The hydroxycinnamic acid content of barley and brewers’ spent grain (BSG) and the potential to incorporate phenolic extracts of BSG as antioxidants into fruit beverages

The hydroxycinnamic acid (HA) content of starting barley for brewers’ spent grains (BSG), whole BSG and phenolic extracts from BSG was measured using high performance liquid chromatography (HPLC) and correlated with antioxidant potential. The effect of BSG phenolic extracts on antioxidant activity of fruit beverages was also assessed (using the total phenolic content (TPC), 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) assays). The concentration of HA present in barley extract and BSG was in the order of ferulic acid (FA), p-coumaric acid (p-CA) derivatives, FA derivatives, p-CA, caffeic acid (CA) and CA derivatives. Results suggested that brewing and roasting decreased the HA content. Antioxidant activity was significantly (P < 0.05) correlated with caffeic acid (R² = 0.8309) and total HA (R² = 0.3942) concentrations. Addition of extracts to fruit beverages resulted in a significant (P < 0.05) increase in antioxidant activity of cranberry juice, measured by the FRAP assay. In vitro digestion significantly (P < 0.05) reduced TPC, DPPH and FRAP activity of the fruit beverages.     

HPLC–MS analyses and bioactivities of novel chemicals in Devil’s club (Oplopanax horridus (Sm.) Miq.)

Devil’s club (Oplopanax horridus (Sm.) Miq.) has traditionally been used as a folk medicine by native North Americans for the treatment of various chronic diseases. A methanolic extract and its sub-fractions by liquid–liquid re-extraction, i.e., chloroform (CHCl₃), ethyl acetate (EtOAc), n-butanol (BuOH), and water fractions, were analysed by their anti-cancer activity with in vitro cell proliferative bioassays, and their antioxidant capacities in terms of the determination of total phenolic content (TPC), ORAC value, and DPPH free radical scavenging activity. The whole extract of the dried root contained high TPC and possessed strong ORAC and DPPH radical scavenging activities. In addition, the extract exhibited a strong anti-proliferative ability against HT-29 cancer cells, e.g., with an inhibitive rate of 56.5% with a 0.2-mg/mL extract. Further investigation by HPLC–UV–MS identified significant bioactive phenolic compounds in the chloroform fraction, including gallic acid, caffeic acid, 4-O-feruloylquinic acid, 5-O-feruloylquinic acid, ferulic acid, methyl feruloylquinate, methyl ferulate, and quercetin. These results suggested that the associated bioactivity of the plant might result from the contribution of phenolic compounds.     

Targeted phenolic analysis in Hericium erinaceum and its antioxidant activities

The ABTS⁺-radical-cation scavenging activity, DPPH radical scavenging activity, ferric reducing/antioxidant power, and nitrite scavenging activity of the methanol extract from Hericium erinaceum and its subfractions were assessed. Among the methanol extract subfractions tested, the chloroform subfraction exhibited the strongest antioxidant activity in the most experiments, except for the ferric reducing/antioxidant power. The Trolox equivalent antioxidant capacity (TEAC) of the chloroform subfraction was 378.89 μmol/g of sample. This subfraction also scavenged 35.80% of DPPH radicals at 500 μg/mL. The highest ferric reducing/ antioxidant power was found in the n-hexane subfraction (174.82 μmol FeSO₄·7H₂O/g). The chloroform, n-hexane, and n-butanol subfractions had high total phenolic compound content, with ferulic acid equivalents of 35.18, 19.08, and 11.23 mg/g, respectively. Flavonoids were found mostly in the chloroform subfraction, and the 4 phenolic compounds were identified in the same fraction as 4-hydroxybenzoic acid, syringic acid, 4-coumaric acid, and ferulic acid by electrospray ionization (ESI) LC-MS/MS analysis.     

Bioprospecting traditional Pakistani medicinal plants for potent antioxidants

Antioxidant potential of four methanol extracts from three selected plant species, namely Salvia nubicola (Lamiaceae), Acer oblongifolium (Aceraceae) and Hedera nepalensis (Araliaceae) was measured using assays in aqueous and lipid systems. Antioxidant activities were investigated in aqueous systems by using DPPH radical-scavenging assay, ABTS radical-scavenging assay and DNA protection assay, while antioxidant activity in a lipid system was determined by using the thiobarbituric acid-reactive substances (TBARS) assay. Additionally, the Folin-Ciocalteu method was used to measure total phenolic content. Methanol extracts of leaves and flowers of S. nubicola showed the highest Trolox equivalent (TE) values in the case of the DPPH assay, 2484 ± 4.9 mmol TE/g extract, as well as total phenolic content, 139 ± 0.2 mg gallic acid equivalents/g extract. Three fractions (A-C) of the methanol extract of S. nubicola leaves and flowers were produced by semi-preparative HPLC. Fraction B was found to be the most active in the DPPH radical-scavenging assay and had the highest total phenol content. HPLC-DAD and LC-MS revealed rosmarinic acid in S. nubicola extracts and chlorogenic acid and rutin in H. nepalensis extracts as the main phenolic antioxidants.     

Chemical composition and antioxidative activity of Moldavian balm (Dracocephalum moldavica L.) extracts

Moldavian balm (Dracocephalum moldavica L., Lamiaceae) is a perennial herb native to central Asia and naturalized in eastern and central Europe. It is commonly consumed as a food-related product and as a herbal preparation because of its reputed medicinal properties. Despite its importance, few reports exist in the literature regarding the chemistry or antioxidant activity of this species. In this study, the aerial material of Moldavian balm collected from Iran was extracted by Soxhlet using seven solvents of different polarity, viz., petroleum ether, dichloromethane, acetonitrile, ethyl acetate, methanol, n-butanol and water. The qualitative-quantitative chemical composition of each extract was determined using high-performance liquid chromatography coupled to photodiode array detection. For each extract, the total phenolic content was estimated as was the in vitro antioxidant activity using the iron(III) reduction assay, the β-carotene-linoleic acid bleaching assay and the 1,1-diphenyl-2-picrylhydrazyl and 2,2′-azinobis(3-ethylbenzothiazoline-6-sulphonate) free radical scavenging assays. Hydroxylated cinnamic acids, their derivatives and flavonoids were identified and quantified within the extracts, with rosmarinic acid being the most abundant component identified. The extracts demonstrated different degrees of potency within each assay, however, the observed pattern was not necessarily replicated between assays indicating the importance of the use of more than one screening technique to estimate the antioxidant activity of plant extracts.     

Antioxidant activity and genotoxic effect on HeLa cells of phenolic compounds from infusions of Quercus resinosa leaves

Water infusions of mature and fresh Quercus resinosa leaves were evaluated for antioxidant activity and genotoxic effects on HeLa cells. Native Mexicans used to drink Q. resinosa leaves tea as a refreshing beverage. The air dried leaves were pulverised and boiled in water, then their phenolic content and condensed tannins were determined. The chromatographic profile of 15 phenolic components in Quercus leaves infusions was also determined by HPLC. In vitro analysis of antioxidant capacity of leaves infusion extracts were performed by the DPPH method and the deoxyribose assay. The genotoxicity of Q. resinosa leaves extracts was evaluated on HeLa cells as well as its underlying mechanism by the single-cell electrophoresis assay (comet assay). Results show that fresh leaves infusions increase the oxidative process and other damage to DNA in transformed human cells. Fresh leaves from Q. resinosa may serve as a potential source of phenolics with anticancer activity.     

Content of polyphenolic constituents and antioxidant activity of some Stachys taxa

Seven Croatian Stachys taxa (S. alpina, S. officinalis, S. palustris, S. recta subsp. recta, S. recta subsp. subcrenata, S. salviifolia and S. sylvatica) have been investigated in order to determine their content of biologically active compounds (polyphenols, tannins, phenolic acids and flavonoids) as well as their antioxidant activity. All taxa tested had a high content of total polyphenols, medium content of total phenolic acids, and a rather low content of tannins and flavonoids. The total phenolic acids content correlated significantly with total polyphenols content and the content of polyphenols unadsorbed on hide powder. A low correlation between plant phenolic acids and tannins was observed. Methanolic, ethanolic and dichloromethane extracts were investigated using DPPH, lipid peroxidase and xanthine oxidase assays. The extracts showed no inhibitory effects against lipid peroxidation and xanthine oxidase, but they had the ability to scavenge DPPH. The most effective in the DPPH assay were methanolic extracts of S. recta sub. recta and S. palustris whose radical scavenging activity was higher then that of the reference rutin. A low correlation between radical scavenging capacities of extracts with total flavonoids content was observed. The results indicate that investigated Stachys taxa exhibit potent antiradical activity and therefore could be a potential material for extracting free radical scavengers.     

Antioxidant activity and rosmarinic acid changes in salicylic acid-treated Thymus membranaceus shoots

In order to characterise the antioxidant activity of Thymus membranaceus Boiss. subsp. membranaceus, an endemic species in Southeast Spain, five different analytical methods were used. Water, methanol and hexane extracts obtained from 60-day-old in vitro-grown shoots were assayed for their antioxidative properties using DPPH (1,1-diphenyl-2-picrylhydrazyl radical), ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonate), FRAP (ferric reducing antioxidant power), reducing power and conjugated diene assays. Total soluble phenol content, as well as rosmarinic acid, in the different extracts were also determined. Methanolic extracts exhibited the best antioxidant activity and the highest amounts of total soluble phenolics. A single application of salicylic acid (10 μM) on culture media resulted in an increase in rosmarinic acid and phenolic levels, which in turn improved the extracts’ antioxidant properties. These current findings open new opportunities for obtaining valuable natural antioxidants for commercial exploitation by using tissue culture systems.     

Effects induced by the nodulation with Bradyrhizobium japonicum on Glycine max (soybean) metabolism and antioxidant potential

This study was conducted in order to assess the effect of the inoculation of Glycine max (soybean) with Bradyrhizobium japonicum on the metabolite profile and antioxidant potential of its aerial parts. Extracts containing phenolic compounds and organic acids were analysed by HPLC–DAD and HPLC–UV, respectively. Volatiles profile was determined by HS-SPME/GC–IT-MS. The antioxidant activity of acidic and methanolic extracts was assessed against DPPH. Nodulation caused by B. japonicum led to an increase in the contents of phenolic compounds and organic acids. The same was observed for volatile compounds, with compounds like linalyl acetate, menthyl acetate and α-farnesene being detected only in inoculated plants. The phenolic extracts showed stronger antioxidant capacity than the organic acid extracts. In addition, extracts from plants nodulated with B. japonicum exhibited significantly higher antioxidant activity than control samples. These findings suggest that the inoculation with nodulating B. japonicum strains may be employed to manipulate the content of interesting metabolites in G. max aerial parts.     

Antioxidant properties of extract and fractions from Enteromorpha prolifera, a type of green seaweed

The ethanol extract and its solvent subfractions, partitioned by n-hexane (HX), chloroform (CF) and ethylacetate (EA), from Enteromorpha prolifera were measured for antioxidant activities, and a structural identification of the active compound was performed using spectroscopic techniques. The CF fraction showed the most potent 2,2-diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl (OH) radical scavenging activities with strong reducing ability. The DPPH and hydroxyl radical scavenging capacities of the CF fraction were comparable to the capacities of the positive controls, BHA and α-tocopherol, at concentrations ranging from 0.25 to 1.0 mg/mL. However, little correlation (r² = 0.03–0.48) was observed between antioxidant activities and total phenolic contents of the extracts. Further fractionation and spectroscopic analysis of the CF fraction suggested that the strong antioxidant activity of the extracts from E. prolifera was because of a chlorophyll compound, pheophorbide a, rather than phenolic compounds.     

Comparative antioxidant activity of extracts from leaves,bark and catkins of Salix aegyptiaca sp.

Leaves, bark and catkins of Salix aegyptiaca L. were extracted into solvents of increasing polarity from cyclohexane (non-polar), butanol, ethanol and water (polar) and analysed for their antioxidant capacity, total phenol and flavonoids. The highest antioxidant activity (19 μg/ml IC₅₀ for inhibition of DPPH radical activity), total phenolic content (212 mg gallic acid equivalents/g of dried extract) and total flavonoid (479 mg catechin equivalents/g of dried extract) was observed in the ethanolic extract of bark. HPLC identification of phenolic compounds from the extracts indicated the presence of gallic acid, caffeic acid, vanillin and p-coumaric acid, myricetin, catechin, epigallocatechin gallate, rutin, quercetin as well as salicin. Our data indicates the presence of high amounts of phenols and flavonoids in different parts of S. aegyptiaca species and propose that extracts from this plant may be utilised as a source of health promoting antioxidants.     

Assessment of the antioxidant potential and fatty acid composition of four Centaurea L. taxa from Turkey

This paper focused on the assessment of antioxidant property and fatty acid composition of four Centaurea species. The antioxidant activity of its methanol extract was evaluated by several in vitro experiments including phosphomolybedum assay, DPPH assay, β-carotene/linoleic acid, ferric and cupric reducing power. Total phenolic and flavonoid contents were also evaluated. The methanol extract of Centaurea pulcherrima var. pulcherrima showed the superior free radical scavenging activity, linoleic acid inhibition capacity, reducing power and also had the highest total phenolic content. A significant relationship between antioxidant capacity and total phenolic components was found. The oils of Centaurea taxa were also analysed for fatty acid concentration by gas chromatography. The principal fatty acids in the species were palmitic acid (23.38–30.49%) and linoleic acid (20.19–29.93%). These findings suggest that the Centaurea species could be used as a potential source of new natural antioxidants and unsaturated fatty acids in food industry, cosmetics and pharmaceutical preparations.     

Phenolic composition,antioxidant and acetylcholinesterase inhibitory activities of Sclerocarya birrea and Harpephyllum caffrum (Anacardiaceae) extracts

Total phenolic content, proanthocyanidins, gallotannins, flavonoids, and antioxidant activities of Sclerocarya birrea and Harpephyllum caffrum methanolic extracts were evaluated using in vitro assays. S. birrea young stem extract contained the highest levels of total phenolic content (14.15 ± 0.03 mg GAE/g), flavonoids (1.21 ± 0.01 mg CE/g) and gallotannins (0.24 ± 0.00 mg GAE/g). H. caffrum stem bark extract had the highest content of proanthocyanidins (1.47%). The EC₅₀ values of the extracts in the DPPH free radical scavenging assay ranged from 4.26 to 6.92 μg/ml, compared to 6.86 μg/ml for ascorbic acid. A dose-dependent linear curve was obtained for all extracts in the ferric-reducing power assay. Dichloromethane and methanol extracts exhibited dose-dependent acetylcholinesterase inhibitory activity. Similarly, all extracts exhibited high antioxidant activity comparable to butylated hydroxytoluene based on the rate of β-carotene bleaching (84.1–93.9%). The two Anacardiaceae species provide a source of natural antioxidants and acetylcholinesterase inhibitors, and may be beneficial to the health of consumers.     

Influence of thermal treatment on phenolic compounds and antioxidant properties of oak acorns from Serbia

The aim of the present work was to investigate and compare phenolic compounds and antioxidant activity of methanol extracts of Quercus robur and Quercus cerris acorn kernels obtained before and after thermal treatment. Content of total phenolics, tannins, non-tannin phenolics and flavonoids was determined spectrophotometrically and content of gallic acid with HPLC. Antioxidant activity of the samples was assayed through FRAP (Ferric Reducing Antioxidant Power), DPPH scavenging test and inhibition of Fe²⁺/ascorbate induced lipid peroxidation. Extracts of native and thermally treated kernels showed high antioxidant activity, with extracts of thermally treated kernels being more active than extracts of native ones. Hydrolysable tannins and gallic acid were identified in all samples. Non-tannin phenolics, including gallic acid, were present in significantly higher quantities in thermally treated samples, whilst tannin content decreased. This indicates that during thermal treatment hydrolysable tannins were degraded. As the result of this degradation and consequent increase of non-tannin phenolics content, and amongst them especially gallic acid, thermally treated samples possess higher antioxidant activity than do the native ones. The obtained results have provided further grounds for establishing Q. robur and Q. cerris acorn kernels as a source for functional food preparation.     

Effect of processing methods on the nutraceutical and antioxidant properties of little millet (Panicum sumatrense) extracts

The effect of germination, steaming and roasting on the nutraceutical and antioxidant properties of little millet (Panicum sumatrense) was investigated. The nutraceutical properties were determined by evaluating the total phenolic, flavonoid and tannin contents while the antioxidant properties were studied by the DPPH free radical scavenging activity and the iron reducing power assay. The results showed that the total phenolic, flavonoid and tannin contents of processed little millet increased by 21.2, 25.5 and 18.9 mg/100 g, respectively, compared to native sample. The DPPH radical scavenging activity and the iron reducing power of roasted millet extract were the highest compared to the other processed millet. Fractionation of phenolic extracts by HPLC showed that the analytes were derivatives of benzoic acid (gallic acid, proto-catechuic acid and vanillic acid), aromatic carboxylic acid (gentisic acid) and cinnamic acid (syringic acid and ferulic acid). The results indicate that processing has significant effects on the nutraceutical and antioxidant properties of little millet phenolic extracts.     

Cytoprotective and antioxidant activity of free,conjugated and insoluble-bound phenolic acids from swallow root (Decalepis hamiltonii)

Swallow root (Decalepis hamiltonii) was extracted for free (SRFP), conjugated (SRCP) and insoluble-bound phenolic acids (SRIBP), and evaluated for cytoprotectivity, 1,1,diphenyl-2-picrylhydrazyl (DPPH) scavenging ability, reducing power and protection to DNA damage. In addition, the constituent phenolic acids in the extracts were also analysed. Results indicated a total phenol content of 20.72, 7.97 and 11.52 mg gallic acid equivalents (GAE)/g for SRFP, SRCP and SRIBP extracts, respectively. At 0.12 μg/mL concentration SRCP showed 87% cytoprotection (on NIH 3T3 cells) compared to SRFP (47%) and SRIBP (65%). DPPH radical scavenging activity indicated an IC₅₀ of 0.046, 0.06 and 0.128 μg/mL for SRCP, SRIBP and SRFP, respectively. Also, SRCP showed higher reducing power and DNA protectivity (80%). HPLC analysis of phenolic acid extracts showed the presence of hydroxybenzoate and cinnamate derivatives. Among the phenolics identified gallic, gentisic, protocatechuic and p-coumaric acids were the major contributors to antioxidant activity.     

Study on antioxidant activity of certain plants in Thailand: Mechanism of antioxidant action of guava leaf extract

The ethanol extracts from 24 samples plant species commonly found in Thailand were investigated and compared on their antioxidant activity by ABTS assay. The ethanol extract from the leaves of guava (Psidium guajava) showed the highest antioxidant capacity with the TEAC value of 4.908 ± 0.050 mM/mg, followed by the fruit peels of rambutan (Nephelium lappaceum) and mangosteen (Garcinia mangostana) with the TEAC values of 3.074 ± 0.003 and 3.001 ± 0.016 mM/mg, respectively. The further investigation of guava leaf extracts from different solvents; n-hexane, ethyl acetate, n-butanol, and methanol, was examined using ABTS and FRAP assays. The total phenolic content was done by Folin–Ciocalteu reaction. The results indicated that the methanol fraction possessed the highest antioxidant activity, followed by the butanol and ethyl acetate fractions, respectively. The hexane fraction showed the lowest antioxidant activity. The results demonstrated that the mechanism of antioxidant action of guava leaf extracts was free radical scavenging and reducing of oxidized intermediates. The phenolic content in guava leaf fraction played a significant role on the antioxidant activity via reducing mechanisms.     

Screening of 70 medicinal plant extracts for antioxidant capacity and total phenols

The total phenolic content and related total antioxidant capacity of 70 medicinal plant infusions was analyzed. Infusions were prepared in common way in which teas are prepared for human consumption. The total phenolics were measured by Folin–Ciocalteau assay. The total antioxidant capacity was estimated by Ferric Reducing/Antioxidant Power (FRAP) assay. To make practical comparison of relative antioxidant potential of phenolics extracted from selected medicinal plants, the phenol antioxidant coefficient (PAC) was calculated for each infusion. The total phenolic content of medicinal plant infusions ranges from 9 to 2218 mg/L. The FRAP range from 0.06 to 25 mM/L. There was significant linear correlation between total phenolic content and FRAP. According to their antioxidant capacity, 70 medicinal plant extracts can be divided in five groups: (a) very low FRAP (<1 mM/L) n = 9; (b) low FRAP (1–5 mM/L), n = 37; (c) good FRAP (5–10 mM/L), n = 15; (d) high FRAP (10–20 mM/L), n = 8; and (e) very high FRAP (>20 mM/L), n = 1 medicinal plant extract. The PAC was ranging from 1.1 to 3.9 (average 2.4). The best results were obtained for Melissae folium infusions: high phenolic concentration, very high FRAP (>20 mM/L) and PAC > 3. The effect of infusion time and infusion temperature on the phenolic content, FRAP, and free radical scavenging ability was tested. DPPH radical scavenging ability of Melissae folium phenolics was similar to (+)-catechin but not as good as for quercetin. Compared to Trolox and vitamin C, Melissae folium phenolics were more efficient free ABTS radical scavengers. The results indicate that Melissae folium infusions could be an important dietary source of phenolic compounds with high antioxidant capacity comparable with red wine or beverages like tea.     

Composition and antioxidant and antimicrobial activity of the essential oil and extracts of Stachys inflata Benth from Iran

Composition and antioxidant and antimicrobial activities of essential oil and methanol extract polar and nonpolar subfractions of Stachys inflata were determined. GC and GC/MS analyse of the essential oil showed 45 constituents representing 95.46% of the oil, the major components linalool (28.55%), α-terpineol (9.45%), spathulenol (8.37%) and (2E)-hexenal (4.62%) constituted 50.99% of it. Essential oil and extracts were also tested for their antioxidant activities using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and β-carotene/linoleic acid assays. In the DPPH test, IC₅₀ value for the polar subfraction was 89.50 μg/ml, indicating an antioxidant potency of about 22% of that of butylated hydroxytoluene (IC₅₀ = 19.72 μg/ml) for this extract. In β-carotene/linoleic acid assay, the best inhibition belonged to the nonpolar subfraction (77.08%). Total phenolic content of the polar and nonpolar extract subfractions was 5.4 and 2.8% (w/w), respectively. The plant also showed a week antimicrobial activity against three strains of tested microorganisms. Linalool and α-terpineol were also tested as major components of the oil and showed no antioxidant but considerable antimicrobial activities.     

RP-HPLC–DAD analysis of phenolic compounds in pomace extracts from five grape cultivars: Evaluation of their antioxidant,antiradical and antifungal activities in orange and apple juices

Phenolic compounds, related to antioxidative and antifungal properties of ethanolic extracts from five commercial grape cultivars (three red and two white) grown in Turkey were determined. A reversed-phase high performance liquid chromatography (RP-HPLC) procedure was developed, and a total 18 different phenolic compounds were identified. Total phenolic contents of the extracts were determined using Folin–Ciocalteau method. Antioxidant activities of the extracts were evaluated by using DPPH radical scavenging and phosphomolybdenum methods. All extracts exhibited strong antioxidant and antiradical activity. Phenolic compounds and antioxidant activities of the extracts were variety dependent. Antifungal activities of the pomaces and extracts were screened by both in vitro agar-well diffusion assay and antifungal activity in apple and orange juices in situ using Zygosaccharomyces rouxii and Z. bailii. Antifungal activities revealed that the pomaces and extracts of Gamay and Kalecik karasi could be more effective antifungal agents than those of Emir, Narince and Okuzgozu grape cultivars.