Quinones plant sources

Covalent quinoproteins possess protein-derived cofactors derived from aromatic amino acid residues. These enzymes contain a posttranslationally modified tyrosine or tryptophan residue into which one or two oxygens has been incorporated (Figure 3). In some cases, the quinolated amino acid residue is also covalently cross-linked to another amino acid residue on the polypeptide. Tyrosine-derived quinone cofactors occur in oxidases from bacterial, mammalian, and plant sources. Tryptophan-derived quinone cofactors have been found thus far in bacterial dehydrogenases. 

The carbazole-l,4-quinones represent an important family of carbazole alkaloids (105,106). Except for clausenaquinone A (112), all carbazole-l,4-quinones isolated from natural sources have a 3-methylcarbazole-l,4-quinone skeleton. The plants of the genus Murray a (Rutaceae) are the major natural source of carbazole-l,4-quinone alkaloids. In 1983, Furukawa et al. reported the first isolation of a carbazole-1, 4-quinone, murrayaquinone A (107), from the root bark of M. euchrestifolia collected in Taiwan (28,29). In subsequent years, the same group reported the isolation of various carbazole-1,4-quinones from the root or stem bark of the same plant murrayaquinone B (108) (28,29), murrayaquinone C (109) (28,29), murrayaquinone D (110) (29), and murrayaquinone E (111) (70) (Scheme 2.21). 

Tanshen (Salvia miltiorrhiza Bung), a medicinal plant, has been used in traditional Chinese medicine for its tranquilizing, sedative, circulation-promoting and bacteriocidal effects. [73], It has proven to be a rich source of abietane o-quinone diterpenoids. Miltirone (197) is a tricyclic diterpenoid quinone which has been isolated from the roots of salvia miltiorrhiza Bung. The isolation of miltirone constitutes a new addition to naturally occurring quinines related to tanshinones [74,75] isolated from the same source. 

Mushrooms and various fungi and lichens are rich in enol metabolites and many exhibit significant bioactivities , such as usnic acid (14) which serves as a regulator for plant growth and shows antitumor and antibiotic activities " . The widely distributed quinone polyporic acid (15a, PPA) from the Purple-Dye Polypore mushroom (Hapalopilus nidu-lans) and other sources is a weak inhibitor (IC50 = 0.1 to >1.5 mM " ) of dihydroorotate... 

Quinones—some related to more complicated aromatic systems (Chap. 30)— have been isolated from biological sources (molds, fungi, higher plants). In many cases they seem to take part in oxidation-reduction cycles essential to the living organism. 

Particulates are another source of respiratory irritation when inhaled. In urban environments, diesel exhaust particles and fly ash residue from power plant oil combustion are the main contributors of respirable particulates of less than 10 pm diameter (PM 10). These contain mixtures of lipo-philes and hydrophiles including various metals, acid salts, aliphatic hydrocarbons, PAHs, quinones, nitroaromatic hydrocarbons, andaldehydes. 151 Diesel combustion particulates contain large surface areas that can adsorb large quantities of organic compounds and deliver these to respiratory tract tissue. Other inhaled particulates can adhere to lung surfaces and adsorb and bond other vapors that are inhaled, thereby increasing their toxicities. PM2.5 particulates (those with diameters of less than 2.5 pm) that reach the lower respiratory tract as far as the alveoli are more toxic than PM 10 particulates of the same composition. 16 ... 

Fig. 2. (A) K-band ESP-EPR spectra of the CPI complex (top) and Rb sphaeroides R26 reaction-center complex (bottom) in the charge-separated states [P700 -A,4 and [P870 Q4, respectively (B) X-band ESP-EPR spectra of spinach PS-I particles extracted with a hexane-MeOH mixture (a), reconstituted with protonated (b) and deuterated (c) vitamin Ki (C) ESP-EPR spectra of spinach PS-I particle in glycine buffer at pH 10.8 and untreated (a), reduced with 50 mM dithionite and 0,5 mM methyl viologen and dark-incubated (b), and the reduced sample dialyzed overnight against glycine buffer and reconcentrated (c). Figure source (A) Petersen, Stehlik, Gast and Thurnauer (1987) Comparison of the electron spin polarized spectrum found in plant photosystem I and in iron-depleted bacterial reaction centers with time-resolved K-band EPR evidence that the photosystem I acceptor is a quinone. Photosynthesis Res 14 22 (B) and (C) Snyder and Thurnauer (1993) Electron spin polarization in photosynthetic reaction centers. In J Deisenhofer and JR Norris (eds) The Photosynthetic Reaction Center, Vol 11 313,315.

ABSTRACT Quinones constitute a structurally diverse class of phenolic compounds with a w ide range of pharmacologial properties, which are the basis for different applications in the broad field of pharmacy and medicine. In traditional medicine all over the world, plants which are rich in quinones are used for the treatment of a variety of diseases. Besides the classical applications of these plants in industry (dyestuffs) and pharmaceutical (laxatives) practice, the relatively new field of biologically active quinones will be discussed. This review gives an account of the work done on naturally occurring bioactive quinones from 1992 to the present date. The biological activity detected in quinones from natural and synthetic sources has been discussed in relation to chemical structure under the respective titles. 

Cultured plant cells may serve as sources of the various quinones characteristic of intact plants in addition, new quinones have been produced in plant cell cultures which are not formed in the corresponding parent plants, while sometimes the cultured cells lack the ability to produce easily detectable amounts of natural quinones. For example, callus tissue of Aloe barbadensis grown in the dark produced two new tetrahydroanthracene glucosides 3,4-dihydro-2,4,8,9-tetrahydroxy-6-methyl-anthracenone-4-... 

Rubiaceaous plants are usually rich in anthraquinones. The first four anthraquinones, 2-methyl-3-methoxyanthraquinone (7), 2-methyl-3-hydroxyanthraquinone (8), 2-methyl-3-hydroxy-4-methoxyanthraquinone (9) and 2,3-dimethoxy-6-methylanthra-quinone (10) reported in genus Hedyotis were isolated from H. diffusa [26]. All the compounds except for (10) are substituted only in ring C. The structure of (10) has been later confirmed by synthesis based on Diels-Alder reaction. This anthraquinone has been the only one reported from a natural source until today. Other anthraquinones possessing the same substitution pattern are synthetic products [27]. 

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