Anthraquinone production

This reaction is noteworthy in its use of the expensive cerium IV salt, which is recycled very efficiently in the anodic oxidation process thus reducing its contribution to the cost of the anthraquinone product. 

To remove the feedback regulation mechanism and to avoid product degradation various adsorbents have been used for the in situ separation of plant cell cultures as shown in Table 1. In situ removal with polymeric adsorbents stimulated anthraquinone production more than the adsorbent-free control in Cinchona ledgeriana cells [35]. It was found that nonionic polymeric resins such as Amberlite XAD-2 and XAD-4 without specific functional groups are suitable for the adsorption of plant metabolite [36]. The use of the natural polymeric resin XAD-4 for the recovery of indole alkaloids showed that this resin could concentrate the alkaloids ajmalicine by two orders of magnitude over solvent extraction [37] but the adsorption by this resin proved to be relatively nonspecific. A more specific selectivity would be beneficial because plant cells produce a large number of biosynthetically related products and the purification of a several chemically similar solutes mixture is difficult [16]. 

Kishi s synthesis of aklavinone (625) (Section 4.1.8.4) exploits the regiodirecting bias of a bromide substituent in dienophile (94) (which parallels that of the phenylthio group in 90) (Scheme 26). The initially formed cycloadduct underwent spontaneous elimination of HBr (neutralized by SrCOa) and oxidation (air, Pt 2NEt) to give the anthraquinone product (97) as the exclusive regioisomer. 

The electron-transfer mechanism (Eq. 34) also explains the various regioselec-tivities observed for different arenes as the direct result of the symmetry of the arene HOMOs involved [161]. Moreover, the solvent effect on the oxidation products (Eq. 32) is now explicable on the basis of MO considerations. Thus, the ion-radical pair is very short-lived in hexane and collapses at the 9,10-positions where the anthracene HOMO is centered. The 9,10-cycloadduct is subsequently further oxidized to the anthraquinone product. In the more polar dichloromethane, the ion-radical pair is better stabilized and its longer lifetime allows relaxation of the original HOMO ion-radical pair to the subjacent (HOMO-1) ion-radical pair which leads to cycloaddition on the terminal ring (Eq. 32) [161]. 

Several investigations reported the stimulation of anthraquinone production in suspension cultures of Cassia acutifolia Del. by salt stress. Pot culture experiments were conducted using NaCl concentrations to assess their impact on the growth and metabolic changes in this plant [317], Suspension cultures of Cassia acutifolia were also established by transferring callus... 

With a few exceptions, the characteristic problem of cultivation of plant explants in in vitro cultures is a low production of secondary metabolites by these cultures. One of the methods which can achieve an increase in the production of natural substances in in vitro cultures, is elicitation of cell cultures with biotic elicitors. For example, hairy root cultures of Cassia obtusifolia L. clones transformed with Agrobacterium rhizogenes strain 9402 were established to investigate anthraquinone production. It was found that changes of the elements in the culture medium and the addition of rare earth element Eu3+ can greatly influence the contents of free anthraquinones in the hairy root [320],... 

Chromic acid in hot glacial acetic acid oxidizes anthracene quantitatively to antlmaquinone in a very smooth reaction, but the method is too expensive for coxnmercial application in competition with synthetic anthraquinone made from cheap phthalic anhydride and benzene by means of the Friedel-Crafts reaction Prior to the development of the present methods of phthalic anhydride manufacture, the process was used extensively for anthraquinone production in Europe. The method has been recommended for anthracene analysis. 

Figure 13. Glyphosate effect on anthraquinone production and shikimate accumulation in G. mollugo cell cultures ( 84j. Cells were harvested 10 days after inoculation with 2 cm of packed cells into 25 mL medium containing glyphosate. Anthraquinone content of the cells was corrected for the amount present in the inoculum.

Although very low levels of alkaloids are produced by the Cinchona cell cultures, they are capable of producing considerable amounts of anth-raquinones, particuleu-ly after elicitation with fungal elicitors. The anth-raquinones are thought to act as phytoalexins in this plant genus (575). Anthraquinone production could be stimulated by adding polymeric adsorbents like Amberlite XAD-7 to the medium. A production rate of 20 mg/liter/day could be obtained in this way (576). 

The DNA photocleaving abiUties of these hybrids were much higher than that of the natural anthraquinone antibiotic, daimomycin (lanes a and b vs lane d in Fig. 8). These results demonstrate that artificial anthraquinone-carbohydrate hybrids are superior to this natural anthraquinone product as a DNA photocleaving agent. 

M.H. Zenk, H. El-Shagi and U. Schulte, Anthraquinone production by cell... 

Chitosan oligomer was also used as an elidtor to stimulate the accumulation of secondary metabolites as taxol from suspension cultures of Taxus cuspidate (Li and Tao 2009), anthraquinones in Rubia tinctorum L. (Vasconsuelo et al. 2004). Chitosan from crab shell with DD > 85% was supplemented into cell culture medium of R. tinctorum at a final concentration of 200 mg/L. Chitosan as an elidtor increased in anthraquinone production up to 110% compared to the control. 

A flow diagram of continuous naphthoquinone production with a high conversion of naphthalene and subsequent anthraquinone production is depicted in Figure 9.11. 

The main use of anthraquinone-1-sulfonic acid is in the production of 1-amino-anthraquinone. Production of 1-aminoanthraquinone by way of sulfonic acid is diminishing, because of the involved use of mercury. In its place, nitration of anthraquinone, followed by the reduction of 1-nitroanthraquinone, is becoming increasingly common, as is pressure ammonolysis. 

Zenk, M.H., H. El-Shagi, and U. Schulte Anthraquinone Production by Cell Suspension Cultures of Morinda citrifolia. Planta Med. Suppl. 1975, 79. 

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