Pseudopurpurin

Alizarin Purpurin Xanthopurpurin Munjistin Pseudopurpurin Other compounds... 

LC ESI MS allows also the identification of other anthraquinones in madder preparations. Based on structural information obtained by NI mass spectra and specific retention times (signals corresponding to quasi-molecular ions [M—H] and fragment ions [M—C02—H] ), pseudopurpurin (peaks at m/z 299.1 and 255.3) and munjistin (at m/z 283.1 and 239.3) are found in the natural material. Alizarin glycoside is identified by deprotonated quasi-molecular ions at m/z 401.1 and ions formed by the loss of glucose at m/z 239.1. Similar ions are found to be characteristic of lucidin... 

Rubia tinctorum roots Alizarin, alizarin glucoside, purpurin, pseudopurpurin, lucidin glucoside, lucidin primeveroside, munjistin, ruberythric acid EtOH/H20, H2S04 A ACN B ammonium formate/FA with EDTA 250, 254 nm/ESI (+) Post column modification of eluent (5% NH3 in H20) for NI mode... 

Rubia tinctorum roots Alizarin, munjistin, purpurin, pseudopurpurin, lucidin, nordamnacanthal (as glycosides or aglycones) MeOH/H20, TFA, HCI, H20 (enzymatic hydrolysis) ACN/AcONH4 254 nm/ESI (+) Hydrolysis optimization, characterization of root components... 

Fig. 2.147. UV (254) trace of a crude extract of Rubia tinctorum roots and mass spectra (single MS) of the chromatographic peaks for individual anthraquinones lucidin primeveroside (1), ruberythic acid (2), pseudopurpurin (5) and munjistin (6). Mass spectra (a-b) were obtained with NI-ESI with post-column addition of ammonia. Reprinted with permission from G. C. H. Derksen et al. [320].

Rubia chinensis Regel Maack R. cordifolia Thunb. R. cordifolia L. f. pratensis (Maxim.) Kitag. R. mungista Roxb. R. sylvatica (Maxim.) Nakai Qian Cao (Madder) (root) Rubierythrinic acid, alizarin, purpurin, pseudopurpurin, munjistin.3349 Hemostatic, shorten the blood clotting time, antibacterial, antitussive, stimulate uterine contractions. 

R. cordifolia L., R. akane, various Galium spp., Relbunium spp., Morinda spp., Oldenlandia spp., Coprosma spp., or Ven-tilago spp. (Rhamnaceae) ). Any changes in the composition of the dyes during its extraction from the dyed material, e.g. the transition from pseudopurpurin to purpurin, can be prevented by suitable preparation of the sample before TLC. 

XXII Pseudopurpurin 75420 1,2,4-Trihydroxyanthra-quinone-3-carboxylic acid... 

The dried root was also found to contain purpuroxanthin (II) formed by separation of CO2. from munjistin (VII). Pseudopurpurin (XXIII) is probably decarboxylated with formation of purpurin (XXI) when the madder root is dried. The dried madder root also contains the following hydroxyanthraquinone dyes in small amounts nordamna-canthal (VI), quinizarin (IX), 1,4-dihydroxy-2-hydroxymethylanthra-quinone (XI), quinizarin-2-carboxylic acid (XII), anthragallol (XVIII), and anthragallol-3-methyl ether (XX) (32, 34, 39). 

Constituents The roots of Wild madder contain galiosin, pseu-dopurpurin (XXII), purpurin (formed in some cases from pseudopurpurin by decarboxylation), and a small amount of alizarin (I) (See tableH). 

Constituents (See also table II) The roots contain alizarin (I), pseudopurpurin (XXII), purpurin (XXI), purpuroxanthin (II) and mun-jistin (VII) (34). Nordamnacanthal (VI), physcion (XV), and 1,4-dihy-droxy-6-methylanthraquinone (XIII) have also been identified (40). 

Constituents (See also tableIIJ The roots contain a glycoside of pseudopurpurin ()b(II) (43-45) that is relatively stable to hydrolysis with dilute mineral acids (46). 

Constituents (See also table II) Relbun roots contain galiosin as the pricipal dye, but pseudopurpurin (XXII) and purpurin (which may have been formed from pseudopurpurin by decarboxylation) may also be present (48). Alizarin has not been found in relbun roots (49). 

In the extraction of powdered madder roots with 10% sulfuric acid, followed by shaking with ethyl acetate, we see that the ethyl acetate contains only a very small amount of pseudopurpurin or not at all. However, when we investigate madder dyeings on old carpets by the same method, the thin-layer chromatogram often shows that pseudopurpurin is present in roughly the same amount as purpurin. What is the explanation for this ... 

In a dyeing, pseudopurpurin is present, for example, as Al-Ca lake. When boiled once with 10% sulfuric acid, this lake is split, and the free pseudopurpurin can immediately be shaken out with ethyl acetate before it is converted into purpurin by decarboxylation. 

In the madder root, however, the pseudopurpurin is present in the form of the relatively hydrolysis-stable glycoside galiosin. In this case., it is necessary to heat for 20-30 minutes with dilute acids before all dyes can be shaken out with ethyl acetate. In this process, the pseudopurpurin is completely decarboxylated. 

With this method, we have found that the sample of "Rose madder" contains only traces of purpurin besides of pseudopurpurin. The method is also useful for investigating madder types that contain only small amounts of purpurin (formed probably from pseudopurpurin) as well as pseudopurpurin, but no alizarin. Examples of these madder types are the South American relbun roots such as Relbunium hypocarpium (L.) HEMSL. and R. ciliatum (L.) HEMSL. and the Japanese madder roots of Rubia akane. 

This improved method of extraction is also useful for preparing reference solutions of dyer s plants for TLC comparisons. In this case, however, the extraction time must be lengthened to about 5 minutes. Despite this, however, the pseudopurpurin is mostly retained, as can be confirmed by thin-layer chromatographic comparison. 

Rubia tinctorum alizarin and purpurin can be clearly identified by the marked spots. Pseudopurpurin has been converted into purpurin by decarboxylation, because the old extraction method (boiling with 10% sulfuric acid, followed by shaking with ethyl acetate) has been used to isolate the dyes from the madder roots. 

Figure 1. TLC of dyes of various madder types. 1, madder (Rubia tinc-torum L.) 2, wild madder (R. peregrina L.) 3, Indian madder (R. cor-difolia L.)i 4, Japanese madder (R. akane) 5, relbun root (Relbunium hypocarpium (L.) HEMSL.) 6, lady s bedstraw (Galium verum L.) 7, alizarin 8, purpurin + pseudopurpurin (lower spot) 9, munjistin.

Figure 2. TLC of dyes of some other dye plant similar to the madder types 1, suranji (Morinda citrifolia L.) 2, mang-kouda (Morinda umbel-lata L.) 3, chay root (Oldenlandia umbellata L.) 4, coprosma root (Coprosma lucida J.R. G. Forst) 5, pitti (Ventilago mad(e)raspatana GARTN.) 6, morindon 7, emodin 8, alizarin 9, purpurin + pseudopurpurin (lower spot).

Rubia peregrina As the new, improved extraction method was used here, the pseudopurpurin spot is most prominent, and purpurin can also be clearly identified. Alizarin is only present in traces. The red spot may be rubiadin (III), until now not mentioned in the literature as a dye in Rubia peregrina. 

Rubia cordifolia In this case, too, the new extraction method was used. The pronouced spot is that of alizarin, and the second is that of pseudopurpurin. The red spot of (probably) rubiadin in contrast to Rubia peregrina cannot be found. 

U Rubia akane Extraction by the old method, but only for two minutes.The relatively stable pseudopurpurin glycoside has not been hydrolyzed by this treatment. 

Relbunium hypocarpium New extraction method. Contains almost exclusively pseudopurpurin and only a small amount of purpurin. 

Galium verum New extraction method. Pseudopurpurin is the main component, but purpurin, and in contrast to Rubia peregrina, alizarin can also be clearly identified. The red spot is, as in the case of Rubia peregrina, probably rubiadin. 

Figure 3. Comparison of the old and the new (improved) extraction methods for madder dyeings and madder pigments (see page 202) by TLC. 1, and 2, extractions of a sample of the artist s pigment Rose Madder Genuine 1, extraction by the new method 2, extraction by the old method 3, pseudopurpurin (lower spot) 4, purpurin 5, alizarin.

Extraction of the "Rose Madder Genuine" sample with a mixture of the same amounts by volume of 10% sulfuric acid and toluene, one minute in the simmering water bath (new extraction method). The chromatogram shows clearly that the sample contains almost exclusively pseudopurpurin, besides traces of purpurin and alizarin, and that any degradation by decarboxylation and conversion into purpurin is, at most, minimum. 

Extraction of the same sample by the old method (see page 201), In this case, the thin-layer chromatogram shows purpurin as the main component thus most of the pseudopurpurin has been destroyed. 

Pseudopurpurin, made from a synthetic pseudopurpurin lake by extraction with the new method. In contrast to the sample of "Rose Madder Genuine" (made from madder roots) besides of the principal dye only traces of purpurin have been found, but not alizarin. Therefore is is possible to distinguish natural and synthetic pseudopurpurin lakes by this method. 

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