Antioxidant and Phenolics: Blackberries

Total pigment has been extracted from blackberries and its antioxidant activity against lipid peroxidation and scavenging capacities towards superoxide anion radicals, hydroxyl radicals and nitrite in different in vitro systems have been investigated. The total pigment extract from blackberries (TPEB) exhibited strong antioxidant activity against lipid peroxidation in a linoleic acid model system and scavenging capacities towards superoxide anion radicals, generated by a pyrogallol autoxidation system or by an illuminating riboflavin system, hydroxyl radicals generated by Fenton reaction, and nitrite. Furthermore, the antioxidant activities were correlated with the concentrations of the TPEB. In the test concentration range, the maximum inhibition percentage against linoleic acid peroxidation was 98.32 % after one week’s incubation, and the maximum scavenging percentages for the free radicals and nitrite inhibition in the above reactive systems reached 90.48, 96.48, 93.58 and 98.94 %, respectively. The TPEB is a natural, edible colorant with excellent antioxidant activities and health benefits and it seems to be applicable in both healthy food and medicine.

Blackberries are an excellent source of natural antioxidants. Fully ripened fruit of 'Apache', 'Arapaho', 'Chester', 'Loch Ness', 'Navaho' and 'Triple Crown' thornless blackberries were evaluated for their physicochemical and antioxidative activity. There were no consistent differences for variation in initial pH, titratable acidity (TA), total soluble sugar (TSS) and TSS/TA ratio values determined. Differences among cultivars with respect to reduced ascorbic acid (AA) were established, but there were no differences in either oxidized ascorbic acid (DHA) or total ascorbic acid (TAA) content. The antioxidant activity as determined by ABTS radical cation procedure for fractionated crude fruit extracts varied in response to parameters evaluated. Hydrophilic antioxidant activity (HAA) was not different among cultivars evaluated. In contrast, differences were found in lipophilic antioxidant activity (LAA) and total antioxidant activity (TAA).

Cold-pressed marionberry, boysenberry, red raspberry, and blueberry seed oils were evaluated for their fatty acid composition, carotenoid content, tocopherol profile, total phenolic content (TPC), oxidative stability index (OSI), peroxide value, and antioxidant properties. All tested seed oils contained significant levels of -linolenic acid ranging from 19.6 to 32.4 g per 100 g of oil, along with a low ratio of n-6/n-3 fatty acids (1.64-3.99). The total carotenoid content ranged from 12.5 to 30.0 moles per kg oil. Zeaxanthin was the major carotenoid compound in all tested berry seed oils, along with -carotene, lutein, and cryptoxanthin. Total tocopherol was 260.6-2276.9 moles per kg oil, including -, -, and -tocopherols. OSI values were 20.07, 20.30, and 44.76 h for the marionberry, red raspberry, and boysenberry seed oils, respectively. The highest TPC of 2.0 mg gallic acid equivalents per gram of oil was observed in the red raspberry seed oil, while the strongest oxygen radical absorbance capacity was in boysenberry seed oil extract (77.9 mol trolox equivalents per g oil). All tested berry seed oils directly reacted with and quenched DPPH radicals in a dose- and time-dependent manner. These data suggest that the cold-pressed berry seed oils may serve as potential dietary sources of tocopherols, carotenoids, and natural antioxidants.

Total anthocyanin pigments increased from 74.7 to 317 mg/100 g fresh weight (FW) from underripe to overripe for Marion blackberries and from 69.9 to 164 mg/100 g FW for Evergreen blackberries. Total phenolics did not show a marked change with maturity with values slightly decreasing from underripe to ripe. Antioxidant activities, while increasing with ripening, also did not show the marked change that total anthocyanins exhibited. The impact of variation due to plots, subsampling, sample preparation, and measurement on Marion composition was examined in detail. Plot-to-plot and sample differences were the major contributors to variation, with sample preparation being an important contributor for some parameters. Measurement variation was a relatively small component of the total variation. Total anthocyanins for 11 blackberry cultivars ranged from 131 to 256 mg/100 g FW (mean = 198), total phenolics ranged from 682 to 1056 mg GAE/100 g FW (mean = 900), oxygen radical absorbance capacity ranged from 37.6 to 75.5 mol TE/g FW (mean = 50.2), and ferric reducing antioxidant power ranged from 63.5 to 91.5 mol TE/g FW (mean = 77.5).

Anthocyanin and flavonol glycosides of various blackberry, blueberry and red wine grape genotypes were identified and measured by a high-performance liquid chromatographic (HPLC) separation method with photodiode array (PDA) and mass spectrometric (MS) detection. With this method, two distinct elution regions of anthocyanins and flavonols were obtained with near baseline separation of most compounds. Blackberry, blueberry and red wine grape genotypes varied markedly in total anthocyanins and total flavonols as well as oxygen radical absorbance capacity (ORAC). The respective ranges of total anthocyanin (TA) and total flavonol (TF) contents of tested samples were: blackberries, 1143.9–2415.4 and 102.0–160.2 mg kg-1; blueberries, 1435.2–8227.3 and 172.5–327.5 mg kg-1; and red wine grapes, 380.9–7904.7 and 21.0–322.2 mg kg-1. Antioxidant activities and contents of total anthocyanins and total flavonols in blackberries, blueberries and red wine grapes were highly correlated, with linear relationships between ORAC and TA (rxy = 0.94) and TF (rxy = 0.90) for grapes, TA (rxy = 0.95) for blueberries and TA (rxy = 0.74) for blackberries. Copyright © 2004 Society of Chemical Industry

OBJECTIVE: To study serum quercetin concentrations of subjects consuming berries or habitual Finnish diets.

DESIGN: Randomized parallel dietary intervention.

SUBJECTS: Forty healthy men (age 60 y).

INTERVENTION: Twenty subjects consumed 100 g/day of berries (black currants, lingonberries and bilberries) for 8 weeks. Twenty subjects consuming their habitual diets served as controls. Fasting blood samples were obtained 2 weeks prior to the study, at baseline, and at 2, 4 and 8 weeks. Intake of quercetin was assessed from 3 day food records collected at baseline and at 8 weeks. RESULTS: The serum quercetin concentrations were significantly higher in the subjects consuming berries compared to the control group (P=0.039 ANCOVA with repeated measures). During the berry consumption period the mean serum concentrations of quercetin ranged between 21.4 and 25.3 micro g/l in the berry group, which was 32-51% higher compared with the control group. According to 3 day food records, there was no difference in quercetin intake at baseline, but at 8 weeks the intake was 12.3+/-1.4 mg/day (mean+/-s.e.m.) in the berry group and 5.8+/-0.6 mg/day in the control group (P=0.001).

CONCLUSIONS: The results indicate that the berries used in this study are a good source of bioavailable quercetin.

Blackberries (Rubus sp.) are a rich source of anthocyanins and other polyphenolic antioxidants. Because of their antioxidant properties, dietary polyphenolics have been associated with a reduced risk of various degenerative conditions including certain cancers and disease. A number of studies have been done to identify germplasm high in ORAC (oxygen radical absorbing capacity) in Rubus species. The present study was done to determine how the ORAC of blackberries was affected by fruit storage. Blackberries of five cultivars, originating from the University of Arkansas breeding program (all tetraploids), grown in Lane, Okla. and harvested in 1998 at the shiny black and dull black stages of ripeness, were held at 2 oC, 95% relative humidity for 7 days plus 2 days at 20 oC. Non-decayed berries were freeze-dried and powder of drupelet and receptacle tissue (no seeds) was extracted with acidified methanol. Samples were prepared for ORAC analysis using a COBAS-FARA II spectrofluorometric centrifugal analyzer. No significant differences were found between shiny and dull black fruit. ORAC values were highest in 'Kiowa' and lowest in 'Shawnee' fruit (4048 and 2690 mmol trolox/g freeze dried tissue, respectively). Values averaged for stored fruit were slightly lower than for fresh berries (3110 vs 3393 mmol trolox/g, respectively). These results indicate that the ORAC of these blackberry cultivars is not significantly increased at the latter stages of ripeness or by fruit storage at 2 oC.

Antioxidant activity [as measured by oxidation radical absorbance capacity (ORAC) assay], total anthocyanins, total phenolics, and quercetin were measured on frozen, fully-mature fruit of 13 and 15 blackberry (Rubus subgenus Rubus Watson) genotypes in 1999 and 2000, respectively. Additionally, in 1999, ellagic acid was measured. Eight genotypes were common among sample years. The highest ORAC value was for 'Kiowa' (67.9 mmol Trolox equivalents/g of whole fruit) in 2000. Next highest was 'Navaho' which had a two-year average of 48.8. The lowest activity was for selection APF-12, 17.3. Total anthocyanins ranged from a high of 3630.9 mg/kg (malvidin-3-glucoside equivalents) for 'Kiowa' in 2000 to 720.6 for APF-12 for the same year. Total soluble phenolics were highest for APF-12, 10,580.8 mg/kg (chlorogenic acid equivalents) in 2000 to 4217.6 for 'Choctaw' in 1999. Quercetin levels ranged from 94.3 mg/kg fresh weight for 'Arapaho' in 2000 to 10.2 for 'Shawnee' in 2000. Ellagic acid ranged from a high of 383.8 mg/kg fresh weight for 'Chickasaw' to 121.0 for 'Kiowa'. Research continues to further characterize genotypic and year-to-year variation for these health-promoting compounds.

Blueberries and blackberries grown at various locations in Georgia were collected and analyzed for flavonoids, total anthocyanins, total polyphenols, and Trolox-equivalent antioxidant capacity (TEAC). Each sample was analyzed for phenolic acids (gallic acid, p-hydroxybenzoic acid, caffeic acid, ferulic acid, and ellagic acid) and flavonoids (catechin, epicatechin, myricetin, quercetin, and kaempferol). A high-performance liquid chromatographic (HPLC) method with photodiode array detection was used for analysis. Compounds were analyzed as aglycons after acid hydrolysis with 1.2 M HCl. Identification of each compound was based on retention time and UV spectra by comparison with pure commercial standards. Phenolic acids ranged from 0.19 to 258.90 mg/100 g fresh weight (FW), and flavonoids ranged from 2.50 to 387.48 mg/100 g FW. Total polyphenols ranged from 261.95 to 929.62 mg/100 g FW, and total anthocyanins ranged from 12.70 to 197.34 mg/100 g FW. TEAC values varied from 8.11 to a maximum of 38.29 M/g FW. A linear relationship was observed between TEAC values and total polyphenols or total anthocyanins. The data indicate that blueberries and blackberries are rich sources of antioxidants.

The activities of the oxygen radical scavenging enzymes [glutathione-peroxidase (GSH-POD), superoxide dismutase (SOD), and guaiacol peroxidase (G-POD)], hydrogen peroxide scavenging enzymes in the ascorbate-glutathione cycle [ascorbate peroxidase (AsA-POD), monodehydroascorbate reductase (MDAR), dehydroascorbate reductase (DHAR), and glutathione reductase (GR)], the nonenzyme components [ascorbate (AsA), dehydroascorbate (DHAsA), glutathione (GSH), and oxidized glutathione (GSSG)], and their antioxidant capacity [oxygen radical absorbance capacity (ORAC)] were measured in the juice of six different thornless blackberry (Rubus sp.) cultivars. The 'Hull Thornless' cultivar contained the highest levels, whereas 'Black Satin' consistently had the lowest activities for all the enzymes tested in this study. ORAC values were also the highest in 'Hull Thornless' and lowest in 'Black Satin'. The highest levels of AsA and DHAsA were in the juice of 'Hull Thornless' blackberries with 1.09 and 0.15 mol/g fresh wt, respectively. 'Hull Thornless' also had the highest ratio of AsA/DHAsA among the six blackberry cultivars studied. The 'Smoothstem' cultivar contained the lowest amounts of AsA and DHAsA. 'Hull Thornless' had the highest GSH content with 78.7 nmol/g fresh wt, while 'Chester Thornless' contained the largest amount of GSSG. The highest GSH/GSSG ratio was 4.90 which was seen in the 'Hull Thornless' cultivar. The correlation coefficient between ORAC values and AsA/DHAsA ratios was as high as 0.972. A correlation (r = 0.901) was also detected between ORAC values and GSH content. The antioxidant activity in blackberry juice was positively correlated to the activities of most antioxidant enzymes (r = 0.902 with SOD; r = 0.858 with GSH-POD; r = 0.896 with ASA-POD; and r = 0.862 with GR).

Fruits 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, fruits were analyzed for total anthocyanin content. Blackberries and strawberries had the highest ORAC values during the green stages, whereas red raspberries had the highest ORAC activity at the ripe stage. Total anthocyanin content increased with maturity for all three species of fruits. Compared with fruits, leaves were found to have higher ORAC values. In fruits, ORAC values ranged from 7.8 to 33.7 mol of Trolox equivalents (TE)/g of fresh berries (35.0-162.1 mol of TE/g of dry matter), whereas in leaves, ORAC values ranged from 69.7 to 182.2 mol of TE/g of fresh leaves (205.0-728.8 mol of TE/g of dry matter). As the leaves become older, the ORAC values and total phenolic contents decreased. The results showed a linear correlation between total phenolic content and ORAC activity for fruits and leaves. For ripe berries, a linear relationship existed between ORAC values and anthocyanin content. Of the ripe fruits tested, on the basis of wet weight of fruit, cv. Jewel black raspberry and blackberries may be the richest source for antioxidants. On the basis of the dry weight of fruit, strawberries had the highest ORAC activity followed by black raspberries (cv. Jewel), blackberries, and red raspberries.