Antioxidant properties and components of bran extracts from selected wheat varieties commercially available in Pakistan

Antioxidant activity of bran extracts from five wheat varieties indigenous to Pakistan, i.e. Punjab-96, Bhakkar-2002, Uqab-2000, SH-2002, and Pasban-90, has been evaluated. All the bran extracts exhibited appreciable total phenolic content (2.12-3.37 mg gallic acid equivalent/g bran), total flavonoid content (epicatechin equivalent 262-304 μg/g bran), chelating activity (ethylenediaminetetracetate equivalent 597-716 μg/g bran), 2,2′-diphenyl-1-picrylhydrazyl radical scavenging activity (51-79%), ABTS radical cation scavenging activity (Trolox equivalent 27-36 μmol/g), oxygen radical absorbance capacity (97-123 μmol/g), and total anthocyanin content (30-38 mg/kg bran). Tocopherol (22-26 ppm) and tocotrienol content (59-74 ppm) were determined by RP-HPLC. For confirmation of tocopherol content, polarographic study was conducted, which further authenticated the results (21-25 ppm). All the varieties exhibited appreciable antioxidant potential and significant differences were observed among the varieties in different systems of antioxidant activity evaluation.     

Phenolic compounds content and antioxidant activity in pomace from selected red grapes (Vitis vinifera L. and Vitis labrusca L.) widely produced in Brazil

The phenolic compounds content and antioxidant activity of pomace from the vinification of grape varieties widely produced in Brazil (Cabernet Sauvignon, Merlot, Bordeaux and Isabel) were investigated with a view to their exploitation as a potential source of natural antioxidants. Cabernet Sauvignon grape pomace was found to have the highest content of total phenolic compounds (74.75 mg gallic acid equivalent (GAE)/g), the highest antioxidant activity (determined using the 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging methods; 485.42 and 505.52 μMol Trolox equivalent antioxidant capacity (TEAC)/g, respectively), and the highest reducing power (determined using the FRAP method; 249.46 μMol TEAC/g). The Bordeaux variety showed the highest oxidation inhibition power (41.13%), determined using the β-carotene/linoleic acid method and the highest content of total anthocyanins (HPLC; 29.17 mg/g). Catechin was the most abundant non-anthocyanic compound identified in the grape pomace (150.16 mg/100 g) for all varieties. In this study, pomaces of the red wine vinification of Cabernet Sauvignon and Bordeaux varieties showed the highest potential as a source of antioxidant compounds and natural colourants, respectively.     

Anti-oxidative analysis,and identification and quantification of anthocyanin pigments in different coloured rice

Anthocyanin pigments in coloured rice cultivars were isolated and identified using high-performance liquid chromatography techniques. Two black rice cultivars (Asamurasaki, Okunomurasaki) contained three major anthocyanins: cyanidin-3-glucoside, peonidin-3-glucoside and malvidin. Chinakuromai (black) rice additionally contained a fourth anthocyanin, petunidin-3-glucoside. Four red rice cultivars contained only malvidin. The total anthocyanin content varied greatly among black rice cultivars (79.5–473.7 mg/100 g), but was lower in red rice (7.9–34.4 mg/100 g). Total phenolic content was similar between red (460.32–725.69 mg/100 g) and black (417.11–687.24 mg/100 g) rice. The oxygen radical absorbing capacity was ranked as follows: red (69.91–130.32 μmol Trolox/g) > black (55.49–64.85 μmol Trolox/g) > green (35.32 μmol Trolox/g) > white (21.81 μmol Trolox/g) rice. The antioxidant capacity resulted mainly from the seed capsule, not the endosperm. The anthocyanin pigments contributed little to the total antioxidant capacity of red (0.03–0.1%) and black (0.5–2.5%) rice cultivars. Hence, the antioxidant capacity is derived mainly from other phenolic compounds.     

Antioxidant and free radical-scavenging activities of seeds and agri-wastes of some varieties of soybean (Glycine max)

In order to find antioxidant potential, seeds of 30 varieties of Glycine max were studied for their total phenolic contents (TPC), flavonoids and antioxidant activity (AOA). The seed extracts showed wide variation of TPC from 6.4 to 81.7 mg GAE/g, flavonoids 3.5 to 44.6 mg QE/g and AOA 7.5% to 74.7%. Free radical-scavenging activity (FRSA), assayed by DPPH in terms of IC₅₀ (inhibitory concentration), ranged from 0.14 to 0.80 mg/ml, EC₅₀ (efficiency concentration) from 6.1 to 34.8 mg/mg DPPH, ARP (anti-radical power) 2.9 to 16.4 and reducing power from 1.9 to 4.7 ASE/ml. Variety Kalitur showed highest the FRSA followed by Alankar and Hara soya, as evident from their low IC₅₀, EC₅₀ and high ARP values. Alankar, Kalitur NRC-37, PK-472, VLS-47, Hara soya varieties were with comparatively higher TPC (52.7–81.7 mg GAE/g), AOA (50.5–74.7%) and showed better inhibition of peroxide formation assayed through ammonium thiocyanate and egg yolk, non-site-specific and site-specific inhibition of hydroxyl radical induced deoxyribose degradation and ferrous ion-chelating capacity than did the other varieties. Seed extracts of these varieties and leaves of Kalitur showed significant protection against DNA damage caused by free radicals. The agri-wastes of some promising varieties, e.g. Alankar, Kalitur, NRC-37 and PK-472, showed TPC ranging from 27.4 to 167 mg GAE/g, total flavanoids from 10.4 to 63.8 mg QE/g and AOA from 26.5% to 84.7% and their values were highest in the leaves, followed by pod pericarp and twigs. Out of all the varieties studied, leaves of Alankar and Kalitur varieties were more potent free radical-scavengers than were seeds, pod pericarp or twigs. The specific phenolic compositions and their quantifications were performed by HPLC and MS/MS, which showed that the seeds of Kalitur were higher in genistin (127 μg/g), seeds and leaves of Alankar in diadzin (113 μg/g) and gallic acid (87.2 μg/g), respectively. The present studies may be of importance in varietal improvement, nutraceuticals, bio-pharmaceuticals and utilization of agri-wastes as possible cost-effective natural antioxidants.     

Major anthocyanins and antioxidant activity of Nasturtium flowers (Tropaeolum majus)

Major anthocyanins, ascorbic acid content, total phenolic content, and the radical scavenging activity against ABTS and DPPH radicals in petals of orange Nasturtium flowers (Tropaeolum majus), were investigated. Anthocyanin (ACN) content in the petals was 72 mg/100 g FW and pelargonidin 3-sophoroside represented 91% of the total ACN content. The ascorbic acid content was 71.5 mg/100 g and the total phenolic content as determined by the Folin–Ciocalteau method was 406 mg GAE/100 g FW. The radical scavenging activities against ABTS and DPPH radicals were 458 and 91.87 μm trolox eq/g FW, respectively. The excellent free radical scavenging activities along with high phenolic and ascorbic acid content of Nasturtium flowers suggest that they could be source of natural pigments and antioxidants for applications in functional foods.     

Inhibitory effect of raspberries on starch digestive enzyme and their antioxidant properties and phenolic composition

Seven primocane fall-bearing raspberry (Rubus idaeus L.) cultivars, Nova (red), Dinkum (red), Heritage (red), Autumn Britten (red), Josephine, Anne (yellow), Fall Gold (yellow) were analysed for potential health promoting properties including their inhibitory effect on starch and fat digestive enzymes, antioxidant activities, and phenolic composition. The tested raspberry extracts showed no detectable inhibition of pancreatic α-amylase and lipase. However, all the extracts exhibited potent inhibition of α-glucosidase with IC₅₀ from 16.8 to 34.2 μg/mL. Four phenolic compounds, ellagic acid, cyanidin-diglucoside, pelargonidin-3-rutinoside, and catechin were identified as the active α-glucosidase inhibitors. The raspberry extracts also possessed significant antioxidant activities with oxygen radical absorbance capacities (ORAC) ranging from 136.7 to 205.2 μmol Trolox equivalents (TE)/g dry weight fruit and DPPH radical scavenging activities from 305 to 351 μmol TE/g. The total phenolic content of raspberry cultivars varied significantly from 40.9 to 98.5 mg of gallic acid equivalents/g dry weight. The anthocyanin content varied widely from 0.1 to 9.5 mg cyanidin 3-glucoside equivalents/g. Nine phenolic acids were quantified in raspberries and their total amounts varied from 157.3 to 713.5 μg/g. The enzyme inhibition and antioxidant properties of raspberry cultivars were not correlated with their total phenolic, anthocyanin, and phenolic acid content. Overall, ‘Dinkum’ and ‘Josephine’ raspberry varieties possess higher total phenolic content, ORAC, DPPH radical scavenging activity, and α-glucosidase inhibitory activity than other five cultivars.     

Antioxidant activity of white and black sesame seeds and their hull fractions

The total phenolic content (TPC), total antioxidant status (TAS), free radical scavenging capacity, inhibition of low density lipoprotein (LDL) cholesterol and metal chelating capacity of extracts of whole black and whole white sesame seeds and their hull fractions in 80% aqueous ethanol were investigated. The TPC of whole black sesame seeds and hull extracts were 29.9 ± 0.6 and 146.6 ± 0.6 mg catechin equivalents/g crude ethanolic extract, respectively. The corresponding values for white sesame were 10.6 ± 1.6 and 29.7 ± 0.9 mg catechin equivalents/g crude ethanolic extract. The TAS as determined by Trolox equivalent antioxidant capacity assay and expressed as Trolox equivalents was highest for black sesame hulls (65.9 ± 1.7) while white seeds showed the lowest (4.4 ± 0.6). Free radical scavenging capacity of sesame extracts (5–40 μg/mL) was measured using 2,2-diphenyl-1-picrylhydrazyl radical. The highest scavenging capacity was obtained at 40 μg/mL and was 94.9 ± 0.8, 25.1 ± 0.4, 14.4 ± 0.9 and 2.5 ± 0.4 for black sesame hulls, black sesame seeds, white sesame hulls and white sesame seeds, respectively. Inhibition of LDL oxidation at 100 ppm level was highest for black sesame hulls (96.7%) followed by those for white sesame hulls (84.6%), black sesame (78.4%) and white sesame seeds (57.3%). Sesame products displayed good ferrous ion chelating capacities, which ranged from 12% to 46% and 17% to 62% at 50 and 100 ppm levels, respectively. Results demonstrated considerable antioxidant activity of sesame products tested especially black sesame hulls.     

Polyphenol composition and in vitro antioxidant activity of amaranth,quinoa buckwheat and wheat as affected by sprouting and baking

This study examined the polyphenol composition and antioxidant properties of methanolic extracts from amaranth, quinoa, buckwheat and wheat, and evaluated how these properties were affected following two types of processing: sprouting and baking. The total phenol content amongst the seed extracts were significantly higher in buckwheat (323.4 mgGAE/100 g) and decreased in the following order: buckwheat > quinoa > wheat > amaranth. Antioxidant capacity, measured by the radical 2,2-diphenyl-1-picylhydrazyl scavenging capacity and the ferric ion reducing antioxidant power assays was also highest for buckwheat seed extract (p < 0.01). Total phenol content and antioxidant activity was generally found to increase with sprouting, and a decrease in levels was observed following breadmaking. Analysis by liquid chromatography coupled with diode array detector revealed the presence of phenolic acids, catechins, flavanol, flavone and flavonol glycosides. Overall, quinoa and buckwheat seeds and sprouts represent potential rich sources of polyphenol compounds for enhancing the nutritive properties of foods such as gluten-free breads.     

Sacha inchi (Plukenetia volubilis): A seed source of polyunsaturated fatty acids,tocopherols, phytosterols,phenolic compounds and antioxidant capacity

Fatty acids (FA), phytosterols, tocopherols, phenolic compounds, total carotenoids and hydrophilic and lipophilic ORAC antioxidant capacities were evaluated in 16 cultivars of Sacha inchi (SI) seeds with the aim to valorise them and offer more information on the functional properties of SI seeds. A high α linolenic (α-Ln) fatty acid content was found in all cultivars (ω3, 12.8–16.0 g/100 g seed), followed by linoleic (L) fatty acid (ω6, 12.4–14.1 g/100 g seed). The ratio ω6/ω3 was within the 0.83–1.09 range. γ- and δ-tocopherols were the most important tocopherols, whereas the most representative phytosterols were β-sitosterol and stigmasterol. Contents of total phenolics, total carotenoids and hydrophilic and lipophilic antioxidant capacities ranged from 64.6 to 80 mg of gallic acid equivalent/100 g seed; from 0.07 to 0.09 mg of β-carotene equivalent/100 g of seed; from 4.3 to 7.3 and, from 1.0 to 2.8 μmol of Trolox equivalent/g of seed, respectively, among the evaluated SI cultivars. Results showed significant differences (p < 0.05) among the evaluated SI cultivars in the contents of ω3, ω6, antioxidant capacities and other evaluated phytochemicals. SI seeds should be considered as an important dietary source of health promoting phytochemicals.     

Antioxidant capacities of Gundelia tournefortii L. extracts and inhibition on glutathione-S-transferase activity

Gundelia tournefortii L. is an important food source and a well-known medicinal plant in Eastern Anatolia. Therapeutic effects of medicinal plants are known to be closely related to their antioxidant capacities. Antioxidant activities of G. tournefortii, both for the aerial parts and seeds, were investigated by using both 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and lipid peroxidation inhibition methods. The seeds were found to have higher antioxidant potential than the aerial, with IC₅₀ values of 0.073 mg/mL for DPPH scavenging and 0.146 mg/mL for lipid peroxidation inhibition capacities. In addition, total phenolic contents of the Gundelia tournefortii L. extracts, especially the seed extracts correlates to its high antioxidant activity with 105.1 ± 8.7 μg gallic acid equivalents (GAEs) per mg of seed extract. Plant extracts with high phenolics content are known to have important effects on various enzymes, as well as glutathione-S-transferases, which are important detoxification enzymes in phase II systems with an important role in developing multi-drug resistance to chemotherapy in tumour cells. Consequently, the effects of G. tournefortii extracts on crude cytosolic glutathione-S-transferase was also studied and the seed extracts have shown effective inhibition of cytosolic GST activity, with an IC₅₀ of 97.51 μg/mL.     

Antioxidant capacity,total phenolics,glucosinolates and colour parameters of rapeseed cultivars

The antioxidant capacity of twenty nine rapeseed varieties was determined by using ferric reducing antioxidant power (FRAP) and 2,2′-diphenyl-1-picrylhydrazyl (DPPH) methods. Mean FRAP (3190–6326 μmol Trolox/100 g) and DPPH (3194–6346 μmol Trolox/100 g) values for methanolic extracts of rapeseed cultivars did not differ significantly. Moreover, the total content of phenolics (756–1324 mg sinapic acid/100 g), glucosinolates (4.2–87.5 μmol/g, respectively), erucic acid (0.0–56.1%) and colour parameters of the studied rapeseed cultivars were analysed. Antioxidant capacity determined by FRAP and DPPH methods correlated significantly with total phenolic content (TPC) in rapeseed cultivars (r = 0.9332, 0.9339, p < 0.001). Also, significant, inverse correlations were found between antioxidant capacity, total phenolics and luminosity (L^∗) or red colour intensity (a^∗) of rapeseed cultivars. Principal component analysis (PCA) allowed the rapeseed varieties to be differentiated based on their antioxidant capacities, total amounts of phenolics, glucosinolates, erucic acid and colour parameters.     

Total phenolic content and antioxidant capacity of extracts obtained from six important fruit residues

The extracts from kinnow peel, kinnow seeds, litchi pericarp, litchi seeds, grape seeds, and banana peel were screened for total phenolic content (TPC), trolox equivalent antioxidant capacity (TEAC), 1,1 diphenyl-2-picryl hydrazyl (DPPH) radical scavenging activity, as well as reducing power. Kinnow peel extract exhibited the highest reducing power, TEAC, and DPPH free radical scavenging activity, whereas, the phenolic content of 37.4 mg GAE/g-dw was highest for grape seed extract. Banana peel extract with a low TPC showed the lowest reducing power, TEAC as well as DPPH free radical scavenging activity among the fruit residue extracts examined in the present study. Correlation analysis between the reducing power and DPPH radical scavenging ability; reducing power and ABTS radical scavenging activity; and ABTS and DPPH radical scavenging abilities showed a high degree of correlation (r² = 0.85-0.91). However, r² of 0.36, 0.66, and 0.49 between TPC and DPPH radical scavenging activity; TPC and reducing power; and TPC and ABTS radical scavenging ability, respectively, indicated that some non-phenolic compounds also contributed to the total antioxidant activity in fruit residue extracts examined in this study. To the best of our knowledge, this is the first paper presenting comprehensive data on TPC, reducing power, and antioxidant activity for the six fruit residues. This study demonstrated that kinnow peel, litchi pericarp, litchi seeds, and grape seeds, can serve as potential sources of antioxidants for use in food and pharmaceutical industry.     

Nutritional constituents and antioxidant properties of indigenous kembayau (Dacryodes rostrata (Blume) H. J. Lam) fruits

The nutritional and antioxidant properties of peels, pulp and seeds of kembayau (Dacryodes rostrata) fruits were evaluated. Kembayau seeds and pulp were rich in fat, while peels had the highest ash contents. Potassium was the most prevalent mineral in peels (380.72-1112.00 mg/100 g). In kembayau fruits, total flavonoid content (1012.74-28,022.28 mg rutin equivalent/100 g) was higher than total phenolic and total monomeric anthocyanin contents. Kembayau seeds exhibited high flavonoid and phenolic contents compared to the contents in peels and pulp. Antioxidant capacities were also higher in seeds as typified by trolox equivalent antioxidant capacity assay (51.39-74.59 mmol TE/100 g), ferric reducing antioxidant power assay (530.05-556.98 mmol Fe²⁺/100 g) and by 1,1-diphenyl-2-picryl hydrazyl radical scavenging activity (92.18-92.19%) when compared to peels and pulp. Pulp and peels of kembayau fruit may be an important source of energy and minerals for human consumption, while seeds have a good potential as antioxidants.     

Physicochemical and antioxidative properties of red and black rice varieties from Thailand,China and Sri Lanka

Nine red and three black rice varieties from Thailand, China and Sri Lanka were analysed to determine their proximate composition and their physicochemical and antioxidant properties. Four groups of rice varieties with different amylose contents were identified. Cyanidin 3-glucoside and peonoidin 3-glucoside were confirmed as the dominant anthocyanins in black rice varieties with contents ranging from 19.4 to 140.8 mg/100 g DM and 11.1–12.8 mg/100 g DM, respectively. Total phenolic content (TPC) differed significantly between the varieties, but not between the colours. Highest TPC was found in the red Thai rice Bahng Gawk (BG) with 691 FA equivalent mg/100 g DM, which showed as well the highest antioxidant properties. In red varieties, the major phenolic acids in the free form were ferulic, protocatechuic and vanillic acid, whereas in black varieties protocatechuic acid was dominant followed by vanillic and ferulic acid. In the bound form, ferulic acid was predominant in both colours, where contents differed significantly, followed by p-coumaric and vanillic acid. The antioxidative capacity did not differ significantly between both colours but amongst genotypes. Antioxidant capacity of rice varieties ranged within 0.9–8.1 mmol Fe(II)/100 g DM for FRAP and 2.1–12.3 mmol TEAC/100 g DM. DPPH scavenging ability ranged from 13.0% to 76.4% remaining DPPH.     

Antioxidant capacity of medicinal plants from the Province of Córdoba (Argentina) and their in vitro testing in a model food system

The total phenols content (Folin–Ciocalteau assay) and antioxidant capacity (ferric reducing/antioxidant power – FRAP) of 41 plants from Córdoba (Argentina) were analyzed. Phenol content ranged from 8.2 to 100.2 mg GAE/g. FRAP ranged from 85.2 to 1862.0 μmol of Fe(II)/g. Capparis atamisguea had the lowest values of total phenols content and antioxidant capacity (8.2 mg GAE/g and 85.2 μmol of Fe(II)/g, respectively), while Ligaria cuneifolia exhibited the highest values (100.2 mg GAE/g and 1862.0 μmol of Fe(II)/g, respectively). A significant linear correlation (p < 0.05) was found (0.9125) between phenols content and antioxidant capacity. Results support the idea that these plants may be a good source of natural antioxidants for food applications. Plants from the Asteraceae family (the most representative of the Córdoba flora) were further tested for their DPPH radical scavenging activity. Some plant extracts were tested in a simple food system to investigate to their potential use in foods.     

Antioxidant and antibacterial activities of Nephelium lappaceum L. extracts

Ether, methanolic and aqueous extracts of lyophilized rambutan (Nephelium lappaceum L.) peels and seeds were evaluated for phenolic contents, antioxidant and antibacterial activities. High amounts of phenolic compounds were found in the peel extracts and the highest content was in the methanolic fraction (542.2 mg/g dry extract). Several potential antioxidant activities, including reducing power, β-carotene bleaching, linoleic peroxidation and free radical scavenging activity, were evaluated. The peel extracts exhibited higher antioxidant activity than the seed extracts in all methods determined (P < 0.05). The methanolic fraction was found to be the most active antioxidant as shown by their 50% DPPH inhibition concentration, 4.94 μg/mL. The results indicated this fraction exhibited greater DPPH radical scavenging activity than BHT and ascorbic acid (0.32 g dry extract/g BHT or ascorbic acid). Antibacterial activity against eight bacterial strains was assessed by disc diffusion and broth macrodilution methods. All peel extracts exhibited antibacterial activity against five pathogenic bacteria. The most sensitive strain, Staphylococcus epidermidis, was inhibited by the methanolic extract (MIC 2.0 mg/mL).     

In vitro antioxidant activity of anthocyanins of black soybean seed coat in human low density lipoprotein (LDL)

The objectives of this study were to determine the phenolic and anthocyanin contents in black soybean Mallika and Cikuray variety seed coat extract and to examine antioxidant activity of extract against DPPH radical and LDL oxidation. Black soybean seed coat of Mallika (M) and Cikuray (C) was extracted using methanol-1%HCl. The phenolic and anthocyanin contents were determined with Folin–Ciocalteu and pH differential methods, respectively. Individual anthocyanidins were identified with HPLCdiode array detector, and antioxidant activity was examined, using DPPH and TBARS assay with LDL as the oxidation substrate. BHT and rutin were used as antioxidant references. The phenolic content in M and C were 8.15 ± 0.23 and 6.46 ± 0.11 g GAE/100 g, respectively. The anthocyanin contents were 11.36 ± 0.12 and 1.45 ± 0.13 g/100 g, respectively. Cyanidin, delphinidin, and pelargonidin were found as individual anthocyanidins. The optimum DPPH radical scavenging capacity (%) of M and C were 92.78% and 91.50%, respectively, BHT and rutin were 77.0% and 91.94%, respectively. The optimum inhibition of TBARS formation from M and C were 37.10 and 30.37 nmol MDA equivalents/g LDL protein, respectively, and rutin were 30.10 nmol MDA equivalents/g LDL protein, respectively. These results suggest that black soybean seed coat has high levels of phenolic and anthocyanin, and also demonstrated considerable antioxidant activity of black soybean seed coat.     

Compositional and functional characteristics of dates,syrups, and their by-products

Three native sun-dried date varieties from Oman (namely Mabseeli, Um-sellah, and Shahal), as well as their syrups and by-products (press cake and seed) were examined for their proximate composition, dietary fibre, total phenolics, and total antioxidant activity. Carbohydrate was the predominant component in all date varieties, syrups, and their by-products, followed by moisture, along with small amounts of protein, fat, and ash. Press cakes had the highest protein content, ranging in concentration from 3.62 g/100 g in Shahal to 5.23 g/100 g in Mabseeli, whereas fat was the highest in seeds and ranged from 5.02 g/100 g in Mabseeli to 5.90 g/100 g in Um-sellah. Seeds and press cakes were found to be good sources of dietary fibre, varied between 77.75 and 80.15 g/100 g fresh weight and between 25.39 and 33.81 g/100 g fresh weight, respectively. Among dates, syrups, and their by-products, seeds had the highest contents of total phenolics (3102–4430 mg of gallic acid equivalents/100 g fresh weight) and antioxidant activity (580–929 μmol of Trolox equivalents/g fresh weight). The results obtained suggest that date by-products (particularly seeds) serve as a good source of natural antioxidants and could potentially be considered as a functional food or functional food ingredient.     

Antioxidant and free radical scavenging activities of phenols from onion (Allium cepa)

Four (red, violet, white and green) varieties of Allium cepa were studied for their total phenolic contents (TPC), antioxidant (AOA) and free radical scavenging activities (FRSA). The TPC varied from 4.6 to 74.1 mg/g GAE, AOA varied from 13.6% to 84.1% and FRSA showed wide range in terms of IC₅₀ (inhibitory concentration) from 0.1 to 15.2 mg/ml, EC₅₀ (efficient concentration) from 4.3 to 660.8 mg/mg and ARP (antiradical power) from 0.15 to 23.2. The outer dry layers of red and violet varieties showed better inhibition of lipid peroxidation assayed by ammonium thiocyanate than α-tocopherol. The non-site-specific inhibition of hydroxyl radical induced deoxyribose degradation was also higher in the outer dry layers of red and violet varieties than in their middle and inner layers. The outer layers were also potential inhibitors of nitroblue tetrazolium chloride (NBT) reduction caused by superoxide anions. On the other hand the ferrous ion chelating capacity of the red and violet varieties was highest in the inner layers. Specific phenolic composition performed through HPLC and LC–MS/MS showed the presence of gallic acid, ferulic acid, protocatechuic acid, quercetin, and kaempferol. The unutilised outer layers of the red variety were a rich source of quercetin (5110 μg/g) with high AOA, FRSA and also showed significant protection of DNA damage caused by free radicals.     

Effect of processing on the antioxidant activity of millet grains

Millets are generally dehulled and subjected to a hydrothermal treatment before consumption, thus the hulls can be used as a potential source of antioxidants. Several millet grains, namely kodo, finger (Ravi), finger (local), proso, foxtail, little and pearl millet were studied. Antioxidant activities of phenolic extracts obtained from whole grains, as well as their corresponding dehulled and cooked grains and hulls were studied for their total phenolic content (TPC), radical scavenging capacity, and antioxidant activity in a β-carotene/linoleate emulsion. The phenolics present in whole grains were identified and quantified using HPLC and HPLC/MS and results were expressed as total for each of the phenolic groups. The TPC ranged from 2 to 112 μmol ferulic acid equivalents/g defatted meal. All varieties exhibited effective inhibition of 2,2-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl, peroxyl and superoxide radicals. Dehulling and cooking affected the TPC and radical scavenging and antioxidant activities of the grains, depending on the variety. In general, the antioxidant activity of phenolic extracts was in the order of hull > whole grain > dehulled grain > cooked dehulled grain With the exception of the two finger millet varieties, hulls of other millet grains had high TPC, thus demonstrating their superior antioxidant activity. Hydroxybenzoic acids, hydroxycinnamic acids and flavonoids in whole grains were identified as contributors to the observed effects. Therefore, dehulling of grain and hydrothermal treatments affect the phenolic content and antioxidant potential of millet grains.