Antioxidant properties of anthocyanins extracted from litchi (Litchi chinenesis Sonn.) fruit pericarp tissues in relation to their role in the pericarp browning

Anthocyanins were extracted and purified from litchi fruit pericarp and their antioxidant properties were investigated. Effects of exogenous anthocyanin treatments on pericarp browning and membrane permeability of harvested litchi fruit were also evaluated. Anthocyanins from litchi fruit pericarp strongly inhibited linoleic acid oxidation and exhibited a dose-dependent free-radical-scavenging activity against DPPH radical, superoxide anions and hydroxyl radical. The degradation of deoxyribose by hydroxyl radicals was shown to be inhibited by anthocyanins acting mainly as chelators of iron ions rather than directly scavenging hydroxyl radicals. Anthocyanins were also found to have excellent reducing power. The reducing power of anthocyanins, ascorbic acid and butylated hydroxytoluene all at 100 μg/ml were 3.70, 0.427 and 0.148, respectively, indicating that anthocyanins from litchi pericarp had a strong electron-donating capacity. Furthermore, application of anthocyanins to harvested litchi fruit significantly prevented pericarp browning and delayed the increase in membrane permeability. It was therefore suggested that anthocyanins could be beneficial in scavenging free radicals and reducing lipid peroxidation of litchi fruit pericarp.     

Chemical constituents with antioxidant activities from litchi (Litchi chinensis Sonn.) seeds

Litchi (Litchi chinensis Sonn.) is widely accepted as a delicious fruit in China and its seeds have been commonly used in traditional Chinese medicine to relieve neuralgic pain. In the present study, chemical investigation of the 95% ethanol extract of Litchi chinensis seeds led to the isolation of four new compounds, 2α,3α-epoxy-5,7,3′,4′-tetrahydroxyflavan-(4β-8-catechin) (5), 2β,3β-epoxy-5,7,3′,4′-tetrahydroxyflavan-(4α-8-epicatechin) (7), litchiol A (9) and litchiol B (12), together with 11 known ones, 2,5-dihydroxy-hexanoic acid (1), soscopoletin (2), coumaric acid (3), protocatechuic acid (4), 2α,3α-epoxy-5,7,3′,4′-tetrahydroxyflavan-(4β−8)-epicatechin (6), pterodontriol d-6-O-β-d-glucopyranoside (8), Narirutin (10), naringin (11), dihydrocharcone-4′-O-β-d-glucopyranoside (13), pinocembrin-7-rutinoside (14), pinocembrin-7-neohesperidoside (15). Their structures were mainly elucidated on the basis of NMR, MS, IR, CD and UV spectral evidences. Antioxidant activities of 14 compounds were determined by DPPH radical-scavenging assay and Trolox equivalent antioxidant capacity assay, and the results showed that four compounds, protocatechuic acid (4), 2α,3α-epoxy-5,7,3′,4′-tetrahydroxyflavan-(4β-8-catechin (5), 2α,3α-epoxy-5,7,3′,4′-tetrahydroxyflavan-(4β−8)-epicatechin (6), 2β,3β-epoxy-5,7,3′,4′-tetrahydroxyflavan-(4α-8)-epicatechin (7), exhibited moderate antioxidant activities.     

Antioxidant properties of polymeric proanthocyanidins from fruit stones and pericarps of Litchi chinensis Sonn

Fruit stones and pericarps of Litchi chinensis, waste products of the food, were studied as a source of polymeric proanthocyanidins. The structures of the polymeric proanthocyanidins isolated from Litchi chinensis were characterized by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) coupled with high performance liquid chromatography electrospray ionization mass spectrometry (HPLC-ESI-MS) analysis. The spectra obtained through MALDI-TOF MS analysis revealed that the dominant A-type procyanidin polymers occurred in each polymer length with one or more A-type linkages. The polymeric proanthocyanidins of litchi fruit stones exhibited longer polymer length than those of fruit pericarps, with polymerization degrees up to 20 and 11 for fruit stones and pericarps, respectively. After depolymerization with toluene-??-thiol, HPLC-ESI-MS analysis showed that epicatechin and A-type dimer were the major constituent units, and the mean polymerization degrees were 15.4 and 5.8 for polymeric proanthocyanidins of fruit stones and pericarps, respectively. The antioxidant properties investigated using DPPH, ABTS and FRAP methods showed that the higher polymerization degree of polymeric proanthocyanidins from litchi fruit stones exhibited higher antioxidant activities than those from litchi pericarps.     

Antioxidant and radioprotective properties of commercially grown litchi (Litchi chinensis) from India

In an earlier study, radiation treatment (0.5 kGy) and low temperature (4 °C) storage were found to extend the shelf life of litchi fruit var. ‘Shahi’ and ‘China’ from India up to 28 days, while maintaining its physical, biochemical and organoleptic properties. The current study was aimed to elucidate the antioxidant and radioprotective properties of the litchi fruit, and the effect of radiation processing on these properties. The litchi fruit was found to be significantly rich in antioxidant and radioprotective properties, and the antioxidant parameters were found to be well correlated with the phenolic and flavonoid contents. A significant protection to pBR322 plasmid DNA and Escherichia coli cells from radiation induced damage was observed in the presence of litchi juice. Plasmid DNA was well protected even at the dose of 5 kGy, whereas, bacterial cells could be protected up to 0.5 kGy. Neither of these properties was found to be sensitive to radiation processing or low temperature storage.     

Identification of phenolic compounds and appraisal of antioxidant and antityrosinase activities from litchi (Litchi sinensis Sonn.) seeds

Antioxidant and antitryrosinase compounds from Litchi sinensis Sonn. seeds were extracted with five different types of polar solvents. The five extracts, namely ethanol extract (EE), 50% ethanol extract (50% EE), methanol extract (ME), 50% methanol extract (50% ME), and water extract (WE), were used for the evaluations of total phenolic content, antioxidant capabilities and antityrosinase activity. The 50% EE showed the highest total antioxidant capacity, scavenging the 1,1-diphenyl-2-picryl hydrazyl (DPPH) radical and inhibitory activity against lipid peroxidation, and it was comparable to the activity of the synthetic antioxidant, butylated hydroxyl toluene. Fifty percent EE showed a better antityrosinase activity compared to the other extracts. After application of reverse phase high performance liquid chromatography, coupled to a diode array detector and electrospray ionisation mass spectra, five phenolic compounds, namely, gallic acid, procyanidin B2, (−)-gallocatechin, (−)-epicatechin and (−)-epicatechin-3-gallate were identified from 50% EE. This study suggests that litchi seed can potentially be used as a readily accessible source of natural antioxidants.     

Antioxidant properties of various solvent extracts of mulberry (Morus indica L.) leaves

The antioxidant properties and total phenolic contents of methanol, acetone and water extracts of mulberry (Morus indica L.) leaves were examined. Various experimental models including iron (III) reducing capacity, total antioxidant capacity, DPPH radical scavenging activity and in vitro inhibition of ferrous sulphate-induced oxidation of lipid system were used for characterization of antioxidant activity of extracts. The three extracts showed varying degrees of efficacy in each assay in a dose-dependent manner. Methanolic extract with the highest amount of total phenolics, was the most potent antioxidant in all the assays used. In addition, the effect of temperature (50 °C and 100 °C), pH (3, 5, 7, 9 and 11) and storage (5 °C) on the antioxidant activity of methanolic extract was investigated. The antioxidant activity of the extract remained unchanged at 50 °C and was maximum at neutral pH. The extract stored at 5 °C in the dark was stable for 30 days after which the antioxidant activity decreased (p ? 0.05) gradually. On the basis of the results obtained, mulberry leaves were found to serve as a potential source of natural antioxidants due to their marked antioxidant activity.     

Evaluation of antioxidant ability of ethanolic extract from dill (Anethum graveolens L.) flower

Antioxidant activities of ethanolic extract from dill flower and its various fractions were evaluated with 2,2-diphenyl-1-picrylhydrazyl radical scavenging, Trolox equivalent antioxidant capacity, reducing power, chelating power, and β-carotene bleaching assays. The flower extract was successively separated into n-hexane, ethyl acetate and ethanol soluble fractions by liquid–liquid partition. Dill leaf and seed extracts were used for comparison. In all assays, the flower extract showed higher antioxidant activity than the leaf and seed extracts. With regard to various fractions of the flower extract, the sequence for antioxidant activity was ethyl acetate fraction > ethanol fraction > original flower extract > n-hexane fraction. Phenols including flavonoids and proanthocyanidins should be responsible for antioxidant abilities of the flower extract. Chlorogenic acid, myricetin, and 3,3’,4′,5,7-pentahydoxyflavan (4 → 8)-3,3′,4′,5,7-pentahydoxyflavan were the major phenolic acid, flavonoid, and proanthocyanidin, respectively, in the dill flower extract.     

Antioxidant properties of extracts from juemingzi (Cassia tora L.) evaluated in vitro

Methanol extract from juemingzi (Cassia tora L.) was fractionated by liquid-liquid partition using ethyl acetate, n-butanol and water, respectively. The antioxidant activity of three different fractions was evaluated using different antioxidant tests, including inhibition of peroxidation of linoleic acid, reducing power, free-radical scavenging and ferrous ions chelating activity. In the above four assays, all the fractions showed antioxidant potential to varying degrees. Among these fractions, ethyl acetate fraction exhibited more antioxidant potency than other fractions. Furthermore, ethyl acetate fraction was found to be more effective in protecting LDL against oxidation in a concentration-dependent manner. The data suggest that juemingzi especially ethyl acetate-soluble fraction may have a preventive effect against atherosclerosis by inhibiting LDL oxidation.     

Composition of flavonoids and phenolic acids in lychee (Litchi Chinensis Sonn.) Flower extracts and their antioxidant capacities estimated with human LDL, erythrocyte, and blood models

Abstract: Lychee (Litchi chinensis Sonn.) flower is a major nectar source in Taiwan. Antioxidant activities of acetone, ethanol, and hot‐water extracts of the flower were estimated through three biochemical models: inhibition of Cu²⁺‐induced oxidation of human low‐density lipoprotein, scavenging ability of oxygen radicals in human blood, and inhibition of human erythrocyte hemolysis induced by peroxyl radicals. Composition and content of flavonoids and phenolic acids in these extracts were also determined by high‐performance liquid chromatography. Results showed that antioxidant effects of all test models as well as contents of flavonoids and phenolic acids for the lychee flower extracts were in the order: acetone extract > ethanol extract > hot‐water extract. Gentistic acid and epicatechin were the major phenolic acid and flavonoid in the extracts, respectively.     

Antioxidant activities of Sechium edule (Jacq.) Swartz extracts

The antioxidant activities (AA) of Sechium edule extracts were tested by three established in vitro methods, namely reducing power, β-carotene linoleate model and 1,1- diphenyl-2 picrylhydrazyl (DPPH) radical-scavenging. Leaf ethanolic extracts and leaf and seed water extracts showed strong inhibitory activity by β-carotene bleaching (AA values of 90%). Furthermore, these extracts exerted hydrogen-donating ability in the presence of DDPH stable radical (IC₅₀ 2 μg/ml). These extracts also showed strong reducing power by the potassium ferricyanide reduction method. Leaf and seed extracts may be exploited as biopreservatives in food applications as well as for health supplements or functional food, to aleviate oxidative stress.     

Antioxidant properties of three extracts from Pleurotus citrinopileatus

Pleurotus citrinopileatus Sing. (Lentinaceae) was successfully cultivated and commercially available in Taiwan. The ethanolic, cold and hot water extracts were prepared from P. citrinopileatus fruit bodies, mycelia and fermentation filtrate and their antioxidant properties studied. For three samples, ethanolic extracts exhibited higher antioxidant activities than water extracts. Reducing powers of three extracts from fruit bodies were effective and 1.03-1.10 at 5 mg/ml. With regard to EC₅₀ values of scavenging abilities on 1,1-diphenyl-2-picrylhydrazyl radicals, the effectiveness was in a descending order: ethanolic>hot water>cold water extracts. Scavenging abilities of water extracts from three samples on hydroxyl radicals were 53.4-80.1% at 20 mg/ml. Chelating abilities of cold and hot water extracts on ferrous ions were higher than those of ethanolic extracts. Contents of total phenols were in the descending order: fruit bodies (8.62-12.38 mg/g)>mycelia (5.84-7.85 mg/g)>filtrate (4.80-5.57 mg/g). Overall, three extracts from fruit bodies were more effective in antioxidant properties assayed than those from mycelia and filtrate. Ethanolic extracts were more effective in antioxidant properties assayed, except for scavenging abilities on hydroxyl radicals.     

Antioxidant flavonoid glycosides from the leaves of Ficus pumila L.

The Okinawan folks in Japan use Ficus pumila L. as a beverage or herbal medicine to treat diabetes and high blood pressure. Four flavonoid glycosides were isolated and identified as rutin (1 and 3), apigenin 6-neohesperidose (2), kaempferol 3-robinobioside (4) and kaempferol 3-rutinoside (5). Among these compounds, rutin exhibited the strongest antioxidant activity in DPPH radical scavenging assay and superoxide radical inhibition assay. The preparation of Ooitabi leaves in water provide sufficient amount of flavonoid glycosides to the Okinawan although 50% of aqueous ethanol extracted these flavonoid glycosides more effectively. These results show the potential of Ooitabi leaves as a natural source of antioxidant for health management.     

Antioxidant properties of methanolic extracts from Antrodia camphorata with various doses of γ-irradiation

The mycelia of Antrodia camphorata (Chang & Chou) Wu, Ryvarden & Chang were irradiated with gamma rays at doses of 2.5, 5, 10, 15 and 20 kGy and the antioxidant properties of the methanolic extracts were studied. At 2.5 mg/ml, antioxidant activities of methanolic extracts from 10 to 20 kGy-irradiated mycelia were significantly higher than those of the non-irradiated control. Reducing powers of methanolic extracts from unirradiated and 0.5–7.5 kGy-irradiated mycelia were comparable except for the 20 kGy-irradiated mycelia. At 2.5 mg/ml, all methanolic extracts showed excellent scavenging abilities of 92.3–103% on DPPH radicals. Scavenging abilities of methanolic extracts from 2.5 to 20 kGy irradiated mycelia were better than that of the unirradiated control at 10 mg/ml. With irradiation at 5–20 kGy, mycelia possessed higher chelating ability on ferrous ions than did the unirradiated control. The EC₅₀ values were below 15 mg/ml, except for values of scavenging ability of the unirradiated control on hydroxyl radicals. Total phenols were the major naturally occurring antioxidant components found in the range of 13.0–15.5 mg/g. In summary, γ-irradiation not only maintained the antioxidant properties of mycelia but also enhanced the antioxidant properties to some extent.     

Antioxidant properties of hot water extracts from Agrocybe cylindracea

Agrocybe cylindracea (DC: Fr.) Mre. was available in the form of fruit bodies, mycelia and fermentation filtrate. From these three forms, hot-water extracts were prepared and their antioxidant properties were studied. Antioxidant activities of hot-water extracts from fruit bodies, mycelia and filtrate were 63.6%, 81.6% and 56.8% at 20 mg ml⁻¹, respectively. EC₅₀ values in reducing power were 2.72, 3.97 and 3.09 mg ml⁻¹ whereas those in scavenging abilities of 1,1-diphenyl-2-picrylhydrazyl radicals were 0.62, 1.66 and 0.82 mg ml⁻¹ for fruit bodies, mycelia and filtrate, respectively. At 20 mg ml⁻¹, the scavenging abilities of hydroxyl radicals were 80.1%, 57.0% and 54.3% for fruit bodies, mycelia and filtrate, respectively. With regard to EC₅₀ values in chelating abilities on ferrous ions, the hot-water extract from filtrate was better than that from mycelia. Total phenols were the major naturally occurring antioxidant components found in hot-water extracts and in the range of 23.74–30.16 mg g⁻¹. From EC₅₀ values obtained, it can be concluded that hot-water extracts from three forms of A. cylindracea were good in antioxidant properties.     

Antioxidant properties of water extracts from Monascus fermented soybeans

Solid-state bioprocessing of soybean by Monascus is a biotechnological strategy to produce Monascus-fermented soybeans (MFS) with more beneficial components. The objective of this study was to evaluate the antioxidant properties of cold and hot water extracts from MFS as compared to uninoculated soybeans. With regard to the EC₅₀ values of antioxidant activities, the effectiveness of cold water extracts was in a descending order: soybeans > MFS-31527 > MFS-31499 whereas that of the hot water extracts: soybeans ∼ MFS-31499 > MFS31527. Cold water extracts showed higher reducing power and lower scavenging ability on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals than hot water extracts. For both extracts, MFS and soybeans showed comparable effective chelating abilities on ferrous ions. Total phenols were the major naturally occurring antioxidant components found. For both extracts, soybeans were more effective in antioxidant activity and scavenging ability on DPPH radicals whereas MFS-31499 and MFS-31527 were more effective in reducing power and scavenging ability on hydroxyl radicals. Based on the results obtained, MFS-31499, MFS-31527 and soybeans were relatively effective in the antioxidant properties assayed and might be potential antioxidants for application in food products.     

Comparative antioxidant activity of extracts from leaves,bark and catkins of Salix aegyptiaca sp.

Leaves, bark and catkins of Salix aegyptiaca L. were extracted into solvents of increasing polarity from cyclohexane (non-polar), butanol, ethanol and water (polar) and analysed for their antioxidant capacity, total phenol and flavonoids. The highest antioxidant activity (19 μg/ml IC₅₀ for inhibition of DPPH radical activity), total phenolic content (212 mg gallic acid equivalents/g of dried extract) and total flavonoid (479 mg catechin equivalents/g of dried extract) was observed in the ethanolic extract of bark. HPLC identification of phenolic compounds from the extracts indicated the presence of gallic acid, caffeic acid, vanillin and p-coumaric acid, myricetin, catechin, epigallocatechin gallate, rutin, quercetin as well as salicin. Our data indicates the presence of high amounts of phenols and flavonoids in different parts of S. aegyptiaca species and propose that extracts from this plant may be utilised as a source of health promoting antioxidants.     

Antioxidant properties of methanolic extracts from Agaricus blazei with various doses of γ-irradiation

Agaricus blazei Murrill (Agariaceae) was irradiated with gamma rays at doses of 2.5, 5, 10, 15 and 20 kGy and the antioxidant properties of its methanolic extracts were studied. At 7.5 and 10.0 mg/ml, antioxidant activities of methanolic extracts from 2.5 to 20 kGy γ-irradiated A. blazei were significantly higher than those of methanolic extract from the nonirradiated control. At 0.5-7.5 mg/ml, reducing powers of methanolic extracts from A. blazei with 2.5, 10, 15 and 20 kGy of irradiation and without irradiation were comparable. All methanolic extracts showed excellent scavenging abilities of 95.2-100.7% against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals at 0.5 mg/ml. With regard to the scavenging ability against hydroxyl radicals, unirradiated and γ-irradiated A. blazei were comparable. Total phenols were the major naturally occurring antioxidant components found in the range of 18.77-21.48 mg/g. All EC₅₀ values were below 10 mg/ml, except values in reducing power, scavenging ability against DPPH radicals and chelating ability against ferrous ions were below 1 mg/ml. That indicates the unirradiated and irradiated A. blazei were good in antioxidant properties. Summarily, up to 20 kGy of irradiation did not remarkably affect the amounts of total antioxidant components in A. blazei.     

Antioxidant properties of aqueous extracts from Terminalia catappa leaves

Aqueous extracts were prepared from green, yellow fallen and red fallen leaves of Terminalia catappa L. (Combretaceae) and their antioxidant activity, scavenging and chelating abilities were evaluated. Aqueous extracts from three different leaves showed high antioxidant activities and moderate scavenging abilities on hydroxyl radicals at 1 mg/ml. EC₅₀ values in antioxidant activity were 0.549-0.557 mg/ml whereas those in scavenging ability on hydroxyl radicals were 0.631-0.686 mg/ml for aqueous extracts prepared from three leaves with boiling water for 3 min. EC50 values in reducing power were 0.15-0.23 mg/ml. EC50 values in scavenging abilities on superoxide anion and 1,1-diphenyl-2-picrylhydryl radicals were 0.36-0.44 and 10.4-35.3 mg/ml, respectively. EC50 values in chelating abilities on ferrous and cupric ions were 0.41-2.50 and 8.96-9.89 mg/ml, respectively. Based on the results obtained, the aqueous extracts displayed higher antioxidant properties. Six phenolic compounds identified in the aqueous were p-hydroxybenzoic acid, 4-hydroxyphenylpropionic acid, m-coumaric acid, 3,4-dihydroxybenzoic acid, p-coumaric acid and gallic acid. Therefore, the aqueous extracts from three different leaves of T. catappa might be a potential antioxidant supplement for application in food products or as a drink.     

Antioxidant properties of methanolic extracts from Agrocybe cylindracea

Agrocybe cylindracea (DC: Fr.) Mre. (Bolbitiaceae) was available in the form of fruit bodies, mycelia and fermentation filtrate. From these three forms, methanolic extracts were prepared and their antioxidant properties studied. The methanolic extract from fruit bodies showed high inhibitory ability on lipid oxidation (90.0-97.3%) at 5-20 mg/ml and had an EC₅₀ value of 0.94 mg extract/ml. EC₅₀ values in reducing power were 2.36, 6.89 and 5.00 mg extract/ml for fruit bodies, mycelia and filtrate, respectively. The scavenging ability of the methanolic extract from fruit bodies on 1,1-diphenyl-2-picrylhydrazyl radicals was 89.0% at 1 mg/ml whereas those from mycelia and filtrate was 91.4% and 94.9% at 10 mg/ml, respectively. The chelating abilities of methanolic extracts from fruit bodies, mycelia and filtrate on ferrous ions were 90.6%, 84.6% and 96.3% at 5 mg/ml, respectively. Total phenols were the major detected naturally occurring antioxidant components found in methanolic extracts from A. cylindracea and in the range of 15.55-23.47 mg/g. Based on EC₅₀ values, A. cylindracea was good in antioxidant properties, except for the scavenging ability on hydroxyl radicals.     

The influences of cultivar and thermal processing on the allergenic potency of lychees (Litchi chinensis SONN.)

This study was aimed at the cultivar-specific allergenic potency of lychees (Litchi chinensis SONN.) and its modification by typical industrial processing, investigating the fresh aril of seven different lychee lots which represented five cultivars. Technological focus was on thermal treatments during fruit preservation by canning. Canned lychee halves in syrup were produced by canning at 90 and 121 °C for various times to analyse the final products immediately after processing and after eight-months storage. SDS–PAGE and non-specific silver staining were performed to characterise the protein pattern. The allergenic potency of the proteins was demonstrated by immunoblotting with sera of probands suffering from lychee allergy. Furthermore, the allergenic potency was determined by inhibitive enzyme allergosorbent tests (EAST-inhibition). Any significant dependence between cultivar and the allergenic potency of the fresh fruit could not be established. According to their heat sensitivity during canning, lychee allergens with different behaviour could be distinguished. After excessive canning, inducing severe loss of sensory quality, the allergenic potency of the fruit decreased, even though high residual allergenic activity was observed.