Sorghum and millet phenols and antioxidants

Sorghum is a good source of phenolic compounds with a variety of genetically dependent types and levels including phenolic acids, flavonoids, and condensed tannins. Most sorghums do not contain condensed tannins, but all contain phenolic acids. Pigmented sorghums contain unique anthocyanins that could be potential food colorants. Some sorghums have a prominent pigmented testa that contains condensed tannins composed of flavan-3-ols with variable length. Flavan-3-ols of up to 8–10 units have been separated and quantitatively analyzed. These tannin sorghums are excellent antioxidants, which slow hydrolysis in foods, produce naturally dark-colored products and increase the dietary fiber levels of food products. Sorghums have high concentration of 3-deoxyanthocyanins (i.e. luteolinidin and apigenidin) that give stable pigments at high pH. Pigmented and tannin sorghum varieties have high antioxidant levels that are comparable to fruits and vegetables. Finger millet has tannins in some varieties that contain a red testa. There are limited data on the phenolic compounds in millets; only phenolic acids and flavones have been identified.     

Evaluation of phenolics and antioxidant activity of black sorghum hybrids

Black sorghums possess very high levels of the rare 3-deoxyanthocyanidins which can be used as natural food colorants with health benefits. However, these sorghum genotypes have undesirable agronomic properties (i.e. high height, low yield, increased weathering). Black sorghum hybrids with improved agronomic properties were developed and their phenolic profiles and antioxidant activity were compared with black sorghum lines. Black sorghum hybrids were significantly lighter in colour than the lines (P < 0.001). All hybrids had a pigmented testa which was indicated by the presence of condensed tannins, which significantly increased total phenol levels and antioxidant activity. The 3-deoxyanthocyanidin, flavan-4-ol, and flavone levels were significantly lower in the hybrids (P < 0.001) and were strongly correlated to pericarp colour (P < 0.001). Flavanone levels were not significantly different among the lines and hybrids (P > 0.05) and pericarp colour did not affect their levels (P > 0.05). Even though the 3-deoxyanthocyanidin levels were lower in black sorghum hybrids than in the lines, the presence of condensed tannins in the hybrids significantly increased their antioxidant activity. Since 3-deoxyanthocanidin levels were dependent on pericarp colour, hybrids with increased blackness intensity should be developed to increase the stable 3-deoxyanthocyanidins.     

Testa development in the caryopsis of Sorghum bicolor (L.) Moench

The development of the testa in type II and type III sorghums was documented with light, fluorescence and scanning electron microscopy. The testa developed from the inner integument. The inner integument had two layers, one of which was pigmented at anthesis. By 10 dpa (days past anthesis), the testa developed into two layers, the outermost layer contained pigments while the innermost was non-pigmented, but the walls contained ferulic acid. Pigmented material was deposited differently in the two sorghum types; type II developed vesicles in which the pigments were deposited, while type III deposited the pigments along the cell walls of the integument. The method of pigment deposition may reflect the difficulty in extraction of procyanidins (tannins) for nutraceutical use. It may be more efficient to extract tannins before physiological maturity. The testa was fully developed in both types of sorghum by 22 dpa. Pigmented materials appeared in the epicarp of type III sorghum at 26 dpa due to the action of the spreader gene.     

Prediction of total phenols,condensed tannins,and 3-deoxyanthocyanidins in sorghum grain using near-infrared (NIR) spectroscopy

The reported high phenolic levels in sorghum have led an interest from sorghum breeding programs in developing and identifying germplasms with high phenolic levels, which require screening a large number of samples to find those with the highest levels. Since wet chemistry screening methods are slow, expensive, and destructive, the use of NIR calibration curves could be an alternative. The objectives of this project were to determine the variation range in total phenols, condensed tannins, and 3-deoxyanthocyanidin levels in a diverse set of sorghum genotypes and to assess the predictive value of NIR curves to estimate these compounds in sorghum. A calibration curve to estimate each compound was developed and validated with an independent validation set. Calibration curve correlations for total phenols, condensed tannins, and 3-deoxyanthocyanidins were r = 0.98, 0.97, and 0.99, respectively. Correlations between NIR-predicted values and reference values in the validation set were significant for total phenols (r = 0.93), condensed tannins (r = 0.81) and 3-deoxyanthocyanidin (r = 0.82). These indicated that sufficient variation for these compounds existed within sorghum and that NIR calibration curves could be used to rapidly and non-destructively predict total phenols, condensed tannins, and 3-deoxyanthocyanidins concentrations in whole grain sorghum.     

Effect of nixtamalization process on the content and composition of phenolic compounds and antioxidant activity of two sorghums varieties

Sorghum, a competitive crop due to its agronomical advantages, has gained interest as functional food. Sorghum contains phytochemicals with health benefits and presents some antinutritional compounds such as condensed tannins (CTs). However, it is well known that CTs exhibit antioxidant capacity. This study evaluated the effect of Mexican nixtamalization on total phenols, CTs and antioxidant capacity using two varieties of sorghum. Different conditions of lime (0, 1 and 2%) and cooking time (20, 30 and 40 min) were tested to obtain the best treatment after optimization using multiple linear regression analysis, aiming to minimize the CTs content and maximize the antioxidant capacity. CTs were reduced at 27% in white sorghum and 90%, in red sorghum. Total phenols, flavonoids and antioxidant capacity had an inverse correlation with lime concentration and cooking time. The best conditions for preserving antioxidant capacity with low content of tannins were 1.13% of lime and 31.11 min cooking. The phenolic profile obtained by HPLC showed reductions in gallic and chlorogenic acids only in white sorghum, whereas catechin and quercetin decreased in both varieties. We concluded that nixtamalization effectively reduced CTs to safety intake values, allowing to preserve other phenolic compounds and antioxidant capacity.     

Evaluation of the Relationship Between Bioactive Components in Seaweeds and Advanced Glycation End-Products Inhibitory Activities Using Principal Component Analysis

This study comprehensively presents the relationship between the bioactive substance of 70% (v/v) aqueous ethanol extract of 38 species of seaweeds (SWEs), and anti-glycation activities. The contents of bioactive substance of SWEs, such as total phenolic, total flavonoid and condensed tannins, were determined through a colorimetric analysis. Among the tested species, Ecklonia bicyclis, Ishige foliacea, and Cladophora urightiana var. minor had the highest amount of total phenolic (255.75 mg GAE/g DW), total condensed tannins (63.36 mg CE/g DW), and total flavonoid content (85.26 mg CE/g DW), respectively. Anti-glycation properties of SWEs were evaluated through advanced glycation end-products (AGEs) formation, AGEs-collagen cross-link formation, and AGEs-collagen cross-link breaking assay. Brown algae species exhibited a more prominent inhibitory activity on AGEs formation and AGEs-collagen cross-links, and the breaking of AGEs-collagen cross-links compared to that exhibited by aminoguanidine and ALT-711 (positive controls). Using principal component analysis, we confirmed that the AGEs formation inhibitory property and AGEs-collagen cross-links breaking activity were closely correlated with total phenolic and the condensed tannin contents contained in SWEs. Therefore, the bioactive substances such as phenolics and condensed tannins in seaweeds can be used as predictive indices in selecting compounds for the development of a therapeutic agent that prevents diabetic complications related to the AGEs. In addition, our results suggest that brown algae species, which contains more bioactive substances than green and red algae species, can be utilized as a promising natural resource for the prevention and alleviation of AGEs-related diabetic complications as AGE inhibitor and cross-links breaker.

     

Effect of processing on the phenolic contents,antioxidant activity and volatile compounds of sorghum grain tea

Sorghum grain is rich in phenolic compounds and may be used to develop functional tea beverages. This work investigated the effect of processing techniques on the phenolic contents, antioxidant activity, and volatile compounds of a white colour sorghum (Liberty) grain tea. Significant (P ≤ 0.05) increase of total phenolic content, total flavonoid content and condensed tannin content were observed during the processing, whereas the antioxidant activity was not statistically enhanced. A total of 63 volatile compounds were detected including 5 alcohols, 13 alkanes, 2 aldehydes, 2 carboxylic acids, 15 esters, 4 ketones, 3 pyrazines and 1 phenylenediamine, which were affected by the processing techniques. The sorghum tea made from powder form infusion had more abundant volatile compounds compared to whole grain form infusion. The findings of this research have potential to expand human consumption of sorghum grain in the new form of grain tea.     

Chemical Characterization and Release of Polyphenols from Pecan Nut Shell [<Emphasis Type="Italic">Carya illinoinensis</Emphasis> (Wangenh) C. Koch] in Zein Microparticles for Bioactive Applications

The pecan nut [Carya illinoinensis (Wangenh) C. Koch] is a natural source of polyphenols with antioxidant properties. In this study, the encapsulation of aqueous and hydroalcoholic extracts of pecan nut shell were evaluated for the release of bioactive compounds and antioxidant potential in order to explore food applications using zein as encapsulating agent. The extracts showed high contents of total phenolics, condensed tannins and high antioxidant activity. Concentrations of proanthocyanidins were 9-fold higher in hydroalcoholic extracts. The LC-DAD analysis showed that catechins were the major phenolic compounds in samples, with epigallocatechin levels up to 138.62 mg mL^?1. Zein microparticles loaded with aqueous extract released 2.3 times more phenolic compounds than the hydroalcoholic extracts and the DSC thermograms showed that extracts of pecan nut shell remained thermally stable up to 240 °C. The zein microcapsules obtained in this study were efficiently encapsulated and represent an interesting additive due its high antioxidant capacity, physicochemical characteristics and morphology. The use of zein microparticles combined with natural extracts constitute a step forward in the improvement of current technology for delivering phenolic compounds with applications in functional foods and nutraceuticals.     

Proximate Analysis and Some Antinutritional Factor Constituents in Selected Varieties of Jamaican Yams (<Emphasis Type="Italic">Dioscorea</Emphasis> and <Emphasis Type="Italic">Rajana</Emphasis> spp.)

Two wild (Dioscorea polygonoides and Rajana cordata) and seven cultivated varieties of Jamaican yams (Dioscorea spp.) were analyzed for their proximate composition and the levels of antinutritional factors. The protein level range was 47.8 ± 2.6 to 88.0 ± 2.5 g/kg dry weight. The lowest level was seen in D. cayenensis. The range for the dietary fiber content in the tubers was 16.3 ± 0.7 to 63.5 ± 0.4 g/kg dry weight. The wild yam varieties recorded higher levels. Saponins level was < 600 mg/kg dry weight in all the tubers analyzed except for bitter yam (2962.5 ± 60.5 mg/kg dry weight). Total phenol content ranged from 1.3 ± 0.1 to 79.3 ± 6.1 g/kg while total condensed tannin content ranged from 0.1 ± 0.0 to 26.7 ± 3.8 g/kg dry weight. Samples that showed high levels of phenols also had high levels of condensed tannins. All the samples analyzed contained low levels of lectins and no alkaloids were detected. The levels of antinutritional factors did not clearly delineate the wild varieties from the edible varieties.     

Condensed tannins extraction from grape pomace: Characterization and utilization as wood adhesives for wood particleboard

The extraction of condensed tannins from grape pomace was examined using water medium in the presence of NaOH, Na₂CO₃, NaHCO₃ eventually in the presence of Na₂SO₃. The tannin fractions reactivity towards formaldehyde was studied by gel time analysis and thermomechanical analysis in bending and it was demonstrated that despite of their lower phenolic contents, some of these extracts displayed promising properties for adhesive applications. A resin formulation in which the total content of tannin is 75% of the total resin solids content gave good results and was employed for the elaboration of the first grape pomace based-wood particleboard which passed relevant international standard specifications for interior-grade panels.     

Preferential binding of sorghum tannins with γ-kafirin and the influence of tannin binding on kafirin digestibility and biodegradation

Kafirins, sorghum prolamins bind with sorghum condensed tannins (CTs). The binding of different kafirin species with sorghum CTs was investigated. Analysis by chemical assay and by sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE), reversed-phase high-performance liquid chromatography (RP-HPLC), and free zone capillary electrophoresis (FZCE), showed that γ-kafirin bound more CTs than the other kafirin species. SDS–PAGE suggested that the γ-kafirin-bound tannins were in the form of aggregates of molecular size >200k. RP-HPLC and FZCE revealed that sample preparation and drying the kafirins prior to the binding assays had a significant impact on γ-kafirin solubility. The effect of tannin binding on kafirin and kafirin film digestibility and film biodegradation was determined. Kafirins bound to tannins had lower digestibilities than unbound kafirins. Films made from tannin-bound kafirin had much lower digestibility and were less biodegradable than films made from unbound kafirin. The increase in kafirin film life by tannin modification appears to be due to a decrease in protein digestibility caused by kafirin–tannin binding. These findings suggest that γ-kafirin content in sorghum may be manipulated to either reduce or increase tannin binding in order to change the functionality of the kafirin in food, feed or film applications.     

Chemical and Functional Characterization of Kañiwa (C<Emphasis Type="Italic">henopodium pallidicaule</Emphasis>) Grain,Extrudate and Bran

Cereals provide a good source of dietary fibre and other important compounds with nutritional potential, such as phenolic compounds, antioxidants, minerals and vitamins. Although native Andean cereals are known to have high nutritional value, their minor components have not been studied thoroughly. In this study, two varieties of a native Andean crop, kañiwa (Chenopodium pallidicaule), were investigated as sources of dietary fibre and specific antioxidant compounds. Two products, an extrudate and bran, were also prepared and their functional properties and bioactive compounds were determined. Both varieties were rich in total dietary fibre and lignin, and the phenolic components analyzed had high antioxidant activity. The extrudates had good functional properties, such as degree of gelatinization, sectional expansion index and water solubility index; the bran was high in bioactive compounds, such as total phenolics. In conclusion, kañiwa may offer an alternative to traditional cereals as a health-promoting food ingredient.     

Amaranth (Amaranthus hypochondriacus) as an alternative crop for sustainable food production: Phenolic acids and flavonoids with potential impact on its nutraceutical quality

The demand for food is increasing, not only to meet food security for growing populations, but also to provide more nutritious food, rich in good quality proteins and nutraceutical compounds. The amaranth (Amaranthus hypochondriacus) plant, in addition to its high nutritive and nutraceutical characteristics, has excellent agronomic features. The objective of the present study was to analyze some physical and proximal-nutritional properties of amaranth seeds obtained from different varieties grown in arid zones and characterize their phenolic acids and flavonoids. Two commercial (Tulyehualco and Nutrisol) and two new (DGETA and Gabriela) varieties of A. hypochondriacus were grown at the Mexican Highlands zone. Tulyehualco and DGETA varieties had higher seed yield of 1475 and 1422 kg ha⁻¹, respectively, comparable to corn and soybean production in agricultural areas. Gabriela had the highest protein content of 17.3%, but all varieties had an adequate balance of essential amino acids. Polyphenols as rutin (4.0–10.2 μg g⁻¹ flour) and nicotiflorin (7.2–4.8 μg g⁻¹ flour) were detected. Amaranth can be cultivated in arid zones where commercial crops cannot be grown; the seeds besides their well known nutritive characteristics could be a source of phenolic compounds of high antioxidant properties.     

Extraction of condensed tannins from grape pomace for use as wood adhesives

The extraction of condensed tannins from grape pomace was examined using a mixture water-sodium hydroxide at 120 °C. The extracts were characterized by solution ¹³C NMR and have showed characteristic consistent with that of condensed tannins with dominant procyanidin units. The tannin fractions reactivity toward formaldehyde was studied by gel time analysis and thermomechanical analysis in bending. It has been demonstrated that the extracts obtained by using 10% of NaOH (w/w) displayed promising properties for adhesive applications.     

Accelerated solvent extraction of phenolic compounds from sorghum brans

Most phenolic compounds in cereals are bound to cell wall components and thus they are difficult to extract. Finding techniques to enhance polyphenol extraction is important due to their potential health benefits. The objective of this study was to evaluate extractability of sorghum phenolic compounds using solvents under high pressure and temperature conditions. Polyphenols from black and tannin sorghum bran were extracted using an accelerated solvent extractor (ASE) at 60, 120 and 150 °C. ASE at 120 and 150 °C using 50 and 70% ethanol/water (v/v) was efficient in extracting similar amount of phenols (45 mg GAE/g) and 12% more antioxidants (628 μmol TE/g) from black sorghum compared to traditional methods using aqueous acetone and acidified methanol. High pressure and temperature did not improve the extraction of phenols and antioxidants in tannin sorghum as much as in black sorghum. This could be due to differences in grain structure and phenolic profile (different molecular weights) between the two samples. Another reason is that tannins may be interacting with proteins and carbohydrates under heat, thus they could be extracted but not measured. Therefore, there is a potential of using ASE extracts from black sorghum bran to produce beverages and colorants containing high antioxidant content.     

Bioactive Compounds and Health-Promoting Properties of Berry Fruits: A Review

This study characterizes biologically active compounds of berry fruits, including non-nutritive compounds such as phenolic compounds, including anthocyanins, phenolic acids, stilbens and tannins, as well as nutritive compounds such as carotenoids and vitamin C. It discusses the biological activity of those compounds, in particular their antioxidant properties and the resulting health benefits.     

<Emphasis Type="Italic">Cornus mas</Emphasis> (L.) Fruit as a Potential Source of Natural Health-Promoting Compounds: Physico-Chemical Characterisation of Bioactive Components

Interest in new sources of anti-inflammatory and antioxidant compounds has recently become a major research issue, with the cornelian cherry (Cornus mas L.) receiving particular attention for its significant amounts of phenolic compounds and vitamins, which exhibit a wide range of biological and pharmacological properties. This study was aimed at increasing knowledge regarding the cornelian cherry in Italy through the analysis of biologically active substances in the locally available genotype “Chieri”. Spectrophotometric methods were applied to evaluate antioxidant activity, total anthocyanin content and total polyphenolic content. Identification and quantification of the main phytochemical compounds (polyphenols, monoterpenes, organic acids and vitamin C) was performed via high performance liquid chromatography coupled to a diode array detector. C. mas extracts showed high levels of total soluble solids and low acidity. High amounts of phenolic secondary metabolites were observed, with particular reference to anthocyanins (134.71 mg_C3G/100 g_FW), which confer remarkable nutraceutical properties to the analysed samples. These results highlight the potential of C. mas fruits as a good source of natural antioxidants, suggesting their use as a functional food. Future studies should focus on identifying other specific phytochemical compounds and the genetic traits of local varieties in order to improve cornelian cherry cultivars for food and medicine production.     

Phenolic compounds,antioxidant capacity and gelling properties of glucoarabinoxylans from three types of sorghum brans

Arabinose to xylose ratio (A/X), phenolics, antioxidant capacity and gelling properties were evaluated in glucoarabinoxylans (GAX) extracted from white (W-GAX), red (R-GAX) and high tannin (T-GAX) sorghum brans (SB). The characterization of arabinoxylans from corn fiber (CFAX) was used as benchmark. Sorghum GAX had higher branched structure (A/X 1.08–1.41) than CFAX (0.59). Nine 3-deoxyanthocyanins (3-DAs) were identified in SB and two glycosylated forms remained associated to the R-GAX and T-GAX extracts. T-GAX was the only that contained tannins (0.41 mg catechin equivalents (CE)/g dry basis (db)) and exerted the highest antioxidant capacity (81.75 mM Trolox equivalents (TE)/g db) followed by R-GAX (48.49 mM TE/g db), which contained the highest amount of 3-DAs (0.11 mg Luteolinidin equivalents (Lut eq)/g db), and W-GAX (35.45 mM TE/g db) that was not significantly different from the CFAX (25.83 mM TE/g db). Among sorghums, only the W-GAX gelled but it formed a weaker gel compared to CFAX likely due to its lower hydroxycinnamic acids (HCA) concentration. The presence of 3-DAs in the structure of R-GAX and T-GAX affected negatively their solubility and gelling properties. The different SB showed potential as sources of GAX with antioxidant capacity.     

Marine bioactives as functional food ingredients: potential to reduce the incidence of chronic diseases

The marine environment represents a relatively untapped source of functional ingredients that can be applied to various aspects of food processing, storage, and fortification. Moreover, numerous marine-based compounds have been identified as having diverse biological activities, with some reported to interfere with the pathogenesis of diseases. Bioactive peptides isolated from fish protein hydrolysates as well as algal fucans, galactans and alginates have been shown to possess anticoagulant, anticancer and hypocholesterolemic activities. Additionally, fish oils and marine bacteria are excellent sources of omega-3 fatty acids, while crustaceans and seaweeds contain powerful antioxidants such as carotenoids and phenolic compounds. On the basis of their bioactive properties, this review focuses on the potential use of marine-derived compounds as functional food ingredients for health maintenance and the prevention of chronic diseases.     

Disease and pest resistance in grains of sorghum and millets

In this review available information on the mechanisms of resistance to insect pests and fungal pathogens in sorghum and millets is discussed. The primary source of resistance lies in the chemical and physical make up of the grain. Phenolic compounds such as ferulic acid and tannins present in some sorghums are potent inhibitors of pests and pathogens. Grain hardness is a major deterrent to infection and infestation in low tannin grains. The prolamins, the grain storage proteins of sorghum, are organized into protein bodies and provide a physical and a nutritional barrier since they are resistant to digestion by insect and fungal proteases. A plethora of proteins that belong to the ‘pathogenesis related protein’ group are distributed in various parts of the grain. Some of them are located in protein bodies. Notwithstanding, sorghum is still susceptible to insect pests and fungal pathogens. An understanding of the natural mechanisms of resistance in the grain is paramount for the development of durable resistance against pests and pathogens. The pyramiding of resistance genes and the development of transgenic lines based on this understanding are two sources of hope for the future protection of sorghum and millets.