Ferric Ion Reducing Antioxidant Power Assays Research Articles

Evaluation of antioxidant activity of selected wild fruits and vegetables from Zambia

Natural antioxidants present in herbs, spices, fruits, and vegetables can inhibit and prevent the deleterious effects of reactive oxygen species (ROS) and, hence are essential in the regulation of oxidative stress which is implicated as a precursor for several pathological conditions, including cardiovascular, neurodegenerative disorders, premature ageing and cancer including diabetes and hypertension. In this report, phytochemical screening of alkaloids, phenol/tannins, flavonoids, phyto-steroids, terpenoids, glycosides, saponins and the antioxidant activity of two traditional vegetables (Cucurbita moschata, CM and, Bidens pilosa, BP) and three edible wild fruits (Tamarindus indica, TI, Adansonia digitata, AD, and Kigelia africana, KA) commonly consumed in Zambia was investigated. Plant materials were macerated in either methanol or ethanol. Resultant crude extracts were analyzed for phytochemicals, total phenolic (TPC) and flavonoid content (TFC) respectively. Antioxidant activity (AA) was determined by the reduction of stable radicals 2,4,6-tripyridyl-s-triazine (TPTZ) in ferric ion-reducing antioxidant power assay (FRAP), 2,2-Diphenyl-1-picrylhydrazyl in the DPPH assay and hydrogen peroxide (H2O2) in the H2O2 radical scavenging assay, respectively. The TPC ranged from (0.53 ± 0.01 to 23.74 ± 0.02 mg GAE/g), and TFC ranged from (0.02 ± 0.00 to 15.03 ± 0.45 mg QE/g). Antioxidant activity with FRAP ranged from (3.59 ± 0.16 to 35.76 ± 0.33 mmol Fe (II)/g), % DPPH inhibition at 100 µg/mL of crude extract ranged from (25.53 ± 0.36 to 77.74 ± 0.48 µg/mL) and % H2O2 inhibition at 100 µg/mL of crude extract ranged from (24.70 ± 0.03 to 64.73 ± 0.02 µg/mL) respectively. For DPPH, the IC50 values of the ethanolic extracts of AD, KA, TI, BP and CM were 149.03, 199.21, 145.33, 35.24 and 172.09, while the methanolic extract values were 121.46, 127.80, 124.84, 35.78 and 65.88 µg/mL respectively. For H2O2, the IC50 values of the ethanolic extracts of AD, KA, TI, BP and CM were 151.34, 209.25, 118.033, 120.44 and 140.07, the methanolic values were 91.80, 158.18, 105.18, 102.21 and 50.26 µg/mL, respectively. The vegetables, BP and CM displayed higher TP/TF content and antioxidant activity than fruits. However, all the samples investigated in this study showed good antioxidant activity (correlation coefficient, R2 > 0.5) and their inclusion in a diet may offer protection from oxidative stress.

Antioxidant activity and inhibitory potential of Hibiscus rosa-sinensis flower extract against the key enzymes relevant for hyperglycemia: in-vitro and in-silico studies

BACKGROUND: The alteration of endogenous antioxidants and generation of reactive oxygen species induce hyperglycemia which may lead to the emergence of chronic problems in diabetes. The key enzymes responsible for hyperglycemia are α-amylase and α-glucosidase. Owing to the various negative consequences caused by synthetic medicines, there is a requirement for natural antioxidants and inhibitors for α-amylase, and α-glucosidase enzymes to attenuate hyperglycemia. This article entails the antioxidant potential as well as the inhibitory potential of the Hibiscus rosa-sinensis flower extracts in contrast to the enzymes involved in regulating hyperglycemia.METHODS: Flower extracts were prepared using solvents with ascending polarity viz. hexane, chloroform, ethyl acetate, n-butanol, methanol, and distilled water by maceration. Antioxidant capacity was investigated using 2,2-diphenyl-1-picrylhydrazyl free radical activity, 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid cation(s) scavenging assay, ferric ion reducing-antioxidant power assay, and total antioxidant capacity. The inhibitory efficacy against α-amylase and α-glucosidase enzyme were investigated by performing α-amylase, and α-glucosidase inhibitory assays. To validate the observed results in in-vitro assays, the existence of polyphenolic compounds in the most potent extract was detected using ultra-high-performance liquid chromatography (UHPLC). Furthermore, in-silico analysis of the detected polyphenols in the most potent extract was done to understand the binding energies and docking at different sites of α-glucosidase and α-amylase enzymes, and it was contrasted to standard (acarbose).RESULTS: The most significant amount of antioxidant activity was noticed in the ethyl acetate extract in all the assays. Moreover, the ethyl acetate extract had a stronger suppressant effect on α-glucosidase and α-ainilase enzymes than other extracts and it was more in the case of α-glucosidase (IC50 value 53.33 µg/mL) as compared to α-amylase (IC50 value 83.02 µg/mL) enzymes There was a finding that among the polyphenolic compounds detected from the ethyl acetate extract via UHPLC, in which the docking studies were carried out, caffeic acid showed maximum binding energy with the α-glucosidase enzyme while epicatechin showed maximum binding energy with the α-amylase enzyme.CONCLUSIONS: The whole study concluded that caffeic acid and epicatechin have shown good interactions with concerned enzymes, and hence might contribute to the inhibition of hyperglycemic conditions and other diabetic problems caused by oxidative stress.

Antioxidant, Antimicrobial and Protease Inhibitory Activity of Potato Peel.

Background: Due to having health hazards of artificial preservatives, natural preservatives having anti-enzymatic, antimicrobial, and antioxidant properties are drawing the attention of food scientists. Objectives: Potato peel can be a cheap and available source of preservatives as it is considered a waste after processing its tuber. Methods: We evaluated the serine protease inhibitory activity, antibacterial activity by Disc diffusion assay, and antioxidant properties by DPPH free radical scavenging assay and Ferric-ion reducing antioxidant power assay (FRAP) of crude methanol and aqueous extract of potato peel. In addition, Total phenol, flavonoid, and tannin content were also quantified in both crude extracts. Results: Crude methanol extract was found more potential to have significant serine protease inhibition activity (IC50 = 534.87 μg/mL), DPPH free radical scavenging activity (IC50 = 183.56 μg/mL), and FRAP (ferric reducing antioxidant power) value of 351.81 µM Fe(II)/100µg of dried extract. Moreover, the total phenol, flavonoid and tannin content of the methanol extract were higher than the aqueous extract. Also, crude methanol extract showed maximum zone of inhibition (ZOI) against Vibrio cholera and Salmonella typhi (13.63 ± 0.53 and 13.25 ± 0.35 mm respectively). Later, column chromatography for the enrichment of total flavonoid content of methanol fractions exhibited elevated flavonoid content and serine protease inhibitory activity than crude methanol extract. Conclusion: This study showed, the methanol extract of potato peel is more potential than water extract.

Biological Characterization and Preliminary Crystallization: A Step Towards the Use of Novel Allium sativum Protease Inhibitor as a Potential Therapeutic Drug

Background: Garlic, being a well-known medicinal plant, is the most commonly used culinary spice worldwide. Investigation of protease inhibitor isolated from garlic leads to a promising contender in pharmacognostic and pharmacological studies. Objective/Introduction: Protease Inhibitor (PI) from 'garlic' (Allium sativum) was analyzed for its biological role as an antioxidant, antimicrobial, and anti-inflammatory agent. Methods: Antioxidant activity was evaluated using ferric ion reducing antioxidant power (FRAP) and 2, 2-diphenyl-1-picrylhydrazyl (DPPH) assays. The anti-inflammatory activity was assessed using trypsin inhibitory assay and heat-induced albumin denaturation method. The antimicrobial activity was examined in broth against E. coli and B. Subtilis. The crystallization was setup using the hanging drop method. Results: ASPI showed DPPH radical scavenging with IC50 values 561±0.337 μg/ml. Also, ASPI showed the highest value of 0.699±0.009 mM at 1000 μg/ml and the lowest i.e. 0.181±0.006 mM at 100 μg/ml in FRAP assay. Ascorbic acid was taken as standard in both cases. ASPI showed IC50 values of 651±0.532 μg/ml and ~657±1.802 μg/ml, respectively. The antibacterial role of ASPI was testified, and results showed maximum inhibition against E. coli (ATCC 25922) i.e., 87.8 ±0.602% but no inhibition against B. subtilis (MTCC 736). Cuboidal shaped crystals of the ASPI were obtained in 4-6 weeks using 0.2M calcium chloride dihydrate, 0.1M sodium acetate trihydrate, 20 % isopropanol. Conclusion: ASPI has tremendous potential in the development of suitable drugs in pharmaceutical industries against diseases due to the generation of reactive oxygen species and cancer. The cuboidal crystals were obtained, which is the first study in the context of crystallization of ASPI to date.

In vitro and in silico antioxidant and anti-inflammatory potential of essential oil of Cymbopogon citratus (DC.) Stapf. of North-Western Himalaya

Cymbopogon citratus (DC.) Stapf is an aromatic perennial herb of Gramineae (Poaceae) family and is known for its application in food and healthcare industry. The present study aimed to evaluate anti-inflammatory and antioxidant potential of C. citratus essential oil (CEO) through in vitro and in silico studies. Chemical characterization of CEO was done using Gas chromatography-mass spectrophotometry (GC-MS) method. In vitro antioxidant activity was evaluated by 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2, 2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid (ABTS) and ferric ion reducing antioxidant power (FRAP) assays, while egg albumin denaturation method was used to evaluate in vitro anti-inflammatory activity of CEO. Molecular docking investigation of major phytocompounds of CEO was done using Autodock vina software against human peroxiredoxin 5 (PDB ID: 1HD2) and human cyclooxygenase 2 (PDB ID: 5IKQ) proteins, which were further analyzed through molecular dynamics (MD) simulation using YASARA. GC-MS analysis of CEO showed the presence of geranial (48%) neral (34.04%), β-myrcene (9.77%), geraniol (1.88%), linalool (0.84%), isogeranial (0.81%), β-caryophyllene (0.80%), D-limonene (0.51%) as major constituents. CEO showed significant antioxidant activity with DPPH (IC50-47.53 ± 2.16 µg/ml), FRAP (IC50-30.7 ± 0.31 µM), and ABTS assays (IC50-27.87 ± 0.09 µg/ml). CEO also exhibited significant in-vitro anti-inflammatory activity with IC50-29.71 ± 1.95 µg/ml as compared to that of Diclofenac sodium (IC50-36.52 ± 1.95 µg/ml). Molecular docking revealed that β-caryophyllene showed considerable binding potential with human peroxiredoxin 5 receptor (-6.0 kcal/mol) and human cyclooxygenase 2 receptor (-10.1 kcal/mol). Further, MD simulations demonstrated considerable and stable interactions of β-caryophyllene with 1HD2 and 5IKQ proteins up to 100 ns. Drug-likeness and ADME/T features also showed that β-caryophyllene can be used as a potential candidate to replace the synthetic anti-inflammatory drugs with side effects and also act as natural antioxidants. Communicated by Ramaswamy H. Sarma

Sea Buckthorn Leaf Powders: The Impact of Cultivar and Drying Mode on Antioxidant, Phytochemical, and Chromatic Profile of Valuable Resource.

Sea buckthorn (Hippophae rhamnoides L. (HR)) leaf powders are the underutilized, promising resource of valuable compounds. Genotype and processing methods are key factors in the preparation of homogenous, stable, and quantified ingredients. The aim of this study was to evaluate the phenolic, triterpenic, antioxidant profiles, carotenoid and chlorophyll content, and chromatic characteristics of convection-dried and freeze-dried HR leaf powders obtained from ten different female cultivars, namely ‘Avgustinka’, ‘Botaniceskaja Liubitelskaja’, ‘Botaniceskaja’, ‘Hibrid Percika’, ‘Julia’, ‘Nivelena’, ‘Otradnaja’, ‘Podarok Sadu’, ‘Trofimovskaja’, and ‘Vorobjovskaja’. The chromatic characteristics were determined using the CIELAB scale. The phytochemical profiles were determined using HPLC-PDA (high performance liquid chromatography with photodiode array detector) analysis; spectrophotometric assays and antioxidant activities were investigated using ABTS (2,2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) and FRAP (ferric ion reducing antioxidant power) assays. The sea buckthorn leaf powders had a yellowish-green appearance. The drying mode had a significant impact on the total antioxidant activity, chlorophyll content, and chromatic characteristics of the samples; the freeze-dried samples were superior in antioxidant activity, chlorophyll, carotenoid content, and chromatic profile, compared to convection-dried leaf powder samples. The determined triterpenic and phenolic profiles strongly depend on the cultivar, and the drying technique had no impact on qualitative and quantitative composition. Catechin, epigallocatechin, procyanidin B3, ursolic acid, α-amyrin, and β-sitosterol could be used as quantitative markers in the phenolic and triterpenic profiles. The cultivars ‘Avgustinka’, ‘Nivelena’, and ‘Botaniceskaja’ were superior to other tested cultivars, with the phytochemical composition and antioxidant activity.

Phytochemical Evaluation and Antioxidant Capacity of Ganoderma lucidum and Pleurotus pulmonarius in Ibadan, Nigeria

Aims: To evaluate the phytochemical constituents and antioxidant properties of two selected mushrooms in Ibadan, Nigeria.
 Study Design: An experimental and descriptive study was conducted using the fruit bodies of Ganoderma lucidum collected from the Botanical garden University of Ibadan and Pleurotus pulmonarius which was bought from a local store in Ibadan. Successive extraction was done on the mushrooms with four solvents of increasing polarity that is from the non-polar (N-hexane) to a more polar solvent(water).Phytochemical and antioxidant analysis were then carried out on the extract fractions.
 Place and Duration of Study: Department of Botany, University of Ibadan, Ibadan, Nigeria and Department of Microbiology, University of Ibadan, Ibadan, Nigeria between May 2018 and February 2020.
 Methodology: The N-Hexane, Ethyl acetate, Ethanol and Aqueous extract fraction of Ganoderma lucidum and Pleurotus pulmonarius were analyzed in different system, including DPPH, Ferric ion Reducing Antioxidant Power (FRAP) and Total Antioxidant Capacity (TAC). The various antioxidant activities were compared to the standard ascorbic acid. Phytochemical include: Phenol, Alkaloids, Flavonoids, Tannins, Steroids, Saponins, Terpenoids Anthraquinones, and Cardiac glycosides were also analysed.
 Results: The Phytochemical screening result shows the presence of Phenol, Alkaloids, Flavonoids, Tannins, Steroids, Saponins, Terpenoids Anthraquinones, and Cardiac glycosides. The quantitative phytochemical screening revealed that the Ethyl acetate fraction of Ganoderma lucidum recorded the highest percentage of Alkaloids (41.70±0.14%) while the Ethanolic fraction of Pleurotus pulmonarius has the lowest percentage of Tannins (0.10±0.24%). DPPH scavenging activity of the Ethanolic extract fraction of Ganoderma lucidum (at 200 µg/ml) was 94.96% higher than that of Pleurotus pulmonarius (22.39%). The extract fraction of all the mushrooms possesses significant TAC content with N-Hexane and Ethyl acetate fraction having the highest. The results of the DPPH, FRAP, and TAC assays indicate that both mushrooms examined showed significant antioxidant activities. Among these, Ganoderma lucidum extract seems to be more effective antioxidant. The antioxidant activity of theses mushrooms has significant importance as it greatly contribute to their nutraceutical properties thus enhancing their nutritive value. Cultivation and production of dietary supplements from Ganoderma lucidum is highly recommended.
 Conclusion: The Mushrooms species analyzed have demonstrated to be good sources of phytochemical and antioxidants hence it can be recommended to pharmaceutical industries for the manufacturing of drugs.

The Effect of UV Irradiation on Vitamin D2 Content and Antioxidant and Antiglycation Activities of Mushrooms.

Mushroom irradiation has been considered a sustainable process to generate high amounts of vitamin D2 due to the role of this vitamin for human health and of the global concerns regarding its deficient or inadequate intake. Mushrooms are also receiving increasing interest due to their nutritional and medicinal properties. However, there is still a knowledge gap regarding the effect of UV irradiation on mushroom bioactive compounds. In this study, two of the most cultivated mushroom species worldwide, Agaricus bisporus and Pleurotus ostreatus, were irradiated with UV-B, and the effect of processing was investigated on the contents of vitamin D2 as well as on antioxidant and antiglycation activities. UV irradiation increased vitamin D2 up to 57 µg/g d.w, which is an adequate level for the fortification of a number of target foods. UV irradiation decreased the antioxidant activity when measured by the Folin–Ciocalteu reagent, the 2,2-diphenyl-1-(2,4,6 trinitrophenyl) hydrazyl radical assay and the ferric ion-reducing antioxidant power assay, but did not decrease the mushroom’s ability to inhibit glycation of a target protein. These results open up a new area of investigation aimed at selecting mushroom species with high nutraceutical benefits for irradiation in order to maintain their potential properties to inhibit oxidative and glycation processes responsible for human diseases.

In vitro antioxidant activity of Ficus carica L. latex from 18 different cultivars

As synthetic antioxidants that are widely used in foods are known to cause detrimental health effects, studies on natural additives as potential antioxidants are becoming increasingly important. In this work, the total phenolic content (TPC) and antioxidant activity of Ficus carica Linn latex from 18 cultivars were investigated. The TPC of latex was calculated using the Folin–Ciocalteu assay. 1,1-Diphenyl-2-picrylhydrazyl (DPPH), 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and ferric ion reducing antioxidant power (FRAP) were used for antioxidant activity assessment. The bioactive compounds from F. carica latex were extracted via maceration and ultrasound-assisted extraction (UAE) with 75% ethanol as solvent. Under the same extraction conditions, the latex of cultivar ‘White Genoa’ showed the highest antioxidant activity of 65.91% ± 1.73% and 61.07% ± 1.65% in DPPH, 98.96% ± 1.06% and 83.04% ± 2.16% in ABTS, and 27.08 ± 0.34 and 24.94 ± 0.84 mg TE/g latex in FRAP assay via maceration and UAE, respectively. The TPC of ‘White Genoa’ was 315.26 ± 6.14 and 298.52 ± 9.20 µg GAE/mL via the two extraction methods, respectively. The overall results of this work showed that F. carica latex is a potential natural source of antioxidants. This finding is useful for further advancements in the fields of food supplements, food additives and drug synthesis in the future.

Finger millet porridges subjected to different processing conditions showed low glycemic index and variable efficacy on plasma antioxidant capacity of healthy adults

Finger millet porridges (FMP), rich in nutrient and non-nutrient compounds have been used in the traditional food cultures in Asia. The aims of the study were to determine the effect of different processing conditions of finger millet grains on glycemic response, phenolic content and the antioxidant activities of FMP and to determine the short term and long term efficacy of its consumption on plasma antioxidant levels of healthy adults. Twelve types of FMP were prepared combining different processing conditions. Phenolic content of porridges as well as antioxidant activities were determined. The glycemic index (GI) and glycemic load (GL) values of FMP were also evaluated. The long term efficacy of FMP consumption on plasma glucose (PG), total cholesterol (TC) levels and plasma antioxidant capacity (PAC) of 18 subjects were investigated using a 24 weeks randomized cross-over study. The short term efficacy of porridge consumption on AC was determined. PAC was measured by trolox equivalent antioxidant capacity (TEAC) and ferric ion reducing antioxidant power (FRAP). All FMP exhibited low GI values (< 55) except the raw roasted flour which showed high and medium GI values for both particle sizes used. Parboiling of finger millet grains with 15 min steaming produced FMP with low glycemic response and possessed high PAC. Compared to baseline, PAC measured using FRAP and TEAC assays increased after 8 weeks consumption of porridge though significant changes were not observed for PG and TC levels. Furthermore, PAC was increased by 23 and 14% after 2 h of porridge consumption as measured by TEAC and FRAP, respectively. FMP consumption increased the plasma total antioxidant capacity of healthy adults. Further research on examining the potential of FMP on improving the antioxidant capacity in patients with diabetes is warranted.Graphical abstract

Antioxidant and antibacterial activities of multiflora honey extracts from the Indonesian Apis cerana bee

ObjectivesHoney is an apiary product with various medicinal properties resulting from its bioactive compounds. Here, we aimed to determine the antioxidant and antibacterial properties of the Indonesian Apis cerana honey extracts and their correlation with total phenolic content (TPC) and total flavonoid content (TFC). MethodsWe extracted ethyl acetate-n-hexane and two types of ethanolic extracts from crude honey. Phenols and flavonoid content were calculated using spectroscopy. The antioxidant activity was evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric ion reducing antioxidant power (FRAP) assays, and it was reflected via the antioxidant activity index (AAI). An agar diffusion test was used to test the antimicrobial activity. ResultsThe ethyl acetate extract of the Karangasem honey provided the highest amount of phenolic and flavonoid content, and the strongest antioxidant activity using DPPH and FRAP assays. The ethanolic honey extracts were active against Bacillus subtilis and Escherichia coli; in this regard, the strongest effect was noticed from the Singaraja honey extract. The positive significant correlations between TPC and AAI were observed in all samples. Similar results also appeared between phenolic and flavonoid compounds and their antibacterial activity in most of the tested samples. ConclusionsIn our study, honey extracts possessed antioxidant and antibacterial activities that were mostly related to the qualitative and quantitative properties of phenols and flavonoids. Geographical origin brought variations in the phytochemical profiles and bioactivities of honey.

Synthesis and Antioxidant Activity of New Selenium-Containing Quinolines.

Quinoline derivatives have been attracted much attention in drug discovery, and synthetic derivatives of these scaffolds present a range of pharmacological activities. Therefore, organoselenium compounds are valuable scaffolds in organic synthesis because of their pharmacological activities and their use as versatile building blocks for regio-, chemo-and stereoselective reactions. Thus, the synthesis of selenium-containing quinolines has great significance, and their applicability range from simple antioxidant agents, to selective DNA-binding and photocleaving agents. In the present study, we describe the synthesis and antioxidant activity in vitro of new 7- chloro-N(arylselanyl)quinolin-4-amines 5 by the reaction of 4,7-dichloroquinoline 4 with (arylselanyl)- amines 3. For the synthesis of 7-chloro-N(arylselanyl)quinolin-4-amines 5, we performed the reaction of (arylselanyl)-amines 3 with 4,7-dichloroquinoline 4 in the presence of Et3N at 120 °C in a sealed tube. The antioxidant activities of the compounds 5 were evaluated by the following in vitro assays: 2,2- diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, 2,2-azinobis-3- ethylbenzothiazoline-6-sulfonic acid (ABTS), ferric ion reducing antioxidant power (FRAP), nitric oxide (NO) scavenging and superoxide dismutase-like activity (SOD-Like). 7-Chloro-N(arylselanyl)quinolin-4-amines 5a-d have been synthesized in yields ranging from 68% to 82% by the reaction of 4,7-dichloroquinoline 4 with arylselanyl-amines 3a-d using Et3N as a base, at 120 °C, in a sealed tube for 24 hours and tolerates different substituents, such as -OMe and -Cl, in the arylselanyl moiety. The obtained compounds 5a-d presented significant results concerning the antioxidant potential, which had an effect in the tests of inhibition of radical's DPPH, ABTS+ and NO, as well as in the analysis that evaluates the capacity (FRAP) and in the superoxide dismutase-like activity assay (SOD-Like). It is worth mentioning that 7-chloro- N(arylselanyl)quinolin-4-amine 5b presented excellent results, demonstrating a better antioxidant capacity when compared to the others. According to the obtained results, 7-chloro-N(arylselanyl)quinolin-4-amines 5 were synthesized in good yields by the reaction of 4,7-dichloroquinoline with arylselanyl-amines and tolerated different substituents in the arylselanyl moiety. The tested compounds presented significant antioxidant potential in the tests of inhibition of DPPH, ABTS+, and NO radicals, as well as in the FRAP and superoxide dismutase-like activity assays (SOD-Like).

Evaluation of antioxidant activities, total phenolic content (TPC), and total catechin content (TCC) of 10 sugar apple (Annona squamosa L.) cultivar peels grown in Thailand

Abstract Antioxidant activities, total phenolic content (TPC), and total catechin content were analyzed in the ethanol extracts of 10 sugar apple (Annona squamosa L.) cultivar peels grown in Thailand. Antioxidant activity assays carried out in the this study were the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, ferric ion reducing antioxidant power (FRAP), 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical cation scavenging activity, and oxygen radical absorbance activity (ORAC). ‘Nhur Thong’, ‘Nung Keaw’, and ‘Fai Keaw’ showed high percentage fruit peel (over 38.0%). ‘Nhur Thong’, ‘Nung Keaw’, and ‘Fai Keaw’ ethanol extracts possessed high antioxidant capacities in the majority of methods used, and thus could be potential candidate of natural antioxidants. ‘Fai Keaw’ showed the best activity in the ABTS (1.57 mmol of trolox/g dry sample), FRAP (0.43 mmol of trolox/g dry sample), and ORAC assays (2.84 mmol of trolox/g dry sample), as well as the highest content of TPC (140.4 mg) per gram dry sugar apple peel among the 10 cultivars. TPC showed a positive correlation compared with all antioxidant activity assays. In conclusion, ‘Fai Keaw’ could be utilized as an excellent phenolic compound source for functional food products.

36H: A Novel Potent Inhibitor for Antimelanogenesis.

N-Hydroxycinnamoylphenalkylamides (36H) exhibited both antioxidation and antityrosinase abilities. The compound was studied for its antioxidative properties, using a 1,1-diphenyl-2-picrylhydrazul- (DPPH-) scavenging test, a ferric ion-reducing antioxidant power assay (FRAP) assessment, and a metal-chelating power assay. The results showed that 36H had antioxidative capabilities in the DPPH-scavenging and ferric-reducing power examinations but the chelating power assay did not demonstrate antioxidative capability. 36H was also measured for tyrosinase inhibitory activity applying various species platforms, including in vitro mushroom, B16F10 mouse melanoma, and human melanocyte cells. In terms of in vitro mushroom tyrosinase suppression, 36H restrained the melanogenesis processes. It is assumed that 36H blocked the tyrosinase active site as a competitive inhibitor for mushroom tyrosinase, hence not decreasing the human normal melanocyte cellular viability. A quantitative real-time polymerase chain reaction (qRT-PCR) and western blot discovered that 36H downregulated melanogenesis-related RNA and proteins, including pigment production (MITF, tyrosinase, TRP-1, and TRP-2), melanosome maturation (Rab27a), and melanosome transportation (Myo5a, MLPH and Mreg). Overall, 36H displayed the biofunctions of antioxidation and melanin suppression, so there was a possibility for its application as a food additive or a skin-whitening agent.

Synthesis, Antimicrobial, and Antioxidant Activities of Chalcogen-Containing Nitrone Derivatives from (R)-citronellal.

Background: The main constituents of Cymbopogonnardus (L) Rendle and C. citratus (DC) Stapfessential oils are (R)-citronellal and citral, respectively. Organochalcogen compounds can boost the biological activities of natural products. Methods: Several chalcogen-containing nitrones derived from (R)-citronellal and citral were prepared and evaluated for their antimicrobial and antioxidant activities. The antimicrobial activity was evaluated by the disc diffusion test and the antioxidant properties were evaluated in vitro by DPPH (1,1-diphenyl-2-picryl-hydrazyl), ABTS (2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid), and FRAP (ferric ion reducing antioxidant power) assays. Results: In the antimicrobial assay, (E)-N,3,7-trimethyl-3-(phenylthio)oct-6-en-1-imine oxide 5c exhibited halos between 21.5 mm (Escherichia coli O157:H7) and 26.0 mm (Listeria monocytogenes), while (E)-N,3,7-trimethyloct-6-en-1-imine oxide 5d presented halos between 22.5 mm (E. coli O157:H7) and 31.0 mm (L. monocytogenes). (E)-N,3,7-Trimethyl-2-(phenylthio)oct-6-en-1-imine oxide 5a showed the lowest minimal inhibitory concentration (MIC) value against Bacillus cereus (0.48 mM), and 5c was the most potent bactericide, with a minimal bactericidal concentration (MBC) of 0.52 mM for E. coli O157:H7. In the antioxidant assays, 5c, 5d, and 10 ((E)-3,7-dimethyl-2-(phenylselanyl)oct-6-enal oxime) were the most actives in the DPPH, ABTS, and FRAP assays, respectively. Conclusions: The presence of a phenylthio group in the nitrone increases its antimicrobial activity against Gram-positive and Gram-negative foodborne pathogens in the disk diffusion test and the antioxidant activity in vitro.

The anti-oxidant effects of melatonin derivatives on human gingival fibroblasts

ObjectivesAim of this in vitro study was to evaluate the anti-oxidant activity of indole ring modified melatonin derivatives as compared with melatonin in primary human gingival fibroblast (HGF) cells. MethodsAnti-oxidant activity of melatonin (MLT), acetyl-melatonin (AMLT) and benzoyl-melatonin (BMLT) was evaluated by5 standard methods as follows: 2, 2-diphenyl-1-picrylhydrazyl (DPPH); ferric ion reducing antioxidant power (FRAP); superoxide anion scavenging; nitric oxide (NO) scavenging; and thiobarbituric acid reactive substances (TBARs).Evaluation of cellular antioxidant activity (CAA) and protectivity against H2O2 induced cellular damage was performed via MTT assay in HGF cells. ResultsAccording to the standard anti-oxidant assays, the antioxidant power of AMLT and BMLT were slightly less than MLT in FRAP and superoxide scavenging assays. In the NO scavenging and TBARs assays, BMLT and AMLT were more potent than MLT, whereas DPPH assays demonstrated that MLT was more potent than others. BMLT and AMLT had more potent anti-oxidant and protective activities against H2O2in HGF cells as compared with MLT. ConclusionsMLT derivatives demonstrated different anti-oxidant activities as compared with MLT, depending upon assays. These findings imply that N-indole substitution of MLT may help to improve hydrogen atom transfer to free radicals but electron transfer property is slightly decreased. Anti-oxidant and protective effects of melatonin derivatives (AMLT and BMLT) on human gingival fibroblasts imply the potential use of these molecules as alternative therapeutics for chronic inflammatory oral diseases.

Antioxidant content and activity in different parts of pomelo [Citrus grandis (L.) Osbeck] by-products

This study aimed to investigate the total antioxidant content and activity in different parts of pomelo by-products, namely flavedo, albedo and segment membrane. Total phenolic content (TPC) was determined using Folin-Ciocalteu method while total flavonoid content (TFC) was determined using aluminium chloride colorimetric method. The total antioxidant activity was determined by performing DPPH free radical scavenging assay and ferric ion reducing antioxidant power (FRAP) assay. Albedo possessed the highest TPC and TFC while flavedo demonstrated the highest antioxidant activity in both assays as compared to other tissues. Pearson correlation tests revealed that there were no correlations between TPC and EC50 as well as FRAP value. There was also a lack of relationship between TFC and antioxidant activity as determined in DPPH and FRAP assays. The pomelo by-products of 'Ledang' possessed higher antioxidant properties than previous studies and therefore can be considered as a new source of natural antioxidants.

Optimization of Microwave‐Assisted Extraction of Bioactive Compounds from Coriolus versicolor Mushroom Using Response Surface Methodology

AbstractResponse surface methodology was applied to optimize microwave‐assisted extraction (MAE) of total phenolic content (TPC) and antioxidant activity from fruiting bodies of Coriolus versicolor mushroom, and to compare its efficiency with conventional reflux extraction. A central composite design was employed for the optimization of three MAE parameters including extraction time (X1, min), ethanol concentration (X2, %) and microwave power (X3, W) for the highest yield of TPC and antioxidant activity measured by 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH), 2,2'‐azino‐bis‐3‐ethylbenzothiazoline‐6‐sulfonic acid (ABTS) and ferric ion reducing antioxidant power (FRAP) assays in C. versicolor extracts. The optimum conditions were predicted as 3.8 min extraction time, 40% ethanol concentration and 125 W microwave power to obtain maximum values of TPC (470 mg GAE/100 g dm) and antioxidant activity measured by DPPH (773 µM TE/g dm), ABTS (2,930 µM TE/g dm) and FRAP (1,710 µM TE/g dm) assays, which were statistically verified by comparing with the experimentally observed values.Practical ApplicationsIn this study, microwave‐assisted extraction (MAE) showed significant potential as a green extraction method for obtaining Coriolus versicolor mushroom extract rich in polyphenols with higher antioxidant activity as compared to the extracts obtained by reflux extraction. Furthermore, MAE resulted in reduced consumption of energy, time and solvent with higher extraction yield and efficiency. This work demonstrated further feasibility studies on MAE of phytochemicals including polyphenols‐rich extracts at industrial scale. Moreover, successful application of response surface methodology has opened future research avenues for optimization of bioactive components from other mushrooms of medicinal importance.

Contribution of phenolic acids isolated from green and roasted boiled-type coffee brews to total coffee antioxidant capacity

The antioxidant capacity (AC) of boiled-type coffee brews (CB) and phenolic acids (PA) isolated from them, obtained from the caffeinated and decaffeinated beans of different geographical origins and species and with different roasting degrees, was examined. The AC of PA and CB samples was tested in five antioxidant assays: a total antioxidants reducing capacity assay using a Folin–Ciocalteu reagent (FCR), a ferric ion reducing antioxidant power (FRAP) assay, a DPPH· radical-scavenging activity (DPPH) assay, a metal chelating activity (MCA) assay and a total radical trapping antioxidant parameter (TRAP) assay. In most samples, the total amount of phenolic acids, determined by HPLC, decreased with the increasing degree of roasting the coffee beans, leading to reduced AC. All used methods showed that CB exhibits higher AC compared with the PA samples. Phenolic acids isolated from CB samples have the main contribution (on average over 95 and 84 % in green and roasted coffee extracts, respectively) in AC of the CB samples in FCR, FRAP and TRAP assays, whereas in DPPH and MCA tests, the phenolic acid contribution in AC of CB samples was below 50 % (on average over 36 and 45 % in green and roasted coffee extracts, respectively). Significant differences between the AC values determined for CB and PA samples were noticed only for the MCA and DPPH methods which reflect the different molecular mechanisms underlying each of the assays. Additionally, the statistical methods, including principal component analysis, applied to results of antioxidant capacity obtained with different analytical techniques confirmed their feasibility to distinguish between coffee brews with different degrees of roasting, regardless of coffee origin.

Folin-Ciocalteu, FRAP, and DPPH• Assays for Measuring Polyphenol Concentration in White Wine

Three methods, the Folin-Ciocalteu (F-C), Ferric Ion Reducing Antioxidant Power (FRAP), and 2,2-diphenyl-1-picrylhydrazyl Radical (DPPH^•) assays were compared to determine polyphenol concentration in white wine and to compare the effects of SO₂. The aim was to determine which method gives the best indication of the concentration of polyphenols that are likely to be oxidized in wine. In the FRAP assay, Fe(III) is a stronger oxidant than in wine and sulfite has the greatest effect. The DPPH^• assay is less robust as results are greatly affected by basic and acidic solvent impurities, and thus the acidity of wine samples is sufficient to slow the rate of reaction relative to that of calibration standards. In the DPPH^• assay, augmentation produced by SO₂ developed slowly, indicating that quinones are not formed initially, unlike the FRAP assay. Though the F-C assay is least selective, giving the highest values, when SO₂ is removed, the three methods rank wines similarly with respect to polyphenol concentration. However, the FRAP assay is preferred, being more robust than the DPPH^• assay and giving a better indication of the concentration of potentially oxidizable polyphenols than the Folin-Ciocalteu method. Values obtained were in the range reported using cyclic voltammetry.