a source of parent material for developing more nutritious strawberry cultivars. The high correlation with antioxidant capacity, relative efficiency, and lack of genotype-by-year interaction in this study suggests that the measurement of total phenolics may be the better assay to use for the later selection stages in a strawberry cultivar development program. Of the evaluated F. virginiana accessions, NC 95-19-1, JP 95-1-1, CFRA 0982, NC 96-5-3, and RH 30 fruit were highest in antioxidant capacity and should prove useful toward development of strawberry cultivars with high antioxidant capacities.

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Polyamine, putrescine, spermidine, and spermine contents were determined during endodormancy in the buds of low-chilling-requiring `Anna' apples (Malus domestics Borkh.). Putrescine, spermidine, and spermine contents increased greatly in buds when their chilling requirement was satisfied. Polyamine biosynthetic inhibitors α -difluoromethylarginine (DFMA) or α -difluoromethylornithine (DFMO) reduced bud break and bud growth in concert with decreased polyamine titers. DFMO or DFMA did not inhibit bud break when it was applied to buds after they received the full chilling requirement. DFMO was more inhibitory than DFMA. The polyamine requirement was much higher for bud growth and bud development than during differentiation and bud break.

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Ethylene biosynthesis and polyamine content were determined in normal and watercore-affected apple (Malus domestics Borkh. cv. Delicious). Fruit with watercore produced more ethylene and contained higher amounts of putrescine (PUT), spermidine (SPD), 1-aminocyclopropane-1-carboxylic acid (ACC), and 1-(malonylamino) cyclo-propane-1-carboxylic acid (MACC). The activities of ACC synthase and ethylene-forming enzyme (EFE) in watercore-affected fruit were also higher than in normal fruit. The EFE activity in severely affected flesh was inhibited, resulting in ACC accumulation and low ethylene production. S-adenosylmethionine (AdoMet) was maintained at a steady-state level even when C2 H4 and polyamides were actively synthesized in normal and affected fruit.

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The ability of low and high temperatures and S-containing compounds to overcome endo- and paradormancy along with the possible mechanisms involved in these treatments for breaking `Anna' apple bud dormancy were studied. All three treatments induced budbreak in paradormant (July) and endodormant (October) buds. Cold, heat, and allyl disulfide increased ascorbic acid, the reduced form of glutathione (GSH), total glutathione, total nonprotein thiol (NPSH), and nonglutathione thiol (RSH), whereas dehydroascorbic acid and oxidized glutathione (GSSG) decreased. The treatments also increased the ratios of ascorbic acid: dehydroascorbate and GSH: GSSG and the activities of ascorbate free-radical reductase (AFR, EC 1.6.5.4), ascorbate peroxidase (EC 1.11.1.11), dehydroascorbate reductase (DHAR, EC 1.8.5.1), ascorbate oxidase (AAO, EC 1.10.3.3), and glutathione reductase (GR, EC 1.6.4.2) in the buds. These results indicate that budbreak induced by cold, heat, and allyl disulfide is associated with the removal of free radicals through activated peroxide-scavenging systems.

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