DPPH Free Radical Scavenging Capacity Research Articles

Effect of drying pretreatment methods on structural features and antioxidant activities of Brauns native lignin extracted from Chinese quince fruit

Chinese quince is one kind of crop that has edibility and historical medical applications. However, the high amount of lignin makes processing Chinese quince fruit difficult; on the other hand, this lignin represents a valuable resource if a way of using it in industrial applications could be found. In this study, the structural features and antioxidant activities of Brauns native lignin (BNL) isolated from Chinese quince fruit after oven drying (60 °C, 75 °C, and 90 °C), sun drying, freeze-drying, and subcritical dimethyl ether drying were assessed. The BNL samples had low molecular weights (Mw, 2604–5511 g/mol), high carbohydrate content (6.10–9.95 %), and high phenolic OH content (1.76–2.29 mmol/g). NMR spectra showed that the BNL is of the SGH-type with the relative content of p-hydroxyphenyl units ranging from 13 to 21 %. Oven drying (90 °C) reduced the carbohydrate content and increased the phenolic hydroxyl content. Freeze-drying reduced the relative content of β-O-4′ linkages and increased the H-unit content. In terms of antioxidant activities, all samples possessed high DPPH free radical scavenging capacity (IC50, 0.12−0.22 mg/mL) and strong reducing power. These results indicate that BNL extracted from Chinese quince fruit is a promising source of natural antioxidant and biomass material.

STUDY ON ANTIOXIDANT ACTIVITY OF PHYTOESTROGEN EXTRACTS FROM SOY GERM

Soy germ is one of the richest phytoestrogen sources and thus has many benefits for health such as improving bone density, cardiovascular health, cancer prevention, and menopausal treatment. In addition, phytoestrogens are reported to act as antioxidants, removing reactive oxygen species and thereby preventing oxidative damage in living tissue. Phytoestrogens in soy germ include isoflavone compounds and their derivatives: daidzein, genistein, glycitein, daidzin, genistin, glycitin, acetyl daidzin, acetyl genistin, acetyl glycitin, malonyl daidzin, malonyl genistin, malonyl glycitin. Isoflavones aglycone forms comprise only about 2-5% of total isoflavones, however, they express more biological effects than the others. The objective of this study was to compare the antioxidant activity among three extracts: purified isoflavone aglycone extract, crude isoflavone aglycone extract and total phytoestrogen extract. The IC50 value of DPPH free radical scavenging capacity of purified isoflavone aglycone extract, crude isoflavone aglycone extract and total phytoestrogen extract were 0.763 ± 0.016; 3.345 ± 0.076; 6.142 ± 0.050 mg/ml, respectively. The IC50 value of reducing power activity of purified isoflavone aglycone extract, crude isoflavone aglycone extract and total phytoestrogen extract were 1.248 ± 0.024; 3.961 ± 0.172; 9.385 ± 0.272 (mg/ml). As our result, the ranking order of the antioxidant activity (from highest to lowest level) was purified isoflavone aglycone extract > crude isoflavone aglycone extract > total phytoestrogens extract.

Antioxidative and α-glucosidase inhibitory constituents of Polyscias guilfoylei: experimental and computational assessments.

Searching for bioactive agents from medicinal plants, eleven constituents were isolated from Polyscias guilfoylei stem for the first time, including a nucleoside uracil (1), two sterols β-sitosterol (2) and daucosterol (3), a saponin androseptoside A (4), two lignans (+)-pinoresinol (5) and (+)-syringaresinol (6), four phenolic acids protocatechuic acid (7), methyl protocatechuate (8), caffeic acid (9), and 5-O-caffeoylquinic acid (10), and a flavonoid quercitrin (11). Metabolites 1, 4, and 6-11 have never been observed in genus Polyscias before. Phenolic compounds 7 and 9 possessed the respective IC50 values of 21.33 and 13.88µg/mL in DPPH (2,2-diphenyl-1-picrylhydrazyl) antioxidative assay, as compared with that of the positive control resveratrol (IC50 = 13.21µg/mL). From density functional theory (DFT) calculated approach, the DPPH free radical scavenging capacity of two compounds 7 and 9 can be explained by the role of OH groups at carbons C-3 and C-4. Antioxidative actions of these two potential agents are followed HAT (H atom transfer) mechanism by OH bond disruption in gas, but SPLET (sequential proton loss electron transfer) mechanism in solvents water and methanol. Compared to 4-OH group, 3-OH group showed better bond disruption enthalpies and better kinetic energies since it reacted with HOO• and DPPH radicals. Sterols 2-3 and flavonoid 11 induced the IC50 values of < 2.0µg/mL better than the positive control acarbose (IC50 = 184.0µg/mL) in α-glucosidase inhibitory assay. Their interactions with human intestinal C- and N-terminal domains of α-glucosidase were explored using molecular docking study. The obtained results proved that compounds 2, 3, and 11 bind relatively stronger with the C-terminal domain than to the N-terminal domain through pivotal residues in the binding site and could be hypothesized as mixed inhibitors.

Effects of Fruit Maturity on Physicochemical Properties, Sugar Accumulation and Antioxidant Capacity of Wild Harvested Kakadu Plum (Terminalia ferdinandiana)

: Terminalia ferdinandiana (Kakadu plum), belonging to the family Combretaceae, is endemic to Australia and has a long history of traditional medicinal applications and food cuisine by the Australian Indigenous people. This study investigated the effects of maturity stages on the morphology, physicochemical parameters (total soluble solids (TSS), total acid content (TAC), and pH), soluble sugar profile and antioxidant capacity of Kakadu plum (KP) fruits that were wild harvested from different trees and classified into four different maturity stages (immature to mature). TSS and TAC were determined by standard assays/procedures, main sugars by UHPLC–MS/MS and antioxidant capacity (total phenolic content (TPC) and DPPH free radical scavenging capacity) by spectrophotometry. The results showed that soluble sugars (glucose, sucrose and fructose) ranging from 1.3 to 17.7% dry weight (DW), TSS (17.0–52.7% DW) and TAC (1.3–6.7% DW) increased with maturity. However, antioxidant capacity (TPC in the range of 7.4–21.9% DW and DPPH free radical scavenging capacity from 22 to 76% inhibition at the extract concentration of 20 g·L−1) did not follow the same trend as the one observed for soluble sugars, TSS and TAC. These differences were associated with the tree-to-tree variability as a consequence of the wild harvest condition. This study provides important information to both the KP industry and Indigenous enterprises regarding the selection of the appropriate maturity stage to harvest KP fruit to target for different markets (e.g., low-sugar vs. high-sugar fruit).

Antioxidant and Anti-inflammatory Metabolites of a Soil-Derived Fungus Aspergillus arcoverdensis SSSIHL-01.

Soil houses avast array of microbial diversity. Cultured soil microbes have been a good source of many commercial drugs. In the present study, a fungal culture (SSSIHL-01) isolated from soil has been identified as Aspergillus arcoverdensis through morphology and ITS gene sequence. Extracellular culture extract and mycelial extract of the strain SSSIHL-01 were obtained using specific conditions and wereevaluated for antioxidant and anti-inflammatory activities. Culture extract at 700µg/mL concentration, showed strong DPPH free radical scavenging capacity with 95.06% comparable with the standard ascorbic acid. At 1mg/mL concentration, mycelial extract inhibited heat induced Bovine Serum Albumin denaturation of about 31.54% compared to that of 51% produced by the standard diclofenac sodium. Chemical profiling of both the culture and mycelial extracts were investigated using gas chromatography-mass spectrometry. Some of the major compounds identified from the culture extract were 2,4-ditert-butylphenol, 1-heptacosanol, 1-octadecene, 1-nonadecene that are known to be antioxidative. Mycelial extract presented some major compounds such as ethyl linoleate, oleic acid, n-hexadecanoic acid and ethyl palmitate that are reported to exhibit anti-inflammatory activity. Thus, our study highlights the significance of Aspergillus arcoverdensis as an effective producer of antioxidant and anti-inflammatory compounds for future utility in pharmaceutical and cosmeceutical applications.

Bioactive compounds in the leaves of Baccharis dracunculifolia: extraction process and characterization

Baccharis dracunculifolia has been used in popular medicine because of its bioactive properties, which include anti-inflammatory, antiulcerative and hepatoprotective potentials. A 2³ central composite rotational design was used to define the best conditions for extracting the bioactive compounds from the leaves of Baccharis dracunculifolia. The parameters studied included the solvent concentration, time and temperature of extraction and the influence of these on the total phenolics content and antioxidant activity. The best conditions were 95 % methanol (v/v), 20 min extraction time, and 70 °C temperature. Under the optimized conditions, high contents of total phenolic compounds (72.5 mg GAE g-1) and high DPPH (865.6 µmol TE g-1) and ABTS (331.11 μmol TE g-1) free radical scavenging capacity and a high ferric reducing antioxidant power (1558.00 μmol FeSO4.7H2O g-1), were obtained. The extract also showed promising anti-microbial activity, demonstrating fungistatic action against C. tropicalis and C. albicans (5 mg mL-1 and 7 mg mL-1, respectively) and bacteriostatic effect against Escherichia coli (60 e 70 mg mL-1), Salmonella enterica typhimurium (40; 60 and 70 mg mL-1) and Staphylococcus aureus (4 mg mL-1). HPLC-DAD analysis showed an extract rich in the phenolic compounds catechin (0.659 mg g-1), caffeic acid (1.135 mg g-1), p-coumaric acid (0.772 mg g-1), ferulic acid (6.24 mg g-1), pinocembrina (0.155 mg g-1) and rutin (0.037 mg g-1).

In vitro inhibitory potential of avocado fruits, Persea americana (Lauraceae) against oxidation, inflammation and key enzymes linked to skin diseases

Avocado (Persea americana Mill.) is a member of Lauraceae with one-seeded berry fruit and cultivated in all tropical, subtropical regions in the world and in the Southern coast region of Turkey. Oxidative damage caused by UV can trigger inflammation, resulting in serious inflammatory skin diseases including eczema, seborrheic dermatitis, hyperpigmentation and ageing. Enzyme inhibitors involved in melanogenesis, such as tyrosinase, have been used recently for hyperpigmentation and skin diseases in cosmetic products. Objective: This study aimed to evaluate the antioxidant, anti-inflammatory, anti-tyrosinase activities and total polyphenolic contents of the different parts of P. americana fruit. Methods: The fruit was divided into exocarp, mesocarp, seed, and then methanol and n-hexane extracts were prepared. DPPH and ABTS free radical scavenging capacities and inhibitory potentials on lipid peroxidation were determined to investigate the antioxidant potentials of the extracts. Anti-inflammatory activities of the extracts were evaluated by measuring the stabilization level of the human red blood cell membrane. The tyrosinase inhibitory activities of the samples were determined using mushroom tyrosinase. Results: In general methanol extracts possessed remarkable higher DPPH free radical scavenging activities than n-hexane extracts. The highest activity was determined in methanol extracts of seed (4.17 ± 0.04 mg/mL) followed by exocarp (5.25 ± 0.05 mg/mL). Overall methanol extracts possessed higher ABTS free radical scavenging activities than n-hexane extracts. The greatest ABTS free radical scavenging activity was obtained in methanol extracts of seed (0.03 ± 0.01 mg/mL). In the anti-lipid peroxidation assay, the greatest activity was noticed in methanol extracts of seed (7.71 ± 0.36 µg/mL) followed by exocarp (12.12 ± 0.34 µg/mL), while all n-hexane extracts were inactive. Overall methanol extracts exhibited higher anti-inflammatory and antioxidant properties than n-hexane extracts. However, the maximum anti-tyrosinase activity was determined in n-hexane extracts of exocarp (0.40 ± 0.01 mg/mL) followed by seed (0.46 ± 0.01 mg/mL). Conclusions: These extracts are promising candidates for use as natural products-based antioxidant and anti-inflammatory properties in inflammation-related disease, and also anti-tyrosinase properties in dermatological applications.

Nutritional value, phytochemical content, and antioxidant activity of three phytobiotic plants from west Cameroon

Abstract The search for natural sources of bioactive compounds known as phytobiotics is becoming a new challenge for industry and scientists. Thus, the present work aimed to study the nutritional value and phytochemical properties of Camellia sinensis, Annona muricata, and Zingiber officinale plants from the West region of Cameroon. The plant powders were used to evaluate their proximate composition and mineral content. The Phytochemical contents (total phenolic and flavonoid contents) and the antioxidant activities were evaluated through the DPPH free radical scavenging capacity, the ability to reduce ferric ion, and hydroxyl radical scavenging ability, using the aqueous extracts of these plants. The results revealed that leaves of Camellia sinensis and flower of Annona muricata powders had high levels of macronutrients (lipids, proteins, and carbohydrates) and mineral contents such as sodium (Na), potassium (K), phosphorus (P), magnesium (Mg), calcium (Ca), iron (Fe), and zinc (Zn) higher than the human recommended daily values. Also, extracts of Camellia sinensis and Annona muricata recorded high values of total phenolic (123.09 and 75 mg GAE/g respectively) and flavonoid (18.49 and 17.86 mg CE/g respectively) contents. The aqueous extracts of these plants showed the highest antioxidant activities compared to that of Zingiber officinale. In conclusion, these plants are important sources of nutrients and bioactive compounds, and as phytobiotics, they can be useful for industrial and research purposes.

Antimicrobial, Antioxidant and Cytotoxic Activities of Cosmos Caudatus extracts

This study aims to investigate the in-vitro antimicrobial potential of Cosmos caudatus against pathogenic bacteria, its antioxidant activity and cytotoxic effect on cancer cell lines. In vitro antimicrobial activities of ethanol and water extracts of Cosmos caudatus herb against pathogenic bacteria, Staphylococcus aureus, Salmonella sp., Pseudomonas aeruginosa and Escherichia coli were tested by agar well diffusion. Antioxidant properties of the extracts was evaluated by 2,2-diphenyl-1-picryl-hydrazyl radical scavenging activity method. Additionally, cytotoxic activity of the extracts on HCT 116 colorectal carcinoma cell line was determined by (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. Vero cells were used as a control. The quantification of these extracts showed that this plant is rich in secondary metabolites. Moreover, the conventional soxhlet extraction technique was more effective than maceration and ultrasonic assisted extraction technique. In antioxidants assay, both the ethanolic and water extracts through ultrasonic extraction method exhibited the highest DPPH free radical scavenging capacity compared to maceration and sohxlet extraction method. In antimicrobial assay, both the water and ethanol extracts showed no inhibitory action against the tested pathogenic bacteria. For anticancer activity, the F2, F7 and F8 fractions showed potent dose dependent cytotoxicity on Human Colorectal Carcinoma Cells with IC50 value of 15.53 ± 0.4, 32.72 ± 0.3 and 34.16 ± 1.4 μg/mL, respectively.

Metabolomic and Biochemical Analysis of Two Potato (Solanum tuberosum L.) Cultivars Exposed to In Vitro Osmotic and Salt Stresses.

Globally, many crop production areas are threatened by drought and salinity. Potato (Solanum tuberosum L.) is susceptible to these challenging environmental conditions. In this study, an in vitro approach was employed to compare the tolerance of potato cultivars ‘BARI-401’ (red skin) and ‘Spunta’ (yellow skin). To simulate ionic and osmotic stress, MS media was supplemented with lithium chloride (LiCl 20 mM) and mannitol (150 mM). GC-MS and spectrophotometry techniques were used to determine metabolite accumulation. Other biochemical properties, such as total phenols concentration (TPC), total flavonoids concentration (TFC), antioxidant capacity (DPPH free radical scavenging capacity), polyphenol oxidase (PPO), and peroxidase (POD) activities, were also measured. The two cultivars respond differently to ionic and osmotic stress treatments, with Spunta accumulating more defensive metabolites in response, indicating a higher level of tolerance. While further investigation of the physiological and biochemical responses of these varieties to drought and salinity is required, the approach taken in this paper provides useful information prior to open field evaluation.

Determination of Antioxidant Capacity, Phenolic and Elemental Composition in Syriac (Mardin) Wines by using Chromatographic and Spectrophotometric Methods

Free radicals are responsible for many health problems, especially oxidative stress-related diseases. With conscious nutrition and the use of natural antioxidants, it is now possible to cope with these diseases or minimize their effects. The aim of this study was to determine pH, total acidity, total SO2, free SO2, relative SO2, dry matter, density, alcohol content, reducing sugar, ash, CUPRAC, DPPH free radical scavenging capacity, total phenolic content, elemental composition, and some phenolic compounds of Syriac (Mardin) wines. Estimated daily intake (EDI), target hazard quotients (THQ), total target hazard quotients (TTHQ), and relative risk (RR) were calculated, to assess a health risk resulting from regular consumption of Syriac wines. The elements EDI values through consumption of wines were less than the recommended dietary allowance values. Obtained THQ values were less than 1. When the obtained results are compared with the levels set by regulatory authorities, the investigated wine consumption does not pose a toxicological risk based on EDI, THQ, TTHQ, and RR values. In addition, this study showed that the Syriac wine’s antioxidant capacities are high and rich in phenolic compounds and elements.

Purification and biochemical characterization of an alkaline feruloyl esterase from Penicillium sumatrense NCH-S2 using rice bran as substrate

ABSTRACT Feruloyl esterases (FAEs) are essential accessory enzymes in the hydrolysis of plant cell wall structure. A novel FAE was obtained from Penicillium sumatrense NCH-S2. Enzyme purification was conducted by ultrafiltration, ammonium sulfate precipitation, anion exchange, and gel filtration chromatography. This FAE has a molecular mass of 36 kDa. Its optimum temperature and pH were 50°C and pH 9.0–10.0, respectively. The FAE demonstrated high pH stability at the pH ranging from 6.0 to 10.0. After enzymatic hydrolysis with FAE, the DPPH free radical scavenging capacity, ferrous ion chelating ability, and total phenolic content (TPC) of defatted rice bran (DRB) hydrolysate significantly increased. Furthermore, the amount of released FA from DRB under a synergistic interaction of FAE and hemicellulose increased by 18–21% in comparison with that of either enzyme acting alone.

Optimization infusion condition on flavonoid and antioxidant activity of herb beverages using response surface methodology

Herbs have potential to be developed as functional beverages to reduce the risk of Covid-19 infection. One of herb ready to serve form is brewed in a bag. This study optimizes the conditions for herb beverages infusion in a silk bag based on their flavonoid content and antioxidant activity. Optimization is completed using the Response Surface Methodology with 33 Central Composite Design models. As the factor X1 is the mass of the herbs in the bag, X2 is the infusion frequency and X3 is the steeping time. Each factor consists of 3 levels. The flavonoid content was determined using the UV-Vis spectrophotometric method. The antioxidant activity was measured based on the DPPH free radical scavenging capacity. The results of this study indicate that the optimal condition is achieved in the herb mass of 1.2 g with an infusion frequency of 18 times and steeping time for 15 minutes. Flavonoids content and antioxidant activity in herb beverages at optimal infusion conditions were 942,353 μg QE / mL (117.79 mg QE / g) and 83.06%, respectively.

English

Injera or Biddena commonly made from tef (Eragrostis tef (Zucc) Trotter) grain and a combination with other grains is a staple food of Ethiopian and neighboring countries. Millet and millet-based food products are rich in polyphenols and antioxidant activities. This study aimed to evaluate millet varieties for their injera making quality and polyphenol content and antioxidant activity. Five millet varieties and one tef variety called Quncho were collected, investigated and compared. A significant (p 0.05) reduction in total phenols, total flavonoids contents and DPPH free radical scavenging capacity. Hence, it is recommended that Tesema and Kola-1 varieties could be used for functional food development and injera making quality, respectively. Key words: Millet varieties, tef, injera, baking, polyphenols, antioxidant effects.

Impact of harvesting time on the chemical composition and quality of fresh lotus seeds

This study compared the physicochemical properties and sensory quality of fresh lotus seeds of ‘Mantianxing’ and ‘No.36 space lotus’. The results showed that along with the maturation of seeds, the seed shell color changed from green to brown and that of the plumule turned from yellow to green. In addition, the moisture content decreased, the hardness significantly increased, and the plumpness remained constant. The above changes occurred 4 days earlier in August than in September. During maturation, the total phenol content and DPPH free radical scavenging capacity decreased; the soluble sugar content and sweet taste first increased and then decreased; and the alkaloid content and bitter taste showed an overall increasing trend. Hence, the quality of fresh lotus seeds is determined by the harvesting time, and lotus seeds harvested on day 14 in August and day 18 in September have the highest fresh quality.

Oxidative Stability of Protease Treated Peanut with Reduced Allergenicity.

Oxidative stability and allergenicity are two major concerns of peanuts. This study evaluated the impact of protease treatment of peanuts on its oxidative stability during storage. The raw and dry-roasted peanut kernels were hydrolyzed with Alcalase solution at pH 7.5 for 3 h. The contents of Ara h 1, Ara h 2, and Ara h 6 in peanuts were determined before and after enzyme treatment by a sandwich ELISA. After drying, the samples were packed in eight amber glass jars and stored at 37 °C for 1–8 weeks. Controls are untreated raw and dry-roasted peanuts packed and stored in the same way as their treated counterparts. Samples were taken biweekly to determine peroxide value (PV) and thiobarbituric acid reactive substances (TBARS) as indicators of oxidation (n = 3), and to determine antioxidant activity. Alcalase treatment reduced intact major allergens Ara h 1, Ara h 2, and Ara h 6 by 100%, 99.8%, and 85%, respectively. The PVs of Alcalase-treated raw and roasted peanuts was lower than those of untreated (p < 0.05) over the 8-week storage. The TBARS of Alcalase-treated raw peanuts were slightly higher than that of untreated (p < 0.05), but the TBARS of Alcalase-treated dry-roasted peanuts were slightly but significantly lower than that of untreated (p < 0.05). The protease treatment increased the antioxidant activities including reducing power, DPPH free radical scavenging capacity, and metal chelating capacity of peanuts.

Influence of kenaf (Hibiscus cannabinus L.) leaves powder on the physico-chemical, antioxidant and sensorial properties of wheat bread

Hibiscus cannabinus L. or commonly known as kenaf is a multipurpose crop with various medicinal and nutritional properties. The aim of this study was to determine the antioxidant, nutritional, and functional properties of kenaf leaves powder. In addition, the effect of kenaf leaves powder fortification in bread properties and consumer acceptability were evaluated by production of three formulations of bread with 0% (control), 4% and 8% substitution of kenaf leaves powder per weight of flour used. From the sensory evaluation, 4% leaves powder bread was the most preferred by the panelists followed by 0% leaves powder bread then 8% leaves powder bread. Therefore, 4% leaves powder bread was chosen as the best formulation for this study and it showed significantly higher value of DPPH free radical scavenging capacity (8.05 mg TE/100 g), total phenolic content (12.9 mg GAE/100 g) and total flavonoid content (13.3 mg QE/100 g) compared to control bread (1.38 mg TE/100 g, 8.17 mg GAE/100 g and 8.77 mg QE/100 g, respectively). Besides, 4% leaves powder bread also showed improvement in calcium and total dietary fibre compared to control bread. Given these results, kenaf leaves powder can be used in baking formulation up to 4% with flour to enhance the functional properties of baking formulation without compromising eating quality.

Stability of Brazilian Apis mellifera L. honey during prolonged storage: Physicochemical parameters and bioactive compounds

The aim of this study was to monitor Apis mellifera L. honey samples from Santa Catarina State, Brazil, during prolonged storage (450 days/20 ± 4 °C), regarding physicochemical parameters (moisture, electrical conductivity, pH, acidity, color, dystasic activity, 5-HMF and sugars), phenolic compounds, reducing capacity (Folin-Ciocalteu reducing capacity and ferric reducing antioxidant power) and DPPH free radical scavenging capacity. Storage did not affect the 5-HMF and sucrose contents, which were below the limit of quantification. Electrical conductivity, pH, diastatic activity, and color (L*) decreased during storage, while acidity and moisture increased. Twenty-one phenolic compounds (11 phenolic acids, nine flavonoids, and one coumarin) were quantified, with salicylic (0.08–0.76 μg g−1) and p-coumaric (0.21–1.93 μg g−1) acids found in all samples studied. In general, the phenolic compounds monitored were stable during the 450 days of storage, while reducing capacity increased and DPPH free radical scavenging capacity had value fluctuations. The results obtained in this study showed that honey stored for 450 days could be considered safe for human consumption considering the physicochemical parameters evaluated, besides maintaining its bioactive components.

C-ring cleavage metabolites of catechin and epicatechin enhanced antioxidant activities through intestinal microbiota

The changes in DPPH radical-scavenging capability of catechin and epicatechin during 24 h incubation with fecal microbiota in vitro and the targeted analysis of the characteristic metabolites by using UPLC-Q-TOF indicated that increase in antioxidant activity was synchronous with the accumulation of C-ring cleavage metabolites. Therefore, C-ring cleavage metabolite, 1-(3′,4′-Dihydroxyphenyl)-3-(2′′,4′′,6′′-trihydroxyphenyl)propan-2-ol (3,4-DHPP-2-ol), was separated from incubation liquid. The antioxidant activities of this metabolite and other 11 metabolites were examined through DPPH and ABTS free radical scavenging capacity and ferric reducing antioxidant capability (FRAC). The results indicated that all metabolites with the structure of 3′,4′-dihydroxylated had high antioxidant activity, especially 3,4-DHPP-2-ol, whose EC50 was 5.97 μM in DPPH assay, 2 times as high as that of catechin, and 1.8 times as high as that of epicatechin. But the metabolites with the structure of monohydroxylated or unhydroxylated on the benzene ring hardly exhibited antioxidant activity.

Solid-state fermentation with probiotics and mixed yeast on properties of okara

The effect of solid-state fermentation with compound probiotics and two types of yeast (Saccharomyces cerevisiae and Hansenula sp.) on the composition and selected quality attributes of okara were studied. Four different fermentation schemes, i.e., compound probiotics fermentation (P), mixed yeast (Saccharomyces cerevisiae and Hansenula sp.) fermentation (SH), co-fermentation of compound probiotics and mixed yeast (P + SH) and two-stage fermentation of compound probiotics and mixed yeast (P-SH) were comparatively assessed for their proximate composition, abilities to improve selected physicochemical, antioxidant, functional properties and sensory attributes (flavor and taste) of okara. The results showed that all the fermentation schemes could significantly improve the proximate composition, physicochemical as well as antioxidant activities and sensory attributes of okara. The bitterness and astringency of the okara were also reduced. The P-SH samples contained crude fiber of 12.0 g/100 g dry sample, total phenols of 154 mg gallic acid equivalence/100 g dry sample, free amino acids of 3.80 g/100 g dry sample. The DPPH free radical scavenging capacity and ABTS free radical scavenging capacity of the P-SH samples were 776 mg Trolox equivalence/100 g dry sample and 487 mg Trolox equivalence/100 g dry sample, respectively. The P + SH sample produced more alcohol, ester and other important flavoring substances than the other three methods. However, the P + SH sample had a relatively acidic taste.