Variation In Phenolic Content Research Articles

Variation in Phenolic Content, Antioxidant Activity and Alpha-amylase and Acetylcholinesterase Inhibitory Capacities of Different Extracts from Tunisian Satureja barceloi (Willk) L.

The antioxidant activity and the anti-α-amylase and anti-acetylcholinesterase capacities of secondary metabolites from different organs (roots, stems, leaves and flowers) of Tunisian Satureja barceloi were determined. The variation in the distribution of phenolic metabolites among roots, stems, leaves and flowers extracts of S. barceloi with various solvent systems (methanol, ethyl acetate, hexane and distilled water) has not been characterized before. Significant variation of phenolic compounds was observed according to organs rather than to extracting solvents. The analyzed organs show a high level of phenolic compounds although the stems contains the highest total polyphenols (132.53±0.48 mg AGE/g Ex), flavonoids (48.99±0.65 mg RE/g Ex) and flavonols (34.93±0.29 mg QE/g Ex) contents. The phenolic fraction was dominated by sagerinic acid, caffeic acid glucoside and epigallocatechin, detected using HPLC-PDA/ESI-MS. The antioxidant activity of all extracts, evaluated by four in vitro tests, was high and varied significantly according to the type of solvent used and the plant organ. The aqueous extracts of leaves exhibited the greatest inhibitory effect on alpha-amylase while the methanolic extract of leaves and stems revealed the most important acetylcholinesterase inhibitory effect. Hence, S. barceloi extracts could be used as a source of various bioactive molecules in pharmaceutical industry.

Metabolomics Analysis of Different Quinoa Cultivars Based on UPLC-ZenoTOF-MS/MS and Investigation into Their Antioxidant Characteristics.

In recent years, quinoa, as a nutritious and sustainable food material, has gained increasing popularity worldwide. To investigate the diversity of nutritional characteristics among different quinoa cultivars and explore their potential health benefits, metabolites of five quinoa cultivars (QL-1, SJ-1, SJ-2, KL-1 and KL-2) were compared by non-targeted metabolomics analysis based on UPLC-ZenoTOF-MS/MS in this study. A total of 248 metabolites across 13 categories were identified. Although the metabolite compositions were generally similar among the different quinoa cultivars, significant variations existed in their respective metabolite contents. Among the identified metabolites, amino acids/peptides, nucleosides, saponins and phenolic acids were the most abundant. Notably, SJ-1 exhibited the most distinct metabolite profile when compared to the other cultivars. Amino acids/peptides and nucleosides were found to be crucial factors contributing to the unique metabolite profile of SJ-1. Collectively, these aforementioned metabolites accounted for a substantial 60% of the total metabolites observed in each quinoa variety. Additionally, a correlation between the DPPH radical scavenging activity and the free phenolic content of quinoa was observed. Variations in phenolic content resulted in different antioxidant capacities among the quinoa cultivars, and SJ-1 exhibited lower phenolic levels and weaker antioxidant activity than the others. These results can provide important information for the development of quinoa resources.

Comparative analysis of the phenolic contents and antioxidant activities of different parts of two pomegranate (Punica granatum L.) Cultivars: 'Tunisia' and 'Qingpi'.

Pomegranate (Punica granatum L.), with its abundant phenolic substances and strong antioxidant activity, holds significant research and utilization potential across various organs. However, there have been few studies on the phenolic content and antioxidant activity of different parts of pomegranate, especially the placenta. This study investigated the phenolic content and antioxidant activity of fruits, flowers, and leaves of two pomegranate varieties, 'Tunisia' and 'Qingpi', throughout their growth and development. Results indicated significant variations in phenolic content among different organs, with petals exhibiting the highest total polyphenol content (TPC, 49.40 mg GAE/g FW) and total anthocyanin content (TMAC, 1938.54 nmol/g FW). Placenta contained the highest levels of total flavonoids (TFC, 173.58 mg RE/g FW) and punicalagin (109.30 mg/g FW). The peel had the highest content of total flavanols (TFAC, 19.42 mg CE/g FW). Over the course of pomegranate development, total polyphenols, total flavonoids, total flavanols, punicalagin, and antioxidant activity declined in different organs. Antioxidant activity followed the order: fruit > flower > leaf, with the placenta exhibiting the highest antioxidant activity among fruits. Antioxidant activity showed a significant positive correlation with total polyphenols (R2=0.77-1.00), total flavonoids (R2=0.71-0.99, except tegmens), and punicalagin (R2=0.71-1.00). This study provides a comparative analysis of the phenolic content and antioxidant activity in different organs of pomegranate, highlighting the placenta as the primary source of punicalagin. This study provides a theoretical basis for the development and utilization of pomegranate phenolic compounds.

Phenolic Compounds from New Natural Sources—Plant Genotype and Ontogenetic Variation

Phenolic compounds (PCs) are widespread secondary metabolites with potent biological activity. Their sources are mainly plants from cultivated and natural states, providing valuable protective and health-promoting extracts. The wide biological activity of PCs (antioxidant, anti-inflammatory, antimicrobial, antiatherosclerotic, antidiabetic, antiallergic, prebiotic, antimutagenic) means that new sources of PCs are constantly being sought, as exemplified by extracting these compounds from tissue culture or agricultural by-products. Plant phenols show marked qualitative and quantitative variation not only at different genetic levels (between and within species and clones) but also between different physiological and developmental stages. Assessing genetic and seasonal variations in phenolic content and activity allows for selecting the best time to harvest the plant. Learning about the causes of PCs' variability and putting this knowledge into practice can significantly increase PCs' yields and extract the most valuable compounds. The health-promoting properties resulting from consuming products rich in plant PCs are undeniable, so it is worth promoting high-phenolic products as a regular diet. This paper presents an overview of different sources of PCs for use as potential therapeutic alternatives. Additionally, factors of variation in the phenolic complex at the genome and ontogeny levels, relevant in practical terms and as a basis for further scientific research, are presented.

Appraisal of wild fig fruits for nutra-pharmaceutical and biological attributes

The fruits of wild fig, native to Soon valley of Pakistan, were appraised for phenolic compounds and high-value nutrients. These fruits were shade-dried and extracted with different solvents of varying polarity to recover a wide range of antioxidant components, where hydroxyethanol exhibited highest extraction yield of antioxidant compounds. Among others, hydroxyethanol-derived crude concentration extracts (CCEs) and phenolic rich fractions (PRFs) showed greater amount of total phenolic, flavonoids and superior biological properties. The fruits of tested fruits were found to possess potassium (11.34 g/kg) and calcium (4.19 g/kg) as major elements, glucose (5.63g/100g DW) as dominant natural sugar and acetic acid (2.40 mg/100 g of dry matter) as principal organic acid. There was a considerable (p < 0.05) variation in phenolic content and biological properties of various extracts recovered with different solvents. Furthermore, the biological properties of tested fruits were found to be significantly correlated with their intrinsic total phenolic content (TPC) and total flavonoid content (TFC). Based upon the findings of present study, the fruits of wild fig could be treated as promising source of beneficial nutrients and potent phenolic components for their applications in the development of nutrapharmaceuticals.

Variations in phenolic content in tea under various processing methods

Variations in the phenolic content (total polyphenols, theaflavins, and thearubigins) of unconventional brands of ready-made tea (white, red, GABA) depending on different processing methods are discussed. Research in this direction has been carried out at the Subtropical Scientific Center of the Russian Academy of Sciences (FRC SSC RAS, Sochi) since 2017. Krasnodar tea was shown to contain polyphenols, theaflavins, and thearubigins in the amount of 18.47, 0.14, and 0.79 mg/g, respectively. Non-fermented and semi-fermented teas contain the highest amounts of polyphenols: white (16.63 mg/g), green (16.51 mg/g), and light GABA (16.47 mg/g). When processing light GABA tea, no change in the content of polyphenols occurs; however, the number of flavonoid pigments reduces significantly. Thus, the content of theaflavins (0.02 mg/g) remains at the level of white tea (0.03 mg/g), while that of thearubigins decreases significantly (0.26 mg/g as compared to 0.43–0.46 mg/g in white and green tea, respectively). The content of polyphenols in fermented teas (black, red) is significantly lower than that in raw material and non-fermented teas (НСР05 = 1.18). At the same time, black tea contains theaflavins (0.04 mg/g) and thearubigins (0.95 mg/g) in higher levels. To a certain extent, red tea is inferior to black tea in terms of polyphenols, although red tea is comparable to white and green teas in terms of flavonoids (0.04 mg/g of theaflavins and 0.39 mg/g of thearubigins). With respect to phenolic components, dark GABA tea approaches nonfermented and semi-fermented teas, which increases its nutritional value. The obtained data can be used when developing approaches to regulating the quality characteristics of ready-made tea produced under humid subtropical conditions in Russia, ensuring the preservation and improvement of product quality.

Analysis of individual anthocyanins, flavanols, flavonols and other polyphenols in Pistacia lentiscus L. fruits during ripening

Pistacia lentiscus L. is a shrub of the Anacardiaceae family whose fruits are used in Tunisian and Algerian diets. The phenolic composition at 5 different physiological stages of the fruit was investigated using two different targeted methodologies: ultra-high-performance liquid chromatography–UV/visible detection (UHPLC-UV/vis) for anthocyanins and UHPLC coupled with tandem mass spectrometry (UHPLC-MS/MS) for the other polyphenols. For the specific analysis of anthocyanins, compound identification was confirmed by UHPLC-MS/MS and LC-NMR analysis. This study revealed the identification of 30 phenolic compounds including 9 anthocyanins, 7 flavanols, 7 flavonols, 2 phenolic acids, 1 stilbene, 2 flavanones, 1 flavanonol and 1 dihydrochalcone. Quantification showed significant qualitative and quantitative variation in phenolic content during the ripening of P. lentiscus fruits, flavonols being the main compounds for the unripe berries and anthocyanins for ripe berries. To the best of our knowledge, our study reports the presence of piceid and protocatechuic acid in P. lentiscus L. fruits, as well as several anthocyanins in Pistacia, for the first time. The results indicate potential applications of P. lentiscus L. fruits as a source of phenolic compounds to be used as nutraceuticals and as food colorants.

Effect of cultivar and ripening on the polyphenol contents of East African highland bananas (Musa spp.)

East African highland bananas (EAHBs) contain high amount of phenolics especially tannins, and are used to produce low-viscosity banana juice by a purely mechanical process. Occasional juice failure and cloudy appearance are the major problems facing juice production. The present work thus examined the variations in phenolic content of EAHB cultivars and their changes during ripening. The aim was to obtain a better knowledge of the various forms and amounts of phenolic compounds in different EAHBs, and how these properties may affect the ability of cultivars to produce low viscosity banana juice. Eleven banana cultivars including juice-producing and cooking bananas were harvested at the green maturity stage and analysed for total phenolic content (TPC), tannin content (TC), and tannin monomers at different ripening stages for five days. Analyses of TPC and TC were performed using the Folin-Ciocalteu method, whereas tannin monomers were identified by High-Performance Liquid Chromatography (HPLC) with UV detection. Multivariate analysis of variance was used to evaluate the relationship between cultivar, ripeness stage, and TPC/TC. A substantial difference in TPC was observed between juice-producing and cooking cultivars. The highest TPC was found in the juice-producing cultivar Kibungara (360.68 ± 17.12 mg GAE/100 g) at day 5 (the ripe stage), while the lowest TPC (8.67 ± 0.22 mg GAE/100 g) was observed in the cooking cultivar Malindi at ripening day 5. The results revealed that TPC and TC of banana pulp seemed to be more related to cultivar (p ≤ 0.05) than physiological changes during ripening (p ≥ 0.05). Further, HPLC analysis showed that among the individual catechins, gallocatechin was the predominant monomer in juice-producing cultivars, whereas in cooking cultivars, gallic acid was dominant. The present work indicated that high amount of total phenolic such as tannins especially gallocatechin in juice-producing banana cultivars favour the release of banana juice, and that analysis of phenolic compounds will provide a basis in the selection of banana cultivars with high potential for juice production.

Drought stress effect on polyphenolic content and antioxidant capacity of cowpea pods and seeds

AbstractCowpea (Vigna unguiculata L. Walp) is a protein‐rich grain legume with high adaptability to heat and drought and can be consumed during all stages of the plant development. Drought is a severe environmental stress with major impacts on plant development and productivity. This study main objective was to understand the effects of drought stress on polyphenolic content and antioxidant capacity in plant tissue at different stages of cowpea development. Four cowpea genotypes grown until the anthesis under well‐irrigate conditions and then were submitted to two watering regimens (0% and 75% of field capacity) for one week. Immature pods and seeds and dry seeds were collected, and polyphenolic content and antioxidant capacity were evaluated by spectrophotometry. In general, differences between genotypes, plant growth stage and treatments were observed. A variation of phenolic content and antioxidant capacity has been detected in all cowpea genotypes and plant tissues at different development stages. Immature pods showed the highest values in all the parameters evaluated, while the dry seed presented the lowest values. The samples submitted to drought stress showed a slight decrease in all the parameters evaluated compared to control samples being this decrease only significant in some parameters and growth stages. This study shows that drought stress did not significantly influence the quality of cowpea through phenolic content and antioxidant capacity.

Phenolic Profile and Thermal Stability of Monovarietal Extra Virgin Olive Oils Based on Synchronous Fluorescence Spectroscopy.

The olive oil production in Pakistan has recently been started with the cultivation of exotic cultivars that are successfully adapted at Barani Agriculture Research center (BARI), Chakwal, Pakistan in Potohar valley. Therefore, characterization of extra virgin olive oil (EVOO) from this agro-climatic region is mandatory in establishing its biochemical profile and thermal stability. Seventeen monovarietal EVOOs extracted from these cultivars were analysed using synchronous fluorescence spectroscopy (SFS) and subjected to heating at 115, 150 and 170°C for 15min to identify their thermal stability. SFS emission spectra differentiated EVOOs on the basis of phenolic compounds that are denatured at high temperature, further chlorophyll contents also decreased with increasing temperature. The strong emission at ca. 351nm, suggested to be vanillic acid, 391-471nm for blue green region (BGR) assigned to other phenolic compounds and two peaks at 672 and 723nm for chlorophyll became the bases for grouping through Hierarchical clustering. Most of the EVOOs were stable at 150°C but showed denatured spectra at 170°C, the only EVOO extracted from Spanish cultivar Arbequina was found to have moderate fluorescence emission from both vanillic acid and BGR that are more likely to impart oxidative stability even after heating at 170°C, also confirmed by lowest values of specific extinction co-efficient (K232 and K270). Moreover, variation in phenolic contents of Arbequina EVOO was observed with different harvesting stages and the early harvested olives produced more thermally stable oil as compared to late harvested olives. Arbequina oil grown in Pakistan can be better suited for cooking at high temperatures, moreover can be blended with other monovarietal EVOOs to enhance the nutritional benefits and thermal stability.

Active phlorotannins from seven brown seaweeds commercially harvested in Brittany (France) detected by 1H NMR and in vitro assays: temporal variation and potential valorization in cosmetic applications

This study was focused on the phenolic content and associated cosmetic activities of seven brown marine macroalgae: Alaria esculenta, Ascophyllum nodosum, Bifurcaria bifurcata, Fucus serratus, Halidrys siliquosa, Himanthalia elongata, and Laminaria ochroleuca, selected for their abundance in Brittany and their phlorotannin production. Phlorotannins were extracted by maceration followed by a liquid/liquid purification to obtain fractions enriched in phlorotannins. Seasonal and yearly variations in phenolic contents were investigated thanks to the Folin-Ciocalteu assay to find the best harvesting season for each species. 1H nuclear magnetic resonance (NMR) was used to validate the presence of phenolic compounds and to compare the species in terms of phenolic signals, as they produce different phlorotannin molecules. Activities required for cosmetic applications (i.e., radical scavenging, antioxidant, photoprotective, and anti-aging activities) were assessed by in vitro tests. Fucales, especially A. nodosum, F. serratus, H. elongata, and H. siliquosa, showed higher phenolic contents than Laminariales. Temporal variations were apparent for five seaweeds with the highest phenolic content, notably in autumn. The phenolic content was high regardless of the season and antioxidant and photoprotective activities were similar to those of commercial molecules, allowing year-round algal harvesting. The anti-aging activity of A. nodosum and F. serratus fractions was higher than the active tea flavonol, epigallocatechin gallate. These results are promising for the use of abundant marine macroalgae as a source of natural active ingredients for cosmetic applications.

Characterization of phenolic compound antioxidant activity in oat varieties using UHPLC–online ABTS and LC Q‐TOF

AbstractBackground and objectivesPhenolic compounds present in oats provide an opportunity for oats to increase its use in the form of functional food. In this study, eight varieties of Australian‐grown whole‐grain oat were investigated for their phenolic composition and antioxidant potential. Ultra‐high‐performance liquid chromatography–online 2,2′‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid), coupled with liquid chromatography quadrupole time‐of‐flight, was used to identify and quantify individual phenolic compounds and their respective antioxidant activity.FindingsConsiderable variation in phenolic content (19.51 ± 1.20–52.49 ± 1.70 mg 100 g−1 GAE) and antioxidant activity was observed among the oat varieties. Several avenanthramides (AVNs) were detected with AVN A and AVN C being the most abundant. AVN C exhibited the highest antioxidant activity followed by caffeic acid, quercetin‐3,4′‐O‐di‐beta‐glucopyranoside derivative, and 6‐hydroxykaempferol 3,5,7,4′‐tetramethyl ether 6‐rhamnoside. Antioxidant activity in AVNs was observed to be the highest in AVN C followed by AVN B and AVN A.ConclusionsHigh levels of AVN C and the range of phenolic compounds present show promise of Australian‐grown oats as an important source of antioxidant compounds. These antioxidant compounds may contribute to consumers' health benefits.Significance and noveltyThis study contributes to the use of oats as potential functional food by characterizing its individual phenolic compounds and their antioxidant activity.

Physicochemical properties, bioaccessibility and antioxidant activity of the polyphenols from pine cones of Pinus koraiensis

This study investigated the physicochemical properties, bioaccessibility and in vitro antioxidant ability of the polyphenols isolated from the pine cones of Pinus koraiensis (PKP) under the simulated gastrointestinal digestion. The results found that PKP was mainly composed by derivatives of apigenin, phloretin, quercetin, myricetin, ellagitannin, and chlorogenic acid, and possessed the flat and smooth lump surface morphology. Through respective establishment of saliva, gastric fluid and small intestinal fluid digestive model in vitro, the compositions of phenolic compounds were totally different due to biotransformation. Compared with the phenolic composition of undigested PKP, the derivatives of apigenin, quercetin and ellagitannin were still detected after simulated digestion. A decrease of antioxidant capacity on free radical in vitro was observed throughout the simulated digestion processes, corresponding to the variation in phenolic content and composition. Our results highlighted that gastrointestinal digestion process might essentially influence the absorption of polyphenols, leading to the reduction of bioavailability.

Cereal phenolic contents as affected by variety and environment

AbstractBackground and objectivesPhenolic compounds found in cereals have been shown to possess antioxidant activity that has ensured an increased interest in their health beneficial properties. This review analyzed studies investigating the phenolic content of rice, barley, oats, and sorghum grown in different geographical locations and the effect environmental factors have on them.FindingsFrom the studies reviewed, it was identified that whole grain pigmented cereals exhibited phenolic profiles with polyphenols such as anthocyanins, proanthocyanidins, and their derivatives that translated to higher total phenolic content and antioxidant activity. Variation in phenolic content was also observed in cereal species grown in different geographical locations and when subjected to variable levels of salinity, water, and temperature.ConclusionsDespite the increasing body of knowledge on the phenolic content of cereals, studies focusing on the effect of environment on cereal phenolic content are limited; hence, more research is warranted.Significance and noveltyThis review examines literature to provide a holistic understanding of how environment plays a role in the regulation of phenolic metabolites in cereals such as oats with a focus on pigmented varieties of rice, barley, and sorghum.

Variation in Phenolic Content, Profile, and Antioxidant Activity of Seeds among Different Paeonia ostii Cultivated Populations in China.

The purpose of this study was to analyze the phenolic profiles of seeds from fifteen Paeonia ostii cultivated populations in China and identify their relationship with antioxidant activities and associated environmental factors. Thirteen individual phenolic compounds were quantitatively determined by HPLC, and (+)-catechin was the most abundant phenolic compound in the seeds. Correlation analysis showed that phenolics were the most effective antioxidant compound class by evaluating DPPH, ABTS, and hydroxyl radical scavenging activities as well as ferric reducing antioxidant power. Latitude and annual rainfall had significant effects on the contents of many phenolic compounds, and elevation was only significantly correlated with gallic acid content. Within fifteen P. ostii cultivated populations, the seeds of Tongling population exhibited the highest phenolic contents and strongest antioxidant activities. These results suggest that Tongling population has a relatively high utilization value and a potential for sources of natural antioxidants.

Seasonal Variation in Phenolic Content and Antioxidant Activity of Glechoma Hederacea L. Harvested from Six Hungarian Populations

Ground ivy (Glechoma hederacea L.) is one of the prosperous plants for the food-industry as natural antioxidant. This fact led us to examine the chemical diversity of six ground ivy populations situated in different natural habitats and to analyse the effect of the harvesting time. Total phenolic content, chlorogenic acid, and rutin content, as well as the antioxidant capacity showed significant differences due to the harvest time. The highest total phenol content (115 mg g–1 GAE) and the strongest antioxidant activity (53.3 mg g–1 AAE) were measured in the population originated from Budapest (GLE 6), harvested in July. The highest chlorogenic acid (357 mg/100 g) and rutin (950 mg/100 g) contents were detected in the July harvested samples from the Soroksár Botanical Garden population (GLE 1). According to our results, the collection time has significant effect on the total phenolic content – first of all on the chlorogenic acid and rutin accumulation levels of ground ivy, while the influence of the habitat seems to be less important.

Evaluation of Phenolic Content Recoveries in Hydrolyzed Extracts of Bergenia ciliata Using RP-HPLC, GC–MS after Silylation, and Validation through Antioxidant Potential

Methanol extracts of Bergenia ciliata treated with chemical and nonchemical medium were comparatively analyzed for optimum recovery of phenolic (PH) and flavonoid (FV) compounds such as Gallic acid, Bergenin, Gallicin, and (+)-Catechin using RP-HPLC coupled to photo diode array detector. The gas chromatography–mass spectrometry method (GC–MS) was also used for identification of targeted compounds after silylation. Methanol extract was treated separately in acid, base, hydrogen peroxide, neutral, and dry heat medium, analyzed and compared using HPLC. After treatment, drastic variation in phenolic content was observed. Out of five treatments, acid treatment was found to enhance the recovery of all studied phenolic compounds, namely Gallic acid (0.415 ± 0.12), Bergenin (1.91 ± 0.14), Gallicin (0.409 ± 0.17), and (+)-Catechin (18.66 ± 0.15). Dry heat and neutral heat specifically enhances the recovery of Bergenin (2.95 ± 0.12), (3.29 ± 0.18), whereas base and hydrogen peroxide did not show significant content variation. Acid treated extract has shown, as expected, maximum antioxidant potential compared to nontreated extracts.

Intra-thallus variation of phenolic compounds, antioxidant activity, and phenolsulphatase activity in Cystoseira tamariscifolia (Phaeophyceae) from southern Spain

Intra-thallus variation in phenolic content, antioxidant activity, and phenolsulphatase activity (EC 3.1.6.1) was studied in Cystoseira tamariscifolia (Phaeophyceae) from southern Spain. Significant differences in the content of phenolic compounds were found among apical, middle, and basal sections of the thallus of C. tamariscifolia. The concentrations of phenolic compounds and of phenolsulphatase activity were highest in the apical section and decreased toward the basal section. There was a highly significant correlation between the concentration of phenolic compounds and antioxidant and phenolsulphatase activities in C. tamariscifolia. Phenol excretion and phenolsulfatase activity were significantly correlated with integrated irradiance. Cystoseira tamariscifolia grows in tightly packed turfs that promote auto-shading in the middle and basal sections of its thalli, and it is thus likely that the higher polyphenol content in the apical section of this species is a response to the higher exposure to ultraviolet radiation and photosynthetically active radiation relative to the middle and basal sections. These results suggest that this excretion of phenolic compounds might function as a protective mechanism serving as a radiation filter in the immediate surroundings of the C. tamariscifolia thalli.

Variation in Phenolic Content and Antioxidant Activity of Fermented Rooibos Herbal Tea Infusions: Role of Production Season and Quality Grade

Data are required to calculate the dietary exposure to rooibos herbal tea flavonoids and phenolic acids. Representative content values for the principal phenolic compounds and total antioxidant capacity of fermented rooibos infusion, taking into account variation caused by production seasons (2009, 2010, and 2011) and quality grades (A, B, C, and D), were determined for samples (n = 114) from different geographical areas and producers. The major phenolic constituents were isoorientin and orientin (>10 mg/L), with quercetin-3-O-robinobioside, phenylpyruvic acid glucoside, and aspalathin present at >5 mg/L. Isovitexin, vitexin, and hyperoside were present at <3 mg/L. Rutin, ferulic acid, and isoquercitrin were present at <2 mg/L. Nothofagin was present at <1 mg/L. Only traces of luteolin-7-O-glucoside and the aglycones quercetin, luteolin, and chrysoeriol were present. Substantial variation was observed in the individual content values of the phenolic compounds and total antioxidant capacity within production seasons and quality grades.

Antioxidant capacity and α-glucosidase inhibitory activity in peel and flesh of blueberry (Vaccinium spp.) cultivars

This study was designed to evaluate cultivar variations in phenolic content, anthocyanin content, and antioxidant activity of peel and flesh; and to determine their potential inhibitory effects on α-glucosidase in 33 blueberry (Vaccinium species) cultivars, including 29 rabbiteye (Vaccinium ashei Reade) blueberries, two V. ashei hybrid derivatives, and two northern highbush (Vaccinium corymbosum L.). The relation of phenolic, anthocyanin, and antioxidant activity to α-glucosidase inhibition in blueberries also was investigated. It was found that peel tissue possessed higher levels of total anthocyanins (TA), total phenolics (TP), antioxidant capacity, and α-glucosidase inhibitory activity than flesh tissue in all blueberries tested. The percentage contributions of peel to whole berry on scavenging capacity against peroxyl free radicals (ROO), hydroxyl radicals (OH), hydrogen peroxide (H2O2), and singlet oxygen (1O2) radicals, were higher than those of flesh, even though the fruit contained much higher amounts of flesh than peel in terms of dry weight. Cultivars with high levels of phenolic compounds, antioxidant capacities, and α-glucosidase inhibitory activities could be selected for use in blueberry breeding programs to develop new lines with improved health benefits.