Non-flavonoid Phenolic Compounds Research Articles

Portuguese Grapevine Leaves: A Neglected By-Product with High Potential

In Portugal, grapevine leaves are generally treated as agro-industrial waste, despite being rich in bioactive compounds that offer benefits to human health. This study compiles the most relevant and current data on the phytochemical composition and bioactive properties of grape leaves from both red and white varieties cultivated in the country. These by-products are abundant in flavonoid and non-flavonoid phenolic compounds, such as flavonols, derivatives of hydroxycinnamic acids, carotenoid pigments, and chlorophylls, as well as fatty acids, which have scientifically proven antioxidant, antimicrobial, anti-inflammatory, antidiabetic, cardio-, neuro- and hepatoprotective properties, among others. The combination of these beneficial properties, along with the low toxicity of their compounds, makes grapevine leaves a by-product with great potential for use in the food, pharmaceutical, and cosmetic industries. The key challenge is to develop sustainable methods to reintegrate this by-product into the supply chain, in alignment with the sustainability goals of the 2030 Agenda.

A Review on the Mechanism and Structure-activity Relationship of Resveratrol Heteroaryl Analogues.

Resveratrol is one of the most interesting naturally-occurring nonflavonoid phenolic compounds with various biological activities, such as anticancer, neuroprotection, antibacterial, and anti-inflammatory. However, there is no clinical usage of resveratrol due to either its poor activity or poor pharmacokinetic properties. Heteroarenes-modified resveratrol is one pathway to improve its biological activities and bioavailability, and form more modification sites. In this review, we present the progress of heteroaryl analogues of resveratrol with promising biological activities in the latest five years, ranging from the synthesis to the structure-activity relationship and mechanism of actions. Finally, introducing heteroarenes into resveratrol is an effective strategy, which focuses on the selectivity of structure-activity relationship in vivo.

Influence of climatic conditions on ripening and the phenolic content of grapes from Cabernet Sauvignon, Gamza and Rubin red vine varieties

During the period 2021-2022, the dynamics of ripening and the phenolic content of grapes from the varieties Cabernet Sauvignon, Gamza and Rubin, grown in the region of the town of Pleven, were studied. The changes in the meteorological indicators throughout the vegetation period were monitored. During the winter months, significantly low temperatures for the vine plant growth were not registered in the region. The onset of the vines’ vegetative development was in the middle (2021) or the early (2022) April. During the grapes ripening period, the dynamics of sugars and total acids were monitored. The Rubin variety showed the fastest sugar accumulation while maintaining a relatively high acidity rate. The Gamza and Cabernet Sauvignon varieties were later ripening and revealed a gradual increase in sugars and a decrease in total acids. The highest sugar accumulation in the Rubin and Gamza varieties was found in 2021, while for Cabernet Sauvignon - in the grapes from the 2022 harvest. Both the weather conditions during the year and the varietal characteristics, specifics and potential had an impact on the phenolic content in the structural elements of the cluster. The varieties had different reserves of total, flavonoid and non-flavonoid phenolic compounds, which increased in the order of berries < skins < rachis < seeds. The Rubin variety had the highest values of the studied phenolic components, followed by Cabernet Sauvignon, and the lowest were in Gamza. The anthocyanin content of the varieties changed in the same sequence. In all three varieties, the anthocyanin content in the skins was significantly higher compared to the berries.

Multivariate Analysis Revealed Ultrasonic-Assisted Extraction Improves Anti-Melanoma Activity of Non-Flavonoid Compounds in Indonesian Brown Algae Ethanol Extract.

Indonesia has high biodiversity of algae that are under-utilised due to limitations in the processing techniques. Here, we observed the effect of two different extraction methods (cold maceration and ultrasonic-assisted extraction (UAE)) on multiple variables of Indonesian brown algae ethanol extracts (Sargassum polycystum, Sargassum cristaefolium, Sargassum aquifolium and Turbinaria ornata). The variables observed included metabolites screening by untargeted metabolomics liquid chromatography-high-resolution mass spectrometry (LC-HRMS), observation of total phenolic content (TPC), total flavonoid content (TFC), anti-oxidant and B16-F10 melanoma cells cytotoxicity. UAE extracts had higher extraction yield and TPC, but no TFC difference was observed. UAE extract had more lipophilic compounds, such as fatty acids (Palmitic acid, Oleamide, Palmitoleic acid, Eicosapentaenoic acid, α-Linolenic acid, Arachidonic acid), lipid-derived mediators (11,12-Epoxyeicosatrienoic acid ((±)11(12)-EET)), steroid derivatives (Ergosterol peroxide), lipophilic metabolite (Fucoxanthin), and lipid-soluble vitamins (all-trans-retinol). Principle component analysis (PCA) revealed that TPC, not TFC, in the UAE extracts was correlated with the anti-oxidant activities and cytotoxicity of the extracts towards B16-F10 melanoma cells. This means other non-flavonoid phenolic and lipophilic compounds may have contributed to its bioactivity. These results suggest that out of the two methods investigated, UAE could be a chosen method to extract natural anti-melanogenic agents from brown algae.

STUDY OF THE PHENOLIC COMPOSITION AND ANTIOXIDANT ACTIVITY OF WHITE AND RED WINES OBTAINED FROM INTRODUCED, LOCAL AND HYBRID GRAPEVINE VARIETIES FROM THE REGION OF CENTRAL NORTHERN BULGARIA

Study on the phenolic composition and antioxidant activity of white and red wines obtained from introduced (Chardonnay, Cabernet Sauvignon), local (Dimyat, Gamza) and hybrid (Druzhba, Rubin) varieties was performed. The wines had optimal chemical parameters. Almost identical total phenolic compounds (TPC) content (700.00 ± 0.0.000 mg/dm3 and 703.33 ± 5.773 mg/dm3) in the white wines of the introduced Chardonnay variety and the local Dimyat was found. The wine of the introduced Cabernet Sauvignon showed the highest quantitative presence of TPC (1666.66 ± 5.773 mg/dm3) from the red wines group. Chardonnay wine showed the highest content of flavonoid phenolic compounds (FPC) (769.84 ± 1.833 mg/dm3), and for the red wines FPC content dominated quantitatively in Rubin (2532.40 ± 49.938 mg/dm3). The wine of the introduced Chardonnay also showed the highest content of non-flavonoid phenolic compounds (NPC) (115.78 ± 0.325 mg/dm3), and in the red wines Gamza (235.63 ± 0.498 mg/dm3) was distinguished by this indicator. The quantitative presence of anthocyanins in the studied red wines followed the order wine - introduced variety > wine - hybrid variety > wine - local variety. The highest antioxidant activity (AA) in white wines was found in Chardonnay. Gamza and Cabernet Sauvignon red wines showed a close percentage of radical scavenging activity, but it was slightly higher in the wine of the local Gamza variety. There was a correlation between the antioxidant activity of red wines and the content of NPC in them, respectively: NPC (AA) Gamza > NPC (AA) Cabernet Sauvignon > NPC (AA) Rubin. The white and red wines from introduced, local and hybrid grapevine varieties from the region of Pleven, Central Northern Bulgaria showed good and balanced phenolic accumulation capacity, resulted in optimal ability for in vitro elimination of free DPPH radicals.

"Good Wine Makes Good Blood": An Integrated Approach to Characterize Autochthonous Apulian Grapevines as Promising Candidates for Healthy Wines.

Wine production represents an ancient human activity and one of the most economically important markets in Europe. Moreover, the health effects of grapes and related products have been largely demonstrated, and mostly depend on their richness in bioactive molecules such as flavonoid and non-flavonoid phenolic compounds. Italy has the highest global wine production and provides one of the richest grapevine germplasm in the Mediterranean area. In this paper, our attention was focused on the evaluation of the total phenol and anthocyanin content in five autochthonous Apulian grapevine cultivars, in both wines and their non-alcoholic extracts. Moreover, the potential antioxidant effects of the non-alcoholic wine extracts on the cell viability of Caco-2 and HeLa carcinoma cell lines were tested. Finally, for the most promising autochthonous selected cultivars (Negramaro, Nero di Troia and Susumaniello), comparative transcriptomic analysis in berries was performed using high-throughput sequencing technology.

Efecto de las condiciones de extracción sobre la concentración de compuestos fenólicos en residuos de orégano mexicano (Lippia graveolens Kunth)

Introduction: Mexican oregano (Lippia graveolens Kunth) leaves are marketed for use in food and for essential oil extraction. Phenolic compounds with antioxidant properties can be obtained from the residues (leaves without oil and stems) under appropriate extraction conditions. Objective: To evaluate the effect of extraction solvent and mass/volume ratio on phenolic compounds concentration and their antioxidant capacity in oregano residues. Materials and methods: Residual leaf (without oil) and stems of oregano were used to obtain extracts with 30, 50 and 80 % aqueous ethanol (ET30, ET50, ET80, respectively) and solvent mass/ volume ratios (1:10, 1:20 and 1:30). Yield in solids, total phenols concentration and flavonoids, and antioxidant capacity were evaluated in the extracts. Similarity analysis between extracts was performed by HPLC-DAD and the main phenols were identified by UPLC-MS. Results and discussion: Extract yields, phenol concentrations and flavonoids and antioxidant capacity for leaves were higher than for stems. The maximum concentration of phenols was obtained with ET80 and 1:30 ratio, which indicates better dissolution in ethanol than in water. The extracts ET50 and ET80 had chromatographic similarity of phenols in both residues; naringenin, taxifolin, eriodictyol, caffeic acid and luteolin were the major compounds. Conclusion: Ethanol-water concentrations and mass/solvent ratios are feasible for obtaining flavonoid and non-flavonoid phenolic compounds with antioxidant capacity from oil-free leaves and stems of oregano.

PHENOLIC CONTENT AND ATIOXIDANT ACTIVITY OF RED GRAPES FROM INTERNATIONAL, LOCAL AND HYBRID GRAPEVINE VARIETIES GROWN IN CENTRAL NORTHERN BULGARIA

A study to determine the phenolic content and antioxidant activity of grapes from red international (Cabernet Sauvignon), local (Gamza) and hybrid (Rubin) grapevine varieties grown in the region of Central Northern Bulgaria was conducted. The phenolic content of the grapes, the phenolic content and antioxidant activity of their must were determined. Rubin shown the best content of Total Phenolic Compounds (TPC), Flavonoid Phenolic Compounds (FPC), Non-Flavonoid Phenolic Compounds (NPC) and anthocyanins in the structural elements of the cluster. This hybrid variety also shown the highest content of TPC in the must (0.74±0.00 g/l), followed by Gamza, and the lowest TPC was found in the Cabernet Sauvignon – control variety (0.25±0.00 g/l). The highest amount of anthocyanins was found in Rubin grape must (19.91±0.48 mg/l). The dynamics of increasing of the anthocyanin content in the must of the studied varieties followed the order international variety (Cabernet Sauvignon) < local variety (Gamza) < hybrid variety (Rubin). In the red varieties, the grape must of the Rubin hybrid shown significant and the highest antioxidant activity of the three studied varieties. It was four times higher than that found in the Cabernet Sauvignon control. A correlation between TPC, anthocyanin content and antioxidant activity in Rubin was found. This proved the close connection between the phenolic composition and the antioxidant capacity of the variety. The study proved that the grape must of the two studied hybrid and local varieties shown high biological potential and activities.

Bioactive Compounds and Metabolites from Grapes and Red Wine in Breast Cancer Chemoprevention and Therapy.

Phytochemicals and their metabolites are not considered essential nutrients in humans, although an increasing number of well-conducted studies are linking their higher intake with a lower incidence of non-communicable diseases, including cancer. This review summarizes the current findings concerning the molecular mechanisms of bioactive compounds from grapes and red wine and their metabolites on breast cancer—the most commonly occurring cancer in women—chemoprevention and treatment. Flavonoid compounds like flavonols, monomeric catechins, proanthocyanidins, anthocyanins, anthocyanidins and non-flavonoid phenolic compounds, such as resveratrol, as well as their metabolites, are discussed with respect to structure and metabolism/bioavailability. In addition, a broad discussion regarding in vitro, in vivo and clinical trials about the chemoprevention and therapy using these molecules is presented.

The protective effect of different extracts of aerial parts of Artemisia ciniformis against H2O2-induced oxidative stress and apoptosis in PC12 pheochromocytoma cells

The major objective of this study is to investigate whether Artemisia ciniformis (A. ciniformis) is able to rescue the PC12 neuronal cells from H 2 O 2 -mediated oxidative stress. Different antioxidant and apoptotic assays were conducted on A. ciniformis. Among different A. ciniformis extracts, three (petroleum ether, dichloromethane, and ethylacetate) were the most proper ones. The protective effects of these extracts against H 2 O 2 -induced cytotoxicity were examined. Ethyl acetate (EA) extract was fractionated and total phenolic and flavonoid contents (TPC and TFC) of fractions were estimated. EA extract was found to be the most effective extract on suppressing the toxicity of H 2 O 2 . It caused up to 35 reduction in H 2 O 2 -induced cellular death, more than 70 decrease in reactive oxygen species (ROS) accumulation, 47 increase in SOD activity, almost 175 decrease in caspase-3 activity, and more than 27 elevation in mitochondrial membrane potential level. After fractionation, the most potent fraction (F3) was found active in protecting PC12 cells from oxidative stress consequences. This fraction possessed the highest ratio of flavonoid to non-flavonoid phenolic compounds (TFC = 125.03 ± 1.31 mg quercetin equivalent/g and TPC = 127.18 ± 6.00 mg gallic acid equivalent/g), suppressed the toxicity mediated by H 2 O 2 and successfully inhibited the overproduction of ROS caused by H 2 O 2 . These results altogether suggested A. ciniformis is a potential choice for preventing different neurodegenerative diseases. © 2019 Leila Hosseinzadeh et al.

Melatonin Treatment Enhances the Polyphenol Content and Antioxidant Capacity of Red Wine

Melatonin and polyphenols are strong antioxidants, and melatonin is also a potential plant growth regulator. The role of melatonin in regulating polyphenol metabolism is unclear. This study assessed the primary impacts of exogenous melatonin treatment on phenolics accumulation and antioxidant capacity of the ‘Moldova’ wine. It was found that two times of 100 µmol·L−1 melatonin treatment clearly enhanced the endogenous melatonin content of ripened berries and wine. Further experiments indicated that melatonin treatment significantly increased the contents of total phenols, flavonoids and anthocyanins in wine. Additionally, the contents of most of the 20 detected individual phenolic compounds were significantly enhanced by melatonin treatment in wine. Particularly, the content of two non-flavonoid phenolic compounds (syringic and coumaric acid) and four anthocyanin compounds [Mv-3-Glu, Mv-3-(6-Coum)Glu-5-Glu, Dp-3-(6-AC)Glu and Dp-3-(6-Coum)Glu-5-Glu] were largely increased by melatonin treatment. In contrast, only Pn-3-(6-Coum)Glu was significantly reduced. Moreover, melatonin treatment significantly enhanced the antioxidant capacity of wine indicated by DPPH and FRAP assays. In summary, melatonin treatment enhanced the polyphenol content and antioxidant capacity of wine.

Determination of Polyphenolic Compounds by Ultra-Performance Liquid Chromatography Coupled to Tandem Mass Spectrometry and Antioxidant Capacity of Spanish Subtropical Fruits

In an analysis of the seven types of subtropical fruits most consumed and produced in southern Spain, UPLC-ESI-MS/MS was used to quantify 14 phenolic species: five hydroxycinnamic acids, seven hydroxybenzoic acids and two flavonoids (quercetin and naringenin). In each case, in addition, antioxidant capacity was determined by FRAP, ABTS and DPPH. Of these fruits, carambola (or starfruit) presented the highest levels of phenolic compounds, cherimoya (custard apple) and kiwi were the richest in non-flavonoid phenolic compounds and papaya had the highest levels of the flavonoids studied. Higher mean values were recorded in home-grown fruits than in imported varieties by ABTS and DPPH methods. Persimmon’s antioxidant capacity was well above that of the other fruits, according to our analyses.

Subcritical water extraction of phytochemicals from Phlomis umbrosa Turcz

Subcritical water extraction (SWE) avoids the use of organic solvents when extracting active compounds. The SWE of phytochemicals from Phlomis umbrosa Turcz (PT) and the effect of antioxidant activity were investigated while varying the extraction temperature (from 100 °C to 200 °C) and time (from 5 to 25 min). The maximum yields of total polyphenols (142.02 ± 5.67 mg/g PT, mean ± SD) and flavonoids (33.69 ± 3.01 mg/g PT) were obtained for an extraction temperature and time of 200 °C and 20 min, respectively. The correlation of antioxidant activities in terms of their total phenolics and flavonoids contents suggest that the ABTS+ assay better reflects the antioxidant contents in SWE from PT than does the DPPH assay for extraction temperatures from 110 °C to 200 °C. At higher temperatures around 200 °C, SWE extracts affect the antioxidant activity due to the presence of not only flavonoids but also nonflavonoid phenolic compounds including prenylated flavonoids. This study used subcritical water extraction (SWE) for the practical applications of the SWE process that extracts antioxidant compounds from medicinal herb such as Phlomis umbrosa Turcz. SWE is excellent technology to selectively extract bioactive compounds using temperature-dependent dielectric constant properties of water. As the temperature of water is increased, the polarity of water decreases. That's why it is selective extraction. The use of SWE in the present study was associated with high efficiency and antioxidant activities. These results indicate that SWE is an efficient and rapid method for extracting phytochemicals, and a safer product only using purified water. SWE has a potential to develop a commercial process for the extraction of phytochemicals. This method can be easily implemented on an industrial scale.

Non-flavonoid phenolics from Averrhoa carambola fresh fruit

The fruit of Averrhoa carambola L. (Oxalidaceae) is a commercially important fruit. Our study on the chemical constituents present in the fresh sweet fruit led to the isolation of eleven non-flavonoid phenolic compounds. Their structures were identified by analyses of spectroscopic data. They were two new alkyl phenol diglucosides, carambolasides K (1) and L (2), four phenylpropanoids, (+)-isolariciresinol 9-O-β-d-glucoside (3), (+)-lyoniresinol 9-O-β-d-glucoside (4), (−)-lyoniresinol 9-O-β-d-glucoside (5), and 1-O-feruloyl-β-d-glucose (6), three benzoic acids, protocatechuic acid (7), 1-O-vanilloyl-β-d-glucose (8), and tecomin (9), a simple phenol, koaburaside (10), and a naphthoquinone, (+)-cryptosporin (11). All of them were reported from A. carambola fruit for the first time. Compounds 1–8 and 10 showed 2,2′-azinobis-(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radical cation scavenging activity comparable to l-ascorbic acid, while compounds 3, 5, and 7 exhibited potent ferric reducing antioxidant power (FRAP). In addition, compounds 6 and 11 demonstrated weak porcine pancreatic lipase inhibitory activity.

Cultivar and rootstock interaction affects the physiology and fruit quality of table grape with different water management – preliminary results

Vine rootstocks are known to have an influence on the vegetative growth and yield of the scion, and also can influence fruit quality in grafted vines with direct effects on the uptake of water and mineral elements, or more indirectly by affecting the balance between fruit and shoot growth. The adaptability of rootstocks to restrictive soil conditions, water and nutrient supply is variable. The impact of different rootstocks on vine performance and scion could be useful information for selecting which rootstock is more suitable for the soils with reduced water availability. This study was conducted in 2013 on three Vitis vinifera L. cultivars ('Summer Royal', 'Crimson seedless' and 'Autumn Royal') grown in Apulia region (southern Italy) and planted in the same trial site. All vines were grafted onto two rootstocks ('140 Ru' and '34 EM') and subjected to two different irrigation practices under controlled water deficit, in order to study the effect of grafting and water deficit on the whole vine growth and productive development. In particular, vine performance was assessed throughout the season by determining the leaf water potential and, at harvest, the crop yield and both the organoleptic and nutritional (organic acids, carbohydrates, flavonoid and non-flavonoid phenolic compounds) grape quality. From the preliminary findings, we can conclude that physiological responses, such as water relations, of table grape vines could be influenced by the rootstock type, whilst metabolomic characterization of mature grapes suggest that the fruit quality was mainly dependent on the cultivar genotype, even though the different size-controlling rootstocks exerted a relevant influence, especially on vines under restricted water regime.

High-performance liquid chromatography-diode array detector determination and availability of phenolic compounds in 10 genotypes of walnuts

ABSTRACTWalnuts contain significant amounts of bioactive compounds such as polyphenols. The aim of the present study was to determine the differences in phenolic composition and polyphenolic in vitro availability of 10 genotypes of walnuts. All analyzed genotypes showed high flavonoid and non-flavonoid phenolic compounds, especially Eureka and Tehama genotypes. Ellagic acid and syringic acid were the mayor non-flavonoids. Regarding flavonoids, catechin and procyanidin B2 were the most abundant, covering about 98% of total flavonoids. The in vitro digestion showed flavonoids as the most available polyphenols, especially catechin, gallocatechin, and epigallocatechin gallate.

Tentative identification of polar and mid-polar compounds in extracts from wine lees by liquid chromatography-tandem mass spectrometry in high-resolution mode.

Sustainable agriculture has a pending goal in the revalorization of agrofood residues. Wine lees are an abundant residue in the oenological industry. This residue, so far, has been used to obtain tartaric acid or pigments but not for being qualitatively characterized as a source of polar and mid-polar compounds such as flavonoids, phenols and essential amino acids. Lees extracts from 11 Spanish wineries have been analyzed by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) in high resolution mode. The high-resolution power of LC-MS/MS has led to the tentative identification of the most representative compounds present in wine lees, comprising primary amino acids, anthocyans, flavanols, flavonols, flavones and non-flavonoid phenolic compounds, among others. Attending to the profile and content of polar and mid-polar compounds in wine lees, this study underlines the potential of wine lees as an exploitable source to isolate interesting compounds.

Use of ethyl lactate to extract bioactive compounds from Cytisus scoparius: Comparison of pressurized liquid extraction and medium scale ambient temperature systems

An important trend in the extraction of chemical compounds is the application of new environmentally friendly, food grade solvents. Ethyl lactate (ethyl 2-hydroxypropanoate), produced by fermentation of carbohydrates, is miscible with both hydrophilic and hydrophobic compounds being a potentially good solvent for bioactive compounds. Despite its relatively wide use as a general solvent, the utilization of ethyl lactate as an extraction solvent has only recently been considered. Here, we evaluate the possible use of ethyl lactate to extract phenolic compounds from wild plants belonging to Cytisus scoparius, and we compare the characteristics of the extracts obtained by Pressurized Solvent Extraction (the total phenolics content, the antioxidant activity and the concentration of the major polyphenols) with those of other extracts obtained with methanol. In order to explore the industrial production of the ethyl lactate Cytisus extract, we also evaluate medium scale ambient temperature setups. The whole plant and the different parts (flowers, branches, and seed pods) were evaluated separately as potential sources of polyphenols. All extracts were analyzed by LC–MS/MS for accurate identification of the major polyphenols. Similar phenolic profiles were obtained when using ethyl lactate or methanol. The main bioactives found in the Cytisus extract were the non-flavonoid phenolic compounds caffeic and protocatechuic acids and 3,4-dihydroxybenzaldehyde; the flavonoids rutin, kaempferol and quercetin; the flavones chrysin, orientin and apigenin; and the alkaloid lupanine. Regarding the comparison of the extraction systems, although the performance of the PLE was much better than that of the ambient-temperature columns, the energy consumption was also much higher. Ethyl lactate has resulted an efficient extraction solvent for polyphenols from C. scoparius, yielding extracts with high levels of plant phenolics and antioxidant activity. The antimicrobial activity of these extracts was also tested, showing antibacterial activity against Gram +ve bacteria. Qualitatively similar extracts were obtained either by using PLE or medium-scale-ambient-temperature systems, these last rendering larger volumes of extract with lower energy cost. Good results have been obtained with whole plant extracts; nevertheless, extracts enriched in a particular polyphenol can be obtained from different parts of the plant.

Phenolics characterization and antioxidant activity of six different pigmented Oryza sativa L. cultivars grown in Piedmont (Italy)

The three principal black rice varieties grown in Piedmont (Artemide, Venere, Nerone) have been studied in comparison with other three at different pigmentations: red (Ermes, Russ) and white, partially refined (Selenio). The extracts from these six different cultivars, processed as “husked” rices, were analyzed by high-performance liquid chromatography coupled with diode array detection and electrospray ionization-mass spectrometry (HPLC-DAD-ESI-MS/MS). Both qualitative and quantitative characterizations of the flavonoids (anthocyanins, flavonols, and flavan-3-ols) and non-flavonoid (hydroxycinnamic acids) phenolic compounds were achieved. 2,2-Diphenyl-1-picrylhydrazyl radical (DPPH) scavenging activity and total phenolic content were evaluated to determine the antioxidant properties of different rices. Black rice showed higher contents of phenolics, flavonoids, and anthocyanins showing higher antioxidant activity when compared to white and partially if compared to red rices. Cyanidin-3-glucoside was the major anthocyanin in black rice grains, followed by peonidin-3-glucoside and cyanidin-3-rutinoside. With respect to the diglycosyl anthocyanins, cyanidin-3-O-gentiobioside was confirmed and quantified in black varieties. Significant differences in phytochemical content and antioxidant activity were achieved also among the three black varieties. The results demonstrate that the black rice varieties contain a rich heterogeneous mixture of phytochemicals which may provide a basis for the potential health benefits, and highlights the rice as a functional food.

Analytical methodology optimization to estimate the content of non-flavonoid phenolic compounds in Argentine propolis extracts

Context: Traditionally, the content of total phenolics (flavonoid phenolics (FP) and non-flavonoid phenolics (NFP)) and flavonoids (flavone/flavonol and flavonone/dihydroflavonol) in propolis has been determined by different methodologies. Until now, the percentage of total phenolic (TP) compounds that corresponds to FP and NFP, expressed in the same units by a spectrophotometric method, has not been determined.Objective: The current study proposes a quick and simple methodology that separates FP and NFP in propolis samples and determines TP, FP, and NFP by the same method.Materials and methods: Propolis samples from five Argentine provinces (Tucumán, Santiago del Estero, Salta, Misiones, and Jujuy) were used. Extraction of TP from the propolis samples was carried out by maceration with 80% ethanol and quantified by Folin–Ciocalteu reagent (FC-R). Then, FP was precipitated with formaldehyde in acid medium. After centrifugation, NFP were determined in the supernatant using FC-R. FP content was calculated as the difference between the content of TP and NFP. The method was also validated using commercial flavonoids and chalcones.Results: FP recovery in all experiments was between 85.95% and 98.29%. Propolis from Tucumán had significantly higher amounts of total phenols than propolis from other provinces. SE5 showed higher content of FP (81.52%) followed by SA1 (74.75%). The propolis from TUC4, SA4, SE3, and MI showed the lowest FP content and highest content of NFP.Conclusions: This method provides a simple, reliable, and specific spectrophotometric assay to estimate the content of NFP, FP, and TP in propolis samples.