Metabolite biodiversity in pepper (Capsicum) fruits of thirty-two diverse accessions: variation in health-related compounds and implications for breeding

A comprehensive study on morphology and biochemical compounds of 32 Capsicum spp. accessions has been performed. Accessions represented four pepper species, Capsicum annuum, Capsicum frutescens, Capsicum chinense and Capsicum baccatum which were selected by their variation in morphological characters such as fruit color, pungency and origin. Major metabolites in fruits of pepper, carotenoids, capsaicinoids (pungency), flavonoid glycosides, and vitamins C and E were analyzed and quantified by high performance liquid chromatography. The results showed that composition and level of metabolites in fruits varied greatly between accessions and was independent of species and geographical location. Fruit color was determined by the accumulation of specific carotenoids leading to salmon, yellow, orange, red and brown colored fruits. Levels of both O- and C-glycosides of quercetin, luteolin and apigenin varied strongly between accessions. All non-pungent accessions were devoid of capsaicins, whereas capsaicinoid levels ranged from 0.07 up to 80 mg/100g fr. wt. in fruit pericarp. In general, pungent accessions accumulated the highest capsaicinoid levels in placenta plus seed tissue compared to pericarp. The non-pungent capsaicinoid analogs, capsiates, could be detected at low levels in some pungent accessions. All accessions accumulated high levels of vitamin C, up to 200 mg/100g fr. wt. The highest vitamin E concentration found was 16 mg/100g fr. wt. Based on these metabolic data, five accessions were selected for further metabolic and molecular analysis, in order to isolate key genes involved in the production of these compounds and to assist future breeding programs aimed at optimizing the levels of health-related compounds in pepper fruit.

Determination of quercetins in onion (Allium cepa) using infrared spectroscopy

The rapid quantification of flavonoid compounds in onions by attenuated total reflectance (ATR) Fourier transform infrared (FT-IR) spectroscopy combined with multivariate analysis was evaluated as a possible alternative to high-performance liquid chromatography (HPLC) analysis. Quercetin content in onion varieties (yellow, red, and sweet) was quantified using ATR FT-IR (4000 to 400 cm⁻¹) spectroscopy and HPLC methods. Quercetin-3,4'-O-diglucoside (3,4'-Qdg) and quercetin-4'-O-glucoside (4'-Qmg) comprised >80% of the total flavonol content detected in the studied varieties. The quercetin compounds (3,4'-Qdg and 4'-Qmg) and total flavonol conjugates were quantified by HPLC, and results correlated closely with ATR-IR values (R > 0.95). Cross-validated (leave-one-out) partial least-squares regression (PLSR) models successfully predicted concentrations of these quercetins. The standard errors of cross-validation (SECV) of 3,4'-Qdg and 4'-Qmg, total quercetin, and total flavonol contents of onions were 20.43, 21.18, and 21.02 mg/kg fresh weight, respectively. In addition, supervised and unsupervised segregation analyses (principal component analysis, discriminant function analysis, and soft independent modeling of class analogue) were performed to classify onion varieties on the basis of unique infrared spectral features. There was a high degree of segregation (interclass distances > 3.0) for the different types of onion. This study indicated that the IR technique could predict 3,4'-Qdg, 4'-Qmg, total quercetin, and total flavonol contents and has advantages over the traditional HPLC method in providing a valid, efficient, and cost-effective method requiring less sample preparation for the quantification of quercetins in onion.

Inhibitory activity of cinnamon bark species and their combination effect with acarbose against intestinal α-glucosidase and pancreatic α-amylase

Inhibition of α-glucosidase and pancreatic α-amylase is one of the therapeutic approaches for delaying carbohydrate digestion, resulting in reduced postprandial glucose. The aim of this study was to evaluate the phytochemical analysis and the inhibitory effect of various cinnamon bark species against intestinal α-glucosidase and pancreatic α-amylase. The results showed that the content of total phenolic, flavonoid, and condensed tannin ranged from 0.17 to 0.21 g gallic acid equivalent/g extract, from 48.85 to 65.52 mg quercetin equivalent/g extract, and from 0.12 to 0.15 g catechin equivalent/g extract, respectively. The HPLC fingerprints of each cinnamon species were established. Among cinnamon species, Thai cinnamon extract was the most potent inhibitor against the intestinal maltase with the IC(50) values of 0.58 ± 0.01 mg/ml. The findings also showed that Ceylon cinnamon was the most effective intestinal sucrase and pancreatic α-amylase inhibitor with the IC(50) values of 0.42 ± 0.02 and 1.23 ± 0.02 mg/ml, respectively. In addition, cinnamon extracts produced additive inhibition against intestinal α-glucosidase and pancreatic α-amylase when combined with acarbose. These results suggest that cinnamon bark extracts may be potentially useful for the control of postprandial glucose in diabetic patients through inhibition of intestinal α-glucosidase and pancreatic α-amylase.

[Chemical constituents from herbs of Erigeron breviscapus]

OBJECTIVE

To study the chemical constituents from herbs of Erigeron breviscapus.

METHOD

The compounds were isolated and purified by various chromatographic techniques. Their structures were identified on the basis of physicochemical properties and spectral analysis.

RESULT

Twelve compounds were isolated and structurally identified as quercetin-3-O-beta-D-glucoside (1), 5, 7-dihydroxychromone (2), 3-O-caffeoyl-gamma-quinide (3), naringenin (4), 3, 5-di-O-caffeoylquinic acid (5), 3,4-di-O-caffeoylquinic acid (6), 4, 5-di-O-caffeoylquinic acid (7), 1,3-di-O-caffeoylquinic acid (8), 1, 5-di-O-caffeoylquinic acid (9), 3-O-caffeoylquinic acid (10), 4-O-caffeoylquinic acid (11) and chlorogenic acid (12).

CONCLUSION

Compounds 1-4 were isolated from this plant for the first time.

Chromatographic fingerprint analysis and rutin and quercetin compositions in the leaf and whole-plant samples of di- and tetraploid Gynostemma pentaphyllum

Gynostemma pentaphyllum (Thunb.) Makino, also known as jiaogulan, has been shown to have antioxidant, antiproliferative, and anti-inflammatory activities. Flavonoid is considered a major contributor for these beneficial effects. To obtain chemical patterns of flavonoids in G. pentaphyllum of different genotypes (di- versus tetraploids) and different parts (leaf versus whole plant) of plants, the extraction condition was optimized and a fingerprinting approach was established by means of high-performance liquid chromatography coupled with diode array detection and mass spectrometry (HPLC-DAD-MS). Eight flavonoids were identified, among which rutin and quercetin were quantified. The highest levels of rutin and quercetin were 23.03 and 12.10 mg/g, respectively, observed in the diploid leaf sample 2L3 and 2L2, while the lowest levels of rutin and quercetin were 1.92 and 0.25 mg/g in the tetraploid whole-plant sample 4W3. The chemical patterns were further analyzed by similarity calculation and principal component analysis (PCA). Seven common characteristic peaks were found in all of the tested samples. Flavonoid patterns of tetraploids were significantly different from those of diploids, whereas different parts of plants showed less difference. The flavonoid pattern of the diploid leaf sample was most similar to that of the reference botanical G. pentaphyllum. The combination of chromatographic fingerprint and quantification analysis could be used for quality assessment of G. pentaphyllum and its derived nutraceutical products.

Antioxidant activity of Convolvulus hystrix Vahl and its chemical constituents

Total alcohol and successive extracts (diethyl ether, chloroform, ethyl acetate and n-butanol) of Covolvulus hystrix Vahl were screened for their antioxidant activity using free radical 2-2-diphenyl-1-picrylhydrazyl (DPPH) and Trolox as reference substance. The tested extracts showed variable antioxidant activities. The highest antioxidant activity was achieved in total alcohol (48.32%) followed by ethyl acetate (37.8%) and n-butanol (32.96%) extracts. From the ethyl acetate extract four compounds were isolated and identified as quercetin, quercetin 3-0-rutinoside and quercetin-7-O-rhamnoside in addition to ferulic acid using different spectroscopic analysis such as, 1HNMR, 13CNMR, COSY, HMBC and HMQC.

Antihypertensive effects of isoquercitrin and extracts from Tropaeolum majus L.: evidence for the inhibition of angiotensin converting enzyme

AIM OF THE STUDY

Previous studies have shown that the extracts obtained from Tropaeolum majus L. exhibit pronounced diuretic properties. In the present study, we assessed whether the hypotensive and/or antihypertensive mechanism of hydroethanolic extract (HETM), semi-purified fraction (TMLR) obtained from T. majus and the flavonoids isoquercitrin (ISQ) and kaempferol (KPF) can be mediated by their interaction with angiotensin converting enzyme (ACE).

METHODS AND METHODS

Firstly, to evaluate changes in mean arterial pressure (MAP), different groups of normotensive and spontaneously hypertensive rats (SHR) were orally and intraduodenally treated with HETM (10-300 mg/kg) and TMLR (12.5-100mg/kg) and intravenously treated with ISQ and KPF being later anesthetized with ketamine (100mg/kg) and xylazine (20mg/kg). The left femoral vein and the right carotid artery were isolated, and polyethylene catheters were inserted for ISQ and KPF (0.5-4 mg/kg) administration and blood pressure recording, respectively. The plasmatic ACE activity was evaluated to indirect fluorimetry, in serum samples after orally treatment with HETM, TMLR, ISQ and KPF.

RESULTS

The oral administration of the HETM and its TMLR significantly reduced, in a dose-dependent manner, the MAP in both normotensive and SHR. In addition, these preparations significantly decreased the MAP for up to 3h after the administration of the extract. Additionally, the intravenous administration of ISQ, but not KPF, decreased MAP in rats. Otherwise, neither the extracts nor ISQ affected the heart rate. The oral administration of the HETM, TMLR or ISQ reduced ACE activity in serum samples at 90 min after administration. Finally, the intravenous administration of ISQ caused a significant reduction in the hypertensive response to angiotensin I, but not angiotensin II in normotensive rats.

CONCLUSION

Our results show that the hypotensive effects caused by the HETM, as well as by its TMLR, may be associated with the high levels of the flavonoid ISQ found in this plant. In addition, ISQ-induced hypotension in rats is an event dependent on the inhibition of angiotensin II generation by ACE.

Polyphenols: planting the seeds of treatment for the metabolic syndrome

Greater understanding about the pathogenesis of metabolic syndrome and potential causes suggests that plant polyphenols might be useful as a treatment. Dietary excess energy can be stored in adipocytes, leading to the release of proinflammatory cytokines and adipose-related hormones that cause vascular injury. Plant polyphenols, organic compounds found in numerous plant species and their fruits, are being actively studied as potential treatments for components of the metabolic syndrome. Individual polyphenols that have been examined include resveratrol, quercetin, epigallocathechin-3-gallate, and curcumin. Resveratrol lowers weight, blood pressure, glucose, and insulin resistance in rodents, and a human trial is currently underway. Quercetin decreases lipid and glucose levels in obese rats, and in a human investigation of subjects with the metabolic syndrome has lowered blood pressure without significant alteration of lipids. Epigallocathechin-3-gallate-induced weight loss has attenuated glucose levels and insulin resistance in rodents and improved hemoglobin A(1c) and lipid in human studies. Plant extracts also can be used. Grape seed and chokeberry extracts have decreased blood pressure and lipid levels in small human trials. Other human investigations have shown the beneficial effects of cocoa, coffee, carob, and Momordica charantia. Thus far, most studies have involved a small number of subjects and have been of short duration. Future studies should be designed to account for a disease process in which the pathogenic factors may take place for years before disease manifestations take place, the possibly limited bioavailability of polyphenols, and the potential need to provide combinations or modifications of polyphenols.

[Study on HPLC fingerprints of Senecio scandens and S. scandens]

OBJECTIVE

To develop an HPLC method for fingerprint study of both Senecio scandens and S. scandens.

METHOD

Fingerprints of the two Senecio herbs were compared. And the concentrations of main peaks in them were semi-quantified as chlorogenic acid or hyperoside. Chromatography was performed on a Shiseido Capcell Pak MG II C18 (4.6 mm x 250 mm, 5 microm) column using a gradient elution of acetonitrile-water containing 0.2% acetic acid. And detection wavelength was 360 nm.

RESULT

Significant difference was found in the fingerprint of the two herbs. Eleven peaks were picked out for the evaluation of S. scandens and S. scandens, respectively. They were identified to be either organic acid compounds or flavones by HPLC-UV and LC-ESI-MS analysis. And semi-quantification of them showed the concentrations of organic acid compounds and flavones in S. scandens were 2.29- and 15.56- folds of those in S. scandens, respectively.

CONCLUSION

The developed HPLC method is suitable for the fingerprint study for both of S. scandens and S. scandens. It is robust and producible enough to be used for the quality evaluation on S. scandens.

Characterization of industrial onion wastes (Allium cepa L.): dietary fibre and bioactive compounds

The food industry produces a large amount of onion wastes, making it necessary to search for possible ways for their utilization. One way could be to use these onion wastes as a natural source of high-value functional ingredients, since onion are rich in several groups of compounds, which have perceived benefits to human health. The objective of this work is to gain knowledge of any differences between the different onion wastes obtained from industry and non-commercial bulbs to use them as food ingredients rich in specific compounds. The results showed that brown skin and top-bottom could be potentially used as functional ingredient rich in dietary fibre, mainly in insoluble fraction, and in total phenolics and flavonoids, with high antioxidant activity. Moreover, brown skin showed a high concentration of quercetin aglycone and calcium, and top-bottom showed high concentration of minerals. Outer scales could be used as source of flavonols, with good antioxidant activity and content of dietary fibre. However, inner scales could be an interesting source of fructans and alk(en)yl cystein sulphoxides. In addition, discarded onions (cvs Recas and Figueres) could be used as a good source of dietary fibre, and cv Recas also as a source of phenolics compounds.

Quercetin and isorhamnetin glycosides in onion (Allium cepa L.): varietal comparison, physical distribution, coproduct evaluation, and long-term storage stability

During onion processing, the outer dried protective layer (outer paper layer) and first two fleshy leaf layers are removed. This coproduct material is a potential commercial source of flavonoids especially quercetin. In the following study, the flavonoid composition was determined in coproduct materials and the press cake (material generated after juice extraction) in several commercially important onion varieties grown in California. Flavonoids were characterized and quantified using LC-(ESI)MS/MS and HPLC. The long-term stability of quercetin glycosides was assessed in dried coproduct materials stored at 4 and 22 °C over a 12 month period. In all varieties, the predominant forms of quercetin were the quercetin 3,4'-O-glucoside and 4'-O-glucoside. The first layer had significantly higher levels of flavonoids than the outer paper, second, and inner flesh layers on a DW basis (p < 0.05). Allium cepa "Milestone" contained the highest levels (p < 0.05) of flavonoids (1703 mg/100 g on a dry weight basis (DW). Onion press cake had significantly higher levels of total quercetin as compared with fresh onions (p < 0.05). The levels of 4'-O-glucoside significantly decreased during the first month of storage and remained stable for 12 months of storage at either 4 or 22 °C (p < 0.05).

Toxicity mechanisms of onion (Allium cepa) extracts and compounds in multidrug resistant erythroleukemic cell line

Onion (Allium cepa) is being studied as a potential anticancer agent, but little is known regarding its effect in multidrug resistance (MDR) cells. In this work, the cytotoxicity of crude onion extract (OE) and fractioned extract (aqueous, methanolic and ethyl acetate), as well as some onion compounds (quercetin and propyl disulfide) were evaluated in Lucena MDR human erythroleukemic and its K562 parental cell line. The capacity of OE to induce apoptosis and/or necrosis in these cells, the possible participation of oxidative stress and DNA damage were also assessed. Similar sensitivities were obtained for both tumoral cells, however only OE caused significant effects in the cells. In K562 cells, a significant increase of apoptosis was verified while the Lucena cells experienced a significant increase of necrosis. An antioxidant capacity was verified for OE discarding oxidative damage. However, OE provoked similar significant DNA damage in both cell lines. Thus, the OE capacity to overcome the MDR phenotype suggests anti-MDR action of OE.

Stability of Pycnogenol® as an ingredient in fruit juices subjected to in vitro gastrointestinal digestion

BACKGROUND

The enrichment of fruit juices with concentrated polyphenolic extracts is an expedient strategy to compensate possible phenolic loss through gastrointestinal processing. Pycnogenol, a standardised procyanidin-rich extract from pine bark, has been proposed as a potential candidate for polyphenol enrichment of foods. In this study the effects of in vitro digestion on the phenolic profile of fruit juices enriched with Pycnogenol were investigated.

RESULTS

After in vitro digestion the level of detectable total phenolic compounds (expressed as gallic acid equivalent) was higher in both pineapple and red fruit juices enriched with Pycnogenol than in non-enriched commercial juices. Five phenolic monomeric compounds were identified by high-performance liquid chromatography, namely chlorogenic acid, caffeic acid, ferulic acid, gallic acid and taxifolin, the last two being predominant. In vitro digestion of both Pycnogenol-enriched pineapple and red fruit juices led to a significant (P < 0.05) increase in detectable chlorogenic and ferulic acids, indicating that hydrolysis of more complex molecules occurs. On the other hand, in vitro digestion of non-enriched juices was associated with a decrease in gallic and caffeic acids in pineapple juice and with a decrease in ferulic acid in red fruit juice. In no case did in vitro digestion increase the amount of detectable phenolic compounds in non-enriched juices.

CONCLUSION

The stability of Pycnogenol after in vitro gastrointestinal digestion makes it a good choice for phenolic enrichment of fruit juices.

Potential of cranberry powder for management of hyperglycemia using in vitro models

Aqueous solutions of two different cranberry powders (CP and CP-SAB) were evaluated for organic acids, sugars, total phenolics, antioxidant activity based on the 2,2-diphenyl-1-picrylhydrazyl radical scavenging assay, and functionality such as in vitro inhibition of α-amylase, α-glucosidase, and angiotensin I-converting enzyme (ACE) relevant for potential management of hyperglycemia and hypertension linked to type 2 diabetes. The total phenolics content was 11 and 51 mg/g of sample dry weight for CP and CP-SAB, respectively. p-Coumaric acid and quercetin derivatives were the main phenolic compounds identified in the cranberry powders. CP-SAB had α-glucosidase inhibitory activity that increased with increased dose (1-5 mg/mL) from 60% to 100% inhibition. There was limited amount of α-amylase inhibitory activity that reached a maximum of 40% inhibition at 5 mg/mL treatment. Significant ACE inhibitory activity was detected for CP-SAB at 100 and 200 mg/mL sample concentrations. These in vitro results indicate the potential of cranberry powders as dietary supplement and food-based strategies for potential hyperglycemia management. This biochemical rationale provides the basis for further design of animal and clinical studies using standardized extracts.

[Determination of quercetin metabolism in UGT1A3 cDNA-expressing cells by RP-HPLC]

OBJECTIVE

To develop a RP-HPLC method for the determination of quercetin in UGT1A3 cDNA-transfected cells.

METHODS

The lysate of cells transfected with human recombinant uridine 5-diphosphate glucuronosyltransferases UGT1A3 cDNA was co-incubated with quercetin, the reaction was terminated with acetonitrile, and luteolin was used as internal standard. The determination was performed on a C(1) reversed phase column with a mobile phase of methanol-0.1% formic acid (V/V) at a flow rate of 1.0 ml/min. The gradient elution was as follows: 0 - 25 min (30:70-80:20, methanol:0.1% formic acid), > 25-25.5 min (80:20), >25.5-27 min (80:20-30:70), > 27-30 min (30:70). A UV-VIS detector was operated at 368 nm.

RESULT

The standard curve was linear over the concentration range of 5-200 μmol/L (r = 0.9999). The limit of detection was 1.25 μmol/L(S/N ≥ 3), and the limit of quantification was 5 μmol/L (S/N >10, RSD = 6.99%). The method afforded recoveries of 99.1%-103.5%, and precisions for inter- and intra-assay were < 2.5% and < 8%, respectively. In addition, kinetic analysis indicated that the K(m), V(max) and CL(int) (V(max)/K(m)) values for quercetin glucuronide were (62.95 ± 13.16) μ mol/L, (284.50 ± 24.35)nmol*min⁻¹*g⁻¹ and 4.52 ml*min⁻¹*g⁻¹, respectively.

CONCLUSION

The method established is accurate and simple and suitable for the determination of quercetin in UGT1A3 cDNA-expressed cells.

[Studies on fingerprints of Centella asiatica by HPLC]

OBJECTIVE

To study the HPLC fingerprints and establish a sensitive and specific method for controlling the quality of Centella asiatica.

METHODS

HPLC gradient elution was applied for the fingerprints of Centella asiatica. All 16 samples are collected from different habitats of China. The columni was Alltech C18 column (250 mm x 4.6 mm, 5 microm), mobile phase was acetonitrile-water, flow rate was 1.0 ml/min, wavelength was 205 nm.

RESULTS

The fingerprint of Centella asiatica was established, 16 samples of different areas of Centella asiatica were detected. There were 15 common peaks in the HPLC fingerprints of Centella asiatica. By comparison with the reference standards and using LC-ESI-MS(n) to corroborate the structure, 5-10 peaks were identified as madecassoside, asiaticoside, quercetin, kaemperol, madecassic acid and asiatic acid respectively. After calculating the similarity of the HPLC fingerprints of 16 habitants, the similarity of different habitats has been bad quite.

CONCLUSION

The method is accurate, reliable and good repeatability. This chromatographic fingerprint method can be used to controll the quality of Centella asiatica.

A simple HPLC method for quantitation of quercetin in herbal extracts

A reversed-phase HPLC method with UV detection was developed for the determination of quercetin. The method produced linear response over a wide concentration range, with an average accuracy of 95% and average intra- and interday variation of 0.75 and 0.3, respectively. The exactness of the method was proven by determining the recovery rates from 50 to 150% of standard concentration, which were found within the acceptable range of 95 to 105%. The method was used for quantitation of quercetin in the extracts of Psidium guajava, Vitis vinifera, and extracts rich in quercetin and other flavonols in the flavonoid family.

HPLC analysis of kaempherol and quercetin derivatives isolated by different extraction techniques from plant matrix

Soxhlet extraction, ultrasound extraction, and accelerated solvent extraction (ASE), followed by RP-HPLC with a photodiode array detector was used for the determination of flavonoids in fruits of Peucedanum alsaticum. Three compounds were identified: a kaempherol derivative (astragalin), and two quercetin derivatives (quercitrin and hiperoside). The highest extraction yields of the selected compounds were obtained by use of exhaustive ASE.

(+)-methyl jasmonate-induced bioformation of myricetin, quercetin and kaempferol in red raspberries

The effect of postharvest treatment with enantiomers of methyl jasmonate (MJ) in conjunction with ethanol on bioformation of myricetin, quercetin and kaempferol in red raspberry was studied. For comparison, postharvest treatment with the commercial stereoisomeric mixture of MJ in conjunction with ethanol was simultaneously accomplished. The levels obtained were contrasted with those determined in untreated (control) samples. Exogenous (+)-MJ induced an enhancement in the levels of myricetin, quercetin and, particularly, kaempferol whereas the exposition to (-)-MJ exhibited the opposite effect. Enzymatic assays were carried out in presence and absence of (-)-MJ and (+)-MJ to evaluate possible changes in the activity of the enzymes regulating the bioformation of flavonols in red raspberries as a consequence of the treatments. From the results of the assays both (-)-MJ and (+)-MJ inhibited the activity of flavanone 3β-hydroxylase (FHT) and flavonol synthase (FLS), which are directly involved in the formation of flavonols from (-/+)-naringenin. From these results, it is speculated that the activity of phenylalanine ammonia lyase (PAL) regulating the formation of (-/+)-naringenin from l-phenylalanine by (+)-MJ in conjunction with ethanol is promoted. Postharvest treatment of red raspberry with (+)-MJ in ethanol is proposed as a mean to increase flavonol content in red raspberries.

[Determination of quercetin and kaempferol in Dysosma plants by RP-HPLC]

OBJECTIVE

To determine quercetin and kaempferol in the plant of genus Dysosma that come from different species, different plant parts or different growing areas, which provide the basis of rational utilization of Dysosma plants.

METHOD

The analysis was performed on a Diamonsil C18 column (4.6 mm x 150 mm, 5 microm) eluted with the mobile phase of methanol-water containing 0.1% phosphoric acid (60:40). The flow rate was 1 mL x min(-1), the detection wavelength was 360 nm; and the column temperature was set at 25 degrees C.

RESULT

The linear ranges of quercetin and kaempferol are 0.22-1.1 microg and 0.42-2.1 microg. The average recoveries of quercetin and kaempferol are 97.1% (RSD 1.4%) and 99.6% (RSD 2.4%); respectively.

CONCLUSION

The contents of flavones in different species of Dysosma are significantly different.

Phenolic profile and free radical-scavenging activity of Cabernet Sauvignon wines of different geographical origins from the Balkan region

BACKGROUND

The phenolic profile, determined by the relative proportions of different phenolic compounds, is characteristic for each grape variety and its corresponding wine. The aim of this study was to determine the phenolic and hydroxycinnamate acid, flavan-3-ol and flavonol contents and free radical-scavenging activity of single-cultivar (Cabernet Sauvignon) wines from selected Balkan vineyard regions by spectrophotometric methods and high-performance liquid chromatography with photodiode array and fluorescence detection.

RESULTS

The contents of phenolic compounds varied depending on the agroclimatic factors and oenological practices of the vineyard region. The antioxidant activity of wine samples was estimated by their ability to scavenge the stable 2,2'-diphenyl-1-picrylhydrazyl free radical (DPPH). All wines showed high DPPH-scavenging activity (70.03-83.53%, mean 73.76%). Significant correlations between catechin (R(2) = 0.8504) and quercetin (R(2) = 0.8488) concentrations and DPPH-scavenging ability of the wines were found.

CONCLUSION

The concentrations of the main components catechin and quercetin can be used as biochemical markers for the authentication of red grape cultivars and their corresponding single-cultivar wines.

[Studies on the chemical constituents from Lobelia chinensis]

OBJECTIVE

To study the chemical constituents of the full plant of Lobelia chinensis.

METHODS

The compounds were isolated and purified using several column chromatographic methods. Their structures were elucidated based on their physicochemical properties and spectral data.

RESULTS

Twelve compounds were isolated from L. chinensis. Their structures were elucidated as 6,7-dimethoxycoumarin (1), fraxinol (2), 5-hydroxy-7-methoxycoumarin (3), tomentin (4), 3'-hydroxygenkwanin (5), apigenin (6), quercetin (7), luteolin (8), linarin (9), luteolin 3',4'-dimethylether-7-O-beta-D-glucoside (10), isoferulic acid (11), and ethyl ros-marinate (12), respectively.

CONCLUSION

Compounds 1 -5 and 10 -12 are isolated from this plant for the first time.

[Simultaneous determination of rutin, isoquercitrin and chlorogenic acid in Farfarae Flos by HPLC]

OBJECTIVE

To develop an HPLC method for simultaneous determination of rutin, isoquercitrin and chlorogenic acid in Farfarae Flos.

METHOD

The analysis was carried out on a Phenomenex Synergi POLAR-RP 80A column (4.6 mm x 250 mm, 4 microm) with gradient elution using methanol-acetonitrile-water (adjusted to pH 2.5 with formic acid) as mobile phase. The flow rate was 1.2 mL x min(-1) and the detection wavelength was at 255 nm.

RESULT

The calibration curves were linear over the range of 0.2-2 000 microg x L(-1) for rutin and isoquercitrin, 10-2 000 microg x L(-1) for chlorogenic acid, respectively. The average recoveries were 99.5% for rutin, 100.1% for isoquercitrin and 99.4% for chlorogenic acid, respectively, with RSD not more than 3.0%.

CONCLUSION

The described method is reliable and could be used for the quality control of Farfarae Flos.

Determination of antioxidant constituents in cactus pear fruits

An analytical study was carried out on the presence of antioxidant constituents and the in vitro antioxidant capacity in the extracts of three species of Spanish red-skinned cactus pear fruits (Opuntia ficus-indica, Opuntia undulata and Opuntia stricta). The cactus pear fruit extracts were analyzed for determined constituents: ascorbic acid, flavonoids (quercetin, isorhamnetin, myricetin, kaempferol and luteolin), betalains, taurine, total carotenoids and total phenolics. The antioxidant capacity was assessed by means of two different methods: the 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (Trolox equivalent antioxidant capacity) method and the 2,2-diphenyl-1-picrylhydrazyl radical method. Opuntia ficus-indica fruit extract had the strongest antioxidant capacity and taurine content. O. stricta fruits were the richest in ascorbic acid and total phenolics, whereas O. undulata fruits showed the highest carotenoid content. Quercetin and isorhamnetin were the main flavonoids detected. This study provides basic information on the presence of bioactive compounds and antioxidant capacity in extracts of cactus pear fruits, in order to consider these extracts as ingredient for the production of health-promoting food.

Engineering of flavonoid O-methyltransferase for a novel regioselectivity

An O-methyltransferase isolated from poplar, POMT7, was identified as a flavone 7-O-methyltransferase. In order to generate a mutant of POMT-7 having a novel regioselectivity, we conducted an error-prone polymerase chain reaction. More than 100 mutants were screened and one of the mutants (POMT-M1) Asp257Gly, methylated the 3-hydroxyl group of flavonols in addition to 7-hydrdoxyl group. The mutation changed asparagine residue at the position of 257 into glycine. The kinetic parameters showed that the wild type POMT7 was better activity toward kaempferol and quercetin than the POMT7-M1. Using E. coli transformant expressing POMT7-M1, 58 microM of 3, 7-O-dimethylquercetin and 70 microM of 3, 7-O-dimethylkaempferol from 100 microM of corresponding substrate were synthesized successfully.