A new computational approach for the determination of 2,2-diphenyl-1-picrylhydrazyl free radical scavenging activity (DPPH-RSA) in food is reported, based on the concept of machine learning. Trolox standard was mix with DPPH at different concentrations to produce different colors from purple to yellow. Artificial neural network (ANN) was trained on a typical set of images of the DPPH radical reacting with different levels of Trolox. This allowed the neural network to classify future images of any sample into the correct class of RSA level. The ANN was then able to determine the DPPH-RSA of cinnamon, clove, mung bean, red bean, red rice, brown rice, black rice and tea extract and the results were compared with data obtained using a spectrophotometer. The application of ANN correlated well to the spectrophotometric classical procedure and thus do not require the use of spectrophotometer, and it could be used to obtain semi-quantitative results of DPPH-RSA.
The best described pharmacological property of flavonoids is their capacity to act as potent antioxidant that has been reported to play an important role in the alleviation of diabetes mellitus. Flavonoids biochemical properties are structure dependent; however, they are yet to be thoroughly understood. Hence, the main aim of this work was to investigate the antioxidant and antidiabetic properties of some structurally related flavonoids to identify key positions responsible, their correlation, and the effect of methylation and acetylation on the same properties. Antioxidant potential was evaluated through dot blot, 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, ABTS+ radical scavenging, ferric reducing antioxidant power (FRAP), and xanthine oxidase inhibitory (XOI) assays. Antidiabetic effect was investigated through α-glucosidase and dipeptidyl peptidase-4 (DPP-4) assays. Results showed that the total number and the configuration of hydroxyl groups played an important role in regulating antioxidant and antidiabetic properties in scavenging DPPH radical, ABTS+ radical, and FRAP assays and improved both α-glucosidase and DPP-4 activities. Presence of C-2-C-3 double bond and C-4 ketonic group are two essential structural features in the bioactivity of flavonoids especially for antidiabetic property. Methylation and acetylation of hydroxyl groups were found to diminish the in vitro antioxidant and antidiabetic properties of the flavonoids.
Cyphomandra betacea is one of the underutilized fruits which can be found in tropical and subtropical countries. This study was conducted to determine the antioxidant activity and phytochemical contents in different parts (i.e., flesh and peel) of the fruits. Antioxidants were analyzed using DPPH and ABTS free radical scavenging assays as well as FRAP assay. Anticholinesterase activity was determined using enzymatic assay using acetyl cholinesterase enzyme. For 80% methanol extract, the peel of the fruit displayed higher antioxidant activity in both FRAP and ABTS free radical scavenging assays while the flesh displayed higher antioxidant activity in the DPPH assay. Total phenolic and total flavonoid content were higher in the peel with the values of 4.89 ± 0.04 mg gallic acid equivalent (GAE)/g and 3.36 ± 0.01 mg rutin equivalent (RU)/g, respectively. Total anthocyanin and carotenoid content were higher in the flesh of the fruit with the values of 4.15 ± 0.04 mg/100 g and 25.13 ± 0.35 mg/100 g. The anticholinesterase was also higher in the peel of C. betacea. The same trends of phytochemicals, antioxidant, and anticholinesterase were also observed in the distilled water extracts. These findings suggested that C. betacea has a potential as natural antioxidant-rich nutraceutical products.
Honey has been used since ancient times for its nutritional as well as curative properties. Tualang honey is collected from wild honey bees' hives on Tualang trees found in the Malaysian rain forest. It has been used traditionally for the treatment of various diseases, where its therapeutic value has partly been related to its antioxidant properties. This study therefore assessed the colour intensity, total phenolic content, antioxidant activity and antiradical activity of gamma irradiated Tualang Honey. The colour intensity at ABS₄₅₀ was 489.5 ± 1.7 mAU, total phenolic content was 251.7 ± 7.9 mg (gallic acid) /Kg honey, total antioxidant activity by FRAP assay was 322.1 ± 9.7 (µM Fe(II)) and the antiradical activity by DPPH assay was 41.30 ± 0.78 (% inhibition). The data confirms that the antioxidant properties of gamma irradiated Tualang honey are similar to other types of honeys reported in the literature.
New derivatives of 7-hydroxy-4-methylcoumarin were synthesized using a chemical method and a microwave-assisted method to compare the feasibility, reaction times, and yields of the product. The newly synthesized coumarins were characterized by different spectroscopic techniques (FT-IR and NMR) and micro-elemental analysis (CHNS). In vitro antioxidant activities of these compounds were evaluated against hydrogen peroxide and were compared with standard natural antioxidant, vitamin C. Our results reveal that these compounds exhibit excellent radical scavenging activities.
A series of six novel heterocyclic chalcone analogues 4(a-f) has been synthesized by condensing 2-acetyl-5-chlorothiophene with benzaldehyde derivatives in methanol at room temperature using a catalytic amount of sodium hydroxide. The newly synthesized compounds are characterized by IR, mass spectra, elemental analysis and melting point. Subsequently; the structures of these compounds were determined using single crystal X-ray diffraction. All the synthesized compounds were screened for their antioxidant potential by employing various in vitro models such as DPPH free radical scavenging assay, ABTS radical scavenging assay, ferric reducing antioxidant power and cupric ion reducing antioxidant capacity. Results reflect the structural impact on the antioxidant ability of the compounds. The IC₀ values illustrate the mild to good antioxidant activities of the reported compounds. Among them, 4f with a p-methoxy substituent was found to be more potent as antioxidant agent.
Antioxidants have been widely used in the food industry to enhance product quality by preventing oxidation of susceptible substances. This work was carried out to maximise the recovery of total phenolic content (TPC), total flavonoid content (TFC), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical-scavenging capacity and 2,2'-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging capacity from Morinda citrifolia fruit via modification of the ethanol concentration, extraction time and extraction temperature at minimal processing cost. The optimised conditions yielded values of 881.57 ± 17.74 mg GAE/100 g DW for TPC, 552.53 ± 34.16 mg CE/100 g DW for TFC, 799.20 ± 2.97 µmol TEAC/100 g DW for ABTS and 2,317.01 ± 18.13 µmol TEAC/100 g DW for DPPH were 75% ethanol, 40 min of time and 57 °C. The four responses did not differ significantly (p > 0.05) from predicted values, indicating that models obtained are suitable to the optimisation of extraction conditions for phenolics from M. citrifolia. The relative amounts of flavonoids were 0.784 ± 0.01 mg quercetin/g of extract and 1.021 ± 0.04 mg rutin/g of extract. On the basis of the results obtained, M. citrifolia extract can be used as a valuable bioactive source of natural antioxidants.
The phenolic acid and flavonoid contents of Malaysian Tualang, Gelam, and Borneo tropical honeys were compared to those of Manuka honey. Ferric reducing/antioxidant power assay (FRAP) and the 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical-scavenging activities were also quantified. All honey extracts exhibited high phenolic contents (15.21 ± 0.51- 42.23 ± 0.64 mg/kg), flavonoid contents (11.52 ± 0.27- 25.31 ± 0.37 mg/kg), FRAP values (892.15 ± 4.97- 363.38 ± 10.57 μM Fe[II]/kg), and high IC₅₀ of DPPH radical-scavenging activities (5.24 ± 0.40- 17.51 ± 0.51 mg/mL). Total of 6 phenolic acids (gallic, syringic, benzoic, trans-cinnamic, p-coumaric, and caffeic acids) and 5 flavonoids (catechin, kaempferol, naringenin, luteolin, and apigenin) were identified. Among the Malaysian honey samples, Tualang honey had the highest contents of phenolics, and flavonoids, and DPPH radical-scavenging activities. We conclude that among Malaysian honey samples, Tualang honey is the richest in phenolic acids, and flavonoid compounds, which have strong free radical-scavenging activities.
The aim of the present study was to characterize the physical, biochemical and antioxidant properties of Algerian honey samples (n = 4). Physical parameters, such as pH, moisture content, electrical conductivity (EC), total dissolved solids (TDS), color intensity, total sugar and sucrose content were measured. Several biochemical and antioxidant tests were performed to determine the antioxidant properties of the honey samples. The mean pH was 3.84 ± 0.01, and moisture the content was 13.21 ± 0.16%. The mean EC was 0.636 ± 0.001, and the mean TDS was 316.92 ± 0.92. The mean color was 120.58 ± 0.64 mm Pfund, and the mean 5-hydroxymethylfurfural (HMF) content was 21.49 mg/kg. The mean total sugar and reducing sugar contents were 67.03 ± 0.68 g/mL and 64.72 ± 0.52 g/g, respectively. The mean sucrose content was 2.29 ± 0.65%. High mean values of phenolic (459.83 ± 1.92 mg gallic acid/kg), flavonoid (54.23 ± 0.62 mg catechin/kg), ascorbic acid (159.70 ± 0.78 mg/kg), AEAC (278.15 ± 4.34 mg/kg), protein (3381.83 ± 6.19 mg/kg) and proline (2131.47 ± 0.90) contents, as well as DPPH (39.57% ± 4.18) and FRAP activities [337.77 ± 1.01 µM Fe (II)/100 g], were also detected, indicating that Algerian honey has a high antioxidant potential. Strong positive correlations were found between flavonoid, proline and ascorbic acid contents and color intensity with DPPH and FRAP values. Thus, the present study revealed that Algerian honey is a good source of antioxidants.
The influence of both acidic and basic hydrolysis on the yield, total phenolic content and antioxidative capacity of methanolic extract of germinated brown rice (GBR) was studied. Total phenolic content (TPC), total flavonoid content (TFC), 2,2'-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS) radical cation scavenging, and ferric reducing antioxidant power (FRAP) tests were used for the measurement of antioxidant ability. There was a significant difference p < 0.05) in the TPC and DPPH radical scavenging assay results when comparing neutral with acidic and basic catalysed hydrolysis. The yield of the crude extract was slightly higher in acidic hydrolysis than in basic hydrolysis p > 0.05). The TPC and TFC were highest in acidic hydrolysis. A significant correlation was observed between ABTS radical cation scavenging and FRAP. The antioxidant activity measured using DPPH radical scavenging assay showed high activity in acidic hydrolysis, while the ABTS radical cationscavenging activity and FRAP showed the highest values in basic hydrolysis. The samples were further evaluated using HPLC to determine the individual phenolic concentrations in different hydrolytic media contributing to the antioxidant effects. This study revealed that acidic and basic hydrolysis can improve the yield, phenolic content, and antioxidant activity of germinated brown rice.
This study was conducted to evaluate the effects of evaporation, gamma irradiation and temperature on the total polyphenols, flavonoids and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activities of Tualang honey samples (n = 14) following storage over three, six or twelve months. The mean polyphenol concentrations of the six gamma irradiated honey samples at three, six and twelve months, respectively, were 96.13%, 98.01% and 102.03% higher than the corresponding values of the eight non-gamma irradiated samples. Similarly, the mean values for flavonoids at three, six and twelve months were 111.52%, 114.81% and 110.04% higher, respectively, for the gamma irradiated samples. The mean values for DPPH radical-scavenging activities at three, six and twelve months were also 67.09%, 65.26% and 44.65% higher, respectively, for the gamma irradiated samples. These data indicate that all gamma irradiated honey samples had higher antioxidant potential following gamma irradiation, while evaporation and temperature had minor effects on antioxidant potential.
The antioxidant activity of several Malaysian plant extracts was analyzed simultaneously with their pro-oxidant capacity. This ratio represents an index (ProAntidex) of the net free radical scavenging ability of whole plant extracts. We observed that ethanolic extracts of Nephelium lappaceum peel, Fragaria x ananassa leaf, Lawsonia inermis leaf, Syzygium aqueum leaf and grape seed had a lower Pro-Antidex than the commercially available Emblica™ extract which is an antioxidant agent with very low pro-oxidant activity. Among the aqueous extracts, Lawsonia inermis leaf, Nephelium mutobile leaf and grape seed had lower pro-oxidant activity compared to the Emblica™ extract. Among these extracts, aqueous extract of Nephelium mutobile leaf had a very low index of 0.05 compared to 0.69 for Emblica™. Most of the extracts had a far lower ProAntidex compared to the Vitamin C. The index enables us to identify extracts with high net free radical scavenging activity potential. The ProAntidex is beneficial as a screening parameter to the food industries and healthcare.
This study was conducted to evaluate the potential antioxidant activity of lignin obtained from black liquor, a hazardous waste product generated during the extraction of palm oil. Antioxidant potential of the extracted lignin was evaluated by dissolving the extracted samples in 2 different solvent systems, namely, 2-methoxy ethanol and DMSO. Results revealed high percent inhibition of the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical in the lignin sample dissolved in 2-methoxy ethanol over DMSO (concentration range of 1-100 microg/ml). Lignin extracted in 2-methoxy ethanol exhibited higher inhibition percentage (at 50 microg/ml, 84.2%), whereas a concentration of 100 microg/ml was found to be effective in the case of the DMSO solvent (69.8%). Fourier transform infrared (FTIR) spectrometry revealed that the functional groups from the extracted lignin and commercial lignin were highly similar, indicating the purity of the lignin extracted from black liquor. These results provide a strong basis for further applications of lignin in the food industry and also illustrate an eco-friendly approach to utilize oil palm black liquor.
The stone fish (Actinopyga lecanora) ethanolic and methanolic tissue extracts were investigated for total phenolic contents (TPCs) as well as antioxidant activity using 2,2-diphenyl-1-picrylhydrazyl (DPPH(•)) radical scavenging activity and ferric reducing antioxidant power (FRAP) assays. Both extracts showed low amount of phenolics (20.33 to 17.03 mg of gallic acid equivalents/100 g dried sample) and moderate antioxidant activity (39% to 34% DPPH(•) radical scavenging activity and 23.95 to 22.30 mmol/100 mL FeSO4 FRAP value). Enzymatic proteolysis was carried out in order to improve the antioxidant activity using six commercially available proteases under their optimum conditions. The results revealed that the highest increase in antioxidant activity up to 85% was obtained for papain-generated proteolysate, followed by alcalase (77%), trypsin (75%), pepsin (68%), bromelain (68%), and flavourzyme (50%) as measured by DPPH(•) radical scavenging activity, whilst for the FRAP value, the highest increase in the antioxidant activity up to 39.2 mmol/100 mL FeSO4 was obtained for alcalase-generated proteolysate, followed by papain (29.5 mmol/100 mL FeSO4), trypsin (23.2 mmol/100 mL FeSO4), flavourzyme (24.7 mmol/100 mL FeSO4), bromelain (22.9 mmol/100 mL FeSO4), and pepsin (20.8 mmol/100 mL FeSO4). It is obvious that proteolysis of stone fish tissue by proteolytic enzymes can considerably enhance its antioxidant activity.
The aim of this study was to develop and validate a rapid and simple high performance thin layer chromatographic (HPTLC) method to screen for antioxidant activity in algal samples. 16 algal species were collected from local Victorian beaches. Fucoxanthin, one of the most abundant marine carotenoids was quantified directly from the HPTLC plates before derivatization, while derivatization either with 2,2-diphenyl-1-picrylhydrazyl (DPPH) or ferric chloride (FeCl3) was used to analyze antioxidants in marine algae, based on their ability to scavenge non biological stable free radical (DPPH) or to chelate iron ions. Principal component analysis of obtained HPTLC fingerprints has classified algae species into 5 groups according to their chemical/antioxidant profiles. The investigated brown algae samples were found to be rich in non-and moderate-polar compounds and phenolic compounds with antioxidant activity. Most of the phenolic iron chelators also have shown free radical scavenging activity. Strong positive and significant correlations between total phenolic content and DPPH radical scavenging activity showed that, phenolic compounds, including flavonoids are the main contributors of antioxidant activity in these species. The results suggest that certain brown algae possess significantly higher antioxidant potential when compared to red or green algae and could be considered for future applications in medicine, dietary supplements, cosmetics or food industries. Cystophora monilifera extract was found to have the highest antioxidant concentration, followed by Zonaria angustata, Cystophora pectinate, Codium fragile, and Cystophora pectinata. Fucoxanthin was found mainly in the brown algae species. The proposed methods provide an edge in terms of screening for antioxidants and quantification of antioxidant constituents in complex mixtures. The current application also demonstrates flexibility and versatility of a standard HPTLC system in the drug discovery. Proposed methods could be used for the bioassay-guided isolation of unknown natural antioxidants and subsequent identification if combined with spectroscopic identification.
Enzyme hydrolysates (trypsin, papain, pepsin, α-chymotrypsin, and pepsin-pancreatin) of Tinospora cordifolia stem proteins were analyzed for antioxidant efficacy by measuring (1) 1,1-diphenyl-2-picrylhydrazyl (DPPH•) radical scavenging activity, (2) 2,20-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS+) radical scavenging capacity, and (3) Fe2+ chelation. Trypsin hydrolysate showed the strongest DPPH• scavenging, while α-chymotrypsin hydrolysate exhibited the highest ABTS+ scavenging and Fe2+ chelation. Undigested protein strongly inhibited the gastrointestinal enzymes, trypsin (50% inhibition at enzyme/substrate ratio = 1:6.9) and α-chymotrypsin (50% inhibition at enzyme/substrate ratio = 1:1.82), indicating the prolonged antioxidant effect after ingestion. Furthermore, gel filtration purified peptide fractions of papain hydrolysates exhibited a significantly higher ABTS+ and superoxide radical scavenging as compared to non-purified digests. Active fraction 9 showing the highest radical scavenging ability was further purified and confirmed by MALDI-TOF MS followed by MS/MS with probable dominant peptide sequences identified are VLYSTPVKMWEPGR, VITVVATAGSETMR, and HIGININSR. The obtained results revealed that free radical scavenging capacity of papain hydrolysates might be related to its consistently low molecular weight hydrophobic peptides.
Recently, the quality-by-design concept has been widely implemented in the optimization of pharmaceutical processes to improve batch-to-batch consistency. As flavonoid compounds in pigmented rice bran may provide natural antioxidants, extraction of flavonoid components from red and brown rice bran was optimized using central composite design (CCD) and response surface methodology (RSM). Among the solvents tested, ethanol was most efficient for extracting flavonoids from rice bran. The examined parameters were temperature, solvent percentage, extraction time, and solvent-to-solid ratio. The highest total flavonoid content (TFC) in red rice bran was predicted as 958.14 mg quercetin equivalents (QE)/100 g dry matter (DM) at 58.5 °C, 71.5% (v/v), 36.2 min, and 7.94 mL/g, respectively, whereas the highest TFC in brown rice bran was predicted as 782.52 mg QE/100 g DM at 56.7 °C, 74.4% (v/v), 36.9 min, and 7.18 mL/g, respectively. Verification experiment results under these optimized conditions showed that the TFC values for red and brown rice bran were 962.38 and 788.21 mg QE/100 g DM, respectively. No significant differences were observed between the predicted and experimental TFC values, indicating that the developed models are accurate. Analysis of the extracts showed that apigenin and p-coumaric acid are abundant in red and brown rice bran. Further, red rice bran with its higher flavonoid content exhibited higher nitric oxide and 2,2-diphenyl-1-picrylhydrazyl scavenging activities (EC50 values of 41.3 and 33.6 μg/mL, respectively) than brown rice bran. In this study, an extraction process for flavonoid compounds from red and brown rice bran was successfully optimized. The accuracy of the developed models indicated that the approach is applicable to larger-scale extraction processes.
Dicofol, a recommended Stockholm convention persistent organic pollutants (POPs) candidate is well known for its endocrine disruptive properties and has been extensively used as an organochlorine pesticide worldwide. The hydrodynamic cavitation (HC) treatment of Dicofol in aqueous media induced by a liquid whistle hydrodynamic cavitaion reactor (LWHCR) has been investigated while considering important parameters such as inlet pressure, initial concentration of Dicofol, solution temperature, pH, addition of H2O2 and radical scavenger for the extent of degradation. The pseudo-first-order degradation rate constant (k) was determined to be 0.073 min-1 with a cavitational yield of 1.26 × 10-5 mg/J at optimum operating conditions and a complete removal of Dicofol was achieved within 1 h of treatment. Considering the removal rate and energy efficiency, the optimal inlet pressure was found to be 7 bar, resulting in a cavitation number of 0.17. High performance liquid chromatography (HPLC) and Gas chromatography mass spectroscopy (GC-MS) analyses indicated a sharp decline in the concentration of Dicofol with treatment time and indicated the presence of degraded products. An 85% total organic carbon (TOC) removal was achieved within 1 h of treatment time, demonstrating successful mineralization of Dicofol. The obtained results suggest that the degradation of Dicofol followed thermal decomposition and successive recombination reactions at bubble-vapor interface. Overall, the attempted hydrodynamic cavitation demonstrated successful and rapid removal of endocrine disruptive chemicals such as Dicofol and is expected to provide efficient solution for wastewater treatment.
The antiradical efficiency (AE) and kinetic behavior of a new ferulate-based protic ionic liquids (PILs) were described using 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical assay. The reduction of the DPPH free radical (DPPH•) was investigated by measuring the decrease in absorbance at 517 nm. The time to reach steady state for the reaction of parent acid (ferulic acid) and synthesized PILs with DPPH• was continuously recorded for 1 h. Results revealed that the AE of 2-butylaminoethanol ferulate (2BAEF), 3-dimethylaminopropanol ferulate (3DMAPF) and 3-diethylaminopropanol ferulate (3DEAPF) PILs have improved compared to ferulic acid (FA) as the reaction class changes from low to medium. This attributed to the strong hydrogen abstraction occurred in the PILs. Furthermore, these PILs were found to have a good kinetic behavior compared to FA due to the high rate constant (k₂) (164.17, 242.84 and 244.73 M-1 s-1, respectively). The alkyl chain length and more alkyl substituents on the nitrogen atom of cation were believed to reduce the cation-anion interaction and speed up the hydrogen atom transfer (HAT) and electron transfer (ET) mechanisms; hence, increased rate constant was observed leading to a strong antioxidant activity of the synthesized PILs.