2-(1H-pyrrolyl)carboxylic acids as pigment precursors in garlic greening

Six model compounds having a 2-(1 H-pyrrolyl)carboxylic acid moiety and a hydrophobic R group were synthesized to study their effects on garlic greening, the structures of which are similar to that of 2-(3,4-dimethyl-1 H-pyrrolyl)-3-methylbutanoic acid (PP-Val) (a possible pigment precursor for garlic greening). The puree of freshly harvested garlic bulbs turned green after being soaked in solutions of all these compounds, and with both increasing concentrations and incubation time the green color of the puree became deeper. In contrast, neither pyrrole alone nor pyrrole combined with free amino acids had the ability to discolor the puree. The compounds exhibited a good relationship between structure and activity of garlic greening, namely, the smaller the size of the R group, the larger the contribution. Also, it was found that the unidentified yellow species can be produced by reacting the model compounds with pyruvic acid at room temperature (23-25 degrees C). Moreover, blue species were formed by incubation of the model compounds with di(2-propenyl) thiosulfinate at room temperature. On the basis of these observations, a pathway for garlic greening was proposed.     

Model studies on precursor system generating blue pigment in onion and garlic

Reactions involved in blue-green discoloration in a mixture of onion (Allium cepa L.) and garlic (Allium sativum L.) were investigated. Vivid-blue color was successfully reproduced by using a defined model reaction system comprising only trans-(+)-S-(1-propenyl)-L-cysteine sulfoxide (1-PeCSO) from onion, S-allyl-L-cysteine sulfoxide (2-PeCSO) from garlic, purified alliinase (EC 4.4.1.4), and glycine (or some other amino acids). Four reaction steps identified and factors affecting the blue color formation were in good agreement with those suggested by earlier investigators. When crude onion alliinase was used in place of garlic alliinase, less pigment was formed. This result was explained by a difference in the amount of thiosulfinates, colorless intermediates termed color developers, yielded from 1-PeCSO by these enzymes.     

Allium discoloration: the precursor and formation of the red pigment in giant onion (Allium giganteum Regel) and some other subgenus Melanocrommyum species

The precursor of the orange-red pigment formed upon wounding the bulbs of Allium giganteum (Allium subg. Melanocrommyum) was isolated and shown to be S-(2-pyrrolyl)cysteine S-oxide. In addition, two other pyrrolylsulfinyl derivatives were found in an extract from the bulbs, namely, 3-(2-pyrrolylsulfinyl)lactic acid and S-(3-pyrrolyl)cysteine S-oxide. Contrary to a previous report, the latter compound was shown not to serve as the precursor of the pigment, being in fact only an artifact formed during isolation. The formation of pyrrolyl-containing compounds following disruption of A. giganteum bulbs was studied by a combination of LC-MS, LC-NMR and DART-MS. It was found that S-(2-pyrrolyl)cysteine S-oxide is cleaved by a C-S lyase (alliinase) to yield 2-pyrrolesulfenic acid. Two molecules of the latter compound give rise to highly reactive S-(2-pyrrolyl) 2-pyrrolethiosulfinate which in turn converts into red 2,2'-epidithio-3,3'-dipyrrole (dipyrrolo[2,3-d:2',3'-e]-1,2-dithiin). Several other pyrrolyl-containing compounds were detected in A. giganteum for the first time, including S-methyl 2-pyrrolethiosulfinate, S-(2-pyrrolyl) methanethiosulfinate, di(2-pyrrolyl) disulfide, and S-(2-pyrrolyl) 2-pyrrolethiosulfonate. It can be concluded that the formation of the orange-red pigment in Allium subg. Melanocrommyum species, despite sharing several analogous features, is of a different nature than the pink discoloration of onion (A. cepa).     

Quantitative determination of allicin in garlic: supercritical fluid extraction and standard addition of alliin

A quantitative method is described for the determination of allicin (2-propene-1-sulfinothioic acid S-2-propenyl ester) in garlic, using standard additions of alliin (l-(+)-S-allylcysteine sulfoxide) in conjunction with supercritical fluid extraction (SFE) and high performance liquid chromatography analysis with UV-vis absorbance detection. Optimum CO(2)-SFE conditions provided 96% recovery for allicin with precision of 3% (RSD) for repeat samples. The incorporation of an internal standard (allyl phenyl sulfone) in the SFE step resulted in a modest improvement in recovery (99%) and precision (2% RSD). Standard additions of alliin were converted to allicin in situ by endogenous alliinase (l-(+)-S-alk(en)ylcysteine sulfoxide lyase, EC 4.4.1.4). Complete conversion of the spiked alliin to allicin was achieved by making additions after homogenization-induced conversion of the naturally occurring cysteine sulfoxides to thiosulfinates had taken place, thus eliminating the likelihood of competing reactions. Concentration values for allicin determined in samples of fresh garlic (Allium sativum L. and Allium ampeloprasum) and commercially available garlic powders (Allium sativum L.) by standard addition of alliin were found in all cases to be in statistical agreement (95% confidence interval) with values determined using a secondary allicin standard (concentration determined using published extinction coefficients). This method provides a convenient alternative for assessing the amount of allicin present in fresh and powdered garlic, as alliin is a far more stable and commercially prevalent compound than allicin and is thus more amenable for use as a standard for routine analysis.     

Isolation and identification of a red pigment from Allium subgenus Melanocrommyum

Three new sulfur-containing compounds were identified in Allium L. species belonging to the subgenus Melanocrommyum as the first examples of sulfur-containing pyrrole derivatives in nature. Some of these species are traditionally used in Southwest and Central Asia as vegetables and herbal drugs. A hypothetical biogenetic scheme is proposed in which L-(+)- S-(3-pyrrolyl)cysteine sulfoxide is enzymically degraded. The resulting 2-lactyl-3'-pyrrolyl sulfoxide is condensed readily to the red pigment 3,3'-dithio-2,2'-dipyrrole. All compounds are chemically unstable, rendering the analysis extremely difficult. Correlation NMR in combination with diffusion NMR allowed the identification of these low molecular weight compounds. For the first time, the compounds involved in the coloring process of Allium plant material have been identified from native plant material.     

Structure and bioactivity of thiosulfinates resulting from suppression of lachrymatory factor synthase in onion

In normal onion (Allium cepa), trans-S-1-propenyl-L-cysteine sulfoxide is transformed via 1-propenesulfenic acid into propanethial S-oxide, a lachrymatory factor, through successive reactions catalyzed by alliinase and lachrymatory factor synthase (LFS). A recent report showed that suppression of the LFS activity caused a dramatic increase in thiosulfinates previously reported as "zwiebelane isomers". After purification by recycle high-performance liquid chromatography and subsequent analyses, we established the planar structure of the putative "zwiebelane isomers" as S-3,4-dimethyl-5-hydroxythiolane-2-yl 1-propenethiosulfinate, in which two of the three molecules of 1-propenesulfenic acid involved in the formation gave the thiolane backbone, and the third molecule gave the thiosulfinate structure. Of at least three stereoisomers observed, one in the (2'R,3'R,4'R,5'R)-configuration was collected as an isolated fraction, and the other isomers were collected as a combined fraction because spontaneous tautomerization prevented further purification. Both fractions showed inhibitory activities against cyclooxygenase-1 and α-glucosidase in vitro.     

Isolation, characterization, and antioxidant activity of bromophenols of the marine red alga Rhodomela confervoides

A total of 19 naturally occurring bromophenols, with six new and 13 known structures, were isolated and identified from the methanolic extract of the marine red alga Rhodomela confervoides. The new compounds were identified by spectroscopic methods as 3,4-dibromo-5-((methylsulfonyl)methyl)benzene-1,2-diol (1), 3,4-dibromo-5-((2,3-dihydroxypropoxy)methyl)benzene-1,2-diol (2), 5-(aminomethyl)-3,4-dibromobenzene-1,2-diol (3), 2-(2,3-dibromo-4,5-dihydroxyphenyl)acetic acid (4), 2-methoxy-3-bromo-5-hydroxymethylphenol (5), and (E)-4-(2-bromo-4,5-dihydroxyphenyl)but-3-en-2-one (6). Each compound was evaluated for free radical scavenging activity against DPPH (α,α-diphenyl-β-dipicrylhydrazyl) and ABTS [2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)diammonium salt] radicals. Most of them exhibited potent activities stronger than or comparable to the positive controls butylated hydroxytoluene (BHT) and ascorbic acid. The results from this study suggest that R. confervoides is an excellent source of natural antioxidants, and inclusion of these antioxidant-rich algal components would likely help prevent the oxidative deterioration of food.     

Allicin and allicin-derived garlic compounds increase breath acetone through allyl methyl sulfide: use in measuring allicin bioavailability

Progress in establishing systemic pharmacological effects for fresh, crushed garlic (Allium sativum L) in humans has been hindered by (1) the inability to measure allicin bioavailability, (2) lack of direct evidence that allicin has significant systemic activity at doses of garlic normally consumed, and (3) lack of a model for an acute effect. We have addressed these problems by quantifying the increases in breath acetone and breath allyl methyl sulfide (AMS). The area under the 48 h curve was measured in humans after consumption of standardized garlic preparations, allicin, and allicin-derived compounds, at the equivalent of 7 g of crushed garlic. It was shown that the allyl thiosulfinates (mainly allicin) are solely responsible for breath AMS and increased breath acetone. Diallyl trisulfide, diallyl disulfide, ajoene, and S-allylmercaptocysteine, at isomolar dithioallyl, showed the same quantitative effects as allicin. Consumption of AMS at isomolar allyl also gave the same effects as allicin, indicating that AMS is the main metabolite of allicin and is an active metabolite. In conclusion, allicin and allicin-derived compounds are rapidly metabolized to AMS, a compound which stimulates the production of acetone and which can be used to measure the bioavailability of allicin and, hence, the ability of garlic supplements to represent fresh garlic.     

Differential inhibition of human platelet aggregation by selected Allium thiosulfinates

Thiosulfinates (TSs) have been implicated as a principle source of the antiplatelet property of raw onion and garlic juice. The in vitro responses of human platelets to dosages of four TSs were measured using whole blood aggregometry and compared by regression analysis. Of the compounds evaluated, methyl methane-TS (MMTS), propyl propane-TS (PPTS), and 2-propenyl 2-propene-TS (allicin) are present in freshly cut Allium vegetables, whereas ethyl ethane-TS (EETS) has not been detected. All TSs were synthesized using a model reaction system. PPTS and allicin had the strongest antiplatelet activity at 0.4 mM, inhibiting aggregation by 90 and 89%, respectively. At the same concentration, EETS and MMTS were significantly weaker, inhibiting 74 and 26%, respectively. Combinations of TSs were not additive in their inhibition of aggregation, indicating that the antiplatelet potential of Allium extracts cannot be easily predicted by quantifying organosulfur components. EETS, PPTS, and allicin were significantly more potent platelet inhibitors than aspirin at nearly equivalent concentrations.     

Aging effect on the pigment composition and color of Vitis vinifera L. Cv. Tannat wines. Contribution of the main pigment families to wine color

Red wines made from Vitis vinifera L. cv. Tannat grapes are known to possess high contents of tannins and intense color, features that are responsible for the originality of these wines. This work aimed to study the evolution of the pigment composition and CIELAB color parameters as Tannat wines become older, as well as to establish the contribution to wine color of the main pigment families. Tannat wines produced in Uruguay from grapes of the same vineyard in six consecutive vintages (1998-2003) and Tannat grapes of the 2003 harvest were analyzed by means of HPLC-DAD-MS and UV-vis spectrometric techniques. The correlations between the different pigment families and the CIELAB parameters revealed the importance of the variations of the percentage, found in anthocyanins and flavanol-anthocyanin acetaldehyde-mediated condensation products (decrease) and pyranoanthocyanins and direct condensation products (increase), in the modification of the color from purple-red hues to more orange-red ones. The color suffered qualitative rather than quantitative changes, that is, the hue (h*ab) increased, whereas the chroma (C*ab) and lightness (L) did not show a defined trend with time.     

Gas-liquid chromatographic determination of resmethrin in corn, cornmeal, flour, and wheat.

A gas-liquid chromatographic (GLC) method was developed for the determination of residues of resmethrin ((5-benzyl-3-furyl)methyl cis-trans-(+/-)-2,2-dimethyl-3-(2-methylpropenyl)-cyclopropanecarboxylate) in corn, cornmeal, flour, and wheat. The commodity, fortified with resmethrin, was extracted by tumbling with pentane and transferred to acetonitrile, the fat was partitioned off, and the sample was chromatographed with 3% ethyl acetate in pentane on Florisil containing 0.5% water. The resmethrin residue was determined by GLC with a flame ionization detector. The results were compared with known standards that had undergone the same cleanup procedures. The method was sensitive to concentrations of resmethrin to 0.2 ppm, recoveries averaged 83%, and reproducibility was good.     

Biological and chemical stability of garlic-derived allicin

This study verifies the instability of garlic ( Allium sativum L.)-derived allyl 2-propenylthiosulfinate (allicin) in various aqueous and ethanolic solutions as well as in vegetable oil through chemical and biological analyses performed simultaneously. Crushed fresh garlic cloves generated antibacterial activity and chemically detectable allicin, a major antibacterial principle, and both declined on a daily basis in aqueous and ethanolic solutions at room temperature, showing biological and chemical half-lives of about 6 and 11 days, respectively. Allicin was more stable in 20% alcohol than in water, but surprisingly unstable in vegetable oil, with an activity half-life 0.8 h, as estimated from its antibacterial activity toward Escherichia coli, and a chemical half-life of 3.1 h, based on chromatographic quantification. In alcoholic and aqueous extracts, the biological half-life of allicin tended to be longer than the chemical one, suggesting the occurrence of bioactive compounds other than allicin in the extracts.     

Photodegradation of the acaricide abamectin: a kinetic study

The acaricide abamectin is a mixture of two colorless homologues in a molar ratio of at least 4:1 with the same structure of macrocyclic lactone. The kinetics of its degradation under direct (254 nm) and dye-sensitized (>400 nm) photoirradiation in methanol solution has been studied by UV-vis spectrophotometry, potentiometric detection of dissolved oxygen, stationary fluorescence, laser flash photolysis, and time-resolved detection of singlet molecular oxygen (O2((1)Delta(g))) phosphorescence. The results indicate that the degradation is very efficient under direct irradiation with UV light (254 nm), with a quantum yield of 0.23. On the contrary, under visible-light irradiation, using the natural pigment riboflavin or the synthetic dye rose bengal as sensitizers, the degradation is very inefficient and proceeds through a O2((1)Delta(g))-mediated mechanism, with a bimolecular rate constant for the overall O2((1)Delta(g)) quenching (the sum of physical and chemical quenching) of 5.5 x 10(5) M(-1) s(-1). This value is similar to those reported for the rate constants of the reactions of O2((1)Delta(g)) with isolated double bonds or conjugated dienes and points to similar processes in the case of abamectin.     

紫色土增施单质硫对大蒜生长发育和硫素营养的影响

对紫色土施用单质硫条件下大蒜生长发育及硫素营养吸收和代谢进行了研究。结果表明,大蒜株高、叶面积、经济产量(蒜头)和经济系数以中等供硫水平最高,而茎粗和生物产量则以高硫水平最大。大蒜能耐高浓度的硫素供应,在0～120kghm-2供硫情况下,其全硫(TS)、水溶性硫(SS)和无机硫(Io-S)含量均随供硫量的增加而上升,小分子水溶性含硫氨基酸含量(Ws-S)以低硫水平最高,而大分子蛋白质硫含量(Wis-S)以中等供硫水平时最高,与大蒜素含量的变化一致。大蒜素含量与不同硫组分比率的关系分析发现,大蒜素含量与Ws-S/TS呈极显著的正相关(r=0.752 ),与Io-S/SS呈显著的正相关(r=0.702 )。全氮含量与全硫含量变化趋势一致,全磷含量以低硫水平时最高,全钾含量以中等供硫水平时最高。     

Variation in gluten strength and yellow pigment in Ethiopian tetraploid wheat germplasm

Ten released varieties and one hundred and eleven tetraploid (2n = 4x = 28, AABB) wheat accessions collected from different major wheat producing regions, consisting of totally 2904 entries were characterized for content of yellow pigment, gluten strength, thousand kernel weights, grain yield, percent of yellow berry, glumes color, awn color, seed color, beak shape and spike density. The objectives were to assess variation with respect to regions of origin, species and altitudinal classes and to study the interrelationships of the qualitative traits used for the study. The accessions and/or released varieties showed significant regional variation for all the traits used in the study, but clinal variation among altitudinal classes and species were significant (P ≤ 0.01) in 6 (60%) and 9 (90%) of the studied traits, respectively. The accessions revealed consistent variation (P ≤ 0.001) within both regions and altitudinal classes for all the traits used in the study. The sedimentation volume was positively correlated with content of yellow pigment, percent of yellow berry, thousand kernel weights, glumes color, awn color, beak shape, seed color and grain yield. The contents of yellow pigment was positively correlated with awn color, beak shape and grain yield, but negatively correlated with seed color and spike density. Generally wide variation was found in the germplasm. Particularly variation was high for the content of the yellow pigment as well as the gluten strength, which provides opportunities to be utilized for genetic improvement.     

Biodegradation of beta-cyfluthrin by fungi

Five fungal species, namely, Trichoderma viride strain 5-2, T. viride strain 2211, Aspergillus niger, A. terricola, and Phanerochaete chrysoporium were screened for degradation study of beta-cyfluthrin. Each fungal species was allowed to grow in Czapek dox medium containing beta-cyfluthrin (5 mg/mL) as the major carbon source of the medium. The highest degradation of beta-cyfluthrin was observed by T. viride 5-2 (T(1/2) = 7.07 days), followed by T.viride 2211 (T(1/2) = 10.66 days). The degradation of beta-cyfluthrin followed first-order kinetics with a fast degradation rate during first 7 days of growth of the fungi. In the case of T. viride strain 5-2, five degradation products were isolated after 20 days of growth of the fungi, out of which three products were identified as alpha-cyano-4-fluorobenzyl-3- (2,2-dichlorovinyl)-2,2-dimethyl cyclopropane carboxylate, alpha-cyano-4-fluoro-3-phenoxy benzyl alcohol, and 3(2,2-dichlorovinyl)-2,2-dimethyl cyclopropanoic acid.     

Effect of nanogrinding on the pigment and bioactivity of Djulis ( Chenopodium formosanum Koidz.)

Betanin is an antioxidant pigment found in djulis, a grain native to Taiwan, and is a natural source food coloring, but the bright red color degrades rapidly if submitted to light, heat, or oxygen. The effects of nanogrinding on the stability of pigments and bioactive components are unknown. In this study, the color characteristics and bioactivity (antioxidant capacity and enzyme activity) of nanoparticle (NP) djulis was compared with those of intact granules (IG) and microparticles (MP). Results showed that the NP samples exhibited the highest betanin content (2.04 mg/g), which was almost twice that of IG. It was observed that nanogrinding resulted in higher pigment extraction efficiency. However, during storage (5-35 °C for 56 days), NP samples showed the most serious pigment degradation, and this color degradation, as expected, had the lowest activation energy. This was more evident when the storage temperature was high. Antioxidant capacities showed the same trends. MP and NP exhibited significantly higher activity of superoxide dismutaste-like activity, lactoperoxidase (LPO), and lysozyme than IG. Gel permeation chromatography confirmed the degradation of larger particles during nanogrinding, which might favor enzyme extraction and their activities. Statistical analysis revealed a close relationship between betanin and antioxidant capacity.     

Antioxidative compounds from the outer scales of onion

Antioxidative compounds were isolated from the methanol extract of dry outer scales of onion (Allium cepa L.). Nine phenolic compounds (1-9) were finally obtained by reversed-phase high-performance liquid chromatography, and their structures were elucidated by NMR and mass spectrometry analyses. They were the six known compounds, protocatechuic acid (1), 2-(3,4-dihydroxybenzoyl)-2,4,6-trihydroxy-3(2H)-benzofuranone (2), quercetin 4'-O-beta-D-glucopyranoside (3), quercetin (5), 4'-O-beta-d-glucopyranoside of quercetin dimer (7), and quercetin dimer (8), and three novel compounds, condensation products of quercetin with protocatechuic acid (4), adduct of quercetin with quercetin 4'-O-beta-D-glucopyranoside (6), and quercetin trimer (9). These phenolic compounds were tested for their antioxidant properties using autoxidation of methyl linoleate in bulk phase or free radical initiated peroxidation of soybean phosphatidylcholine in liposomes. The flavonoid compounds having o-dihydroxy substituent in the B-ring were shown to be effective antioxidants against nonenzymic lipid peroxidation.     

牡丹花红色素理化性质研究

目前牡丹主要是用于观赏,其综合加工技术没有突破。为了为牡丹花保鲜、护色和色素加工提供理论支持,该文对从牡丹红色品种洛阳红中提取的牡丹红色素进行理化性质研究。结果显示:牡丹红色素水溶性好,颜色随pH值变化而变化。pH值小于3时比较稳定,最大吸收波长为526.5 nm。在酸性条件下该色素对光、热有很好的稳定性;耐氧化性和还原性较差;Zn²⁺、Mg²⁺、Fe²⁺、K⁺、Cu²⁺、Ca²⁺离子对牡丹花红色素的稳定性影响不大,但Sn²⁺、Fe³⁺离子可使色素溶液变色,稳定性差。     

Spectrophotometric determination of yellow pigment content and evaluation of carotenoids by high-performance liquid chromatography in durum wheat grain

The so-called "yellow pigment" content of durum wheat has been used for a long time as an indicator of the color quality of durum wheat and pasta products. For decades the chemical nature of these pigments has been assigned to carotenoids, mainly to the xanthophyll lutein and its fatty acid esters. The chemical composition of the yellow pigments of eight German durum wheat cultivars was studied. Grains were milled on a laboratory mill. Pigment extraction of millstream fractions was performed according to the optimized ICC standard method 152 procedure, and the chemical composition of the extract was analyzed by isocratic reversed phase high-performance liquid chromatography. all-trans-Lutein ranged from 1.5 to 4 mg kg(-1), and zeaxanthin was found in traces. No lutein esters and carotenes were detected. Surprisingly, the fraction of carotenoids of the complete yellow pigment content amounted to only 30-50% of the yellow pigment quantities, so there are still compounds in durum wheat not yet identified that contribute considerably to the yellow color of the grain extracts. The isolation and chemical identification of those pigments are under investigation.