Predominant Flavonoid Research Articles

Temperature-dependent studies on the total phenolics, flavonoids, antioxidant activities, and sugar content in six onion varieties

Heating effect on total phenol, flavonoids, antioxidant activity, and sugar content of six onion varieties has been quantitatively investigated to explore the effect of different temperatures. The onion varieties comprised one red-skinned variety, two white-skinned varieties, and three yellow-skinned varieties. The heating temperature was scanned at 80°C, 100°C, 120°C, and 150°C for 30 minutes each, and quantitative analysis was performed relative to the powdered onion at ambient temperature. Quercetin, glucosides and sugar content were analyzed using high-performance liquid chromatography. The total phenolic and antioxidant content increased in all six varieties. The total flavonoid levels showed a considerable change. On heating the onion samples at 120°C for 30 minutes, the red-skinned variety showed the highest level of total phenolic content [13712.67 ± 1034.85 μg of gallic acid equivalent/g dry weight (μg GAE/g DW)] and total flavonoids [3456.00 ± 185.82 μg of quercetin equivalents/g dry weight (μg Q/g DW)], whereas the content of total phenolics and total flavonoids were 13611.83 ± 341.61 μg GAE/g DW and 3482.87 ± 117.17 μg Q/g DW, respectively, for the yellow-skinned (Sunpower) variety. Quercetin and its glucoside contents increased up to 120°C and then decreased at 150°C, whereas the sugar content continuously decreased with heating. All cultivars showed the same pattern in the heating effect, and the predominant flavonoids were destroyed at higher temperatures. Therefore, it is improper to expose onion powder to a temperature higher than 120°C.

Potential of Gynura procumbens leaves as source of flavonoid-enriched fractions with enhanced antioxidant capacity

Gynura procumbens has been consumed for a longtime in tropical regions as a vegetable with health promoting activities. We investigated phenolic antioxidants that were fractionated from the crude extract of G. procumbens leaves by Sephadex LH-20 column chromatography. Sub-fraction 3 had the highest antioxidant activity as well as its total phenolic and flavonoid contents. The IC50 values of sub-fraction 3 were 19 and 12 µg/ml, which were lower than those of ascorbic acid and trolox for DPPH• and ABTS•+ assays, respectively. The major phenolic acids identified in sub-fraction 3 were ferulic acid and sinapic acid, whereas predominant flavonoids were myricetin and kaempferol. There was a strong positive correlation between antioxidant activity and total flavonoid content; however, no correlation existed between those and total phenolic content. Our findings suggest that the strongest antioxidant activity in sub-fraction 3 came from the flavonoids, especially myricetin and kaempferol, rather than phenolic acids.

Impact of processing on the phenolic profiles of small millets: Evaluation of their antioxidant and enzyme inhibitory properties associated with hyperglycemia

The effects of germination, steaming and microwave treatments of whole grain millets (barnyard, foxtail and proso) on their phenolic composition, antioxidant activities and inhibitory properties against α-amylase and α-glucosidase were investigated. Compositional analysis of phenolics by HPLC revealed that vanillic and ferulic acids were the principal phenolic acids and kaempferol was the predominant flavonoid found in raw millets. Different processing treatments brought about relevant changes in the composition and content of certain phenolic acids and flavonoids in processed millets. Phenolic extracts of raw and processed millets exhibited multiple antioxidant activities and are also potent inhibitors of α-amylase and α-glucosidase. In general, germinated millets showed highest phenolic content as well as superior antioxidant and enzyme inhibitory activities. These results suggest that germinated millet grains are potential source of phenolic antioxidants and also great sources of strong natural inhibitors for α-amylase and α-glucosidase.

Hesperidin, nobiletin, and tangeretin are collectively responsible for the anti-neuroinflammatory capacity of tangerine peel (Citri reticulatae pericarpium)

Inhibiting microglial activation-mediated neuroinflammation has become a convincing target for the development of functional foods to treat neurodegenerative diseases. Tangerine peel (Citri reticulatae pericarpium) has potent anti-inflammatory capacity; however, its anti-neuroinflammatory capacity and the corresponding active compounds remain unclear. To this end, the composition of a tangerine peel ethanolic extract was analysed by LC–MS, and the anti-neuroinflammatory ability was evaluated using a lipopolysaccharide (LPS)-activated BV2 microglia culture system. Hesperidin is the most predominant flavonoid in tangerine peel, followed by tangeretin and nobiletin. Among the eight tested flavanone glycosides and polymethoxy flavones, only nobiletin displayed a capacity of>50% to inhibit LPS-induced proinflammatory NO, TNF-α, IL-1β and IL-6 secretion at a concentration of 100μM. At 2mg/ml, tangerine peel extract attenuated LPS-induced NO, TNF-α, IL-1β and IL-6 secretion by 90.6%, 80.2%, 66.7%, and 86.8%, respectively. Hesperidin, nobiletin, and tangeretin individually (at concentrations of 135, 40, and 60μM, respectively) in 2mg/ml tangerine peel extract were only mildly inhibitory, whereas in combination, they significantly inhibited LPS-induced proinflammatory cytokine expression at levels equal to that of 2mg/ml tangerine peel extract. Overall, tangerine peel possesses potent anti-neuroinflammatory capacity, which is attributed to the collective effect of hesperidin, nobiletin, and tangeretin.

Optimization of ultrasonic-assisted extraction of phenolic compounds from bovine pennyroyal (Phlomidoschema parviflorum) leaves using response surface methodology

The ultrasound-assisted extraction (UAE) was applied to optimize the experimental conditions for the extraction of phenolic compounds from bovine pennyroyal (Phlomidoschema parviflorum) leaves by response surface methodology (RSM) and to compare its efficiency with maceration extraction (ME). The Box–Behnken design was employed for the optimization of three extraction parameters, including extraction time (X1, min), temperature (X2, °C) and pH (X3) for the achievement of high yields of dry matter (DM), total phenolics (TP) and antioxidant activity (AA) measured by the DPPH assay [expressed as 50% effective concentration (EC50)] and the Rancimat method [expressed as induction period (IP)]. The optimum extraction conditions were as follows: extraction time 49.3min, extraction temperature 41.5°C and pH 6.5. Under these conditions, DM, TP, EC50 and IP were 25,185mg/kg sample, 15.4mgGAE/g DM, 0.48mg/ml and 5.7h, respectively. The comparison between the UAE and ME methods showed the suitability of UAE for extracting phenolic compounds from bovine pennyroyal plant. The evaluation of antioxidant activity by DPPH assay indicated that the phenolic compounds from bovine pennyroyal plant had significant antioxidant activity. The results of HPLC analysis showed that caffeic acid and quercetin were the predominant phenolic acid and flavonoid in the plant extract, respectively.

Flavonoid composition and antioxidant activities of Chinese local pummelo (Citrus grandis Osbeck.) varieties

China is one of the most important diversity centres of the genus Citrus L. and is particularly rich in pummelo germplasm. In this study, the flavonoids in the peels and pulps of 28 Chinese local pummelos and four grapefruits were determined by optimised Ultra Performance Liquid Chromatography (UPLC), and their antioxidant capacities were evaluated using 2,2-diphenyl-1-picrylhydrazyl radicals (DPPH), ferric reducing/antioxidant power (FRAP) and superoxide anion methods. We found that naringin was the predominant flavonoid in pummelo, while naringin and neohesperidin were the predominant flavonoids in grapefruit. The fruit peels of Citrus paradisi cvs. Rio Red and Cocktail had the highest contents of naringin (9871.69mg/kg FW) and neohesperidin (7011.15mg/kg FW), respectively. Overall, C. paradisi cvs. Cocktail, Rio Red and Changshanhuyou, Citrus grandis cvs. 28-19, Chandler, and Hongxinyou contained more flavonoids and exhibited higher antioxidant capacities and are potentially good sources of phytochemicals and natural antioxidants.

Flavonoid intakes by adults in the United States: What We Eat in America, NHANES 2007‐2008 (245.5)

Flavonoids, polyphenolic compounds found in plants, exhibit anti‐inflammatory, anti‐tumor, and antioxidant activity. This study’s objective was to calculate national intake estimates for 6 flavonoid classes (including only the 29 predominant dietary flavonoids). One day of dietary data from 5,420 adults age 蠅20 years in What We Eat in America (WWEIA), NHANES 2007‐2008 was analyzed. Based on a preliminary version of USDA’s Expanded Flavonoid Database for the Assessment of Dietary Intakes, flavonoid values were calculated for every food in USDA’s Food and Nutrient Database for Dietary Studies 4.1, the database used in WWEIA 2007‐2008. Mean total intake of the flavonoids studied was 253.3 mg/day, with flavan‐3‐ols accounting for 81% of the total. Though total flavonoid intake did not differ by gender, men’s intakes of flavones (0.9 mg) and flavonols (21.5 mg) were higher than women’s (0.8 mg and 17.5 mg, respectively; p<0.01). No significant differences were found by age group (20‐49 vs. 50+ years) within gender. Nearly all (99%) adults consumed some flavonoids on the intake day, but intake of the flavonoid classes was not universal: Only 38% of adults consumed isoflavones; 64%, flavanones; and 69%, anthocyanidins. New public‐use databases will enable researchers to quantify flavonoid intakes of the U.S. population and allow further investigation of associations between flavonoid intake and health.Grant Funding Source: Supported by ARS, USDA, with additional funding provided by the Office of Dietary Supplements

Food sources of flavonoids for adults in the United States: What We Eat in America, NHANES 2007‐2008 (369.5)

Flavonoids are compounds from plants that may play important roles in preventing chronic diseases including heart disease and cancer. This study’s objective was to identify top food contributors of 6 classes of flavonoids (including only the 29 most predominant dietary flavonoids) to the diets of American adults. One day of dietary data from 5,420 adults age 蠅20 years in What We Eat in America (WWEIA), NHANES 2007‐2008 was analyzed. Based on a preliminary version of USDA’s Expanded Flavonoid Database for the Assessment of Dietary Intakes, flavonoid values were calculated for every food in USDA’s Food and Nutrient Database for Dietary Studies 4.1, the database used in coding foods reported in WWEIA 2007‐2008. Similar foods were grouped using the WWEIA Food Categories before determining percentage contributions to flavonoid intake. Overall, tea accounted for 81% of total flavonoid intake. Tea was also the food category providing the largest percentage of flavan‐3‐ols (94% of total) and flavonols (40% of total). Other top contributors to intake of flavonoid classes were soy‐based protein powders (isoflavones); berries and wine (anthocyanidins); citrus fruits and juices (flavanones); and mixed dishes and vegetables (flavones). Findings derived using new public‐use databases can inform efforts to monitor flavonoid intakes and educate the public about connections between foods and health.Grant Funding Source: Supported by ARS, USDA, with additional funding provided by the Office of Dietary Supplements

Does a sorghum–cowpea composite porridge hold promise for contributing to alleviating oxidative stress?

The effect of compositing red non-tannin sorghum with cream-coloured cowpea and porridge preparation on phenolic profile and radical scavenging activity was studied. A maize–soybean composite porridge representing a similar product on the South African market was used as reference sample. UPLC–QToF-MS-ESI was used to determine phenolic composition of the grain flours, their composites and porridges. Total phenolic content was determined using Folin–Ciocalteu method while radical scavenging activity was determined using the ABTS, DPPH and NO radical scavenging assays. Four benzoic acid derivatives and five cinnamic acid derivatives were identified in the samples. The predominant flavonoid subclasses identified in sorghum were flavan-3-ols, flavanones and flavones while cowpea had mainly flavan-3-ols and flavonols with soybean having mainly isoflavones. Compositing the cereals with legumes significantly (p<0.01) increased their total flavonoid content and radical scavenging activities. Sorghum–cowpea composite porridge showed better promise in contributing to alleviating radical induced oxidative stress than maize–soybean composite porridge.

Antioxidant activity and phenolic compounds in 10 selected herbs from Vrujci Spa, Serbia

There is a growing research interest on investigation of appropriate alternatives of natural origin to synthetic additives used in food products. The aim of this study was to investigate correlation of chemical composition of the best known biomarker plants from the locality of Vrujci Spa, Serbia with their antioxidant activity in vitro, in terms of their potential usage as feedstock materials in the food industry. Total phenolic (TP), total tannins (TT) and total flavonoid (TF) contents were determined using spectrophotometric methods. Qualitative and quantitative analyses of major phenolics by high-performance liquid chromatography (HPLC) were also used. Major phenolic acids identified in analyzed species were chlorogenic, caffeic and ferulic acid, while predominant flavonoids were flavonols (hyperoside, rutin, isoquercitrin, quercetin) and, in lesser extent flavones (luteolin, apigenin and their 7-O-glucosides). Vitexin 2-O″-rhamnoside was found only in Crataegus species. Antioxidant capacity was estimated by the following methods: 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) test and ferric reducing antioxidant power (FRAP). Majority of investigated plants had high levels of phenolics and exhibited noteworthy antioxidant activity. Moreover, a positive linear correlation was found between TP and TT with antioxidant capacities regarding both methods used. The plants showing the highest antioxidant activities were Veronica officinalis, Mentha pulegium and Fragaria vesca. Hypericum perforatum demonstrated by far the most potent antioxidant activity, as well as TP and TT content. Our results indicate that, in addition to their traditional usage in folk medicine, these plants represent a valuable source of natural antioxidants, and thus may be considered as great potential for the food industry, representing possible alternatives to synthetic additives.

Rutin suppresses atopic dermatitis and allergic contact dermatitis

Atopic dermatitis (AD) and allergic contact dermatitis (ACD) is a common allergic inflammatory skin disease caused by a combination of eczematous, scratching, pruritus and cutaneous sensitization with allergens. The aim of our study was to examine whether rutin, a predominant flavonoid having anti-inflammatory and antioxidative potential, modulates AD and ACD symptoms. We established an atopic dermatitis model in BALB/c mice by repeated local exposure of house dust mite (Dermatophagoides farinae) extract (DFE) and 2,4-dinitrochlorobenzene (DNCB) to the ears. In addition, 2,4-dinitroflourobenzene-sensitized a local lymph node assay was used for the ACD model. Repeated alternative treatment of DFE/DNCB caused AD symptoms. Topical application of rutin reduced AD based on ear thickness and histopathological analysis, in addition to serum IgE levels. Rutin inhibited mast cell infiltration into the ear and serum histamine level. Rutin suppressed DFE/DNCB-induced expression of interleukin (IL)-4, IL-5, IL-13, IL-31, IL-32 and interferon (INF)-γ in the tissue. In addition, rutin suppressed ACD based on ear thickness and lymphocyte proliferation, serum IgG2a levels, and expression of INF-γ, IL-4, IL-5, IL-10, IL-17 and tumour necrosis factor-α in ACD ears. This study demonstrates that rutin inhibits AD and ACD, suggesting that rutin might be a candidate for the treatment of allergic skin diseases.

Comparative analysis of antioxidant activity of honey of different floral sources using recently developed polarographic and various spectrophotometric assays

Hydrogen peroxide scavenging (HPS) activity of honey of different floral sources and its constituents such as predominant honey flavonoids, phenolic acids, amino and organic acids, and carbohydrates have been assessed by direct current (DC) polarographic assay. The assay was based on decrease of anodic current of hydrogen peroxide complex, formed in alkaline solution, at the potential of mercury dissolution. High correlations between honey HPS activity, its total phenolic content (FC-GAE), antioxidant activity measured by four standard methods (DPPH, TEAC, FRAP and ORAC), and also the relative antioxidant capacity index, were obtained. Statistical evaluation by ANOVA and F-test further confirmed the assay validity. The results for individual compounds showed that HPS activity of honey reflects an integrated action of a wide range of constituents, both phenolics and non-phenolics. The polarographic assay applied is a fast, reliable and low cost alternative to spectrophotometric antioxidant assays commonly applied in analysis of honey and can serve as an indicator of honey quality.

СРАВНИТЕЛЬНОЕ ИССЛЕДОВАНИЕ КОМПОНЕНТНОГО СОСТАВА ТРАВЫ ФАРМАКОПЕЙНЫХ ВИДОВ ЗВЕРОБОЯ МЕТОДОМ ВЫСОКОЭФФЕКТИВНОЙ ЖИДКОСТНОЙ ХРОМАТОГРАФИИ

Проведено сравнительное фитохимическое исследование с использованием метода ВЭЖХ образцов травы зверобоя продырявленного (Hypericum perforatum L.) и зверобоя пятнистого (Hypericum maculatum Grantz). Установлено, что доминирующим флавоноидом травы зверобоя пятнистого является гиперозид, обладающий антидепрессантной активностью. Выявлены отличия химического состава сравниваемых видов. Установлено, что содержание гиперозида в траве зверобоя пятнистого в три раза больше, чем в зверобое продырявленном.

The molecular and enzymatic basis of bitter/non‐bitter flavor of citrus fruit: evolution of branch‐forming rhamnosyltransferases under domestication

Domestication and breeding of citrus species/varieties for flavor and other characteristics, based on the ancestral species pummelo, mandarin and citron, has been an ongoing process for thousands of years. Bitterness, a desirable flavor characteristic in the fruit of some citrus species (pummelo and grapefruit) and undesirable in others (oranges and mandarins), has been under positive or negative selection during the breeding process of new species/varieties. Bitterness in citrus fruit is determined by the composition of branched-chain flavanone glycosides, the predominant flavonoids in citrus. The flavor-determining biosynthetic step is catalyzed by two branch-forming rhamnosyltransferases that utilize flavanone-7-O-glucose as substrate. The 1,2-rhamnosytransferase (encoded by Cm1,2RhaT) leads to the bitter flavanone-7-O-neohesperidosides whereas the 1,6-rhamnosytransferase leads to the tastelessflavanone-7-O-rutinosides. Here, we describe the functional characterization of Cs1,6RhaT, a 1,6-rhamnosyltransferase-encoding gene directing biosynthesis of the tasteless flavanone rutinosides common to the non-bitter citrus species. Cs1,6RhaT was found to be a substrate-promiscuous enzyme catalyzing branched-chain rhamnosylation of flavonoids glucosylated at positions 3 or 7. In vivo substrates include flavanones, flavones, flavonols and anthocyanins. Cs1,6RhaT enzyme levels were shown to peak in young fruit and leaves, and gradually subside during development. Phylogenetic analysis of Cm1,2RhaT and Cs1,6RhaT demonstrated that they both belong to the branch-forming glycosyltransferase cluster, but are distantly related and probably originated separately before speciation of the citrus genome. Genomic data from citrus, supported by a study of Cs1,6RhaT protein levels in various citrus species, suggest that inheritance, expression levels and mutations of branch-forming rhamnosyltransferases underlie the development of bitter or non-bitter species/varieties under domestication.

Correlation of Rutin Accumulation with 3-O-Glucosyl Transferase and Phenylalanine Ammonia-lyase Activities During the Ripening of Tomato Fruit

In tomato, the predominant flavonoid is quercetin-3-rutinoside (rutin). In this study, we aim to investigate the phenylalanine ammonia-lyase (PAL) and the quercetin-3-O-glucosyl transferase (3-GT) reactions in the formation of rutin during tomato fruit ripening. Tomatoes of the Moneymaker variety at different development stages (green, breaker, turning, pink, red, and deep red) were divided into flesh and peel fractions. In each sample, both the content of rutin and the enzymatic activities for PAL and 3-GT were recorded. The highest activities of PAL were recorded in the peel of turning fruit (3,000μkat/mg fresh weight). In fruit flesh, maximal activity was observed in red fruit (917.3μkat/mg). For both tissues, PAL activity strongly decreased at the final (deep red) fruit stage. The activity of 3-GT in peel peaked in the turning fruit stage (50.7pkat/mg), while in flesh maximal activity (33.4pkat/mg) was observed in green fruit, which rapidly declined at the turning stage. Higher levels of rutin were detected in the tomato peel compared to the flesh part with the highest level being found at the green stage. The relation of PAL and 3-GT activities to rutin content is also evaluated.

Total polyphenols, catechin profiles and antioxidant activity of tea products from purple leaf coloured tea cultivars

Black (aerated) and green (unaerated) tea products, processed from 10 green and 18 purple leaf coloured cultivars of Kenyan origin, and two tea products, from the Japanese cultivars, Yabukita and Yutakamidori, were assayed for total polyphenols (TP) content, individual catechin profiles and in vitro antioxidant capacity (AA). In addition, the phenolic content of the tea products was determined using the Folin–Ciocalteu phenol reagent. Catechin fractions were identified using reverse phase high performance liquid chromatography (HPLC) with a binary gradient elution system.The AA% of the tea products was determined using a 2,2′-diphenyl picrylhydrazyl (DPPH) radical assay method. The results showed that TPs, catechin profiles and antioxidant activities were significantly (p⩽0.05) higher in unaerated than in aerated teas. Tea products from the purple leaf coloured tea cultivars had levels of TPs, total catechin (TC) and antioxidant activities similar to those from the green leaf coloured cultivars, except for teas from the Japanese cultivars that were very low in the assayed parameters. Caffeine content was significantly (p⩽0.05) lower in products from the purple leaf coloured cultivars than in those from the green leaf coloured tea cultivars. Antioxidant activity (%) was higher in tea products from the Kenyan germplasm than in those from the Japanese cultivars. Antioxidant potency of tea products was significantly (r=0.789∗∗, p⩽0.01) influenced by the total anthocyanin content of the purple leaf coloured cultivars. Cyanidin-3-O-glucoside was the anthocyanin most highly correlated with AA% (r=0.843∗∗, p⩽0.01 in unaerated tea). Total catechins in the unaerated products from the green leaf coloured tea cultivars were also significantly correlated with antioxidant capacity (r=0.818∗∗, p⩽0.01). Results from this study suggest that the antioxidant potency of teas is dependent on the predominant flavonoid compound, the type of tea cultivar and the processing method.

Salt effect on phenolics and antioxidant activities of Tunisian and Canadian sweet marjoram (Origanum majoranaL.) shoots

Two varieties of Origanum majorana (Canadian and Tunisian) were evaluated for their phenolic, flavonoid and tannin contents, individual phenolic compounds and antioxidant activities under NaCl constraint. The results showed a significant variability in phenolic composition and antioxidant behavior between the two varieties under salt stress. The phenolic composition of methanolic extracts was determined by reversed-phase high-performance liquid chromatography. Amentoflavone was the predominant flavonoid compound; in addition, trans-2-hydrocinnamic acid became the major phenolic acid with salt treatment of the Tunisian variety. In the control, Canadian variety extract was characterized by high levels of gallic acid and amentoflavone. However, under 75 mmol L(-1) NaCl, gallic acid content doubled, whereas amentoflavone content was maintained in the Canadian variety. Stimulation of phenolic acid biosynthesis was observed in these two varieties under salt treatment despite the fact that shoots of the Tunisian variety showed higher antioxidant activities compared to those from the Canadian variety. Tunisian O. majorana might have developed tolerance to salinity and avoided tissue damage by activating enzymes involved in the galactosylation of quercetin into quercetin-3-galactoside and quercetin-3-rhamnoside. Our results confirmed the tolerance of Tunisian O. majorana plants.

Purification of berry flavonol glycosides by long-bed gel permeation chromatography

While Sephadex LH-20 gel is frequently employed as a stationary phase during pre-separations and in open column chromatography systems, its separation power in long-bed gel permeation chromatography (GPC) applications is much less prevalent. Aimed at the characterization of bioactive constituents, a long-bed GPC protocol was established for lingonberry juice concentrate. The method included pre-fractionation over HP-20 resin to eliminate sugars and organic acids as well as a major part of other predominant berry flavonoids (anthocyanins, flavan-3-ols and proanthocyanidins), prior to the elution of the fraction containing 10% (w/w) of quercetin glycosides (QGs). Subsequently, seven major QGs were purified using a 10-m Sephadex LH-20 system and isocratic elution with methanol. The total mass recovery was 99.3±1.4%, after eluting the highly-retained compounds from the employed pre-column with 70% acetone. Injecting 1070mg per run, the yield of purified QGs ranged from 2 to 6mg per collected single fraction. The LC–UV/PDA purities of isolated Q-3-O-α-rhamnoside and Q-3-O-β-galactoside were 82 and 94area% at 250nm, while the three Q-pentosides showed purities of 59, 30, and 57area%. By comparison, purity assessment of these isolates by quantitative 1H NMR (total integral and modified 100% method) led to significantly lower purities of 70 and 52% for Q-rha and Q-gal and 38, 25 and 46% for Q-pentosides, respectively. This can be explained by the presence of hidden residual complexity (RC), which is revealed by the quantitative NMR method. This finding has potentially broader implication as it reveals an unexpected degree of RC in GPC fractions. Despite remarkable separation power for congeneric flavonoids, long-bed GPC on Sephadex LH-20 produces materials, which require careful analysis of purity before interpreting bioassay results.

Urushiol이 제거된 발효옻 추출물의 제조와 특성

본 연구에서는 옻의 식품사용을 위해서 urushiol의 제거된 추출물을 제조하고 이의 특징을 살펴보았다. 생옻은 물추출에서 3.4mg%의 urushiol이 용출되는 반면 발효옻에서는 용출되지 않았다. 발효옻의 물추출조건은 고형분, 폴리페놀, 플라보노이드 함량이 고려되었으며, <TEX>$100^{\circ}C$</TEX>에서 6-8시간 추출하는 것이 적정하였다. 발효옻 추출물의 pilot scale 생산에서 추출수율은 5.7%이었다. 추출물은 수분 4.34%, 조지방 1.69%, 조단백질 10.21%, 조회분 15.80%의 일반성분으로 이루어져 있었으며, 3종류의 phenolic acid와 4종류의 flavonoid가 검출되었다. Phenolic acid중에서는 gallic acid(1,090.5 mg%)가 가장 많이 함유되어 있었으며, flavonoid중에서는 fisetin(135.7 mg%)의 함량이 가장 높았다. 발효옻 추출물에 존재하는 유리당은 mannitol 3.48%, glycerol 0.19%, glucose 0.19%이었으며, 3,034 ppm의 유리아미노산을 함유하고 있었다. Alanine(244 ppm), serine(231 ppm), leucine(218 ppm)이 주요 유리 아미노산 이었으며, 필수아미노산의 함량은 31.9%이었고 <TEX>${\gamma}$</TEX>-aminobutyric acid 함량은 122 ppm이었다. The water extract of the fermented <TEX>$Rhus$</TEX> <TEX>$verniciflua$</TEX> stem bark (FRVSB) was prepared by hot water extracting at <TEX>$100^{\circ}C$</TEX> for 8 h. The urushiol content of the FRVSB water extract was determined by HPLC. The urushiol was not contained in FRVSB water extract, whereas <TEX>$Rhus$</TEX> <TEX>$verniciflua$</TEX> stem bark (RVSB) water extract contained 3.4 mg%. At the lab scale size, suitable water extraction condition for a total solid, polyphenol and flavonoid from FRVSB was at over <TEX>$100^{\circ}C$</TEX> for 6-8 h. The total solid contents was reduced in pilot scale processing system, with 5.7% of the extraction yield. The proximate composition (%) of FRVSB water extract obtained from industrial installation was moisture 4.34, crude fat 1.69, crude protein 10.21, and crude ash 15.80. Gallic acid (1,090.5 mg%) was the most abundant compound in phenolic acids, while fisetin (135.7 mg%) was the predominant flavonoid. The free sugar content was mannitol of 3.48%, glycerol of 0.19%, and glucose of 0.19%. Alanine (244 ppm), serine (231 ppm), and leucine (218 ppm) were predominant amino acids.

Re-examination of Chromogenic Quantitative Assays for Determining Flavonoid Content

Flavonoids in plants have gained worldwide attention because of their benefits for human health. This study compared three analytical procedures commonly used for determining flavonoid content in plant samples in terms of chromogenic relationships and the reaction products of different flavonoid structures by means of using flavonoid standards with flavone, flavonol, flavanone, flavanol, and isoflavone and analytes such as phenolic acids commonly found in plant extracts. Procedure A produced a stable color reaction between 3-hydroxy-4-keto-flavonoids (flavonols) and 5-hydroxyflavones and was highly sensitive. Procedure B produced color reactions among most of the flavonoids, but the reaction products had different colors and faded over time. Procedure B also produced a color reaction with caffeic and chlorogenic acid. Procedure C was the most sensitive. It produced a color reaction and, like procedure A, could be used to quantify flavonols and 5-hydroxyflavones, but also showed color reaction toward caffeic and chlorogenic acid. On the basis of the results, the current three procedures are not satisfactory for determining all of the types of flavonoid. Two issues needed to be clarified before a promising determination of flavonoid content could be performed with chromogenic assays. The first is a survey of the literature to screen the possible predominant component of flavonoid in analytes. The other is guided by the predominant flavonoid; a promising calibration curve for flavonoid detection can be established on the basis of the selection of an appropriate method and a chemical standard with an equivalent dose response to the predominant flavonoid.