Antioxidant and Type 2 Diabetes Related Functional Properties of Phytic Acid Extract from Kenyan Local Food Ingredients: Effects of Traditional Processing Methods

Emerging scientific evidences reveal that phytic acid has several positive effects on human health. The antioxidant and type 2 diabetes related enzyme inhibition properties of phytic acid extract prepared from raw and traditionally processed local grains and vegetables collected from Kenya were evaluated. Phytic acid content of raw grains and vegetables ranged between 2.81–3.01 and 0.29–3.23 g/100 g DM, respectively. The phytic acid extract from raw samples revealed 59%–89% of DPPH radical scavenging capacity, 27–3,526 mmol Fe(II)/g extract of reducing power, 20%–72% of α-amylase inhibition activity and 8%–91% of α-glucosidase inhibition activity. Cooking and roasting improved the antioxidant and health relevant functionality of phytic acid extracts obtained from Kenyan local vegetables and grains, respectively.     

Flavonoid content in ethanolic extracts of selected raw and traditionally processed indigenous foods consumed by vulnerable groups of Kenya: antioxidant and type II diabetes-related functional properties

The present study evaluated the flavonoid content, antioxidant as well as type II diabetes-related enzyme inhibition activities of ethanolic extract of certain raw and traditionally processed indigenous food ingredients including cereals, legumes, oil seeds, tubers, vegetables and leafy vegetables, which are commonly consumed by vulnerable groups in Kenya. The vegetables exhibited higher flavonoid content (50-703?mg/100?g) when compared with the grains (47-343?mg/100?g). The ethanolic extract of presently studied food ingredients revealed 33-93% DPPH radical scavenging capacity, 486-6,389?mmol Fe(II)/g reducing power, 19-43% α-amylase inhibition activity and 14-68% α-glucosidase inhibition activity. Among the different food-stuffs, the drumstick and amaranth leaves exhibited significantly higher flavonoid content with excellent functional properties. Roasting of grains and cooking of vegetables were found to be suitable processing methods in preserving the functional properties. Hence, such viable processing techniques for respective food samples will be considered in the formulation of functional supplementary foods for vulnerable groups in Kenya.     

Flavonoid content in ethanolic extracts of selected raw and traditionally processed indigenous foods consumed by vulnerable groups of Kenya: antioxidant and type II diabetes-related functional properties

The present study evaluated the flavonoid content, antioxidant as well as type II diabetes-related enzyme inhibition activities of ethanolic extract of certain raw and traditionally processed indigenous food ingredients including cereals, legumes, oil seeds, tubers, vegetables and leafy vegetables, which are commonly consumed by vulnerable groups in Kenya. The vegetables exhibited higher flavonoid content (50–703 mg/100 g) when compared with the grains (47–343 mg/100 g). The ethanolic extract of presently studied food ingredients revealed 33–93% DPPH radical scavenging capacity, 486–6,389 mmol Fe(II)/g reducing power, 19–43% α-amylase inhibition activity and 14–68% α-glucosidase inhibition activity. Among the different food-stuffs, the drumstick and amaranth leaves exhibited significantly higher flavonoid content with excellent functional properties. Roasting of grains and cooking of vegetables were found to be suitable processing methods in preserving the functional properties. Hence, such viable processing techniques for respective food samples will be considered in the formulation of functional supplementary foods for vulnerable groups in Kenya.     

Bioactive compounds extracted from Indian wild legume seeds: antioxidant and type II diabetes-related enzyme inhibition properties

Seven different wild legume seeds (Acacia leucophloea, Bauhinia variegata, Canavalia gladiata, Entada scandens, Mucuna pruriens, Sesbania bispinosa and Tamarindus indica) from various parts of India were analyzed for total free phenolics, l-Dopa (l-3,4 dihydroxyphenylalanine), phytic acid and their antioxidant capacity (ferric-reducing antioxidant power [FRAP] and 2,2-diphenyl-1-picrylhydrazyl [DPPH] assay) and type II diabetes-related enzyme inhibition activitiy (α-amylase). S. bispinosa had the highest content in both total free phenolics and l-Dopa, and relatively low phytic acid when compared with other seeds. Phytic acid content, being highest in E. scandens, M. pruriens and T. indica, was highly predictive for FRAP (r = 0.47, p < 0.05) and DPPH (r = 0.66, p < 0.001) assays. The phenolic extract from T. indica and l-Dopa extract from E. scandens showed significantly higher FRAP values among others. All seed extracts demonstrated a remarkable reducing power (7-145 mM FeSO4 per mg extract), DPPH radical scavenging activity (16-95%) and α-amylase enzyme inhibition activity (28-40%).     

Phenolic composition and antimicrobial and antiquorum sensing activity of an ethanolic extract of peels from the apple cultivar Annurca

This study investigated the phenolic composition and antioxidant capacity of an ethanolic extract from the peel of the Annurca (Malus domestica var. Annurca), which is widespread in the Campania region of southern Italy. The antimicrobial effect of the extract on different pathogens was also examined. The potential antiquorum sensing activity of the extract was tested by using the microorganism Chromobacterium violaceum. Ultra-performance liquid chromatography revealed that rutin, epicatechin, dicaffeoylquinic acid, and caffeic acid were the most abundant phenolic compounds in the extract; these compounds constituted 27.43%, 24.93%, 16.14%, and 15.3% of the total phenols, respectively. The test for 2,2-diphenyl-1-picryl-hydrazyl free radical-scavenging activity showed that the extract possessed an impressive antioxidant capacity (50% effective concentration of 2.50 μg/g of product). Furthermore, the extract clearly exhibited antimicrobial activity against Bacillus cereus (11- to 14-mm diameter of inhibition halo, depending on the strain) and Escherichia coli serotype O157:H7 (10-mm diameter of inhibition halo). No activity was observed against the probiotic lactobacilli tested or against Staphylococcus aureus. Antiquorum sensing activity was reported for the first time for apple extracts. In conclusion, these results indicate the potential of this extract for treating some microbial infections through cell growth inhibition or quorum sensing antagonism, thereby validating the health benefits of apples.     

Chelating,antioxidant and hypoglycaemic potential of Muscari comosum (L.) Mill. bulb extracts

Abstract

The metal chelating activity, antioxidant properties and the effect on carbohydrate-hydrolysing enzyme inhibition of Muscari comosum extracts have been investigated. M. comosum bulbs contain a total amount of the phenols with a value of 56.6 mg chlorogenic acid equivalent per gram of extract and a flavonoid content of 23.4 mg quercetin equivalent per gram of extract. In order to evaluate the non-polar constituents, n-hexane extract was obtained. Gas chromatography–mass spectrometry analysis revealed the presence of fatty acids and ethyl esters as major constituents, with different aldehydes and alkanes as minor components. Ethanolic extract had the highest ferric-reducing ability power (66.7 μM Fe(II)/g) and DPPH scavenging activity with a concentration giving 50% inhibition (IC₅₀) value of 40.9 μg/ml. Moreover, this extract exhibited a good hypoglycaemic activity with IC₅₀ values of 81.3 and 112.8 μg/ml for α-amylase and α-glucosidase, respectively. In conclusion, M. comosum bulbs show promising antioxidant and hypoglycaemic activity via the inhibition of carbohydrate digestive enzymes. These activities may be of interest from a functional point of view and for the revalorization of this ancient non-cultivated vegetable of Mediterranean traditional gastronomy.     

Hypoglycemic effect of basil (Ocimum basilicum) aqueous extract is mediated through inhibition of α-glucosidase and α-amylase activities: an in vitro study

The present study investigated the in vitro hypoglycemic activity of basil (Ocimum basilicum) aqueous extract. Preliminary phytochemical screening of the extract revealed the presence of reducing sugars, cardiac glycosides, tannins, saponins, glycosides, flavonoids and steroids. The total polyphenols content (TPC), flavonoids content (FC), percentage diphenylpicrylhydrazyl (DPPH( · )) radical inhibition and total antioxidant status (TAS) were estimated. The FC was 41 ± 2.2 rutin/g dry extract, the TPC was 146 ± 5.26 mg catechin/g dry extract and the TAS was 5.12 ± 0.7 mmol/L. The %DPPH( · ) free radical inhibition was 60%, 54%, 49% and 43%, respectively, for different extract concentrations; 20, 18.2, 16.3 and 14.5 mg/ml, respectively. The extract elicited significant dose-dependent pattern against rat intestinal sucrase (RIS; IC(50) = 36.72 mg/ml), rat intestinal maltase (RIM; IC(50) = 21.31 mg/ml) and porcine pancreatic α-amylase (PPA; IC(50) = 42.50 mg/ml) inhibitory activities. The inhibition was greater against maltase compared with sucrase. These effects may be attributed to the high TPC and FC levels. The linear regression analysis revealed strong significant positive correlations between %DPPH( · ) radical inhibition and each of %RIS, %RIM and %PPA inhibiting activity. Also, strong significant positive correlations between %RIS and either %RIM or %PPA inhibition activity were observed. We concluded therefore that basil aqueous extract via antioxidant and possibly α-glucosidase and α-amylase inhibiting activities, offered positive benefits to control diabetes.     

In vitro antioxidant and hypoglycemic activities of Ethiopian spice blend Berbere

The metal chelating activity, antioxidant properties, and the effect on carbohydrate-hydrolyzing enzymes of Ethiopian spice blend Berbere have been investigated. Berbere contains a total amount of phenols corresponding to 71.3 mg chlorogenic acid equivalent per gram of extract and a total flavonoid content of 32.5 mg quercetin equivalent per gram of extract. An increase of the resistance towards forced oxidation was obtained when Berbere was added to sunflower oil. In order to evaluate the bioactivity of the non-polar constituents, an n-hexane extract was obtained from Berbere. The gas chromatography-mass spectrometry analysis revealed the presence of 19 fatty acids constituents (98.1% of the total oil content). Among them, linoleic acid was the major component (72.0% of the total lipids). The ethanolic extract had the highest ferric-reducing ability power (35.4 μM Fe(II)/g) and DPPH scavenging activity with a concentration giving 50% inhibition (IC(50)) value of 34.8 μg/ml. Moreover, this extract exhibited good hypoglycemic activity against α-amylase (IC(50) = 78.3 μg/ml). In conclusion, Ethiopian spice blend Berbere showed promising antioxidant and hypoglycemic activity via the inhibition of carbohydrate digestive enzymes. These activities may be of interest from functional point of view and for the revalorization of the spice blend in gastronomy also outside the African country.     

Bioactive compounds extracted from Indian wild legume seeds: antioxidant and type II diabetes–related enzyme inhibition properties

Seven different wild legume seeds (Acacia leucophloea, Bauhinia variegata, Canavalia gladiata, Entada scandens, Mucuna pruriens, Sesbania bispinosa and Tamarindus indica) from various parts of India were analyzed for total free phenolics, l-Dopa (l-3,4 dihydroxyphenylalanine), phytic acid and their antioxidant capacity (ferric-reducing antioxidant power [FRAP] and 2,2-diphenyl-1-picrylhydrazyl [DPPH] assay) and type II diabetes–related enzyme inhibition activitiy (α-amylase). S. bispinosa had the highest content in both total free phenolics and l-Dopa, and relatively low phytic acid when compared with other seeds. Phytic acid content, being highest in E. scandens, M. pruriens and T. indica, was highly predictive for FRAP (r = 0.47, p < 0.05) and DPPH (r = 0.66, p < 0.001) assays. The phenolic extract from T. indica and l-Dopa extract from E. scandens showed significantly higher FRAP values among others. All seed extracts demonstrated a remarkable reducing power (7–145 mM FeSO4 per mg extract), DPPH radical scavenging activity (16–95%) and α-amylase enzyme inhibition activity (28–40%).     

First isolation of tryptophan from edible lotus (Nelumbo nucifera Gaertn) rhizomes and demonstration of its antioxidant effects

Abstract

Various vegetables were investigated for antioxidant activities in two assays, namely, inhibition of lysis of erythrocytes induced by peroxyl radicals and inhibition of lipid peroxidation. The lotus (Nelumbo nucifera Gaertn) rhizome showed the strongest antioxidant activity in both assays. The crude extract (L) of lotus rhizome was chromatographed on a macroporous adsorption resin named NKA. The resulting three fractions were designated L1, L2 and L3, respectively. L2 showed the highest antioxidant activity and was further fractionated by Sephadex LH-20 chromatography. Eight fractions were obtained and named from L2a to L2h, respectively. L2c showed the strongest activity in inhibiting hemolysis of erythrocytes and was further purified by high-performance liquid chromatography. L2c-3 was identified as tryptophan. Its inhibitory concentration of 50% (IC₅₀) value in inhibiting hemolysis of erythrocytes was 156.3 μg/ml (i.e. 765.4 μM). This is the first report on isolation of tryptophan from the aqueous extract of lotus rhizome and demonstration of their antioxidant activities.     

Antioxidant activity of eugenol: a structure-activity relationship study

Eugenol (4-allyl-2-methoxyphenol), a major phenolic component from clove oil (Eugenia caryophyllata), has several biological activities. To estimate the capacity of eugenol to act as an antioxidant, the following were studied: 1,1-diphenyl-2-picryl-hydrazyl-, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid)-, and N,N-dimethyl-p-phenylenediamine-scavenging activity; total antioxidant activity; and ability to reduce ferric ions and cupric ions. Eugenol inhibited 96.7% (r(2)=0.9319) lipid peroxidation of a linoleic acid emulsion at a 15-μg/mL concentration. Butylated hydroxyanisole, butylated hydroxytoluene, α-tocopherol, and Trolox(?) displayed 95.4% (r(2)=0.8482), 99.7% (r(2)=0.7798), 84.6% (r(2)=0.9272), and 95.6% (r(2)=0.8511) inhibition of peroxidation, respectively, at the 15-μg/mL concentration. According to the results of this study, eugenol had the most powerful antioxidant activity and radical-scavenging activity. This study should prompt further studies of the antioxidant properties of eugenol.     

Alpha-glucosidase inhibitory and antioxidant activities of Vietnamese edible plants and their relationships with polyphenol contents

The prevention and treatment of non-communicable diseases by using the beneficial biological effects of polyphenolic plants have attracted increasing interest from nutritional scientists. The a-glucosidase inhibitory and antioxidant activities of aqueous and methanolic extracts from 28 common Vietnamese edible plants, comprising 4 groups (plants used for making drinks, edible wild vegetables, herbs, and dark green vegetables), were investigated in vitro. The polyphenol contents of these extracts were determined by the Folin-Ciocalteu method and calculated as catechin equivalents. The extracts from plants used for making drinks showed the highest activities for both a-glucosidase inhibition and as antioxidants, followed by edible wild vegetables, herbs, and dark green vegetables. Positive relationships among alpha-glucosidase inhibitory activities, antioxidant activities and polyphenol contents of these 28 edible plants were found in both aqueous and methanolic extracts. Four new promising materials that are similar to or better than guava leaf extract, including Syzygium zeylanicum, Cleistocalyx operculatus, Horsfieldia amygdalina and Careya arborea demonstrated high alpha-glucosidase inhibitory activity (93, 76, 68 and 67%, respectively) at the final concentration of 0.8 mg lyophilized material/mL solution and antioxidant activity (85, 87, 78 and 80%, respectively) at the final concentration of 30 pg lyophilized material/mL solution. These four edible plants contained significantly high polyphenol contents (equivalent to 251.7, 146.6, 136.6 and 168.6 mg of catechin/g dry weight, respectively). Thus, these four materials might be possible new sources of a-glucosidase inhibition and antioxidants suitable for use as functional foods in the future.     

In vitro antioxidant and hypoglycemic activities of Ethiopian spice blend Berbere

The metal chelating activity, antioxidant properties, and the effect on carbohydrate-hydrolyzing enzymes of Ethiopian spice blend Berbere have been investigated. Berbere contains a total amount of phenols corresponding to 71.3 mg chlorogenic acid equivalent per gram of extract and a total flavonoid content of 32.5 mg quercetin equivalent per gram of extract. An increase of the resistance towards forced oxidation was obtained when Berbere was added to sunflower oil. In order to evaluate the bioactivity of the non-polar constituents, an n-hexane extract was obtained from Berbere. The gas chromatography–mass spectrometry analysis revealed the presence of 19 fatty acids constituents (98.1% of the total oil content). Among them, linoleic acid was the major component (72.0% of the total lipids). The ethanolic extract had the highest ferric-reducing ability power (35.4 μM Fe(II)/g) and DPPH scavenging activity with a concentration giving 50% inhibition (IC₅₀) value of 34.8 μg/ml. Moreover, this extract exhibited good hypoglycemic activity against α-amylase (IC₅₀ = 78.3 μg/ml). In conclusion, Ethiopian spice blend Berbere showed promising antioxidant and hypoglycemic activity via the inhibition of carbohydrate digestive enzymes. These activities may be of interest from functional point of view and for the revalorization of the spice blend in gastronomy also outside the African country.     

The antioxidant and radical scavenging activities of black pepper (Piper nigrum) seeds

Water and ethanol crude extracts from black pepper (Piper nigrum) were investigated for their antioxidant and radical scavenging activities in six different assay, namely, total antioxidant activity, reducing power, 1,1-Diphenyl-2-picryl-hydrazyl (DPPH) free radical scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, and metal chelating activities. Both water extract (WEBP) and ethanol extract (EEBP) of black pepper exhibited strong total antioxidant activity. The 75?µg/ml concentration of WEBP and EEBP showed 95.5% and 93.3% inhibition on peroxidation of linoleic acid emulsion, respectively. On the other hand, at the same concentration, standard antioxidants such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and α-tocopherol exhibited 92.1%, 95.0%, and 70.4% inhibition on peroxidation of linoleic acid emulsion, respectively. Also, total phenolic content in both WEBP and EEBP were determined as gallic acid equivalents. The total phenolics content of water and ethanol extracts were determined by the Folin-Ciocalteu procedure and 54.3 and 42.8?µg gallic acid equivalent of phenols was detected in 1?mg WEBP and EEBP.     

Zinc absorption from a low-phytic acid maize

BACKGROUND: Phytic acid reduction in cereal grains has been accomplished with plant genetic techniques. These low-phytic acid grains provide a strategy for improving the mineral (eg, zinc) status in populations that are dependent on grains, including maize (Zea mays L.), as major dietary staples. OBJECTIVE: The objective was to compare the fractional absorption of zinc from polenta prepared from maize low in phytic acid with that prepared from a wild-type isohybrid maize (control) after short-term consumption by adults whose habitual diet is low in phytic acid. DESIGN: Healthy adults served as their own control subjects in a crossover design. All meals on 1 d consisted of polenta prepared from a low-phytic acid maize homozygous for the recessive low phytic acid 1-1 (lpa1-1). On the preceding or following day, all meals consisted of polenta prepared from a sibling isohybrid homozygous wild-type maize with a "normal" phytic acid content. The low-phytic acid maize contained approximately 60% less phytic acid than did the wild-type maize. All test meals were extrinsically labeled with zinc stable-isotope tracers. The fractional absorption of zinc was determined on the basis of fecal enrichment. RESULTS: The molar ratios of phytic acid to zinc in the polenta prepared from lpa1-1 maize and the wild-type maize were 17:1 and 36:1, respectively. The corresponding fractional absorptions of zinc were 0.30 +/- 0.13 and 0.17 +/- 0.11, respectively (P < 0.005). CONCLUSION: Substitution of a low-phytic acid grain in a maize-based diet is associated with a substantial increase in zinc absorption.     

Proximate composition, phytic acid, polyphenols and digestibility (in vitro) of four brown cowpea varieties

Four cultivars of brown cowpea (Vigna unguiculata. L. Walp) were analysed for their proximate composition, phytic acid, polyphenols and protein and starch digestibility (in vitro). Crude protein values ranged from 20.07 to 24.60%. Ether extract and crude fiber contents varied from 1.77 to 1.96% and 4.27 to 4.95%, respectively. All the four cowpea varieties differed significantly for their starch content which ranged from 46.84 to 53.63%. Antinutrients, phytic acid and polyphenols, showed significant variations among the varieties. In vitro digestibility of protein and starch of grains had a narrow variation. The variety CS-46 containing minimum amount of antinutritional factors had the highest protein digestibility.     

In vitro studies of polyphenol compounds, total antioxidant capacity and other dietary indices in a mixture of plants (Prolipid)

The best health and nutrition results can be achieved not only from the consumption of fruits and vegetables with high antioxidant capacities, but also from medicinal plants and herbs. Therefore, in the present investigation, the bioactive compounds (polyphenols and flavonoids) and the radical scavenging capacities of Prolipid, a mixture of herbs, were studied. Water extracts showed relatively high capacity of about 61.5% inhibition with the beta-carotene linoleic acid assay. In order to support the data obtained with beta-carotene-linoleic acid assay, three different antioxidant assays were used: ferric-reducing/antioxidant power, trolox equivalent antioxidant capacity, and 1,1-diphenyl-2-picrylhydrazyl radical with prolonged time of their reactions. It was found that the amounts of polyphenols in water and methanol extracts were 22.849+/-2.267 and 3.241+/-0.325 mg gallic acid equivalent/g dry weight, and the antioxidant capacities in same extracts as determined by the 2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) test after 120 min were 275.81+/-27.58 and 62.25+/-6.11 micromole Trolox equivalents (microMTE) g dry weight, respectively. The correlation coefficients between polyphenols and antioxidant capacities of Prolipid with 1,1-diphenyl-2-picrylhydrazyl radical and beta-carotene linoleic acid assay were about 0.97 and 0.98. In conclusion, the bioactivity of Prolipid was high and the total polyphenols were the main contributors to the overall antioxidant capacity. The results of our investigation in vitro are comparable with other medicinal plants and fruits widely used in the treatment of humans without known side effects. Prolipid, a mixture of herbs, can therefore be used as a supplement for nutritional and healthy purposes.     

Potential of commonly consumed green leafy vegetables for their antioxidant capacity and its linkage with the micronutrient profile

Green leafy vegetables (GLV) offer a cheap but rich source of a number of micronutrients and other phytochemicals having antioxidant properties. The potential of 30 GLV in the raw and cooked form as natural antioxidant supplements for vegetarian diets was assessed. There was a large variability in the values of antioxidant activity of various GLV extracts in the lipid micelles (1.5-5.6 mM vitamin E/100 g for raw samples and 1.6-3.8 mM vitamin E/100 g for cooked samples). Similar to thiobarbituric acid reactive substances values, the super oxide scavenging ability values also exibited large variation (10.6-55.9), with significantly higher values in the raw state than the cooked state (P<0.001). Omum leaves, radish leaves and lettuce had high values for this index. The range of values for ferrous iron chelating activity was from 9.3 to 65.7 mM EDTA/100 g food material, indicating again a large variability in this assay. Leaves of coriander, amaranthus viridis, colcasia green and drumstick showed high values, while Amaranthus p. Colocasia black and amaranthus red exibited low values. Differences between raw and cooked values were highly significant for all the three indices (P<0.001).     

In vitro antioxidant activities of Stevia rebaudiana leaves and callus

Leaf extract of Stevia rebaudiana promotes effects on certain physiological systems such as the cardiovascular and renal and influences hypertension and hyperglycemia. Since these activities may be correlated with the presence of antioxidant compounds, leaf and callus extracts of Stevia rebaudiana were evaluated for their total phenols, flavonoids content and total antioxidant capacity. Total phenols and flavonoids were analyzed according to the Folin–Ciocalteu method and total antioxidant activity of water and methanolic extracts of stevia leaves and callus was assessed by ferric reducing/antioxidant power (FRAP) assay as well as 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. The total phenolic compounds were found to be 25.18 mg/g for stevia leaves and 35.86 mg/g for callus on dry weight basis. The flavonoids content was found to be 21.73 and 31.99 mg/g in the leaf and callus, respectively. The total antioxidant activity was expressed as mg equivalent of gallic acid, ascorbic acid, BHA and trolox per gram on dry weight basis. Total antioxidant activity found was ranged from 9.66 to 38.24 mg and 11.03 to 36.40 mg equivalent to different standards in water and methanolic extract of stevia leaves, respectively. In case of stevia callus, it was found to be 9.44 to 37.36 mg for water extract and 10.14 to 34.37 mg equivalent to standards for methanolic extract. The concentrations required for 50% inhibition (IC₅₀) of DPPH radicals were 11.04, 41.04 and 57.14 μg/mL for gallic acid, trolox and butylated hydroxyanisole (BHA), respectively. The percent inhibition of DPPH radical of various extracts of stevia leaves and callus found were ranged from 33.17% to 56.82%. The highest percent of inhibition was observed in methanolic extract of callus.     

Antioxidant activities of New Zealand-grown tomatoes

The objective of this study was to compare the antioxidant activities, total phenolics, lycopene and ascorbic acid content of four commercial tomato cultivars (Excell, Tradiro, Flavourine and Campari) of New Zealand, grown under similar hydroponic conditions. The mean antioxidant activity of the four cultivars, as measured with the ABTS radical decolourization assay, ranged from 2329 to 3268 micromole TEAC/100 g dry matter (DM) in the hydrophilic extracts and from 178 to 303 micromole TEAC/100 g DM in the lipophilic extracts. The major antioxidant components per 100 g DM were phenolics (343-451 mg gallic acid equivalents in hydrophilic extract and 53-74 mg gallic acid equivalents in lipophilic extract), flavonoids (175-204 mg rutin equivalents), ascorbic acid (153-195 mg) and lycopene (33-54 mg). Ascorbic acid and flavonoids were found to contribute 28-38% and 29-34%, respectively, to the antioxidant activity of the hydrophilic extract of tomatoes. The results showed that the smallest cultivar (Campari) had significantly (P < 0.05) higher antioxidant activities, total phenolics and flavonoids than the larger sized cultivars (Excell, Tradiro and Flavourine). This could be attributed to the significantly (P < 0.05) higher surface area/volume ratio of the small cultivar (0.15) when compared with the large-sized cultivars (0.10-0.12). The tomato cultivar (Flavourine) with a brighter red colour (higher a*/b* value), had a higher lycopene content as well, which suggests that the a*/b* value of tomatoes can be used as an indicator of their lycopene content. The phenolics (r = 0.84**) and flavonoids (r = 0.88**) were significantly related to the antioxidant activity of the hydrophilic extract, which suggests that measurement of total phenolics or flavonoids can be used as indicators of the antioxidant activity of tomatoes.