Plant compounds, anthraquinon

A variety of plant substances with planar, polycyclic, aromatic structures can intercalate with DNA, examples being the quinoline alkaloid camptothecin and the furanocoumarin phenolic psoralen (Table 12.1). A variety of plant-derived anthraquinones and naphthoquinones bind to DNA and it is notable that the structurally related anthraquinones mitox-antrone and adriamycin are clinically employed as anticancer drugs (Table 12.1). DNA-binding compounds that interfere with DNA repair, DNA replication and gene expression are cytotoxic and have potential as anticancer agents (see Chapter 9). 

Anthraquinone dyes are derived from several key compounds, ie, dye intermediates. Production of these dye intermediates often requires sophisticated production processes and a large amount of investment in plant constmction. The competitiveness of final products, dyestuffs, depends on that of the intermediates, ie, quaUty, cost, and availabiUty. 

In the world of red colourants, anthraquinones, which are obtained from plants or animals, are the largest group. They can be separated by RPLC due to diverse polarity caused by the presence of various polar groups in their structure. However, forms of identified compounds depend mostly on extraction and hydrolysis conditions. 

Stretford A process for removing hydrogen sulfide and organic sulfur compounds from coal gas and general refinery streams by air oxidation to elementary sulfur, using a cyclic process involving an aqueous solution of a vanadium catalyst and anthraquinone disulfonic acid. Developed in the late 1950s by the North West Gas Board (later British Gas) and the Clayton Aniline Company, in Stretford, near Manchester. It is the principle process used today, with over 150 plants licensed in Western countries and at least 100 in China. 

Unripe fruits of many plants contain compounds such as quinines that impart an aversive taste and discourage fruit eaters from consuming them before they are ripe and their seeds are mature and ready for dispersal. Unripe fruit of some Rhamnus species contain emodin, an anthraquinone that deters birds and mammals from feeding. Anthraquinone reduced red-winged blackbird feeding on rice by 84%, and 71% in boat-tailed grackles (Avery etal, 1997). 

Naphthaquinones are rare. Among the naphthaquinones juglone (1.64) is relatively common. It is found in walnuts. Anthraquinone is the most widely distributed of the quinones in higher plants and fungi. There are numerous compounds. The anthtraquinone emodin (1.65) occurs as a rhamnoside in rhubarb roots. 

The simplest quinones are o- and p-benzoquinone [(3) and (4) respectively]. This quinonoid structural feature is widespread in naturally occurring compounds isolated from moulds, fungi, lichens, plants and insects,52 which include not only substituted benzoquinones but also substituted polycyclic quinones [i.e. the substituted analogues of, for example, 1,2-naphthoquinone (5), 9,10-anthraquinone (6), and 9,10-phenanthraquinone (7)]. 

This study evaluated the impurity profile of untreated water from a textile plant in Portugal [35]. The organic material was concentrated by extraction from 11 of water into dichloromethane and HPLC-NMR and HPLC-MS experiments were carried out using a reverse-phase separation with an acetonitrile/ D2O gradient elution with H NMR spectroscopic observation at 600 MHz. For the HPLC-NMR studies, the samples were further fractionated into two pools according to their HPLC retention times. The HPLC-NMR studies were carried out in the stop-flow mode and the combination of NMR and MS results yielded the identification or tentative identification of 14 compounds, comprising mainly surfactants, anthraquinone dyes and nonylphenol-related molecules. 

The fiber is first treated with metal salts (mordanted). Highly adhesive, basic metal compounds are formed on the fiber. These compounds are capable of producing insoluble colored complexes (lakes) with certain azo and anthraquinone derivatives. Alizarin is the best-known anthraquinone derivative for this process (see Section 2.3). It used to be isolated from the root of the madder plant but has now been replaced by the synthetic product. Suitable azo dyes contain, e.g., hydroxyl or carboxyl groups in the position ortho to the azo group on one or both of the aromatic nuclei. The shade of the dyeing depends on the type of metallic mordant used. Alizarin with aluminum or calcium salts produces the well-known Turkey red. 

Additional noteworthy applications of CEC include natural products such as the plant flavonoids hesperetin and hesperidin [160], anthraquinones extracted from rhubarb and from Chinese medicine [161], and heterocyclic compounds present in oils of bergamot, mandarin, and sweet orange [162], The CEC analysis of retinyl esters has been investigated by Roed et al. in nonaqueous mode for the separation of liver extracts of arctic seal [163]. Carotenoid isomers were also separated on C30 stationary phases by nonaqueous CEC [164]. It was found that CEC offered increased resolution compared to HPLC, and in CEC... 

Remarkably, the same compound can be produced in different ways by different organisms. The best known example is probably the polyketide anthraquinone, chrysophanol 9, which occurs in both eukaryotes (higher plants, lichens, fungi and insects) and prokaryotes, but is produced through different folding modes of polyketide chains.10 Similarly, it has also been demonstrated that the biosynthesis of gibberellins involves different metabolic sequences in fungi and plants.11... 

Aromatic natural products of polyketide origin are less prevalent in plants compared with microorganisms. The majority of the plant constituents that contain aromatic stmctures are known to arise from the shikimate pathway (see below). Unlike those derived from the shikimate pathway, aromatic products of the polyketide pathway invariably contain a meta oxygenation pattern because of their origin from the cyclization of polyketides. Phenolic compounds such as chrysophanol-anthrone (Bl), and emodin-anthrone (B2), and the anthraquinones, aloe-emodin (B3) and emodin (B4) (Fig. 2), are products of the polyketide pathway and are found to occur in some plants of the genera Cassia (Leguminosae) (21), Rhamnus (Rhamnaceae) (22), and Aloe (Liliaceae) (23). The dimer of emodin-anthrone (B2), namely hypericin, (B5) is a constituent of the antidepressant herbal supplement, St. John s wort (Hypericumperforatum, Hy-pericaceae) (24). 

Aloe is a medicinal plant that has been used since ancient times by cultures in many countries and continents for many of the same applications. Africa is blessed with a wide variety of Aloe spp. each used by the indigenous cultures. Fleshy leaves are the source of two of the main products, gel and latex, with both products showing distinct differences in their chemical composition. Chemical composition of gel consists mainly of water with carbohydrate polymers and a range of other organic and inorganic components. In contrast, the chemical composition of the latex includes many phenolic compounds such as anthraquinones and chromones. The objective of this paper is to review the the botany, chemistiy and pharmacological properties of Aloes from Africa. 

---