New Source Of Natural Antioxidants Research Articles

CARROT LEAVES: ANTIOXIDATIVE AND NUTRITIVE VALUES

This study was carried out for chemical assess of yellow carrot leaves and possibility to use its methanol and acetone extracts as a new source of natural antioxidants instead of artificial antioxidants due to its negative effect on human health. So, chemical composition of carrot leaves were estimated, as well as methanol and acetone extracts content of phenolic compounds using liquid chromatography and also, antioxidant activity of both extracts were studied prior to the sunflower oil stored in opened bottles stored at 63°C as an oxidation accelerated conditions for 60 days using acid number, peroxide value, antioxidant effectiveness and thiobarbituric acid value changes. Obtained results showed that carrot leaves could be considered as a source of carbohydrates and protein, which represented 61.36% and 20.27% (dry weight), respectively. Also, it was a good source of some minerals such as potassium (975.00 ppm). It was observed that extraction efficiency of methanol was higher than acetone where, it contained 82.07 mg/ml total phenols as galic acids. Both of two extracts had antioxidant effect. It was found that there were no significant differences between control treatment and all treatment up to 45 days of storage and the best antioxidant effectiveness was observed for D treatment (0.15% acetone extract) compared with other treatments. The results also showed that thiobarbituric acid values did not show significant differences between all treatments up to 30 days of storage and it ranged between 0.515 to 0.788 mg malonaldehyde/kg oil. Therefore, it was recommended to use carrot leaves as a new source of natural antioxidants, as well as source of some minerals to fortify some food products.

Antioxidant and antimicrobial effect of some natural plant extracts added to lamb patties during storage

Natural plants are considered an important target to investigate in order to provide a new source of natural antioxidants and/or antimicrobial agents. The optimum concentrations of some natural plant (jojoba, jatropha, ginseng and ginger) extracts were determined and added to lamb patties. Some chemical and microbial characteristics of the prepared patties during storage for 9 days at 4°C were evaluated. Both the addition of these extracts and storage time had a significant effect on the patties throughout the storage period. The effectiveness of the tested natural extracts can be listed in the following order of decreasing Thiobarbituric acid reactive substance (TBARS) values: ginseng > jatropha > jojoba > ginger. Aerobic plate count, mould and yeast counts decreased significantly with addition of the extracts during the storage period. Also, the addition of the extracts was significantly effective in reducing histamine, tyramine and putrescine formation during the storage period. Compared to control patties, the addition of these natural extracts was effective as antioxidant and antimicrobial agents for improving the properties of lamb patties.

Antioxidant condensed tannins from Machilus pauhoi leaves

The acetone-water (1:1, v/v) was more effective solvent for extracting total phenolics and extractable condensed tannins from Machilus pauhoi leaves than methanol, ethanol, acetone, water, methanol-water (1:1, v/v), and ethanol-water (1:1, v/v). The matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) analysis revealed that catechin/epicatechin was the basic units occurring in M. pauhoi leaf condensed tannins, and A-type and B-type linkages were most common among the structural units of polymers. Thiol degradation with cysteamine indicated that the polymer was constituted of (+)-catechin and (-)-epicatechin as the terminal units and (-)-epicatechin as the extension units. The mean degree of polymerization (mDP) of the condensed tannins was 6.96. The condensed tannins from M. pauhoi leaves had more effective 2,2-diphenyl-1-picrylhydrazyl (DPPH) and diammonium salt (ABTS) free radicals scavenging abilities than the ascorbic acid and butylated hydroxyanisole (BHA), and may be considered as a new source of natural antioxidants for food and nutraceutical products. Key words: Machilus pauhoi, condensed tannins, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, reversed phase high performance liquid chromatography, antioxidant activity.

Wild Mediterranean Plants as Traditional Food: A Valuable Source of Antioxidants

Some wild Mediterranean plants used as traditional food are an extraordinary source of antioxidants. We tested some properties of 10 of these herbaceous plants, used in Liguria (Northwest Italy) to prepare a traditional dish known as "prebuggiun." A total of 9 of them were found to have a polyphenol content and antioxidant properties similar or better than those of red chicory and blueberry, which are, in the case of vegetables and fruits, among the richest of antioxidants. Practical Application: In this article, we reported a study on wild plants growing in the Mediterranean area. These herbs have been neglected and this study aimed to revalue these plants because they are an extraordinary source of antioxidants. The increasing demand for natural antioxidants (additives in the food industry too) justifies the search for new sources of natural antioxidants. The revaluation of these plants will be interesting for: (1) consumer health, rediscovering a vegetable source of high antioxidant power; (2) possibility of producing new commercial products, such as food supplements of high quality and low cost; (3) pharmacological applications.

Assessment of the Content of Phenolics and Antioxidant Action of Inflorescences and Leaves of Selected Species from the Genus Sorbus Sensu Stricto

In order to find new sources of natural antioxidants, the antioxidant potential of 70% methanolic extracts from the inflorescences and leaves of 16 species from the genus Sorbus s.s. was evaluated using two complementary in vitro test systems: the DPPH (2,2-diphenyl-1-picrylhydrazyl) radical-scavenging assay and the AAPH [2,2′-azobis-(2-amidinopropane)dihydrochloride]-induced linoleic acid (LA) peroxidation test. The radical-scavenging capacities of the extracts towards the DPPH radical were in the range of 0.25−0.86 millimolar Trolox® equivalents/g dry weight. They were significantly correlated (r = -0.8089, p < 0.001) with the results of the LA-peroxidation test, indicating the Sorbus extracts to be universal antioxidants. Significant linear correlations were also found between the different antioxidant potentials and total phenolic contents as estimated by the Folin-Ciocalteu method and further verified by serial determinations of proanthocyanidins, chlorogenic acid isomers and flavonoids (|r| in the range of 0.71−0.95, p < 0.001). Cluster analysis of the data matrix identified the ten samples (inflorescences of S. aucuparia, S. pohuashanensis, S. decora, S. koehneana, S. commixta, S. gracilis, and S. sitchensis, and the leaves of S. wilfordii, S. pogonopetala, and S. gracilis) exhibiting the highest antioxidant activity and total phenolic levels and therefore the greatest potential as effective sources for natural health products.

Protective effect of areca inflorescence extract on hydrogen peroxide-induced oxidative damage to human serum albumin

The protective effect of 3 areca inflorescence extracts (boiling water extract, ambient temperature water extract and ethanol extract) on hydrogen peroxide-induced oxidative damage to human serum albumin was investigated by comparing with Trolox, the water soluble vitamin E. Protein carbonyl groups, protein hydroperoxides,1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, hydrogen peroxide scavenging activity and total phenolic content were examined. The results showed that boiling water extract had the most protective effect on human serum albumin damage induced by hydrogen peroxide, comparable to Trolox, followed by the room ambient temperature water extract and ethanol extract. The total phenolic content of boiling water extract, ambient temperature water extract, and ethanol extract was 1.949±0.003, 1.842±0.001 and 0.983±0.011mg gallic acid equivalent/ml extract, respectively, and six phenolic compositions such as gallic acid, coumalic acid, epicatechin, fumalic acid, naringenin and rutin have been found in these areca inflorescence extracts. These data suggest that areca inflorescence is a new source of natural antioxidants.

Chemical composition, antioxidant and antibacterial properties of the essential oils of Etlingera elatior and Cinnamomum pubescens Kochummen

Plant essential oils are widely used as fragrances and flavours. Therefore, the essential oils from the leaves of Cinnamomum pubescens Kochummen (CP) and the whole plant of Etlingera elatior (EE) were investigated for their antioxidant, antibacterial and phytochemical properties. CP and EE were found to contain appreciable levels of total phenolic contents (50.6 and 33.41 g kg(-1) as gallic acid equivalent) and total flavonoid contents (205.6 and 244.8 g kg(-1) as rutin equivalent), respectively. DPPH free radical scavenging activity of CP is superior to EE (P < 0.05) showing IC(50) of 77.2 and 995.1 µg mL(-1), respectively. Methicillin-resistant Staphylococcus aureus (MRSA), Bacillus subtilis, Pseudomonas aeruginosa and Salmonella choleraesuis were tested against CP and EE. Only MRSA was the most susceptible bacteria to CP. GC/MS studies resulted in the identification of 79 and 73 compounds in CP and EE, respectively. The most abundant components of EE included β-pinene (24.92%) and 1-dodecene (24.31%). While the major compound in CP were 1,6-octadien-3-ol,3,7-dimethyl (11.55%), cinnamaldehyde (56.15%) and 1-phenyl-propane-2,2-diol diethanoate (11.38%). This study suggests that the essential oils from Cinnamomum pubescens Kochummen and Etlingera elatior could be potentially used as a new source of natural antioxidant and antibacterial in the food and pharmaceutical industries.

Antioxidant constituents from Lawsonia inermis leaves: Isolation, structure elucidation and antioxidative capacity

The antioxidant potential of different fractions of Lawsonia inermis (Lythraceae) was investigated. The n-butanolic fraction showed the highest yield of extraction; it also exhibited a strong antioxidant activity in the DPPH assay and a potent capacity in preventing linoleic acid oxidation. Five phenolic glycosides were identified in this fraction. The structure of a new compound was established as 1,2,4-trihydroxynaphthalene-1-Ο-β- d-glucopyranoside. In addition, the known 2,4,6-trihydroxyacetophenone-2-Ο-β- d-glucopyranoside was described for the first time in this species. The three other compounds, lalioside (2,3,4,6-tetrahydroxyacetophenone-2-Ο-β- d-glucopyranoside), lawsoniaside (1,2,4-trihydroxynaphthalene-1,4-di-Ο-β- d-glucopyranoside) and luteolin-7-Ο-β- d-glucopyranoside, have been previously reported in L. inermis. The antioxidant activity of these glycosides was evaluated by DPPH and β-carotene assays, and compared to those of commercial standards. 1,2,4-Trihydroxynaphthalene-1-Ο-β- d-glucopyranoside was the most active in the DPPH free-radical scavenging test ( EC 50 = 6.5 μg/ml) and showed a moderate inhibition in the β-carotene bleaching assay. Chemical components of L. inermis have good antioxidant capacities and this species could be used as a potential source of new natural antioxidants.

Screening of Natural Antioxidants from Traditional Chinese Medicinal Plants Associated with Treatment of Rheumatic Disease

In order to find new sources of natural antioxidants, the antioxidant capacities of 50 medicinal plants associated with treatment of rheumatic diseases were systemically evaluated using the ferric-reducing antioxidant power (FRAP) and Trolox equivalent antioxidant capacity (TEAC) assays, and their total phenolic contents were measured by the Folin–Ciocalteu method. Their antioxidant activities of some of these plants were analyzed for the first time. The FRAP and TEAC assay results suggested that the antioxidant compounds in these plants possessed free radicals scavenging activity and oxidant reducing power. A positive linear correlation between antioxidant capacities and total phenolic contents implied that phenolic compounds in these plants could be the main components contributing to the observed activities. The results showed that Geranium wilfordii, Loranthus parasiticus, Polygonum aviculare, Pyrrosia sheaeri, Sinomenium acutum and Tripterygium wilfordii possessed the highest antioxidant capacities and total phenolic content among 50 plants tested, and could be rich potential sources of natural antioxidants.

Antioxidant activity of Cladophoropsis sp. alga, from North of Persian Gulf

Antioxidant compounds play an important role against different diseases. They are employed in medicine, cosmetic industry and food production (1). In searching for safe and effective antioxidants from natural resources, marine organisms are a new source (2). In recent years, algae have attracted great attention of researchers as their primary or secondary metabolites can be biologically active (3). They are also rich in proteins, minerals and polysaccharides (2). There are about 153 species of algae in Persian Gulf and Arabian Sea that can be a new source of natural antioxidants (4). The goal of this study was assessing the antioxidant activity and phenolic content of Cladophoropsis sp., from north of Persian Gulf. At the first step, the algae was lyophilized and extracted by 90% ethanol. For examination the antioxidant activity, two methods including radical scavenging test by using DPPH and reducing activity test, were carried out. Phenolic content (antioxidant compound) was also examined by using folin ciocalteu. The results showed radical scavenging activity with IC50=0.9mg/ml and reducing activity with absorbance of 0.5at the concentration of 1.48mg/ml. The IC50 of Gallic acid (0.82µg/ml) as powerful antioxidant standard was less than algal extract (P&lt;0.0001). Its total phenolic content was 2.1mg/g of extract. The results indicate moderate radical scavenging activity and reducing power of alga. In comparison with the others studies, this algae are rich in phenolic compounds.

Antioxidant activity of selected plant species; potential new sources of natural antioxidants

The aim of this study was to examine six plants from Serbia for their potential antioxidant activity. Therefore, six antioxidant activity assays were carried out, including: total antioxidant capacity, DPPH free-radical scavenging, the inhibitory activity toward lipid peroxidation, Fe 3+- reducing power, Fe 2+- chelating ability and hydroxyl radical scavenging activity. Total phenolic and flavonoid contents were also determined for each alcoholic extract. Cotinus coggygria extract contained the highest amount of total phenols (413 mg GAE /g dry extract), while the highest proportion of flavonoids was found in the Echium vulgare methanol extract (105 mg RU/g). Cotinus coggygria and Halacsya sendtneri alcoholic extracts showed the highest total antioxidant capacity (313 and 231 mg AA/g dry extract), as well as DPPH free-radical scavenging (IC 50 = 9 and 99 μg/ml), inhibitory activity toward lipid peroxidation (IC 50 = 3 and 17 μg/ml) and reducing power. Whereas, the greatest hydroxyl radical scavenging activity, as well as ferrous ion chelating ability showed Echium vulgare, Echium rubrum and Halacsya sendtneri.

Antioxidant Tannins from Stem Bark and Fine Root of Casuarina equisetifolia

Structures of condensed tannins from the stem bark and fine root of Casuarina equisetifolia were identified using MALDI-TOF MS and HPLC analyses. The condensed tannins from stem bark and fine root consist predominantly of procyanidin combined with prodelphinidin and propelargonidin, and epicatechin is the main extension unit. The condensed tannins had different polymer chain lengths, varying from trimers to tridecamer for stem bark and to pentadecamer for fine root. The antioxidant activities were measured by two models: 1,1-diphenyl-2- picrylhydrazyl (DPPH) radical scavenging activity and ferric reducing/ antioxidant power (FRAP). The condensed tannins extracted from C. equisetifolia showed very good DPPH radical scavenging activity and ferric reducing/ antioxidant power, suggesting that these extracts may be considered as new sources of natural antioxidants for food and nutraceutical products.

Effect of fractionation on antiradical efficacy of ethyl acetate extract of Terminalia chebula Retz.

There is currently an upsurge of interest in phytochemicals as new sources of natural antioxidants. The aim is to use them in foods and pharmaceutical preparations in order to replace synthetic antioxidants, which are being restricted due to their potential health risks and toxicity. The relative levels of antioxidant activity and the total phenolic content of ethyl acetate extract/fractions of Terminalia chebula have been determined using DPPH, Deoxyribose, Reducing power, Chelating power, Lipid peroxidation, DNA nicking assay and the Folin- Ciocalteu colorimetric method. There was a positive linear correlation between antioxidant activity and total phenolic content of ethyl acetate extract/fractions. Thus, it was concluded that phenolic compounds were the predominant antioxidant components in the fruits of T. chebula. The extract was prepared by maceration method at room temperature and further fractionated with ethyl acetate and water. It was observed that the free radical scavenging activity of fractions was comparatively more as compared to their crude extract and ethyl acetate fraction showed the maximum effect in all assays. The percent inhibition with ethyl acetate fraction (EAF) of ethyl acetate extract was observed to be 71.5, 90.0, 75.1, 74.3 and 77.6% in DPPH, site specific and non-site specific deoxyribose, chelating power and lipid peroxidation assays, respectively at maximum concentration tested. Key words: Terminalia chebula, oxidative stress, phytochemicals, antioxidants, lipid peroxidation.

Antioxidant Efficacy of Mulberry (Morus Indica L.) Leaves Extract and Powder in Edible Oil

The antioxidant activity of mulberry (Morus Indica L.) leaves was evaluated in rice bran oil (RBO). The oil was subjected to accelerated oxidation at 100° C for 5 days and heat treatment at 180°C for 1 h. In order to examine its potential antioxidant activity, the oxidative stability of the oils was evaluated by employing peroxide value (PV), radical scavenging activity (RSA), thiobarbituric acid reactive substances assay (TBARS), and percent free fatty acids (FFA). Mulberry in two forms viz: the methanolic extract and powder were applied to RBO at 200 ppm and 0.05%, respectively, and results were compared with RBO treated with a synthetic antioxidant-BHT. The PV, RSA, TBARS, and FFA values indicated that both mulberry extract and powder were effective in inhibiting lipid oxidation when compared to synthetic antioxidant BHT. Thus, mulberry leaves may serve as a new source of natural antioxidant for use in food systems.

Determination of the phenolic content and antioxidant potential of crude extracts and isolated compounds from leaves of Cordia multispicata and Tournefortia bicolor

In this work, the total phenolic content and antioxidant activity of extracts and four flavonoids isolated from leaves of two Boraginaceae species (Cordia multispicata Cham. and Tournefortia bicolor Sw.) were evaluated using Folin-Ciocalteu reagent, DPPH free radical scavenging and inhibition of peroxidation of linoleic acid by FTC method. For comparison, ascorbic acid, α-tocopherol and BHT were used. In general, extracts from T. bicolor (68.8 ± 0.001 to > 1000 mg/g) showed higher phenolic content than C. multispicata (66.1 ± 0.009 to 231 ± 0.07 mg/g), and also scavenged radicals (IC50 12.8 ± 2.5 to 437 ± 3.5 mg/L) and inhibited lipid peroxide formation (IC50 51.2 ± 2.29 to 89 ± 0.59 mg/L). For these extracts a good correlation between the phenolic content and antioxidant activity was observed, suggesting that T. bicolor is richer in phenolic compounds and that it could serve as a new source of natural antioxidants or nutraceuticals with potential applications. Chromatographic procedures monitored by antioxidant assays afforded seven compounds, which were identified by spectral analyses (IR, MS and 1D and 2D NMR) and comparison with reported data as being trans-phytol (1), taraxerol (2), 3,7,4’-trimethoxyflavone (3), 5,3’-dihydroxy-3,7,4’-trimethoxyflavone (4), quercetin (5), tiliroside (6), and rutin (7). Compounds (4-7) were also evaluated and were effective as DPPH quenching (IC50 7.7 ± 3.6 to 79.3 ± 3.4 mg/L) and as inhibition of lipid peroxidation (IC50 80.1 ± 0.98 to 88.7 ± 3.62 mg/L). This is the first report on the total phenolic content, radical-scavenging and antioxidant activities of these species.

Antioxidant activity of fungi isolated from soil of different areas of Punjab,India

The study was carried outto investigate the antioxidant activity of fungi isolated from soil of different areas of Punjab, India and compare their efficiency with a known antioxidant, ascorbic acid. The antioxidant potential of fungal extracts was quantified by DPPH and reducing power assay. Total phenolic contents were estimated using Folins-Ciocalteau (FC) reagent. Out of 113 fungal isolates selected, 51 were having antioxidant potential and these were further assayed quantitatively. All of these showed good activity against DPPH radical while 32 of these isolates demonstrated reducing potential also. In addition, some were equally good as ascorbic acid. The present study demonstrated potential of soil fungi to have antioxidant activity similar to plants and mushrooms. High phenolic content of fungi further highlight their significance as new sources of natural antioxidants. These fungi may provide easier set up for production and purification of natural antioxidants as compared to higher plants.

Plantain (Plantago L.) Species as Novel Sources of Flavonoid Antioxidants

To examine the antioxidant properties of methanol extracts of selected Plantago species (P. argentea Chaix., P. holosteum Scop., P. major L., P. maritima L., and P. media L.), various assays that measure free radical scavenging ability were carried out: DPPH, hydroxyl radical, superoxide anion, and nitric oxide scavenger capacity tests, reducing power (FRAP) assay, and Fe(2+)/ascorbate induced lipid peroxidation. In all of the tests extracts showed a potent antioxidant effect compared with BHT, a well-known synthetic antioxidant, and the extract of P. major, accepted as an official remedy. Besides, in examined extracts the total phenolic amount (ranging from 38.43 to 70.97 mg of GAE/g of dw) and the total flavonoid content (5.31-13.10 mg of QE/g of dw) were determined. Furthermore, the presence and content of selected flavonoids (luteolin-7-O-glucoside, apigenin-7-O-glucoside, luteolin, apigenin, rutin, and quercetin) were studied using LC-MS/MS technique. LC-MS/MS analysis showed noticeable qualitative and quantitative differences between the species according to which the examined Plantago species could be regarded as a possible new source of natural antioxidants. In this study three of the species examined, P. maritima, P. argentea, and P. holosteum, have been analyzed for the first time.

CHARACTERIZATION AND ANTIOXIDANT ACTIVITY OF FLAVONOID-RICH EXTRACTS FROM LEAVES OF AMPELOPSIS GROSSEDENTATA

Leaves of Ampelopsis grossedentata have been consumed in southern China as health tea and herbal medicine. In this study, two kinds of flavonoid-rich extracts from leaves of A. grossedentata were prepared by traditional solvent extraction (product A) and recrystallization (product B). By analysis of ultraviolet-visible (UV) spectrometry, infrared (IR) spectrometry, electrospray ionization mass spectrometry (ESI-MS), nuclear magnetic resonance (NMR) spectrometry and high-performance liquid chromatography (HPLC)-ESI/MS, the major flavonoid in two products was identified as (+)-dihydromyricetin (DMY). Also, by HPLC, the contents of DMY in leaves, product A and product B were measured to be 32.96 ± 1.18%, 77.15 ± 1.98% and 95.12 ± 2.86%, respectively. Various antioxidant tests (1,1-diphenyl-2-picrylhydrazyl radical scavenging, reducing power, antioxidant activity in linoleic acid system) showed that the antioxidant activity of the flavonoid-rich extracts could be comparable with that of tertiary butylhydroquinone. The flavonoid-rich extracts from A. grossedentata leaves have a promise to be a new natural antioxidant with potential application in food industry. PRACTICAL APPLICATION Leaves of Ampelopsis grossedentata are consumed in southern China as health tea (Tengcha) and herbal medicine. In this study, the flavonoid-rich extracts from leaves of A. grossedentata, which were rich in (+)-dihydromyricetin, were prepared by traditional solvent extraction and recrystallization. Also, the antioxidant activity of the extracts can be comparable with that of tertiary butylhydroquinone. The results obtained in this study suggest that leaves of A. grossedentata may have potential as a new source of natural antioxidant and health food with great commercial interest in the food and phytopharmaceutical market.

OPTIMIZATION OF EXTRACTION CONDITIONS FOR ANTIOXIDANT PHENOLIC COMPOUNDS FROM MALT ROOTLETS USING RESPONSE SURFACE METHODOLOGY

ABSTRACT Significant levels of antioxidant phenolic compounds were detected in malt rootlets, indicating that malt rootlets may serve as an excellent source of natural antioxidants for disease prevention and health promotion. To improve this by-product value, response surface methodology (RSM) was used for the optimization of extraction conditions for obtaining the maximum amount of antioxidant phenolic compounds from malt rootlets in the malting industry. The Box-Behnken experimental design was used to investigate the effects of three independent invariables on total antioxidant activity (TAA). These three independent variables were solvent composition (% v/v), extraction temperature (C) and time (min), respectively. By RSM and canonical analysis, the optimal conditions for higher TAA were: 50%, 84C, 22 min. Under optimal conditions, the predicted response value for TAA reached 9.49 µmol Trolox equivalent (TE). Verification of the optimization showed that 9.79 µmol TE was observed under the optimal condition, which was a 3.13-fold increase of TAA at the lowest level. PRACTICAL APPLICATIONS Antioxidant phenolic compounds have gradually been used in the medicine industry with the ability of reducing risks of cardiovascular diseases and certain cancers. On the one hand, they are beneficial to grains, fruits and vegetables through several possible mechanisms, such as directly quenching free radicals, chelating transition metals, reducing peroxides and stimulating the antioxidative defense enzyme activities. On the other hand, many of the biological functions, such as antimutagenity, anticarcinogenity and antiaging, originate from this property of antioxidant phenolic compounds. Generally, a great deal of malt rootlets are produced in the malting industry and treated as by-products for animal feed. However, significant levels of antioxidant phenolic compounds were detected in malt rootlets, indicating that malt rootlets may serve as an excellent source of natural antioxidants for disease prevention and health promotion. While the optimization of extraction conditions for antioxidant phenolic compounds from malt rootlets would not only add value to this by-product, but also offer a new source of natural antioxidant.

A new class of natural glycopeptides with sugar moiety-dependent antioxidant activities derived from Ganoderma lucidum fruiting bodies.

A water-soluble glycopeptide (PGY), fractionated and purified from the aqueous extract of the fruiting bodies of Ganoderma lucidum via two-step dialysis, anion exchange, and gel permeation chromatography, was constituted of two moieties of carbohydrate and peptide. Carbohydrate characterization with component analysis, methylation analysis, periodate oxidation, Smith degradation, enzymic hydrolysis, and IR and NMR experiments demonstrated that the carbohydrate moiety possessed a backbone of approximately 33 (1-->3)-linked beta-d-glucopyranosyl residues and side chains, at positions 6, of single alpha-l-arabinofuranosyl residues for every three Glcp residues in the main chain. On the basis of the results of amino acid composition and trypsin digestion, the peptide moiety, shown to consist of Arg, Ser, Ala, and Gly in a ratio of 1:1:2:2, exhibited the sequence of Ser-Arg-[(Ala)2(Gly)2] and was O-attached to the carbohydrate moiety via Ser. To contribute toward our understanding of the structure-activity relationship, a series of expected derivatives generated from PGY by trypsin digestion, debranching, and NaIO4 oxidation following reduction experiments, including PTC, DB-PGY, and PPP, were obtained. All of them, as well as PGY and a reference compound (butylated hydroxytoluene, BHT), were evaluated with two conventional antioxidant testing systems of 1,1-diphenyl-2-picrylhydrazyl (DPPH) and superoxide radical scavenging and found to have their respective antioxidant activities in a concentration-dependent manner. Comparable radical-scavenging activities observed between PTC and PGY demonstrated that the removal of Ala and Gly in a peptide moiety did not result in the variation of biological functions of PGY. However, it was very interesting to note that the scavenging activity of PPP was higher for DPPH radicals, with an SC(50) value of 116.4 +/- 5.1 microg/mL, and lower for superoxide radicals, with an SC(50) value of 205.2 +/- 14.4 microg/mL, than that of PGY with corresponding SC(50) values of 133.5 +/- 5.5 and 140.5 +/- 7.7 microg/mL, and, moreover, DB-PGY displayed the weakest scavenging potency in the tested samples, indicating that the carbohydrate moiety, in particular the side chain of nonreducing end units of Araf residues as the functional region, played a vital role in the structure and antioxidant activity. In addition, compared with the SC(50) value of BHT, PGY showed lower DPPH radical-scavenging activity but possessed higher superoxide radical-quenching potency, suggesting that it could be presented as a possible new source of natural antioxidants.