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Antioxidant capacity and phenolic compounds in commercially grown native Australian fruits
Abstract
Hydrophilic phytochemicals and antioxidant capacities of eight commercially grown native Australian
fruits were determined. Kakadu plum (Terminalia ferdinandiana) contained a 6-fold higher level of total
phenolic compounds and quandong (Santalum acuminatum) a 1.9-fold higher level of total phenolic compounds
(TP, Folin–Ciocalteu assay) than blueberry (Vaccinum sp., cv. Biloxi). Both fruits displayed superior
oxygen radical-scavenging capacity (ORAC-H assay) that was, respectively 4.1-fold and 6.5-fold of
that of blueberry. The total reducing capacity (TRC; ferric reducing antioxidant power (FRAP) assay) of
Kakadu plum and quandong exceeded the TRC of blueberry, respectively, 13.1- and 2.3-times. The primary
sources of antioxidant capacities in the evaluated fruits were phenolic acids (benzoic and cinnamic)
and flavonoids (flavonols, flavanones and anthocyanins) tentatively detected by liquid chromatography–
mass spectrometry (LC–PDA–MS/MS). A high level of vitamin C was recorded for Kakadu plum and Australian
citrus fruits. The major organic acids detected were citric and malic acid.
... Total phenolic content was determined using the Folin À Ciocalteu assay (Singleton & Rossi 1965;Ainsworth & Gillespie 2007), with minor modifications as described previously (Konczak et al. 2010). Briefly, 25 lL of plant extracts (1 mg/mL) were mixed with 125 lL Folin-Ciocalteu reagent earlier diluted with MilliQ water (1:10, v/v) in 96-well microplates and shaken for 3 min. ...
... Ferric reducing antioxidant power (FRAP) assay Total reducing capacity was determined using the FRAP assay (Benzie & Strain 1996) with minor modifications as described previously (Konczak et al. 2010). Briefly, the FRAP reagent consisted of 10 mL of 300 mM acetate buffer, 10 mL of 20 mM FeCl 3 and 1 mL of 10 mM TPTZ solution. ...
... Oxygen radical scavenging capacity was determined using the ORAC assay according to Prior et al. (2005) with some modifications (Konczak et al. 2010). Preparations of fluorescein (120 nM) and AAPH (360 mM) were dissolved in phosphate-buffered saline (PBS; 75 mM, pH 7.0). ...
Context: Sempervivum davisii Muirhead (Crassulaceae) is a traditional medicinal herb from Eastern Anatolia. To date the composition of phytochemicals and physiological properties of this herb were not subjected to any research.
Objective: This study identifies compounds in S. davisii hydrophilic extracts and evaluates their potential biological properties.
Materials and methods: Ethanol-based lyophilized extracts were obtained from aerial parts of plant (10 g of ground dry plant material in 200 mL of acidified aqueous ethanol, shaken for 2 h at 22 °C with supernatant collected and freeze-dried under vacuum). Phytochemical composition was investigated by liquid chromatography mass spectrometry (LC-MS/MS, phenolics) and gas chromatography mass spectrometry (GC-MS, volatiles). Phenolic compounds were quantified by high-performance liquid chromatography (HPLC) and the Folin–Ciocalteu assay. Subsequently, antioxidant capacity [ferric reducing antioxidant power (FRAP), oxygen radical absorbance capacity (ORAC) assays] and enzyme inhibitory properties (isolated porcine pancreatic lipase) of the extracts were determined.
Results: Polyphenolic compounds were the main constituents of lyophilized extracts, among which kaempferol glycosides and quercetin hexoside dominated. The extracts exhibited potent antioxidant (FRAP values of 1925.2–5973.3 μM Fe²⁺/g DW; ORAC values of 1858.5–4208.7 μM Trolox Eq./g DW) and moderate lipase inhibitory (IC50: 11.6–2.96 mg/mL) activities. Volatile compounds (nonanal, dehydroxylinalool oxide isomers, 2-decenal, 2-undecenal, 2,6-di-tetr-butylphenol) were also found.
Conclusions: Phenolic compounds with the dominating kaempferol and quercetin derivatives are the sources of potent antioxidant properties of S. davisii hydrophilic extracts. The extracts exhibit moderate inhibitory properties towards isolated pancreatic lipase.
... Kakadu plum is among the richest known sources of Vitamin C (Brand et al., 1982;Konczak, Zabaras, Dunstan, & Aguas, 2010), although a high degree of variability exists, possibly due to factors such as genetic diversity, climate and soil condition, ripening stage and storage conditions. The fruit is a rich source of phenolic compounds, responsible for its high antioxidant capacity (Konczak et al., 2010). ...
... Kakadu plum is among the richest known sources of Vitamin C (Brand et al., 1982;Konczak, Zabaras, Dunstan, & Aguas, 2010), although a high degree of variability exists, possibly due to factors such as genetic diversity, climate and soil condition, ripening stage and storage conditions. The fruit is a rich source of phenolic compounds, responsible for its high antioxidant capacity (Konczak et al., 2010). Recent studies towards evaluation of potential physiological activities of Kakadu plum, as identified in an array of cell culture based assays, revealed pronounced anti-inflammatory and chemopreventative properties of phenolic-rich fruit extract (Tan, Konczak, Ramzan, & Sze, 2011). ...
... Vitamin C was extracted from powdered samples and stabilised using 4.5% meta-phosphoric acid as previously described (Konczak et al., 2010). ...
... Yield, total phenolic and total flavonoid content Recent reports described a high antioxidant capacity of selected edible native Australian plants and phenolic compounds were identified as the major source of this capacity (Konczak et al. 2010a(Konczak et al. , 2010bKonczak et al. 2009). Pure phenolic compounds evaluated individually, as well as crude phenolic-rich extracts obtained from plants are powerful antioxidants, responsible for a number of health properties of plant-originating foods (Noroozi et al. 1998;Liu 2004;Bagchi et al. 1999). ...
... Among fruits, Davidson's plum extract exhibited superior antioxidant capacity, with the oxygen radical scavenging ability 1.5-fold that of quandong and 2.5-fold that of the blueberry references and the TRC 3-fold that of quandong and 2-fold that of the southern highbush blueberry reference. A different result has been reported earlier for crude extracts from the same fruits, where the oxygen radical scavenging capacity of Davidson's plum was only 50 per cent of that of quandong and the TRC was 1.8-fold that of quandong (Konczak et al. 2010b;Konczak et al. 2009). ...
... Previous research into other Terminalia species has shown that they are generally self-incompatible with hermaphrodite flowers at the base of the raceme and male flowers at the tip, i.e. andromonoecious (Srivastava et al. 1996;Pither et al. 2003;Begoude Boyogueno 2010;Solomon Raju et al. 2012). There is considerable variability of fruit production (timing of flowering and fruiting, and yields) and fruit quality (fruit size and properties) across the range of T. ferdinandiana that limits its commercialisation (Woods 1995;Konczak et al. 2010Konczak et al. , 2014Gorman et al. 2016). The results from the present study will be useful for both increasing supply from wild stock and for planning and maximising yields from plantations by manipulating pollinator numbers. ...
Terminalia ferdinandiana Exell., also known as the Kakadu plum, is an important food plant endemic to northern Australia. The fruit has substantial commercial demand as it contains sought-after antioxidants and the greatest concentration of ascorbic acid of any fruit known worldwide. Better knowledge of its reproductive biology is required to increase fruit production from wild stands and sustain commercial demand. Experiments demonstrate that T. ferdinandiana is andromonoecious and self-incompatible, relying on cross-pollination for successful fruit production. Wild stocks of this species are pollen limited, likely caused by pollinator satiation in dense, synchronously flowering stands. These findings indicate that enhanced fruit production requires supplementation of suitable pollinators in wild stands.
... Similarly, the aqueous leaf extract had an antioxidant capac- ity of 340 mg ascorbic acid equivalents. Previous studies have reported that the high antioxidant content of T. ferdi- nandiana fruit is largely due to high levels of ascorbic acid (23,24). Although the A. franciscana nauplii lethality assay is generally quite robust, it is noteworthy that brine shrimp are sensitive to changes in pH (25). ...
Terminalia spp. are characterized by their high antioxidant contents and several species have anticancer activity. This study examined T. ferdinandiana fruit and leaf extracts for antiproliferative and apoptotic activities against a panel of human carcinoma cell lines. All extracts inhibited Caco2, HeLa, Jeg-3, JAR, MC3T3-E1, and MG63 proliferation. The leaf ethyl acetate extract was the most potent inhibitor of proliferation (MC3T3-E1 IC50 = of 6 µg/ml; Caco2 IC50 = 102 µg/ml). Furthermore, IC50's < 500 µg/ml were determined against all cell lines tested against that extract. The methanolic leaf extract was also a potent inhibitor of cell proliferation (Jeg-3 IC50 = 147 µg/ml; MC3T3-E1 IC50 = 40 µg/ml). The fruit extracts were also good inhibitors of carcinoma cell proliferation. Cell imaging studies detected morphological features consistent with apoptosis in Caco2 cells exposed to the ethyl acetate, methanolic, and aqueous extracts. Caspase 3 activity was significantly elevated in Caco2 cells exposed to these extracts, indicating that apoptosis was induced. The leaf ethyl acetate extract contained a high diversity and relative abundance of tannins and flavonoids. All T. ferdinandiana fruit and leaf extracts displayed either no toxic or low toxicity in the Artemia franciscana bioassay and in a HDF viability assay.
... However, during recent years epidemiological studies have shown the possible health risks related to the consumption of synthetic antioxidants and strict regulations now control their use in foods. Therefore, attention has been directed towards the development/isolation of natural antioxidants from botanical sources, especially edible plants (Hinneburg et al., 2006; Hossain et al., 2008; Konczak et al., 2010; Wangensteen et al., 2004). In this sense, herbs and spices are one of the most important targets to search for natural antioxidants from the safety point of view (Yanishlieva et al., 2006). ...
Herbs and spices have been used for many purposes including medicine, flavourings, and preservatives, etc. Constituents of herbs and spices can function as natural antioxidants and thus improve human nutrition and health. The main objective of this study was to evaluate the total phenolic and flavonoid contents of 35 different Turkish herbs and spices and to determine their antioxidant activity. Total phenolics, flavonoids, and total antioxidant capacities were analysed by four different methods: 2,2’-azinobis(3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt (ABTS), 1,1-diphenyl-2-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP) and cupric ion reducing antioxidant capacity (CUPRAC) assay. The correlation coefficients (R2) between spectrophotometric assays were calculated. Wide variation in total phenolics (TP; 0.36-104 mg GAE/g), flavonoids (TF; 0.44-53.7 mg CE/g) and antioxidant capacity (TAC; 0.88-1007 mg trolox equivalent/g) was observed. Clove (Eugenia caryophyllata), yarrow (Achillea millefolium) and rosemary (Rosmarinus officinalis) showed the highest TP, TF and TAC values, respectively, whereas mahaleb (Prunus mahaleb) showed the lowest TP and TAC. The relationships between TP, TF and TAC generally indicated a weak correlation, ranging from R2=0.163 (between ABTS and CUPRAC) to R2=0.760 (between FRAP and CUPRAC). This study provides direct comparative data on TP, TF and TAC of the 35 commonly consumed herbs and spices in Turkey.
... Among phytonuntrients responsible for this health benefit are phenolic compounds. 1 Their preventative effects against the development of degenerative diseases, such as cancer, 2 cardiovascular diseases, 3 neural degeneration, 4 diabetes and obesity 5 have been reported. Phenolic compounds are generally strong antioxidants and the primary explanation of their * Corresponding author: brankastojanovic81@gmail.com action is the protection of cell constituents against oxidative damage through the scavenging of free radicals, thereby averting their deleterious effects on nucleic acids, proteins and lipids in cells. ...
The present study was performed to evaluate the antioxidant
capacity, the polyphenol and metal content of the vineyard peach
which was cultivated in Southern Serbia. The antioxidant
capacity of the vineyard peach extracts was evaluated using
2,2-diphenil-1-picrylhydrazil radical-scavenging assay. The
polyphenol contents of vineyard peach samples were 89.1 to
355.0 mg GAE/100 g f.w. The high polyphenol content was
significantly correlated with the high antioxidant capacity.
Vineyard peaches contained only cyanidin based pignents. The
predominant hydroxicinnamic acid is caffeic acid. Flavonols
identified in vineyard peach samples were quercetin derivates.
The metal levels were analysed by inductively coupled plasma
atomic emission spectrometry method (ICP-OES). The trace
levels of metals such as Na, K, Mg, Ca, Co, Cr, Cu, Fe, Mn, Ni,
Pb, Zn, and Cd were determined in all analyzed vineyard peach
samples. Generally, the vineyard peaches cultivated in Southern
Serbia are a rich source of phenolics, which show evident
antioxidant activity. Also, they are a rich source of minerals
required for a human organism.
... Many pharmacological studies have been carried out in different Syzygium species. Antimicrobial activities [2] [3] , antifungal, antitumor, antihyperglycemic, antihyperlipidemic, antioxidant, antidiabetic and antigastric ulcer activities of Syzygium cumini and Eugeina jambolana extracts [4] [5] [6] [7] [8] [9] [10] , cyctotoxicity of Syzygium samarangense [11] [12] , superoxide anion radical scavenging activities of Syzygium aromaticum buds [13] , antioxidant activities of Syzygium aqueum [14] , oxygen radical absorbance, total reducing capacity and ferric reducing power of Syzygium anisatum [15] , antiulcerogenic activities of Syzygium jambos [16] and superoxide radical and hydroxyl radical scavenging activities of Syzygium aromaticum buds [17] have been studied. Recently, Syzygium cumini and Syzygium jumbo leaves extracts are used for synthesis of silver nanoparticles [18] [19] . ...
Objective
To determine the minerals, Iron (Fe), Sodium (Na), Potassium (K), Manganese (Mn) and trace elements, Lead (Pb), Copper (Cu), Cadmium (Cd) and Zinc (Zn) in two tropical medicinal plants (Syzygium caryophyllatum and Syzygium densiflorum).Methods
All the elements were determined by using atomic absorption spectrophotometer (AAS).ResultsThe average concentrations of Fe, Zn, Cu, Mn, Pb and Cd detected in leaves of Syzygium caryophyllatum and Syzygium densiflorum were 99.275±0.022, 17.302±0.010, 45.498±0.072, 47.344±0.021, 7.634±0.050, 0.253±0.003 and 93.829±0.015, 17.412±0.064, 64.866±0.058, 31.777±0.051, 6.768±0.010 and 0.343±0.004, respectively.Conclusions
The mineral contents in the medicinal plants are at different levels. Therefore, these medicinal plants are rich in some essential elements and very least amount in trace elements, especially Fe and Mn which are essential for human health.
... To date, information on the presence of phytochemicals associated with health benefits of Australian native fruits has been missing. Recently, major phenolic compounds, organic acids, vitamin C levels, and antioxidant capacity of hydrophilic extracts obtained from commercially grown native Australian fruits have been reported (Konczak, Zabaras, Dunstan, & Aguas, 2010). This study evaluates for the first time the oxygen radical absorbance capacity of lipophilic (ORAC-L) extracts of the same fruits, their contribution to the total oxygen radical absorbance capacity (ORAC-T) and possible sources of this capacity. ...
Faba bean phenolic compounds encompassed phenolic acids, flavonols, proanthocyanidins and anthocyanins. Roasting faba beans for 120 min decreased the total phenolic, flavonoid and proanthocyanidin contents by 42, 42 and 30 %, respectively. Roasting beans for 120 min decreased the 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity, total equivalent antioxidant capacity and ferric reducing antioxidant power by 48, 15 and 8 %, respectively. High performance liquid chromatography-post column derivatisation revealed the generation of new phenolic compounds as a result of roasting. Antioxidant mechanism of bean less-polar phenolic compounds was largely based on free radical scavenging activity. The bean phenolic compounds with reducing capability were heat stable. Roasted faba bean extracts (70 % acetone, v/v) were fractionated into relatively polar and non-polar fractions; the latter contributed the majority of the antioxidant capacity. The extracts from beans with different seed coat colours differed in their phenolic compositions, which suggest different levels of potential benefits to health. Although roasting initially lowers the bean antioxidant capacity, prolonged roasting at 150 °C for 60 min and longer causes generation of new phenolic compounds and an increased antioxidant capacity. The findings encourage a wider ultilisation of faba beans for human foods particularly in baked/roasted products.
Kakadu plum (Terminalia ferdinandiana Exell, Combretaceae) and Illawarra plum (Podocarpus elatus Endl., Podocarpaceae) extracts were fractionated, using a bioassay-guided approach and screened for antioxidant activity [oxygen radical absorbance capacity (ORAC) and cellular antioxidant activity (CAA) assays] and antiinflammatory activity (nitrite concentration and prostaglandin E(2) release in lipopolysaccharide (LPS)-activated murine macrophages). Among 8 fractions obtained from KP and 5 fractions obtained from IP, fraction KPF5 from KP exhibited superior activity in all assays, with an ORAC value of 3,776 ± 603 μmol Trolox/g DW and a CAA value of 52.2 ± 8.6 μmol quercetin equivalents/g DW. In addition, KPF5 further demonstrated an upregulation of the Nrf2/Keap1 ratio in Hep G2 cells. KPF5 also inhibited the expression of COX-2 and iNOS in LPS-activated murine macrophages, potentially through the NF-κB, p44/42 mitogen activated protein kinase and Akt pathways. KPF5 also induced apoptosis and DNA damage in HT-29 cells, as determined by the cytokinesis block micronucleus cytome assay.
Unlabelled:
Davidson's plum (Davidsonia pruriens, F. Muell.), a native to Australian rainforests, large, crimson-red fruit, which superficially resembles plum, has been commercially cultivated in Australia since 1990s. The current production volume exceeds market demands therefore this study was designed to evaluate the suitability of Davidson's plum extract as a source of anthocyanin-based food colorant. The stability of the Davidson's plum extract towards heat treatment at 95 °C was higher than that of commercial mulberry colorant, but inferior to colorants derived from red cabbage and purple sweetpotato. An addition of a variety of phenolic acids significantly increased color intensity indicating the formation of copigmentation complexes. Commercial chlorogenic acid as well as extract from a native Australian herb rich in chlorogenic acid, Tasmannia pepper leaf (Tasmannia lanceolata, R. Br.), were both tested in model soft drink solutions subjected to light irradiation and heat treatment. In both cases, the addition of the copigment resulted in a lasting increase in color intensity. In conclusion, Davidson's plum extract can successfully be utilized as a source of natural food color. Extract from Tasmania pepper leaf can be used as a co-pigment for Davidson's plum anthocyanins.
Practical application:
The color properties of an anthocyanin colorant derived from the native Australian fruit Davidson's plum are comparable to those of mulberry, which is currently applied as a food colorant in Australian food products. Utilization of Davidson's plum fruit as a source of natural color will allow the industry to increase the range of natural pigments and will create new opportunities for the emerging native food industry.
For at least 40-50,000 years, plants played an important but supplementary role in the animal-dominated diet of Australian Aboriginal (AA) hunter-gatherers. New knowledge of the nutrient composition and the special physiological effects of their foods provides another perspective in the current debate on the composition of the 'prudent' diet and the diet on which humans evolved. In the present paper we have calculated the average nutrient composition of over 800 Aboriginal plant foods (in total and by food group) and highlighted the differences between these and modern cultivated foods. The data enable us to calculate the absolute contribution of plant foods to total food and nutrient intake of traditional living AA. If plants provided 20-40% of the energy in the diet (the most likely range), then plants would have contributed 22-44 g protein, 18-36 g fat, 101-202 g carbohydrate, 40-80 g fibre and 90-180 mg vitamin C in a 12500 kJ (3000 kcal) diet. Since all the carbohydrate came from plant foods, the traditional AA diet would have been relatively low in carbohydrate (especially starch) but high in dietary fibre in comparison with current recommendations. Over half the carbohydrate could have been in the form of sugars derived from fruit and honey. The low glycaemic index of their carbohydrate foods, however, would generate a relatively low demand for insulin secretion and this characteristic may have protected AA from a genetic predisposition to insulin resistance and its consequences (non-insulin-dependent diabetes mellitus, coronary heart disease, obesity). The dietary pattern and active lifestyle of recent hunter-gatherers such as AA may be a reference standard for modem human nutrition and a model for defence against diseases of affluence.
A method is described for determining and quantitating organic acids (oxalic, malic, citric, and fumaric) and vitamin C by liquid chromatography with a UV-visible detector that allows simultaneous monitoring at 2 wavelengths. The method was applied to samples of green beans (Phaseolus vulgaris L.). Recoveries were 97.8% for oxalic acid, 98.9% for malic acid, 98.7% for citric acid, 99.2% for fumaric acid, and 98.5% for vitamin C. Method precisions (coefficients of variation) were 1.7% for oxalic acid, 0.8% for malic acid, 0.9% for citric acid, 1.5% for fumaric acid, and 1.2% for vitamin C. Measurement precisions (coefficients of variation) were 1.32% for oxalic acid, 0.33% for malic acid, 0.62% for citric acid, 1.01% for fumaric acid, and 0.39% for vitamin C. Limits of detection were 0.025 mg/mL for oxalic acid, 0.022 mg/mL for malic acid, 0.024 mg/mL for citric acid, 1.0 x 10(-4) mg/mL for fumaric acid, and 2.7 x 10(-4) mg/mL for vitamin C.
We investigated whether the consumption of fruit and vegetables lowered cancer mortality in a cohort of 2112 Welsh men ages 45-69 years (The Caerphilly Study), which was followed-up for 13.8 years. At baseline (between 1979 and 1983), participants completed a 56-item food frequency questionnaire from which the consumption of fruit and vegetables was calculated. Relative risks (RR) were estimated with Cox proportional hazard analysis, with death from various types of cancer as a dependent variable, and fruit, vegetables, vitamin C, beta-carotene, dietary fiber, and potential confounders as independent variables. Mean consumption of vegetables and fruit at baseline was 118 g/day and 83 g/day, respectively. During follow-up 114 men died from cancer, including 51 men who died from respiratory tract cancer and 45 men who died from digestive tract cancer. Fruit consumption and the intake of dietary fiber were inversely related to respiratory tract cancer, but after adjustment for potential confounders including age, smoking, and social class, the association with fruit consumption became nonsignificant. Vegetable and fruit consumption was, independently from other risk factors, inversely related to mortality from cancer of the digestive tract (P for trend = 0.021), mainly due to an inverse association with fruit consumption (RR for the highest quartile versus the lowest was 0.3; 95% CI, 0.1-0.8). Vitamin C, beta-carotene, and dietary fiber were not significantly associated with cancers of the digestive tract. Vegetable and fruit consumption was also inversely related to all-cause cancer mortality, and the strongest association was observed for fruit consumption (RR in the highest versus lowest quartile was 0.5; 95% CI, 0.3-1.0). Consumption of vegetables and particularly the consumption of fruit could considerably lower the risk of dying from cancer in middle-aged men.
Polyphenols in food plants are a versatile group of phytochemicals with many potentially beneficial activities in terms of disease prevention. In vitro cell culture experiments have shown that polyphenols possess antioxidant properties, and it is thought that these activities account for disease-preventing effects of diets high in polyphenols. However, polyphenols may be regarded as xenobiotics by animal cells and are to some extent treated as such, ie, they interact with phase I and phase II enzyme systems. We recently showed that dietary plant polyphenols, namely, the flavonoids, modulate expression of an important enzyme in both cellular antioxidant defenses and detoxification of xenobiotics, ie, gamma-glutamylcysteine synthetase. This enzyme is rate limiting in the synthesis of the most important endogenous antioxidant in cells, glutathione. We showed in vitro that flavonoids increase expression of gamma-glutamylcysteine synthetase and, by using a unique transgenic reporter mouse strain, we showed increased expression in vivo, with a concomitant increase in the intracellular glutathione concentrations in muscles. Because glutathione is important in redox regulation of transcription factors and enzymes for signal transduction, our results suggest that polyphenol-mediated regulation of glutathione alters cellular processes. Evidently, glutathione is important in many diseases, and regulation of intracellular glutathione concentrations may be one mechanism by which diet influences disease development. The aim of this review is to discuss some of the mechanisms involved in the glutathione-mediated, endogenous, cellular antioxidant defense system, how its possible modulation by dietary polyphenols such as flavonoids may influence disease development, and how it can be studied with in vivo imaging.
Methods available for the measurement of antioxidant capacity are reviewed, presenting the general chemistry underlying the assays, the types of molecules detected, and the most important advantages and shortcomings of each method. This overview provides a basis and rationale for developing standardized antioxidant capacity methods for the food, nutraceutical, and dietary supplement industries. From evaluation of data presented at the First International Congress on Antioxidant Methods in 2004 and in the literature, as well as consideration of potential end uses of antioxidants, it is proposed that procedures and applications for three assays be considered for standardization: the oxygen radical absorbance capacity (ORAC) assay, the Folin-Ciocalteu method, and possibly the Trolox equivalent antioxidant capacity (TEAC) assay. ORAC represent a hydrogen atom transfer (HAT) reaction mechanism, which is most relevant to human biology. The Folin-Ciocalteu method is an electron transfer (ET) based assay and gives reducing capacity, which has normally been expressed as phenolic contents. The TEAC assay represents a second ET-based method. Other assays may need to be considered in the future as more is learned about some of the other radical sources and their importance to human biology.
The Australian native edible plant industry is rapidly expanding. We provide a review of the horticultural research that has been carried out on the top 14 commercially significant Australian native edible plants; Acacia spp. Miller (wattle), Acronychia acidula F.Muell. (lemon aspen), Backhousia citriodora F.Muell. (lemon myrtle), Eremocitrus glauca (Lindl.) Burkill (desert lime) and Microcitrus spp. Swingle (native lime), Hibiscus heterophyllus Vent. and Hibiscus sabdariffa L. (rosella), Kunzea pomifera F.Muell. (muntries), Podocarpus elatus R.Br. ex Endl. (Illawarra plum), Prostanthera spp. La Billardiere (native mint), Santalum acuminatum R.Br. (quandong), Solanum centrale Black (bush tomato), Syzygium leuhmannii F.Muell. (riberry), Tasmannia spp. R.Br. (native pepper), Terminalia ferdinandiana (= T. latipes Benth.subsp.psilocarpa Pedley) (kakadu plum) and Tetragonia tetragonioides (Pallas) Kuntze (warrigal greens). The research on most of these species has focused on propagation, breeding, cultivation, nutritional value and the isolation of natural products. On none of the species has research been completed in all these areas, and three species have no research published on them. We describe horticultural research on two other commercial species, Backhousia anisata Vickery (aniseed myrtle) and Davidsonia pruriens F.Muell. var. pruriens and var. jerseyana (Davidson's plum), and one species with commercial potential, Pringlea antiscorbutica R.Br. ex Hook.f. (kerguelen cabbage). We identify areas that require further research and issues of concern, such as indigenous intellectual property rights and environmental implications.
Acerola (Malpighia emarginata DC.) is a wild plant from Central America. This fruit is well known as an excellent food source of vitamin C, and it also contains phytochemicals such as carotenoids and polyphenols. The present work evaluates the antioxidant capacity of hydrophilic extracts of acerola pulps and juices by 2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), ORAC and 1,1-diphenyl-2-picrylhydrazyl (DPPH) methods. Antioxidant activity values obtained for acerola juice were higher than those reported for other fruit juices particularly rich in polyphenols such as strawberry, grape and apple juices, among others. Vitamin C, total phenol index (TPI), total anthocyanins and polyphenolic compounds by high performance liquid chromatography (HPLC), as main factors responsible for antioxidant activity, were determined. Contents in total ascorbic acid ranged from 6.32 to 9.20gkg−1 of pulp and 9.44 to 17.97gL−1 of juice. Five different polyphenolic compounds were identified in the samples by means of HPLC and diode-array detection: chlorogenic acid, (−)-epigallocatechin gallate, (−)-epicatechin, procyanidin B1 and rutin, being the two last predominant. By means of solid phase extraction (SPE) three soluble polyphenolic fractions (phenolic acids, anthocyanins and flavonoids) were separated from the different sample extracts, and their respective antioxidant activities calculated. Among them, phenolic acids are the main contributors to the antioxidant activity.
High performance liquid chromatography combined with laboratory robotic extraction procedures was utilized to determine the ascorbic acid and the dehydroascorbic acid content of the principal sources of vitamin C in the American diet. Variation of the vitamin content from sample to sample and source to source is studied and it is concluded that human diet studies should be accompanied by nutrient composition studies to determine reliable vitamin C intake. A case study on broccoli provided guidelines for the proper storage conditions required, if necessary, in order to obtain reliable data on vitamin C intake.
An analytical procedure to determine major sugars and organic acids, including vitamin C, in fruits was developed using a C18 Sep-Pak cleanup process and an ion exclusion HPLC column. Dual UV monitoring and refractive index were performed for detection. To attain optimal separation and quantitation, 0.0085N H2SO4 was used as the mobile phase and the column temperature was maintained at 23 °C. This procedure was compared to others for the individual quantitation of sugars, organic acids, and vitamin C. Recovery and reproducibility of this analytical procedure were quite acceptable for strawberry and four other common fruits, allowing the analysis of all the components using a single-injection HPLC analysis in <22 min. Keywords: Simultaneous analysis; high-performance liquid chromatography; sugars; organic acids; vitamin C; strawberry; fruits
Organic acids were determined in juices and peels of mature fruits of Washington Navel and Valencia oranges, grapefruit, lemon, tangerine, and Palestine sweet lime. Juices and peels were freeze-dried, and organic acids were determined by silicic-acid chromatography. Cation-exchange resin in the hydrogen form was used for acidification of peel prior to extraction of acids with methanol. Citric acid predominated in all juices except that of the sweet lime (in which citrate level was so low that malate exceeded it). Malate occurred in all juices in low but measurable concentrations. Oxalate predominated in the peels, but in the lime, malonate appeared in equivalent amounts. Malonate appeared in all peels in measurable amounts, and in some peels was exceeded only by oxalate. Malic and citric acids were also determined in each peel. At least 15 peaks appeared with each peel, and paper chromatography of the effluents indicated the presence of more than one component in several peaks.
Twelve native Australian fruits, finger lime (red and yellow), riberry, brush cherry, Cedar Bay cherry, muntries, Illawarra plum, Burdekin plum,
Davidson's plum, Kakadu plum, Molucca raspberry and Tasmanian Pepper, were investigated for their antioxidant capacity and presence of
phenolic compounds, anthocyanins and ascorbic acid. The radical scavenging activities of five of the evaluated fruits were significantly higher (3.1
to 5.2-fold in the TEAC assay and 1.2 to 4.2-fold in the PCL assay, respectively) than that of the control blueberry, cv. Biloxi. The total phenolics
level (Folin–Ciocalteu assay) in six of the twelve fruits was 2.5 to 3.9-fold of that of blueberry. Kakadu plum was identified as the richest source
of ascorbic acid (938-fold of that of control). A high correlation between total phenolics (but not anthocyanins) and antioxidant capacity was
observed. The HPLC-DAD/ESI/MS-MS profiles revealed simple anthocyanin composition (one to four individual pigments) with cyanidin as the
dominating type. Australian native fruits investigated in this study are shown to be a novel rich source of antioxidant compounds.
The quality attributes and gas production of fresh-cut kiwifruit slices (Actinidia deliciosa cv. Hayward) were studied to identify the optimum ranges of storage temperature, relative humidity, and atmospheric composition. Also the effects of wounding, C2H4 addition or removal, and chemical treatments (calcium, ascorbic acid, citric acid) on deterioration rate were investigated. Flesh softening was the major quality loss of stored fresh-cut kiwifruit slices. Fresh-cut kiwifruit slices had a shelf-life of 9–12 days if treated with 1% CaCl2 or 2% Ca lactate, and stored atO-2°C and >90% relative humidity in an C2H4-free atmosphere of 2 to 4 kPa O2 and/or 5to10kPaCO2.
Capsicums (green and red), cucumbers, custard apples, lemons, lychees, mandarins, mangoes, nectarines, papaws, peaches, persimmons, and zucchinis were irradiated at 0, 75, or 300 Gy in replicated factorial experiments. Commodities were analyzed shortly after irradiation and again after 3 to 4 weeks of storage at 1–7°C for soluble solids, pH, titratable, acidity, internal color, total vitamin C, dehydroascorbic acid, organic acids, and sugars. Significant (p < 0.05) small changes were recorded in some variables for some commodities. Storage effects were greater than irradiation effects however.
High CO2 concentrations as well as controlled atmosphere storage are widely used to extend the storage and shelf-life of many fruits. To investigate the effect of these storage procedures on several berry fruits, strawberries, raspberries, currants and blackberries were stored at three different elevated CO2 concentrations, with or without a parallel reduction in O2. Vitamin C content (ascorbic acid plus dehydroascorbic acid) was reduced by high CO2 concentrations (10–30% CO2), particularly in strawberries. This reduction in vitamin C was moderate in black currants and blackberries and almost absent in raspberries and red currants when compared with strawberries. Reducing the O2 concentration in the storage atmosphere in the presence of high CO2 had little effect on the vitamin C content. Ascorbic acid was more diminished at high CO2 than dehydroascorbic acid. This suggests a stimulating effect of high CO2 concentrations on the oxidation of ascorbic acid and/or an inhibition of mono- or dehydroascorbic acid reduction to ascorbic acid.
The total antioxidant activity of 12 fruits and 5 commercial fruit juices was measured in this study using automated oxygen radical absorbance capacity (ORAC) assay. On the basis of the wet weight of the fruits (edible portion), strawberry had the highest ORAC activity (micromoles of Trolox equivalents per gram) followed by plum, orange, red grape, kiwi fruit, pink grapefruit, white grape, banana, apple, tomato, pear, and honeydew melon. On the basis of the dry weight of the fruits, strawberry again had the highest ORAC activity followed by plum, orange, pink grapefruit, tomato, kiwi fruit, red grape, white grape, apple, honeydew melon, pear, and banana. Most of the antioxidant capacity of these fruits was from the juice fractions. The contribution of the fruit pulp fraction (extracted with acetone) to the total ORAC activity of a fruit was usually less than 10%. Among the commercial fruit juices, grape juice had the highest ORAC activity followed by grapefruit juice, tomato juice, orange juice, and apple juice.
A simple, automated test measuring the ferric reducing ability of plasma, the FRAP assay, is presented as a novel method for assessing "antioxidant power." Ferric to ferrous ion reduction at low pH causes a colored ferrous-tripyridyltriazine complex to form. FRAP values are obtained by comparing the absorbance change at 593 nm in test reaction mixtures with those containing ferrous ions in known concentration. Absorbance changes are linear over a wide concentration range with antioxidant mixtures, including plasma, and with solutions containing one antioxidant in purified form. There is no apparent interaction between antioxidants. Measured stoichiometric factors of Trolox, alpha-tocopherol, ascorbic acid, and uric acid are all 2.0; that of bilirubin is 4.0. Activity of albumin is very low. Within- and between-run CVs are <1.0 and <3.0%, respectively, at 100-1000 micromol/liter. FRAP values of fresh plasma of healthy Chinese adults: 612-1634 micromol/liter (mean, 1017; SD, 206; n = 141). The FRAP assay is inexpensive, reagents are simple to prepare, results are highly reproducible, and the procedure is straightforward and speedy. The FRAP assay offers a putative index of antioxidant, or reducing, potential of biological fluids within the technological reach of every laboratory and researcher interested in oxidative stress and its effects.
In order to ascertain the role of dietary flavonoids as antioxidants in vivo it is necessary to understand the chemical nature of the absorbed forms in the circulation in vivo and how the multiplicity of research findings in vitro reflect the bioactivity of flavonoids in vivo. Only when we gain adequate information on the circulating forms can we begin to understand the targeting to the tissues, whether flavonoids cross the blood-brain barrier, for example, and in what forms. Flavonoids are powerful antioxidants in vitro, but their overall function in vivo has yet to be clarified, whether antioxidant, anti-inflammatory, enzyme inhibitor, enzyme inducer, inhibitor of cell division, or some other role. It should also be emphasised that the reducing properties of flavonoids might contribute to redox regulation in cells, independently of their antioxidant properties, and thus might protect against cell ageing, for example, by working together with the intracellular reductant network. To gain understanding of these issues the factors influencing the absorption of flavonoids in the gastrointestinal tract needs to be established, namely the questions of: de-glycosylation before absorption, conjugation in the small intestine through glucuronidation, sulphation or methylation etc, metabolism and degradation in the colon to smaller phenolic molecules. The forms in which they circulate in vivo will influence their polarity and, thus, their localization and bioactivities in vivo. Finally if antioxidant activities are important, the elucidation of how such properties in vitro relate to the potential for conjugates and metabolites in vivo to act as antioxidants is required. The absorbed flavonoid components might function in the aqueous phase (like vitamin C) or in the lipophilic milieu (as vitamin E) in vivo. This will depend on their polarity properties on uptake, how they are metabolised on absorption, and their resulting structural forms in the circulation.
Phenolic profiles of a total of 26 berry samples, together with 2 apple samples, were analyzed without hydrolysis of glycosides with HPLC. The phenolic contents among different berry genera varied considerably. Anthocyanins were the main phenolic constituents in bilberry, bog-whortleberry, and cranberry, but in cowberries, belonging also to the family Ericaceae genus Vaccinium, flavanols and procyanidins predominated. In the family Rosaceae genus Rubus (cloudberry and red raspberry), the main phenolics found were ellagitannins, and in genus Fragaria (strawberry), ellagitannins were the second largest group after anthocyanins. However, phenolic acids were dominant in rowanberries (genus Sorbus) and anthocyanins in chokeberry (genus Aronia). In the family Grossulariaceae genus Ribes (currants and gooseberry), anthocyanins predominated, as well as in crowberries (family Empetraceae genus Empetrum). In apples, hydroxycinnamic acids were the main phenolic subgroup. Extraction methods for berries and apples were studied to produce phenolic extracts with high antioxidant activity. Evaluation of antioxidant activity was performed by autoxidazing methyl linoleate (40 degrees C, in the dark). The extraction method affected remarkably both the phenolic composition and the antioxidant activity, but with statistical analysis the observed activity could not be well explained with the contents of individual phenolic subgroups.
An improved method of oxygen radical absorbance capacity (ORAC) assay has been developed and validated using fluorescein (3',6'-dihydroxyspiro[isobenzofuran-1[3H],9'[9H]-xanthen]-3-one) as the fluorescent probe. Our results demonstrate that fluorescein (FL) is superior to B-phycoerythrin. The oxidized FL products induced by peroxyl radical were identified by LC/MS, and the reaction mechanism was determined to follow a classic hydrogen atom transfer mechanism. In addition, methodological and mechanistic comparison of ORAC(FL) with other widely used methods was discussed. It is concluded that, unlike other popular methods, the improved ORAC(FL) assay provides a direct measure of hydrophilic chain-breaking antioxidant capacity against peroxyl radical.
There is an increasing awareness of the role of certain nutritional components, including dietary flavonoids found in fruit, vegetables and beverages, in the maintenance of health and prevention of chronic diseases. In this regard, recent studies highlight an exciting role with respect to their potential neuroprotective actions, in particular towards deficits commonly observed with aging, such as reduced performance of cognitive, memory and learning tasks. These neurological functions, and possible mechanisms involved in controlling them, can be influenced by supplementation of single dietary flavonoids, or as part of a flavonoid-rich preparation. With this, a renewed emphasis is aimed at further understanding their modes and sites of action. Moreover a common theme among many in vitro studies examining mechanisms of neuroprotection is the failure to include biologically relevant metabolites of the flavonoids known to enter the circulation, and thus most likely to be bioavailable to cells and tissues. This oversight will ultimately influence the mechanisms of action proposed to explain the neuroprotection observed in animals and human studies. As such, emerging findings suggest a variety of potential mechanisms of action of flavonoids and their bioavailable metabolites in cytoprotection against oxidative stress, which may be independent of conventional antioxidant reducing activities. Such mechanisms might involve their interaction with cell signalling cascades, their influence on gene expression and the down regulation of pathways leading to cell death.
Anthocyanins, which are used as a food coloring, are widely distributed in human diets, suggesting that we ingest large amounts of anthocyanins from plant-based foods. Mice were fed control, cyanidin 3-glucoside-rich purple corn color (PCC), high fat (HF) or HF + PCC diet for 12 wk. Dietary PCC significantly suppressed the HF diet-induced increase in body weight gain, and white and brown adipose tissue weights. Feeding the HF diet markedly induced hypertrophy of the adipocytes in the epididymal white adipose tissue compared with the control group. In contrast, the induction did not occur in the HF + PCC group. The HF diet induced hyperglycemia, hyperinsulinemia and hyperleptinemia. These perturbations were completely normalized in rats fed HF + PCC. An increase in the tumor necrosis factor (TNF)-alpha mRNA level occurred in the HF group and was normalized by dietary PCC. These results suggest that dietary PCC may ameliorate HF diet-induced insulin resistance in mice. PCC suppressed the mRNA levels of enzymes involved in fatty acid and triacylglycerol synthesis and lowered the sterol regulatory element binding protein-1 mRNA level in white adipose tissue. These down-regulations may contribute to triacylglycerol accumulation in white adipose tissue. Our findings provide a biochemical and nutritional basis for the use of PCC or anthocyanins as a functional food factor that may have benefits for the prevention of obesity and diabetes.
Epidemiologic studies suggest that higher polyphenol intake from fruits and vegetables is associated with decreased risk for cardiovascular disease. The mechanisms explaining this observation remain unclear. This review summarizes data suggesting that flavonoids improve endothelial function and inhibit platelet aggregation in humans. The vascular endothelium is a critical regulator of vascular homeostasis, and endothelial dysfunction contributes to the pathogenesis and clinical expression of coronary artery disease. Platelet aggregation is a central mechanism in the pathogenesis of acute coronary syndromes, including myocardial infarction and unstable angina. For these reasons, the observed effects of flavonoids on endothelial and platelet function might explain, in part, the observed beneficial effects of flavonoids on cardiovascular disease risk.
The antioxidant activity of phenolics in fruits of blueberry (Vaccinium corymbosum cv. Sierra), cranberry (Vaccinium macrocarpon cv. Ben Lear), wild chokeberry (Aronia melanocarpa), and lingonberry (Vaccinium vitis-idaea cv. Amberland) was determined in this study. The phenolic constituents and contents among the different berries varied considerably. Anthocyanins were found to be the main components in all these berries. Chlorogenic acid in blueberry, quercetin glycosides in cranberry and lingonberry, and caffeic acid and its derivative in chokeberry were also present in relatively high concentrations. Chlorogenic acid, peonidin 3-galactoside, cyanidin 3-galactoside, and cyanidin 3-galactoside were the most important antioxidants in blueberry, cranberry, wild chokeberry, and lingonberry, respectively. The contribution of individual phenolics to the total antioxidant capacity was generally dependent on their structure and content in the berries. Phenolics such as quercetin and cyanidin, with 3',4'-dihydroxy substituents in the B ring and conjugation between the A and B rings, had highly effective radical scavenging structures in blueberries, cranberries, chokeberries, and lingonberries. Phenolic acids such as caffeic acid also showed high antioxidant activity, probably due to its dihydroxylation in the 3,4 positions as hydrogen donors.
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