Reduction kinetics of the antiradical probe 2,2-diphenyl-1-picrylhydrazyl in methanol and acetonitrile by the antiradical activity of protocatechuic acid and protocatechuic acid methyl ester

Optimization of cellulase-assisted extraction process and antioxidant activities of polysaccharides from Tricholoma mongolicum Imai

BACKGROUND

Tricholoma mongolicum Imai is a well-known edible and medicinal mushroom which in recent years has attracted increasing attention because of its bioactivities. In this study, water-soluble polysaccharides were extracted from T. mongolicum Imai by cellulase-assisted extraction and their antioxidant activities were investigated.

RESULTS

In order to improve the yield of polysaccharides, four variables, cellulase amount (X1 ), pH (X2 ), temperature (X3 ) and extraction time (X4 ), were investigated with a Box-Behnken design. The optimal conditions were predicted to be cellulase amount of 20 g kg(-1) , pH of 4.0, temperature of 50 °C and extraction time of 127 min, with a predicted polysaccharide yield of 190.1 g kg(-1) . The actual yield of polysaccharides under these conditions was 189.6 g kg(-1) , which matched the predicted value well. The crude polysaccharides were purified to obtain four fractions, and characterization of each was carried out. In addition, antioxidant properties of four polysaccharides assessed by 1,1-diphenyl-2-picryldydrazyl (DPPH) and hydroxyl radical-scavenging assays indicated that polysaccharides from T. mongolicum Imai (TMIPs) possessed antioxidant activity in a dose-dependent manner.

CONCLUSION

TMIPs show moderate antioxidant activities in vitro. Therefore it is suggested that TMIPs are potential natural antioxidants for use in functional foods. © 2016 Society of Chemical Industry.

Determination of the antiradical activity and kinetics of pomegranate juice using 2,2-diphenylpicyrl-1-hydrazyl as the antiradical probe

Whole fruit pomegranate (Punica granatum L.) juice of the 'Wonderful' cultivar was characterized through the elucidation of its antiradical kinetics and activity using 2,2-diphenyl-1-picrylhydrazyl as the antiradical probe. Time-dependent concentration of 2,2-diphenyl-1-picrylhydrazyl during its reduction by the juice has been adjusted through a non-linear parametric fitting. Determined total antiradical activity was high, able to reduce 84.58 µmol/l of 2,2-diphenyl-1-picrylhydrazyl per concentration unit of juice (µl/ml), equivalent to a concentration of 42.29 mmol/l of ascorbic acid (or Trolox). Partial antiradical activities due to the fast-, medium- and slow-kinetics were 49.09, 18.16 and 17.33 µmol/l of reduced 2,2-diphenyl-1-picrylhydrazyl per concentration unit of juice (µl/ml), respectively. The corresponding rate constant for the fast-, medium- and slow-kinetics were κ 1 = 6.03, κ 2 = 0.169 and κ 3 = 0.0094 (μl l)/(ml µmol min), respectively. This methodology allows characterization of samples through the accurate determination of the kinetics of their antiradical features, avoiding the use of empirical approximations that hinder the realistic comparison between extracts independently of their origin.

Bioassay-guided isolation and identification of antioxidative compounds from the bark of Eugenia polyantha

Eugenia polyantha bark extracts were found to have potential antioxidative activities. This study is an effort to investigate the antioxidative compounds in E. polyantha. In vitro antioxidatve assay were used as guided tools for the isolation of antioxidative compounds. The methanol-water extracts showed the highest level of free radical-scavenging activity (ED50) = 180 microg mL(-1) and protection from beta-carotene bleaching (8.7 microg mL(-1)). The methanol-water (1:1) extracts exhibited strong DPPH scavenging activity and protection against beta carotene bleaching and was subjected to repeated silica gel column chromatography. The n-butanol, acetone and ethyl acetate solubles exhibited the highest antioxidative activities, derivatization was conducted to the isolated antioxidative compounds prior to identification. Catechin, gallic acid and rutin were isolated from those solubles as active compounds present in the Eugenia polyantha bark.

Activity-guided isolation of antioxidants from the leaves of Terminalia arjuna

An activity-guided isolation and purification process was used to identify the l,l-diphenyl-2-picrylhydrazyl (DPPH) free radical-scavenging components of the food plant (Terminalia arjuna) of Antheraea mylitta. Dry leaves of T. arjuna were extracted with different solvents and tested for their antioxidant activity against DPPH(•). The acetone-water (8:2) extract expressed strong DPPH radical-scavenging activity, and was subjected to column chromatography over silica gel. Gallic acid, apigenin, luteolin, quercetin, epicatechin, ellagic acid and 1-O-β-galloyl glucose were isolated as active components and characterised by using different spectroscopic techniques.

Identification of a novel phenolic compound in litchi (Litchi chinensis Sonn.) pericarp and bioactivity evaluation

Litchi (Litchi chinensis Sonn.) is a delicious fruit widely accepted by consumers all over the world. In this work, phytochemical investigation of litchi pericarp methanol extracts led to the isolation of a novel phenolic, 2-(2-hydroxyl-5-(methoxycarbonyl) phenoxy) benzoic acid, together with kaempferol, isolariciresinol, stigmasterol, butylated hydroxytoluene, 3,4-dihydroxyl benzoate, methyl shikimate and ethyl shikimate. Most were found in litchi pericarp for the first time. Their structures were mainly elucidated by NMR and MS evidences. Antioxidant activities of the eight compounds were determined by a DPPH radical scavenging assay and the results showed that 2-(2-hydroxy-5-(methoxycarbonyl) phenoxy)benzoic acid, kaempferol, isolariciresinol, butylated hydroxytoluene and 3,4-dihydroxy benzoate exhibited good antioxidant activities. An interesting finding was that butylated hydroxytoluene was detected as a natural antioxidant in this work, which was usually taken as a synthesized antioxidant. Furthermore, the novel compound exhibited no inhibitory effects against tyrosinase and α-glucosidase activities.

Activity-guided isolation of antioxidant xanthones from Swertia chirayita (Roxb.) H. Karsten (Gentianaceae)

An activity-guided isolation and purification process was used to identify the DPPH (l,l-diphenyl-2-picrylhydrazyl) radical-scavenging components of Swertia chirayita. A dry, whole plant of S. chirayita was extracted with different solvents and tested for its DPPH radical-scavenging activity. The acetone : water (8 : 2) extract showed the highest total phenolic content (TPC) and DPPH radical-scavenging activity, which was column chromatographed to obtain decussatin, swertianin, bellidifolin, isobellidifolin, amarogentin, swertianolin and mangiferin as active components. Good correlation was observed between TPC and DPPH scavenging activity among the extracts. The unique structure of xanthones, including the catecholic moiety and the completely conjugated system, enables them to be promising antioxidants.

Reactions of reactive oxygen species (ROS) with curcumin analogues: Structure-activity relationship

Three curcumin analogues viz., bisdemethoxy curcumin, monodemethoxy curcumin, and dimethoxycurcumin that differ at the phenolic substitution were synthesized. These compounds have been subjected for free radical reactions with DPPH radicals, superoxide radicals (O(2)(•-)), singlet oxygen ((1)O(2)) and peroxyl radicals (CCl(3)O(2)(•)) and the bimolecular rate constants were determined. The DPPH radical reactions were followed by stopped-flow spectrometer, (1)O(2) reactions by transient luminescence spectrometer, and CCl(3)O(2)(•) reactions using pulse radiolysis technique. The rate constants indicate that the presence of o-methoxy phenolic OH increases its reactivity with DPPH and CCl(3)O(2)(•), while for molecules lacking phenolic OH, this reaction is very sluggish. Reaction of O(2)(•-) and (1)O(2) with curcumin analogues takes place preferably at β-diketone moiety. The studies thus suggested that both phenolic OH and the β-diketone moiety of curcumin are involved in neutralizing the free radicals and their relative scavenging ability depends on the nature of the free radicals.