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Antioxidant Properties of African Oil Bean (pentaclethra macrophylla benth) Seed Phenolics as Influenced by Extraction Solvents and Heat Treatments. Proceedings of the 4th Regional Food Science and Technology Summit (ReFOSTS) Akure, Ondo State Nigeria.
Abstract
Three commonly used extraction solvents (70% ethanol, 80% acetone and acidic 70% acetone) were evaluated for yields of phenolic substances and subsequent antioxidant capacity of the extracts from three samples (raw, dried and autoclaved) of African oil bean (Pentaclethra Macrophylla Benth) seed in a 3x3x4 factorial design. The contents of selected phytochemicals, namely, total phenolic content (TPC), total flavonoid content (TFC) and condensed tannin content (CTC) were investigated. In addition, antioxidant activities were tested using 2,2-diphenyl-1-picryphydrazyl (DPPH). The results show that for extraction, 70% ethanol gave more yields of extracts from raw and dried samples, while 80% acetone gave more yield of extract from the autoclaved sample. Moreover, the acidic 70% acetone gave the highest yield among the three solvents for extracting TPC from the three samples while for the TFC 80% acetone gave the highest yield. The best extraction solvent for DPPH antioxidant assay was 70% ethanol.
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TROSZYŃSKA A., CISKA E. (2002): Phenolic compounds of seed coats of white and coloured varieties of pea (Pisum sativum L.) and their total antioxidant activity. Czech J. Food Sci., 20: 15-22. The purpose of this study was to compare the composition and contents of phenolic acids and condensed tannin in the seed coats of white and coloured varieties of pea and to examine the antioxidant properties of methanol and acetone extracts containing these phenolic compounds. The contents of phenolic acids were quantified by the HPLC analysis. The sum of free phenolic acids, those liberated from soluble esters and those liberated from soluble glycosides, was higher for coloured seed coat (78.5 3 g per g dry matter) than for the white seed coat (17.17 g/g dry matter). Protocatechuic, gentisic and vanillic acids were found dominant in the coloured seed coat, while ferulic and coumaric acids in the white seed coat. The content of condensed tannins was 1560 mg of catechin equivalent/100 g of coloured seed coat as determined by a vanillin assay. No condensed tannins were detected in the white seed coat. The antioxidant activity of extracts was measured by the oxidation of phosphatidylcholine to hydroxyperoxidephosphatidyl choline in the liposome system. Strong antioxidant properties were observed in a crude tannin extract from the coloured seed coat. These properties were slightly changed after the seed coat was cooked in water for 30, 60 and 90 min.
The objectives of this study were to determine best conditions for the extraction of phenolic compounds from fresh, frozen and lyophilized basil leaves. The acetone mixtures with the highest addition of acetic acid extracted most of the phenolic compounds when fresh and freeze-dried material have been used. The three times procedure was more effective than once shaking procedure in most of the extracts obtained from fresh basil leaves – unlike the extracts derived from frozen material. Surprisingly, there were not any significant differences in the content of phenolics between the two used procedures in the case of lyophilized basil leaves used for extraction. Additionally, the positive correlation between the phenolic compounds content and antioxidant activity of the studied extracts has been noted. It is concluded that the acetone mixtures were more effective than the methanol ones for polyphenol extraction. The number of extraction steps in most of the cases was also a statistically significant factor affecting the yield of phenolic extraction as well as antioxidant potential of basil leaf extracts.
The phenolic extracts of the seeds of African yam bean (Sphenostylis stenocarpa) were studied using different extrac-tion solvents (70% ethanol, 80% acetone and acidic 70% acetone) and two heat treatment methods (dry heating on a hot plate with acid-washed sea sand at 135˚C for 25 min and wet heating in an autoclave at 120˚C for 20 min). The study examined the total phenolic content (TPC), total flavonoid content (TFC), and condensed tannin content (CTC) of the seed extracts, as well as their free radical scavenging and antioxidant properties. The raw African yam bean seed was dry heated in air oven at 100˚C for 5 min (control). Heat treatments application affected the phenolic contents of the seeds significantly (p < 0.05). The free radical scavenging activity of the phenolics were done using 2,2-diphenyl-1-picrylhydrazyl (DPPH). The effectiveness of the extract was determined using DPPH at 50 mg/g, 10 mg/g and 5 mg/g of the extracts. At 5 mg/g, the extract was most effective indicating that higher concentration of extract gave higher an-tioxidant activity. The seed has high antioxidant capacity and an appreciable amount of phenolic extracts.
Purpose
The purpose of this paper is to examine pure culture isolates from traditionally fermented product of African oil bean seeds ( ugba ) with a view to identifying the appropriate starters.
Design/methodology/approach
The isolates were purified and characterized, and used singly and in combination to ferment freshly prepared oil bean seed slices for 72 h at 37 ○ C. The pH and microbial load of fermenting beans were monitored daily, and organoleptic tests using semi‐trained panelists were employed to assess the fermented products based on quality attributes of flavour, appearance, texture and overall acceptability.
Findings
The isolates included Bacillus subtilis, Bacillus licheniformis and Pseudomonas fluorescens . Total viable counts ranged from 1.3 × 10 ⁷ ‐9.3 × 10 ⁹ cfu/g, 7.0 × 10 ⁶ ‐4.0 × 10 ⁹ cfu/g, and 3.0 × 10 ⁶ ‐1.5 × 10 ⁹ cfu/g, respectively for the three isolates; while counts for the mixed culture fermentation ranged from 7.0 × 10 ⁶ ‐1.72 × 10 ¹⁰ cfu/g. The mixed culture fermentation gave the best rated product, indicating a synergy among the isolates. The pH values increased steadily in the samples fermented by Bacillus sp. and the mixed culture organisms, showing that the production of ugba follows alkaline fermentation pattern.
Research limitations/implications
The African oil bean seed fermentation is a bacterial mixed culture and alkaline fermentation. The major organisms involved are B. subtilis and B. licheniformis , while the P. fluorescens was insignificant.
Originality/value
Most of the local fermentations in Africa, including oil bean fermentation, are still at the wild, natural inoculation level. The present study has helped in understanding of the fermentative organisms involved in Pentaclethra seed fermentation, and gave insight into an optimized ugba production.
The acidified vanillin method for determination of plant tannins has been reassessed. Excluding light and controlling the temperature of the reaction mixture increased the colour stability of the vanillin tannin adduct. Selection of optimum concentrations of reactants and solvents enabled the method to be used in the range 5-500 μg of condensed tannin with a precision and accuracy greater than 1 μg.
The levels of anti‐nutritional factors and the chemical composition of five underutilized and not well known commercial oilseeds – castor bean, conophor nut, ‘egusi’ melon, African oil bean and locust bean – were determined. The crude protein values for the respective oilseeds were 201.8, 227.5, 314.1, 206.3 and 290.6 g kg ⁻¹ DM, whereas the crude fat values were 449.6, 491.8, 439.3, 522.8 and 261.9 g kg ⁻¹ DM respectively. The results show that oilseeds may be a good source of vegetable oils, whereas defatted cakes might be useful in food fortification or as animal feed ingredients. The crude fibre contents of oilseeds were found to be significant (31.4–90.6 g kg ⁻¹ DM), which suggests that consumption of oilseeds and their products would aid bowel functioning.
The seeds were found to contain high concentrations of phosphorus and potassium (2.6–4.6 and 3.9–6.5 g kg ⁻¹ DM, respectively); the low sodium content observed is in agreement with the generally low sodium encountered in unprocessed foods. The energy values of the seeds range from 4.1 Mcal kg ⁻¹ DM in locust bean to 5.9 Mcal kg ⁻¹ DM in conophor nut, which could be considered adequate for supplying useful amounts of calories.
Oxalates, phytates and tannins occurred in varying concentrations in the oilseeds. Whereas castor bean contained the highest level of oxalates (6.5 g kg ⁻¹ DM), the same seed was relatively low in its content of the other anti‐nutritional factors analysed. Phytic acid, phytate phosphorus and tannins had their highest values in African oil bean seed (4.1, 1.2 and 0.8 g kg ⁻¹ DM, respectively), which may be considered a major barrier to the use of the seed. However, it is expected that traditional methods employed in processing the seeds, namely hydrothermal treatment, soaking and fermentation, would considerably reduce the levels of the anti‐nutritional factors.
The thermal processing variables for starter culture fermented African oil bean (Pentaclethra macrophylla Benth) seed product ugba in three media (brine, refined groundnut oil and tomato sauce) and at three temperatures (110℃, 116℃ and 121℃) were investigated. Thermal inactivation studies using Bacillus stearothermophilus 1518 spores showed that the z-values for the thermal processing were 10.5℃, 12.5℃ and 11.0℃ for brine-, oil-and sauce-canned samples, respectively. At 121℃ processing temperature, the D values of 2.2 min (brine), 3.5 min (oil) and 3.2 min (sauce) would give 5D process times of 11.0, 17.5 and 16.0 min, respectively, as the targeted F values, which are lower than the experimental F values obtained for the three media. Heat penetration studies showed that process times according to general method were in the range 39.3–42.7 min at 121℃, 45.5–49.4 min at 116℃, and 51.4–57.2 min at 110℃. Brine-canned samples had the shortest process times at 121℃. The process times by the general method were higher than those by the formula method. The heating rate index f h was lower in the sauce-canned samples than that in the other samples, especially at 121℃ also higher sterilization temperatures resulted in lower f h values for all the media employed in the canning process. This was attributed to an increase in sterilization value due to faster heat penetration. Citation: Victor N. Enujiugha, Charles T. Akanbi. Optimization of canning process conditions for fermented African oil bean (Pentaclethra macrophylla Benth) seeds in three different media. Agric Eng Int: CIGR Journal, 2010, 12(2): 95－103.
The !-amylases of raw and fermented seeds of African oil bean (Pentaclethra macrophylla Benth) were isolated, partially purified (tenfold) and subjected to different thermal and pH conditions. The specific activities of the purified enzyme from raw and fermented seeds were 0.037 ml-1 min-1 and 0.88 ml-1 min-1 respectively. The !-amylase from fermented seeds was more thermostable with optimum activity at 70 C, compared to the optimum temperature of 60 C obtained for the raw seed enzyme. The assayed !-amylases were stable over a wide range of pH (3.0-7.0), with optimum activity found at pH 6.0 and pH 5.0 for raw and fermented seeds respectively. The results show that the !-amylase of Pentaclethra macrophylla complements the microbial amylases in the mainly bacterial fermentation of African oil bean seeds to 'ugba', a highly nutritious food condiment. While the !-amylase in the raw seeds was basically the plant enzyme, that isolated from the fermented seeds was a combination of plant and microbial !-amylases.
Acetone powders were obtained from freshly harvested dormant seeds of African oil bean (Pentaclethra macrophylla Benth) and the activity as well as substrate specificity of the isolated crude lipase (glycerol ester hydrolase E.C. 3.1.1.3) were examined. The enzyme was more active on lauric oils (containing short-chain fatty acids), especially coconut oil. Hexane at 1:2 v/w solvent:substrate ratio was optimal in enhancing lipolysis of the oils. Optimum substrate concentration was 5 g in 2.5 ml of solvent, above which enzyme inhibition resulted. Lipolysis increased with enzyme concentration (non-linearly), with optimum rate at between 0.5 and 0.75 g and 60 min incubation. Optimum temperature for the activity of the oil bean lipase was 30 °C, although substantial lipolysis was still evident at 80 °C indicating the fairly high thermostability of the enzyme. pH optimum for enzyme activity was near neutrality. The effects of different ions on the activity of the isolated lipase were also investigated. The presence of Ca2+ increased activity by 64% while sodium chloride and mercuric chloride inhibited activity by 36% and 28.5%, respectively. On addition of EDTA, an inhibition in activity of 28% was observed. The results of the present study show that the oil bean seed will deteriorate with storage.
Significant levels of antioxidant activities and phenolic components have been detected in wheat and wheat-based food products, indicating that wheat may serve as an excellent dietary source of natural antioxidants for disease prevention and health promotion. Several solvent systems have been used to prepare antioxidant extracts from wheat and wheat-based food products. This makes it difficult to compare and understand the antioxidant activities of wheat reported from different research groups. The purpose of this study was to evaluate the effects of four selected solvent systems at ambient temperature for 15h and Soxhlet extraction with absolute ethanol on antioxidant activity measurements. The four solvent systems included 50% acetone (v/v), 70% methanol (v/v), 70% ethanol (v/v), and ethanol, and antioxidant activities were tested using ORAC, radical scavenging activities against stable DPPH• and cation ABTS•+, and total phenolic content. The results showed that the extracting solvent significantly altered the antioxidant property estimations of wheat bran, and 50% acetone is a recommended solvent for extracting phenolic antioxidants from wheat bran for analytical purpose.
Publisher Summary This chapter discusses the analysis of total phenols and other oxidation substrates and antioxidants by means of Folin-Ciocalteu reagent. Analyses of the Folin-Ciocalteu (FC) type are convenient, simple, and require only common equipment and have produced a large body of comparable data. Under proper conditions, the assay is inclusive of monophenols and gives predictable reactions with the types of phenols found in nature. Because different phenols react to different degrees, expression of the results as a single number—such as milligrams per liter gallic acid equivalence—is necessarily arbitrary. Because the reaction is independent, quantitative, and predictable, analysis of a mixture of phenols can be recalculated in terms of any other standard. The assay measures all compounds readily oxidizable under the reaction conditions and its very inclusiveness allows certain substances to also react that are either not phenols or seldom thought of as phenols (e.g., proteins). Judicious use of the assay—with consideration of potential interferences in particular samples and prior study if necessary—can lead to very informative results. Aggregate analysis of this type is an important supplement to and often more informative than reems of data difficult to summarize from various techniques, such as high-performance liquid chromatography (HPLC) that separate a large number of individual compounds .The predictable reaction of components in a mixture makes it possible to determine a single reactant by other means and to calculate its contribution to the total FC phenol content. Relative insensitivity of the FC analysis to many adsorbents and precipitants makes differential assay—before and after several different treatments—informative.
Extracts of polyphenolic compounds were obtained from seeds of faba bean, broad bean, adzuki bean, red bean, pea, red lentil and green lentil using 80% (v/v) acetone. The total antioxidant activity (TAA) of extracts was determined and their astringency (Sensation Astringency Indices – SAI) investigated using the sensory scaling method. The content of tannins in extracts was expressed as absorbance values at 500 and 550 nm after color developed with vanillin/HCl reagent and after n-butanol-HCl hydrolysis, respectively. A statistically significant correlation was found between the TAA values and total phenolics (P = 0.01), TAA and tannins determined by vanillin method (P = 0.05), TAA and tannins determined after n-butanol-HCl hydrolysis (P = 0.05), SAI values and tannins determined with vanillin method (P = 0.10), SAI values and tannins determined after n-butanol-HCl hydrolysis (P = 0.05), SAI values and total phenolics (P = 0.01), total phenolics and tannin content determined by vanillin method (P = 0.01), total phenolics and tannin content determined after n-butanol-HCl hydrolysis (P = 0.05), tannins determined with vanillin method and tannins determined after n-butanol hydrolysis (P = 0.02).
Polyphenols in cereals and legumes have been receiving considerable attention largely because of their adverse influence on color, flavor, and nutritional quality. These compounds belong to the flavonoid and tannin groups and are mostly located in the seed coat or pericarp of the grains. The pearl millet flavonoids have been identified as C-glycosylflavones by the combined use of paper chromatography and UV spectroscopy. Although nontoxic, physiological and nutritional significance of these compounds occurring in high amounts in the pearl millet grain are still not clearly understood. In view of aesthetic quality, bleaching of the millet grains in acidic solution is recommended. A large proportion of current assays involves spectrophotometry of tannin or its chromogen and tannin-protein interaction. Sorghum and legume tannins have been characterized as condensed tannins. Several factors such as plant type, age of the plant or plant parts, stage of development, and environmental conditions govern the polyphenol contents in plants. Polyphenols are known to interact with proteins and form tannin-protein complexes leading to either inactivation of enzymes or making proteins insoluble. These are implicated in decreasing the activities of digestive enzymes, protein and amino acid availabilities, mineral uptake, vitamin metabolism, and depression of growth. Polyphenols are known to cause certain ultrastructural changes in the different parts of experimental animals. A correlation between dietary tannins and occurrence of esophageal cancer has been established. Bird resistance and seed germination in food crops have been correlated to high contents of polyphenols. The antinutritional activity of polyphenols can be reduced by removing polyphenols from the grains by chemical treatments or removing pericarp and testa by pearling. Treatment of alkaline reagents and ammonia can remove 90% of the polyphenols. Supplementation of polyphenols-rich diet with protein can alleviate the growth-depressing effect of polyphenols.
Antioxidants may be present in foods as endogenous factors or may be added to preserve their lipid components from quality deterioration. Synthetic antioxidants such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), propyl gallate (PG) and tert-butylhydroquinone (TBHQ) are commonly used in food formulations. However, due to safety concerns, interest in natural antioxidants has intensified. To address the demand by consumers, mixed tocopherols, herbal extracts such as those of rosemary and sage, as well as tea extracts have been commercialized for food and nutraceutical applications. An overview of the topic is provided in this article.
1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity of the 70% aqueous acetone extract from the seed coat of the brown soybean variety, Akita-Zairai, was investigated. The activity of the seed coat of Akita-Zairai was much higher than that of three other reddish-brown varieties, but lower than that of two black varieties, and was closely dependent on the content of phenolic compounds. In the LH20 column chromatography of Akita-Zairai, high DPPH radical-scavenging activities were detected in the fractions eluted with MeOH and 70% aqueous acetone. Proanthocyanidins were also detected in fractions showing high radical-scavenging activities. Matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry analysis showed that the degree of polymerization (DP) of the procyanidins contained in the brown or black soybean seed coat was as high as DP30.
Twelve different seed coat color genotypes of Phaseolus vulgaris L. were extracted and pure flavonoids isolated from 10 of these. The seed coat methanol extracts, tannin fractions, and pure flavonoids all displayed antioxidant activity in a fluorescence-based liposome assay. The relatively high activity of the condensed tannin (proanthocyanidin) fractions indicates that these may play an important role in the overall activity of the extracts. This activity also indicates that although these polyphenols cause problems in digestibility, they may be important dietary supplements with beneficial health effects. The pure anthocyanins delphinidin 3-O-glucoside (1), petunidin 3-O-glucoside (2), and malvidin 3-O-glucoside (3) and the flavonol quercetin 3-O-glucoside (4) isolated from seed coats also had significantly higher antioxidant activity than the Fe(2+) control. The activity of kaempferol 3-O-glucoside (5) was not different from that of the Fe(2+) control. These findings suggest that variously colored dry beans may be an important source of dietary antioxidants.
The objective of this study was to investigate how 6 commonly used solvent systems affected the yields of phenolic substances and the antioxidant capacity of extracts from 8 major classes of food legumes. Several antioxidant-related phytochemical compositions, namely, total phenolic content (TPC), total flavonoids content (TFC), and condensed tannins content (CTC), were investigated. In addition, antioxidant activities were tested using 2,2-diphenyl-1-picryhydrazyl (DPPH) free radical scavenging, ferric-reducing antioxidant power (FRAP), and the oxygen radical absorbance capacity (ORAC). The results showed that the 50% acetone extracts exhibited the highest TPC for yellow pea, green pea, chickpea, and yellow soybean. Acidic 70% acetone (+0.5% acetic acid) extracts exhibited the highest TPC, TFC, and FRAP values for black bean, lentil, black soybean, and red kidney bean. The 80% acetone extracts exhibited the highest TFC, CTC, and DPPH-free radical scavenging activity for yellow pea, green pea, chickpea, and yellow soybean. The 70% ethanol extracts exhibited the greatest ORAC value for all selected legumes. These results indicated that solvents with different polarity had significant effects on total phenolic contents, extracted components, and antioxidant activities. High correlations between phenolic compositions and antioxidant activities of legume extracts were observed. The information is of interest to the nutraceutical food/ingredient industries since legumes are a rich source of antioxidants.
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