Antioxidant peptides isolated from the marine rotifer,Brachionus rotundiformis

Protein derived from the rotifer Brachionus rotundiformis was hydrolyzed using different proteases (Alcalase, α-chymotrypsin, Neutrase, papain, pepsin and trypsin) for production of antioxidant peptide. Antioxidant activities of hydrolysates were evaluated using DPPH radical scavenging activity. Peptic hydrolysate exhibited the highest antioxidative activity compared to other hydrolysates. To identify antioxidant peptides, peptic hydrolysate was purified using consecutive chromatographic methods, and antioxidant peptides were identified to be Leu-Leu-Gly-Pro-Gly-Leu-Thr-Asn-His-Ala (1076 Da), and Asp-Leu-Gly-Leu-Gly-Leu-Pro-Gly-Ala-His (1033 Da) by Q-TOF ESI mass spectroscopy. EC₅₀ values of purified peptides were 189.8 and 167.7 μM, respectively. Antioxidant activities of peptides purified from the rotifer protein hydrolysate were evaluated, with results showing that peptides significantly quenched free radicals.     

A multiple free-radical scavenging (MULTIS) study on the antioxidant capacity of a neuroprotective drug,edaravone as compared with uric acid,glutathione, and trolox

Edaravone (3-methyl-1-phenyl-2-pyrazoline-5-one) is a neuroprotective drug that has been used for brain ischemia injury treatment. Because its activity is speculated to be due to free radical scavenging activity, we carried out a quantitative determination of edaravone’s free radical scavenging activity against multiple free radical species. Electron spin resonance (ESR) spin trapping-based multiple free-radical scavenging (MULTIS) method was employed, where target free radicals were hydroxyl radical, superoxide anion, alkoxyl radical, alkylperoxyl radical, methyl radical, and singlet oxygen. Edaravone showed relatively high scavenging abilities against hydroxyl radical (scavenging rate constant k = 2.98 × 10¹¹ M⁻¹ s⁻¹), singlet oxygen (k = 2.75 × 10⁷ M⁻¹ s⁻¹), and methyl radical (k = 3.00 × 10⁷ M⁻¹ s⁻¹). Overall, edaravone’s scavenging activity against multiple free radical species is as robust as other known potent antioxidant such as uric acid, glutathione, and trolox. A radar chart illustration of the MULTIS activity relative to uric acid, glutathione, and trolox indicates that edaravone has a high and balanced antioxidant activity with low specificity.     

Purification and evaluation of a novel antioxidant peptide from corn protein hydrolysate

In the present study, corn protein hydrolysate (CPH) with antioxidant activity was obtained by enzymatic hydrolysis. Corn gluten meal (CGM) was hydrolyzed using two proteases (Alcalase and Protamex) to produce the antioxidant peptide. Extrusion and starch removal of corn protein were used as pretreatment procedures before proteolysis. Hydrolysis by Alcalase has more remarkable digesting efficiency on corn protein than that by Protamex. Therefore, the hydrolysate catalyzed by Alcalase was fractionated by ultrafiltration, and peptide with the highest antioxidant activity was purified from <6 kDa molecular weight fraction. The amino acid sequence of the novel peptide was Gln-Gln-Pro-Gln-Pro-Trp as identified by a quadrupole time-of-flight mass spectrometer (Q-TOF2), with molecular weight of 782.34 Da, which was matched to γ-zein f (50–55). The new peptide was further synthesized by Fmoc solid-phase method. It showed scavenging activity against DPPH, ABTS, and hydroxyl free radicals in dose dependent manner with EC₅₀ values of 0.95, 0.0112 and 4.43 mg/mL, respectively. It also exhibited notable reducing power of 0.54 at 2.0 mg/mL, but showed weaker Fe²⁺-chelating capacity with EC₅₀ value of 6.27 mg/mL. These results suggest that the hexapeptide is a potential natural antioxidant that can be used as drug or functional food ingredient.     

Antioxidant, α-amylase inhibitory and oxidative DNA damage protective property of Boerhaavia diffusa (Linn.) root

Boerhaavia diffusa Linn. of family Nyctaginaceae is a known traditional medicinal plant and has been used in the treatment of many free radical mediated diseases. Excessive formation of free radicals, either reactive oxygen species (ROS) or reactive nitrogen species (RNS) is responsible for damaging various biomolecules like DNA, lipids and proteins. The present investigation was initially carried out to explore the possible link between antioxidant, oxidative DNA damage protective and α-amylase inhibitory property of B. diffusa root extract and their bioactive fraction. Our results illustrated an enhanced DPPH radical scavenging activity/antioxidant power of methanol root extract (IC₅₀ < 250 μg/ml) than ethanol (IC₅₀ = 250 μg/ml) and aqueous extract (IC₅₀ > 250 μg/ml). In addition, the methanol root extract also showed better oxidative DNA damage protective activity and α-amylase inhibitory property than ethanol and aqueous root extract. Phytochemical screening of B. diffusa ethanol and methanol root extract showed the presence of saponins, alkaloids, flavonoids, glycosides and terpenoids in large amount. By means of repetitive preparatory TLC and HPLC the potent antioxidant and α-amylase inhibitory fraction was isolated from methanol root extract. Our results illustrated that DPPH radical scavenging activity (IC₅₀ < 250 μg/ml) and oxidative DNA damage protective and α-amylase inhibitory activity of the isolated/purified bioactive compound from methanol extract were significantly closer to that of crude extract, which in turn confirm that antioxidant and antidiabetic property of methanol root extract resides in this fraction and established a significant correlation between antioxidant and inhibitory α-amylase property of this bioactive fraction compound. These profound effects of B. diffusa methanol root extract and its purified fraction against oxidative plasmid DNA damage, antioxidant and α-amylase inhibitory activity may explain its extensive use in daily life and possible health benefits.     

Antioxidant activity and protection of human umbilical vein endothelial cells from hydrogen peroxide-induced injury by DMC,a chalcone from buds of Cleistocalyx operculatus

The aim of this work was to study the antioxidant activity and the protective effect of 2′,4′-dihydroxy-6′-methoxy-3′,5′-dimethylchalcone (DMC), the main compound from the buds of Cleistocalyx operculatus, on human umbilical vein endothelial cells against cytotoxicity induced by H₂O₂. The antioxidant activities of DMC were measured by ABTS assay, ferric reducing antioxidant power (FRAP) and hydroxyl radical scavenging activity, and protective effects of DMC on human umbilical vein endothelial cells against cytotoxicity induced by H₂O₂ were tested. DMC was found to have high ABTS radical scavenging activity (176.5 ± 5.2 μmol trolox equivalents/500 μmol DMC) and strong ferric reducing antioxidant power (213.3 ± 5.8 μmol trolox equivalents/500 μmol DMC). In addition, DMC scavenged the hydroxyl radicals, with IC₅₀ values of 243.7 ± 6.3 μM, slightly lower than the reference antioxidant ascorbic acid (ASC). Moreover, DMC could protect the human umbilical vein endothelial cells against H₂O₂-induced cytotoxicity by decrease intracellular and extracellular ROS levels, reduction in catalase (CAT) activity and increment in malondialdehyde (MDA) level. These results suggested that DMC has the potential to be used in the therapy of oxidative damage.     

Comparison in antioxidant action between α-chitosan and β-chitosan at a wide range of molecular weight and chitosan concentration

Antioxidant activity in α- and β-chitosan at a wide range of molecular weight (Mw) and chitosan concentration (CS) was determined by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, reducing ability, chelating ability, and hydroxyl radical scavenging activity. The form of chitosan (FC) had significant (P <0.05) effect on all measurements except DPPH radical scavenging activity, and antioxidant activity was dependent on Mw and CS. High Mw (280–300 kDa) of β-chitosan had extremely lower half maximal effective concentrations (EC₅₀) than α-chitosan in DPPH radical scavenging activity and reducing ability. The 22–30 kDa of α- and β-chitosan showed significantly (P <0.05) higher activities in DPPH radical scavenging, reducing ability, and hydroxyl radical scavenging than samples at other Mw, while chelating ability was the highest in 4–5 kDa chitosan. CS had significant effect on all measurements and the effect was related to Mw. The antioxidant activity of 280–300 kDa chitosan was affected by coil-overlap concentrations (C¹) in the CS range of 4–10 mg/mL, forming entanglements. Reducing ability and hydroxyl radical scavenging activity were more predominant action in antioxidant activity of chitosan as shown by the lower EC₅₀ values than those in other antioxidant measurements.     

Synthesis,antioxidant, and antimicrobial evaluation of some 2-arylbenzimidazole derivatives

A series of 2-arylbenzimidazole derivatives (3a–3p and 4a–4i) were synthesized and evaluated as potential antioxidant and antimicrobial agents. Their antioxidant properties were evaluated by various in vitro assays including hydroxyl radical (HO) scavenging, superoxide radical anion (O₂^?) scavenging, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, and ferric reducing antioxidant power. Results demonstrated that compounds with hydroxyl group at the 5-position of benzimidazole ring had a comparable or better antioxidant activity in comparison to standard antioxidant tert-butylhydroquinone (TBHQ). Markedly, compound 4h that showed the highest HO scavenging activity (EC₅₀ = 46 μM) in vitro had a significant reduction of 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH)-induced intracellular oxidative stress and H₂O₂-induced cell death. In addition, these compounds showed moderate to good inhibitory activity against Staphylococcus aureus selectively at noncytotoxic concentrations.     

Evaluation of in vitro free radical scavenging potential of Streptomyces sp. AM-S1 culture filtrate

The present study was carried out to determine the free radical scavenging potential of culture filtrate of Streptomyces sp. AM-S1. Antioxidant activity of culture filtrate, lyophilized culture filtrate and ethyl acetate extract of Streptomyces sp. AM-S1 was determined by various in vitro assays such as ferric reducing power assay, phosphomolybdenum reduction, DPPH and ABTS radical scavenging activities. The results revealed that the culture filtrate of Streptomyces sp. AM-S1 effectively scavenged DPPH (IC₅₀ 90.2 μl/ml) and ABTS (IC₅₀ 13.2 μl/ml) radicals in a concentration dependent manner. In all the assays, ethyl acetate extract registered higher antioxidant activity when compared with the lyophilized culture filtrate (LCF). In addition, ethyl acetate extract (1123.4 μmole Fe(II)/mg extract) exhibited higher ferric reducing activity than the standard BHA (814.4 μmole Fe(II)/mg extract). Further works are needed on the isolation and identification of antioxidant molecules from the ethyl acetate extract of Streptomyces sp. AM-S1 culture filtrate.     

Identification of novel acetylcholinesterase inhibitors: Indolopyrazoline derivatives and molecular docking studies

The synthesis of novel indolopyrazoline derivatives (P1-P4 and Q1-Q4) has been characterized and evaluated as potential anti-Alzheimer agents through in vitro Acetylcholinesterase (AChE) inhibition and radical scavenging activity (antioxidant) studies. Specifically, Q3 shows AChE inhibition (IC₅₀: 0.68 ± 0.13 μM) with strong DPPH and ABTS radical scavenging activity (IC₅₀: 13.77 ± 0.25 μM and IC₅₀: 12.59 ± 0.21 μM), respectively. While P3 exhibited as the second most potent compound with AChE inhibition (IC₅₀: 0.74 ± 0.09 μM) and with DPPH and ABTS radical scavenging activity (IC₅₀: 13.52 ± 0.62 μM and IC₅₀: 13.13 ± 0.85 μM), respectively. Finally, molecular docking studies provided prospective evidence to identify key interactions between the active inhibitors and the AChE that furthermore led us to the identification of plausible binding mode of novel indolopyrazoline derivatives. Additionally, in-silico ADME prediction using QikProp shows that these derivatives fulfilled all the properties of CNS acting drugs. This study confirms the first time reporting of indolopyrazoline derivatives as potential anti-Alzheimer agents.     

Synthesis and SAR study of 4,5-diaryl-1H-imidazole-2(3H)-thione derivatives,as potent 15-lipoxygenase inhibitors

A series of 4,5-diaryl-1H-imidazole-2(3H)-thione was synthesized and their inhibitory potency against soybean 15-lipoxygenase and free radical scavenging activities were determined. Compound 11 showed the best IC₅₀ for 15-LOX inhibition (IC₅₀ = 4.7 μM) and free radical scavenging activity (IC₅₀ = 14 μM). Methylation of SH at C₂ position of imidazole has dramatically decreased the 15-LOX inhibition and radical scavenging activity as it can be observed in the inactive compound 14 (IC₅₀ >250 μM). Structure activity similarity (SAS) showed that the most important chemical modification in this series was methylation of SH group and Docking studies revealed a proper orientation for SH group towards Fe core of the 15-LOX active site. Therefore it was concluded that iron chelating could be a possible mechanism for enzyme inhibition in this series of compounds.     

Remarkable antioxidant properties of a series of hydroxy-3-arylcoumarins

In the present work we synthesized a series of hydroxy-3-arylcoumarins (compounds 1–9), some of them previously described as MAO-B selective inhibitors, with the aim of evaluating their antioxidant properties. Theoretical evaluation of ADME properties of all the derivatives was also carried out. From the ORAC-FL, ESR and CV data it was concluded that these derivatives are very good antioxidants, with a very interesting hydroxyl, DPPH and superoxide radicals scavenging profiles. In particular compound 9 is the most active and effective antioxidant of the series (ORAC-FL = 13.5, capacity of scavenging hydroxyl radicals = 100%, capacity of scavenging DPPH radicals = 65.9% and capacity of scavenging superoxide radicals = 71.5%). Kinetics profile for protection fluorescein probe against peroxyl radicals by addition of antioxidant molecule 9 was also performed. Therefore, it can operate as a potential candidate for preventing or minimizing the free radicals overproduction in oxidative-stress related diseases.     

Isolation,chemical characterization and antioxidant activities of two polysaccharides from the gel and the skin of Aloe barbadensis Miller irrigated with sea water

Two polysaccharides, GAPS-1 and SAPS-1, were isolated from the gel and the skin of Aloe barbadensis Miller irrigated with sea water for 3.5 years through a combination of anion-exchange column chromatography and repeated gel chromatography and their chemical characterization and antioxidant activities in vitro were investigated. GAPS-1 and SAPS-1 were composed of Man:Glc:Gal in a ratio of 120:2:3 and 296:36:1 with their molecular weight 1.74 × 10⁵ and 3.97 × 10⁴ Da, respectively. IR and ¹³C NMR study of GAPS-1 and SAPS-1 demonstrated that the main skeletons of GAPS-1 was β-(1 → 4)-D linkaged mannose with acetylation at C-6 and C-3 of manopyranosyl and SAPS-1 was β-(1 → 4)-D linkaged galactoglucomannan with acetylation at C-6 of pyranosyl. In a concentration-dependent manner, GAPS-1 and SAPS-1 were demonstrated to have strong scavenging activities against superoxide radical, moderate ferrous chelating effect, moderate scavenging activities of hydroxyl radical, moderate reductive power and moderate inhibition of lipid peroxidation. Furthermore, GAPS-1 exhibited moderate scavenging activity of hydrogen peroxide, while SAPS-1 exhibited weak scavenging activity of hydrogen peroxide. GAPS-1 demonstrated more effective antioxidant activities than SAPS-1. The more acetyl group in GAPS-1 molecules probably contributes to the activities.     

Biological activities of two macroalgae from Adriatic coast of Montenegro

In the present investigation the acetone extracts of macroalgae Ulva lactuca and Enteromorpha intestinalis were tested for antioxidant, antimicrobial and cytotoxic potential. Antioxidant activity was evaluated by measuring the scavenging capacity of tested samples on DPPH and superoxide anion radicals, reducing the power of samples and determination of total phenolic and flavonoid compounds in extracts. As a result of the study, U. lactuca extract was found to have a better free radical scavenging activity (IC₅₀ = 623.58 μg/ml) than E. intestinalis extract (IC₅₀ = 732.12 μg/ml). Moreover, the tested extracts had effective ferric reducing power and superoxide anion radical scavenging. The total content of phenol in extracts of U. lactuca and E. intestinalis was 58.15 and 40.68 μg PE/mg, while concentrations of flavonoids were 39.58 and 21.74 μg RE/mg, respectively. Furthermore, among the tested species, extracts of U. lactuca showed a better antimicrobial activity with minimum inhibitory concentration values ranging from 0.156 to 5 mg/ml, but it was relatively weak in comparison with standard antibiotics. Bacillus mycoides and Bacillus subtilis were the most susceptible to the tested extracts. Contrary to this Aspergillus flavus, Aspergillus fumigatus and Penicillium purpurescens were the most resistant. Finally, cytotoxic activity of tested extracts was evaluated on four human cancer cell lines. Extract of E. intestinalis expressed the stronger cytotoxic activity towards all tested cell lines with IC₅₀ values ranging from 74.73 to 155.39 μg/ml.     

Isolation and purification of salvianolic acid A and salvianolic acid B from Salvia miltiorrhiza by high-speed counter-current chromatography and comparison of their antioxidant activity

Water-soluble salvianolic acid A (Sal A) and salvianolic acid B (Sal B) were successfully isolated and purified from the crude extract of Salvia miltiorrhiza by high-speed counter-current chromatography (HSCCC). The solvent system was n-hexane–ethyl acetate–methanol–water (3:6:6:10, v/v/v/v). 4.27 mg of Sal A and 32.09 mg of Sal B were obtained from 260 mg of the crude sample. The purities of Sal A and Sal B were 96.67% and 97.43%, respectively. Their structures were identified by ¹H NMR and ¹³C NMR. Antioxidant activities of Sal A and Sal B were also evaluated and compared by the methods of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay and 2,2-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid (ABTS⁺) radical cation decolourisation assay. Both Sal A and Sal B showed high radical scavenging activities with their EC₅₀ values being 1.43 ± 0.09 and 1.81 ± 0.01 μg/ml in DPPH radical method. The ABTS results showed that Sal A and Sal B exhibited high total antioxidant activities, their EC₅₀ values were 1.35 ± 0.00 and 1.43 ± 0.01 μg/ml, respectively.     

Carboxymethylation of a polysaccharide extracted from Ganoderma lucidum enhances its antioxidant activities in vitro

The chemical carboxylmethylated polysaccharide (C-GLP), which derived from water-insoluble crude Ganoderma lucidum polysaccharide (GLP), was prepared. Water solubility, chemical characterization, and antioxidant activities in vitro of C-GLP were determined. The solubility of C-GLP in distilled water reached 100 mg/ml, which was much higher than the solubility of GLP. Chemical analysis indicated that C-GLP was composed of Glc:Man:Gal = 33.0:1.0:3.4 with a molecular weight of 1.8 × 10⁶ Da and a carboxymethyl content of 11.07%. The signals of carboxymethyl were found in IR and ¹³C NMR spectra. Moreover, a high antioxidant activity of C-GLP was observed, especially in scavenging of hydroxyl radical (83.7% at 5 mg/ml) and hydrogen peroxide (51.6% at 10 mg/ml). This study indicates the effects of carboxymethylation on water-insoluble polysaccharide and explores a potential antioxidant in food industry and pharmaceuticals.     

Antioxidant activity of aqueous methanol extracts from the lucanid beetle,Serrognathus platymelus castanicolor Motschulsky (Coleoptera: Lucanidae)

The objective of this study was to evaluate the antioxidant properties of extracts of the lucanid beetle, Serrognathus platymelus castanicolor Motschulsky, obtained at different growth stages. The antioxidant activities of six different extracts were determined using 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), and singlet oxygen (¹O₂). The activity level of pupal methanol extracts (PME) was higher in the DPPH and ABTS radical scavenging assays, whereas that of the water extracts was weaker in all assays. The ¹O₂ quenching ability of the PME was comparable to that of ascorbic acid (effective concentration of 50% ¹O₂ quenching: EC₅₀ = 0.184 mg/ml^-1 and 0.167 mg/ml^-1, respectively). The free radical scavenging antioxidant ability of the extracts significantly altered phenolic contents, important factors in the potency of antioxidant capacity. Our results suggest that these extracts may reduce oxidative stress in living organisms and reduce oxidative damage in insects under unfavorable conditions.     

Glutathione S-transferase pi (GST-pi) inhibition and anti-inflammation activity of the ethyl acetate extract of Streptomyces sp. strain MJM 8637

To investigate the anti-cancer properties of soil-borne actinobacteria, MJM 8637, the glutathione S-transferase pi (GST-pi) assay, anti-tumor necrosis factor (TNF)-α assay, the level of antioxidant potential by DPPH radical scavenging activity, NO scavenging activity, and ABTS radical scavenging activity in ethyl acetate extract were determined. The 16S rDNA sequencing analysis revealed that Streptomyces sp. strain MJM 8637, which was isolated from Hambak Mountain, Korea, has 99.5% similarity to Streptomyces atratus strain NBRC 3897. The physiological and the morphological characteristics of the strain MJM 8637 were also identified. The ethyl acetate extract of MJM 8637 inhibited TNF-α production approximately 61.8% at concentration 100 μg/ml. The IC₅₀ value of the strain MJM 8637 extract on GST-pi was identified to be 120.2 ± 1.6 μg/ml. In DPPH, NO, and ABTS radical scavenging assays, the IC₅₀ values of the strain MJM 8637 extract were found to be 977.2 μg/ml, 1143.7 μg/ml, and 454.4 μg/ml, respectively. The ethyl acetate extract of the strain MJM 8637 showed 97.2 ± 1.3% of cell viability at 100 μg/ml in RAW 264.7 cell viability assay. The results obtained from this study suggest that the ethyl acetate extract of Streptomyces sp. strain MJM 8637 could be considered as a potential source of drug for the cancers that have multidrug resistance with its GST-pi inhibition and anti-inflammation activities, and low cytotoxicity.     

Design,synthesis and anti-Alzheimer properties of dimethylaminomethyl-substituted curcumin derivatives

Eight dimethylaminomethyl-substituted curcumin derivatives were designed and synthesized. The antioxidant test revealed that the synthesized compounds had higher free radical scavenging activity towards both 2,2-diphenyl-1-picrylhydrazyl free radicals (DPPH) (IC₅₀ 1.5–29.9 μM) and galvinoxyl radicals (IC₅₀ 4.9–41.1 μM) than the lead compound curcumin. Besides, compound 3a could effectively inhibit the Aβ self-aggregation in vitro. Investigated in phosphate-buffered solutions (pH = 7.4) in the presence or absence of 0.1% FBS 3a showed a good stability while curcumin did not. Furthermore, 3a showed a good lipophilicity (log P = 3.48), suggesting a potential ability to penetrate the blood–brain-barrier. The aqueous solubility of the hydrochloride salt of 3a (16.7 mg/mL) has also been significantly improved as compared with curcumin (<0.1 mg/mL).     

Scavenging and antioxidant activities of immunomodulating polysaccharides isolated from Salvia officinalis L.

Crude polysaccharides, isolated from the aerial parts of sage (Salvia officinalis L.) by sequential extraction with water (A), hot ammonium oxalate (B), dimethyl sulfoxide (C), 1 M (D) and 4 M (E) potassium hydroxide solutions, and six ion-exchange fractions of A were examined for their ability to inhibit peroxidation of liposome lipid by hydroxyl radicals and to reduced DPPH radical content. The highest inhibition of liposome lipid peroxidation was found with crude polysaccharides A, B and D, antioxidant activities reached ～37%. The purified fractions A1 and A2 inhibited the liposome peroxidation to ～35%. However, the radical scavenging abilities of the most active crude polysaccharides A, B and C on DPPH radicals were found in the range 80–90%, while the most active purified fractions A₃–A₆ in three or fourfold doses achieved 75–92%. The least effective tested polysaccharides succeeded 20% inhibition using both methods.