A new HPLC-ELSD method to quantify indican in Polygonum tinctorium L. and to evaluate beta-glucosidase hydrolysis of indican for indigo production

A method to quantify the indigo precursor indican (indoxyl-beta-D-glucoside) in Polygonum tinctorium L. has been developed. Plant material was extracted in deionized water, and indican was identified and quantified using high performance liquid chromatography (HPLC) coupled to an evaporative light scattering detector (ELSD). Results confirmed that with this method it is possible to measure indican content in a short time, obtaining reliable and reproducible data. Using this method, leaf indican content was quantified every 15 days during the growing season (from May to October) in P. tinctorium crops grown in a field experiment in Central Italy. Results showed that indican increased along the growing season until flowering and was positively affected by photosynthetic active radiation (PAR). Indican is naturally hydrolyzed by native beta-glucosidase to indoxyl and glucose, the indoxyl yielding indigo. The activity of two enzymes, sweet almond beta-glucosidase and Novarom G preparation, were compared with P. tinctorium native beta-glucosidase to evaluate indigo production. Results showed that the ability to promote indigo formation increased as follows: almond beta-glucosidase 相似文献   

冻伤蓝变对广义虾脊兰属植物中4种吲哚基衍生物含量的影响

以6种广义虾脊兰属植物和2种树兰亚科植物为材料,利用液相色谱 串联三重四极杆质谱仪(LCMS QQQ)测定了冻伤处理前后花和叶片中靛苷、靛红、靛蓝和靛玉红4种吲哚基衍生物的含量,分析广义虾脊兰属植物吲哚基衍生物的生成及种属间含量的差异。结果显示：(1)4种吲哚基衍生物在所测定的6种广义虾脊兰属植物中均被检出,但在2种树兰亚科植物五唇兰和足茎毛兰中均未被发现。(2)在所测定的6种广义虾脊兰属植物花和叶片中,冻伤处理后的靛蓝、靛玉红和靛红含量均显著上升,而靛苷含量显著下降,同时花中的吲哚基衍生物含量均高于叶片。(3)6种广义虾脊兰属植物花和叶中吲哚基衍生物总含量以黄兰花最高,三褶虾脊兰叶最低。研究表明,冻伤处理引起靛苷向靛蓝的大量转化是导致冻伤后广义虾脊兰属植物组织中呈现出蓝色的主要原因,推测吲哚基衍生物可能也是一类与植物防御相关的化合物,在植物抵御逆境中扮演着重要的角色。     

Beta-glucosidase-catalyzed hydrolysis of indican from leaves of Polygonum tinctorium

In this article, a HPLC method to identify and quantify the dyes and the indigo precursors produced in Polygonum tinctorium is described. Using this technique, indican has been positively identified in extracts of P. tinctorium. Our work with two cultivars of P. tinctorium has confirmed that the quantity of indican is dependent on the cultivars, harvest period, and age of the leaves. Two enzymes, Novozym 188 (cellobiase) and Novarom G (beta-glucosidase), are compared on the basis of their activities to hydrolyze the indican at several pH values. We observed that Novarom G is more active than Novozym 188 whatever the pH and that optimum pH of both enzymes for indican hydrolysis is 3. Liberated indoxyl can be oxidized in alkaline media and transformed into indigo and indirubin.     

Formation of the indigo precursor indican in genetically engineered tobacco plants and cell cultures

The production of the blue dye indigo in plants has been assumed to be a possible route to the introduction of novel coloration into flowers or fibres. As the human cytochrome P450 mono-oxygenase 2A6 (CYP2A6) can form indigo in bacterial cultures, we investigated whether the expression of the corresponding cDNA in transgenic plants could lead to indigo formation. In a first attempt, we generated tobacco cell suspension cultures expressing the cDNA encoding human CYP2A6. Supplementation of the medium with indole led to the generation of indican (3-hydroxyindole-β- d -glucoside), a metabolite usually exclusively present in indigoferous dye plants. Hence, the recombinant CYP2A6 converted indole to the reactive metabolite 3-hydroxyindole (indoxyl), whereas rapid glucosylation is obviously conducted by ubiquitous plant glucosyl transferases (GTs). Interestingly, of nine additionally tested plant cell suspension cultures from various plant families, five were also capable of the formation of indican after indole supplementation, although this metabolism was more pronounced in transgenic tobacco cell suspension cultures expressing CYP2A6 cDNA. To evaluate whether indican or even indigo could be produced in whole plants, we generated transgenic tobacco plants harbouring active CYP2A6 together with an indole synthase (BX1) from maize. The genetically engineered tobacco plants accumulated indican, but did not develop a blue coloration. Although the de novo formation of indican in transgenic tobacco plants hampered indigo formation, it supports the contention that biosynthetic pathways can be efficiently mimicked by metabolic engineering.     

Mining and identification of a glucosidase family enzyme with high activity toward the plant extract indican

The present study described that the systematic mining and identification of potentially active β-glucosidase family enzymes toward indican, which extracted from the plant Polygonum tinctorium as one of precursors of production for indigo-blue. Some of the mined enzymes were previously identified as glycosyl hydrolases or putative enzymes with unknown properties. In addition, there were no reports on the hydrolytic activity toward indican. In order to confirm the activity, we analyzed the activity on indican or related substrates in selective medium and amplified four genes from mined strains using PCR, then cloned into E. coli. Using a related fluorescent substrate MUG, we verified successful cloning through checking the expression of genes and comparing characteristics with wild-type strains. Then, using recombinant enzymes and chemically synthesized pure indican or the plant extract, it was confirmed that indican was readily converted into indigo-blue. For the overexpression of an enzyme derived from Shinorhizobium meliloti, which was found to be the most active through comparative analyses, we subcloned the gene in pMAL-c2X vector and expressed it as a MBP fusion protein. The resulting enzyme was overexpressed (>35% of whole cell protein) and found mainly in soluble fraction. The purified enzyme was determined to be a monomer with calculated molecular mass of 52 kDa and showed a specific activity (0.8 unit/mg protein) on the plant extract including indican. These results demonstrated that the mined enzymes not only could be an alternative resource for indigo-blue production, but also might be useful in the production of indigo from the plant indican by a single process.     

Identification of an indigo precursor from leaves of Isatis tinctoria (Woad).

Indole is presumably a product of indole-3-glycerol phosphate catabolism in Isatis tinctoria. It is oxidized into indoxyl and stored in young leaves as indigo precursor. Further oxidation and dimerization of indoxyl produces indigoid pigments. In this work, we describe an HPLC method dedicated to the identification and quantification of indigoid pigments (indigo, indirubin, isoindigo and isoindirubin) and indigo precursors produced in I. tinctoria (Woad). This work, carried out with two cultivars of I. tinctoria, has confirmed that the quantity of indigo precursors is dependent on the species and the harvest period. In addition we have shown for the first time that young leaves of I. tinctoria, harvested in June contained a new indigo precursor in addition to isatan B (indoxyl-5-ketogluconate) and indican (indoxyl-beta-D-glucoside). We suggest the name "isatan C" for this new indigo precursor in I. tinctoria. Its chemical characteristics point to an dioxindole ester with PM of 395. We have shown that isatan C reacts with isatan B increasing the red pigment production.     

r{beta}-Glucosidase in the Indigo Plant: Intracellular Localization and Tissue Specific Expression in Leaves

rß-Glucosidase of indigo plant (Polygonum tinctorium)has a high substrate specificity for indican (indoxyl rß-D-gIu-coside).To examine the localization of this rß-glucosidase,we fractionated the cells of the leaves and analysed them im-munocytochemically.Immunoelectron micrographs with specific antibodies againstthe rßglucosidase clearly showed that the rß-glucosidasewas localized in the stroma of the chloroplasts in mesophyllcells, but not in the thylakoid membrane. Chloroplasts wereisolated from the crude ho-mogenate of the fresh leaves by Percolldensity gradient centrifugation and then subjected to suborganellarfrac-tionation. rßGlucosidase activity was specificallydetected in the stromal fraction, but not in the thylakoid membrane.This was also supported by the result of an immunoblot of thefractions with anti-rßglucosidase antibodies. Therß-gIu-cosidase was immunocytochemically localizedin the chloroplasts of mesophyll cells, but not in any chloroplastsin marginal cells of the vascular bundle or epidermal cells;ribulose 1,5-bisphosphate carboxylase (Rubisco), a typical stromalprotein, was observed in all chloroplasts in these cells. Theseresults suggest that rß-glucosidase is tissue specificin its expression in the leaves of the indigo plant. (Received April 14, 1997; Accepted July 10, 1997)     

The content of indigo precursors in Isatis tinctoria leaves--a comparative study of selected accessions and post-harvest treatments

We recently clarified the nature of indigo precursors in woad (Isatis tinctoria L.), by identifying the major indoxyl glycoside as isatan A (indoxyl-3-O-(6'-O-malonyl-beta-D-ribohexo-3-ulopyranoside)), and by correcting the structure of the related isatan B (indoxyl-3-O-beta-D-ribohexo-3-ulopyranoside). A quantitative densitometric assay for isatans A and B, and indican, was established and validated. HPTLC separation on silica gel was followed by densitometric analysis of indigoid pigments formed after treatment with dilute acid or base. The seasonal variation of indoxyl glycosides in woad leaves was investigated with first-year plants (rosette stage) of five defined I. tinctoria L. and one I. indigotica L. accessions. Isatan A content reached up to 7.6% of dry weight in I. tinctoria, and up to 21.8% in I. indigotica. The influence of various post-harvest treatments was studied. High concentrations of isatans A and B were found in freeze-dried leaf samples, whereas the content of indican was lowest. Conventional drying at ambient or 40 degrees C led to complete disappearance of isatans A and B. The concentration of indican, in contrast, was 3- to 5-fold higher in leaf samples submitted to drying at ambient and 40 degrees C, respectively.     

On the preparation of indoxyl red from indican and some new characteristics

An indole compound with a strong purple–red color was produced by boiling a solution of indican under acidic conditions and purified by chromatographies on DEAE-650S Toyopearl TSK-gel and silica-gel columns. The purple-red compound purified was identified as indoxyl red, on the basis of FAB Mass, ¹³C NMR, ¹H NMR, UV–visible spectra, and IR spectra. Although indoxyl red was first synthesized by Seidel⁹ 70 years ago, very little information has been available on its characteristics. We repot here that the compound was purple-red colored at acidic pH and green at pH 13, and showed antiproliferative and cytotoxic activities to the mouse B cell lymphoma cell line NSF202.     

Quantitative analysis of indigo and indigo precursors in leaves of Isatis spp. and Polygonum tinctorium

Analysis of extracts from two woad species (Isatis tinctoria and Isatis indigotica) and Polygonum tinctorium revealed that only one indigo precursor (indican) was present in Polygonum, but two precursors were found in Isatis spp. This was done using high performance liquid chromatography (HPLC), coupled to an evaporative light scattering detector (ELSD). In Isatis spp., the indigo precursors indican and a fraction representing isatan B were identified. The proportion of indican and isatan B was different between the two Isatis spp. tested. For the first time, it was possible to quantify the precursors in woad plant species, and the results were found to be in good agreement with those made from total indigo quantification using two different spectrophotometric methods or a derivatization technique.     

The elusive indigo precursors in woad (Isatis tinctoria L.)--identification of the major indigo precursor, isatan A, and a structure revision of isatan B

A metabolite-profiling study of shock-frozen leaves of Isatis tinctoria L., an old indigo dye plant and medicinal herb, revealed a complex pattern of indigo-forming compounds with higher polarities than the known indigo precursors isatan B and indican. These highly unstable compounds underwent rapid post-harvest transformation and were not detected in air-dried leaves. The major indigo precursor, named isatan A (4), was isolated by rapid normal-phase and gel chromatography, along with isatan B (3). A full spectral data set of 3 showed that the previous structure assignment as 'indoxyl-5-ketogluconate' has to be revised to 1H-indol-3-yl beta-D-ribohex-3-ulopyranoside. Isatan A (4) was identified as 1H-indol-3-yl 6'-O-(carboxyacetyl)-beta-D-ribohex-3'-ulopyranoside. In aqueous solution, glycosides 3 and 4 occur as hydrates and undergo rapid hydrolysis under very mild acidic or basic conditions.     

Cloning of an enzyme that synthesizes a key nucleotide-sugar precursor of hemicellulose biosynthesis from soybean: UDP-glucose dehydrogenase.

Hemicellulose is a major component of primary plant cell walls. Many of the glycosyl residues found in hemicellulose are derived from the sugar precursor UDP-glucuronic acid, which can be converted into UDP-arabinose, UDP-apiose, UDP-galacturonic acid, and UDP-xylose. The enzyme controlling the biosynthesis of UDP-glucuronic acid, UDP-glucose dehydrogenase (EC 1.1.1.22), was cloned from soybean (Glycine max [L.] Merr.) by an antibody screening procedure. This enzyme is surprisingly homologous to the bovine sequence, which is the only other eukaryotic UDP-glucose dehydrogenase sequence known. The characteristic motifs of the enzyme, the catalytic center, a NAD-binding site, and two proline residues for main chain bends, are conserved within the prokaryotic and eukaryotic sequences. The soybean full-length cDNA clone encodes a protein of 480 amino acids with a predicted size of 52.9 kD. The enzyme is highly expressed in young roots, but lower expression levels were observed in expanding tissues of the epicotyl and in young leaves. The expression pattern of the enzyme in different developmental stages strengthens the argument that UDP-glucose dehydrogenase is a key regulator for the availability of hemicellulose precursors.     

Indoxyl-UDPG-glucosyltransferase from Baphicacanthus cusia

The enzyme catalyzing the transfer of glucose from uridine diphosphate glucose to indoxyl yielding the indoxyl glucoside indican was isolated from Baphicacanthus cusia Bremek (Acanthaceae). The indoxyl-uridine diphosphate glucose (UDPG)-glucosyltransferase was purified to homogeneity in six chromatographic steps. The decisive step for the recovery of a homogeneous enzyme was the application of immobilized metal affinity chromatography yielding an 863-fold purified enzyme. From a total of 60 substances tested, in addition to the natural substrate 3-OH-indole (indoxyl), only 4-OH-, 5-OH-, 6-OH-, and 7-OH-indole were accepted as substrates by the glucosyltransferase. However, the latter substrates were metabolized to varying extent. The optimum pH of the enzyme was 8.5, the optimum temperature was 30 degrees C and the isoelectric point was pH 6.5. The M(r) of the enzyme was determined to be 60 +/- 2 x 10(3). Indoxyl as substrate yielded a K(m) of 1.2 mM, while a K(m) of 1.7 mM was found for UDPG.     

A tetrazolium method for non-specific alkaline phosphatase

Summary A technique for the histochemical demonstration of non-specific alkaline phosphatase was developed using a medium containing indoxyl phosphate and a tetrazolium salt, Nitro B.T. The tetrazolium salt was reduced to diformazan by the hydrogen ions released by the formation of either indigo or indigo white by reaction of the enzyme on the indoxyl phosphate.The localization in the organs investigated was similar to that obtained by the standard azo dye and lead techniques.     

How Drugs Interact with Transporters: SGLT1 as a Model

Drugs are transported by cotransporters with widely different turnover rates. We have examined the underlying mechanism using, as a model system, glucose and indican (indoxyl-beta-D: -glucopyranoside) transport by human Na(+)/glucose cotransporter (hSGLT1). Indican is transported by hSGLT1 at 10% of the rate for glucose but with a fivefold higher apparent affinity. We expressed wild-type hSGLT1 and mutant G507C in Xenopus oocytes and used electrical and optical methods to measure the kinetics of glucose (using nonmetabolized glucose analogue alpha-methyl-D: -glucopyranoside, alphaMDG) and indican transport, alone and together. Indican behaved as a competitive inhibitor of alphaMDG transport. To examine protein conformations, we recorded SGLT1 capacitive currents (charge movements) and fluorescence changes in response to step jumps in membrane voltage, in the presence and absence of indican and/or alphaMDG. In the absence of sugar, voltage jumps elicited capacitive SGLT currents that decayed to steady state with time constants (tau) of 3-20 ms. These transient currents were abolished in saturating alphaMDG but only slightly reduced (10%) in saturating indican. SGLT1 G507C rhodamine fluorescence intensity increased with depolarizing and decreased with hyperpolarizing voltages. Maximal fluorescence increased approximately 150% in saturating indican but decreased approximately 50% in saturating alphaMDG. Modeling indicated that the rate-limiting step for indican transport is sugar translocation, whereas for alphaMDG it is dissociation of Na(+) from the internal binding sites. The inhibitory effects of indican on alphaMDG transport are due to its higher affinity and a 100-fold lower translocation rate. Our results indicate that competition between substrates and drugs should be taken into consideration when targeting transporters as drug delivery systems.     

Isolation and characterization of multiple forms of maize leaf sucrose-phosphate synthase

Sucrose-phosphate synthase SPS; (EC 2.4.1.14) from maize (Zea mays L. cv. Pioneer 3184) leaves was partially purified and kinetically characterized. Maize SPS was activated by glucose-6-phosphate (G-6-P) due to an increase in Vmax and a decrease in the Km for UDP-glucose. The UDP-glucose saturation profile was biphasic; thus two Km values for UDP-glucose were calculated. Inhibition by inorganic phosphate was observed only in the presence of G-6-P. Chromatography of partially purified maize leaf extracts on hydroxyapatite resolved two forms of SPS activity, which differed in their affinity for UDP-glucose and in the degree of activation by G-6-P. SPS was partially purified from maize leaves that were harvested in the light and in the dark. The light enzyme had a higher specific activity than the enzyme isolated from dark harvested leaves, and this difference persisted during enzyme purification. The apparent molecular weight (Stokes radius) of the light enzyme was 547 kDa, which was greater than that of the dark enzyme (457 kDa). Light and dark SPS differed in their affinities for UDP-glucose in the absence G-6-P. Both the light and the dark SPS were activated by G-6-P; the Km for UDP-glucose of the light enzyme was lowered by G-6-P, while the Km for UDP-glucose for the dark enzyme remained unchanged. These results suggest that light activation involves a conformational change that results in differences in maximum velocity, substrate affinities and regulation by metabolites. Chromatography of either the light or dark SPS on hydroxyapatite yielded two peaks of enzyme activity, suggesting that the occurrence of the two activity peaks was not due to an interconversion of the light and dark forms.     

Process balance and product quality in the production of natural indigo from Polygonum tinctorium Ait. applying low-technology methods.

Indigo is the most important blue component in the class of natural dyes for cellulose and protein fibres. In the moderate European climate Polygonum tinctorium Ait. could be an interesting source for natural indigo (Vat blue 1). Following a cultivation of the plant material a simple procedure for the extraction of the indigo precursor indican was investigated with regard to crop and quality of dye obtained. The dependence of the crop on the storage conditions of the harvested plant material was investigated. The results quantify the distinct sensitivity of the fresh material to the time of storage before extraction with regard to the amount of natural indigo obtained, the photometrically determined indigo content in the product and the shade and colour depth observed in standardised dyeing experiments. A basic set of data is presented, which describes the process in terms of consumption of energy, water and chemicals and organic waste released from the extraction step.     

Oligomerization,Membrane Association,and in Vivo Phosphorylation of Sugarcane UDP-glucose Pyrophosphorylase

Sugarcane is a monocot plant that accumulates sucrose to levels of up to 50% of dry weight in the stalk. The mechanisms that are involved in sucrose accumulation in sugarcane are not well understood, and little is known with regard to factors that control the extent of sucrose storage in the stalks. UDP-glucose pyrophosphorylase (UGPase; EC 2.7.7.9) is an enzyme that produces UDP-glucose, a key precursor for sucrose metabolism and cell wall biosynthesis. The objective of this work was to gain insights into the ScUGPase-1 expression pattern and regulatory mechanisms that control protein activity. ScUGPase-1 expression was negatively correlated with the sucrose content in the internodes during development, and only slight differences in the expression patterns were observed between two cultivars that differ in sucrose content. The intracellular localization of ScUGPase-1 indicated partial membrane association of this soluble protein in both the leaves and internodes. Using a phospho-specific antibody, we observed that ScUGPase-1 was phosphorylated in vivo at the Ser-419 site in the soluble and membrane fractions from the leaves but not from the internodes. The purified recombinant enzyme was kinetically characterized in the direction of UDP-glucose formation, and the enzyme activity was affected by redox modification. Preincubation with H₂O₂ strongly inhibited this activity, which could be reversed by DTT. Small angle x-ray scattering analysis indicated that the dimer interface is located at the C terminus and provided the first structural model of the dimer of sugarcane UGPase in solution.     

The measurement of toluene dioxygenase activity in biofilm culture of Pseudomonas putida F1

Toluene dioxygenase (Tod) enzyme activity can be measured by the conversion of indole to indigo. Indigo is measured spectrophotometrically at 600 nm. However, this method is inadequate to measure the whole-cell enzyme activity when interference by suspended biomass is present. Indoxyl is a highly fluorescent intermediate in the conversion of indole to indigo by Tod. A fluorescence-based assay was developed and applied to monitor Tod activity in whole cells of Pseudomonas putida F1 biofilm from a continuously operated biofilter. Suspended growth studies with pure cultures indicated that indoxyl, as measured by fluorescence, correlated with indigo production (r(2)=0.89) as measured by spectrophotometry. Whole-cell enzyme activity was followed during growth on a minimal medium containing toluene. The maximum normalized whole cell enzyme activity of 19+/-1.5x10(-4) mg indigo (mg protein)(-1) min(-1) was reached during early stationary phase. P. putida F1 cells from a biofilm grown on vapor phase toluene had a normalized whole-cell enzyme activity of 5.0+/-0.2x10(-4) mg indigo (mg protein)(-1) min(-1). The half-life of whole-cell enzyme activity was estimated to be between 5.5 and 8 h in both suspended and biofilm growth conditions.     

Seasonal variation of indigo precursors in Isatis tinctoria L. and Polygonum tinctorium Ait. as affected by water deficit

In order to identify new crop suitable for indigo production in Italy, seasonal variation in productivity of indigo precursors was studied in woad (Isatis tinctoria L., Family Cruciferae) and in dyer's knotweed (Polygonum tinctorium Ait., Family Polygonaceae), grown in central Italy under temperate climate. Indigo precursors, indoxyl-3-ketogluconate (isatan B) and indoxyl-β-d-glucoside (indican), were measured in leaves by HPLC analysis under well watered versus rain fed field conditions, and the amount of indigo derived by stoichiometric calculations.Woad showed lower indigo potential than dyer's knotweed, evaluated as either amount of indigo either per leaf weight or per plant. However, in water stress conditions, woad appeared to be drought tolerant as opposed to dyer's knotweed revealed very sensitive. In fact, in dyer's knotweed leaf yield was over 50% reduced in water stress field conditions, characterizing central and southern Italy during July and August, as compared to some 30% in woad. Dyer's knotweed appears to be more productive, providing water is supplied appropriately, thus making proper irrigation plans necessary to achieve sustainable high yields.