Hydroquinone, biological activities

Additionally, during the search for biologically active sponge metabolites belonging to the sesterterpenoid class, a sulfated sesterterpene hydroquinone, halisulphate, Fig. (20), was isolated from the dark brown sponge Halichotidriidae sp. 

The sesquiterpene quinones and hydroquinones display a wide range of biological activities.4 Some of the compounds are cytu-toxic, whereas others show antimicrobial characteristics. Avarol (2) has been the subject of investigation as a consequence of its ability to inhibit reverse transcriptase, but no clinical value (as an anti-AIDS agent, for example) has yet been established.3... 

The potent biological activity (insect antifeedant, antitumour, antifungal) of warburganal (35) has stimulated considerable synthetic interest in this compound. Three total syntheses of this compound have been recorded in the period under review. " The synthesis by Tanis and Nakanishi has additional flexibility since the key intermediate diol (34) can be used in the syntheses of cinnamolide (36), drimenin (37), and polygodial (38). Both norisoambreinolide (39 R = O) and isoambrox (39 R = H2) have been synthesized from (40), the product of the stannic chloride-catalysed cyclization of farnesyl phenyl sulphone. Yahazunol (41), a bicyclofarnesyl hydroquinone, has been identified in the brown seaweed... 

LPDE solution also catalyzes the conjugate allylation of quinones. This is an important reaction in the preparation of biologically active isoprenoid quinones such as vitamin E, vitamin K, coenzyme Qi, and plastoquinones. If 123 is reacted with the allylsi-lane in 5.0 m LPDE for 15 h at 40 °C, allylhydroquinone 124 is obtained in 73 % yield, together with non-allylated hydroquinone 125 (Sch. 63) [113]. 

The biological activity of rifamycins has been described [179b]. Rifamycin S (102) results from the oxidation of rifamycin B (98) to rifamycin O (101) and final hydrolysis, and rifamycin SV (103) is given by reduction of rifamycin S (98) to the corresponding hydroquinone. The biological activity is retained by all compounds. Rifampicin, a hydrazone derivative of 3-formyl rifamycin SV, is a widely used orally active tuberculostatic agent [182]. 

For simplicity consider first reduction of a drug such as a quinone Q, or oxidation of a hydroquinone QH2, by one or two electrons. Some examples of quinones that are drugs or biologically-active substances are shown in Figure 1, 1-7. One-electron reduction of Q (equation (1)) or oxidation of QH2 (equation (2)) generates the same intermediate, the free radical Q" /QH, which may be involved in prototropic equilibria such as equation (3) ... 

Compounds Derived by Alkylation with Geranyl-OPP Monoterpene-Derived Compounds of Marijuana Hydroquinone Derivatives in Cordia Species Chemosystematic Use of Monoterpene Chemical Data Chemosystematic Study of Citrus Species Chemosystematic Study of Gymnosperms Chemosystematic Studies in Mints Biological Activity... 

Moore s group has also exploited his methodology for the synthesis of a variety of 7V-heterocyclic quinones and hydroquinones such as piperidinoquinones 37, dihydrophenanthridinediols 38, benzophenanthridine 39, and assoanine 40, a member of a series of biologically active pyrrolophenanthridine alkaloids. ... 

Sladic, D. and Gasic, M.J. (2006) Reactivity and biological activity of the marine sesquiterpene hydroquinone avarol and related compoimds from sponges of the order Dictyoceratida. Molecules, 11,1-33. 

Kondradd, M.-L. and Guyot, M. (1989) Biologically active quinone and hydroquinone sesquiterpenoids from the sponge Smenospongia sp. Tetrahedron, 45, 1995-2004. 

To reach the reductive step of the azo bond cleavage, due to the reaction between reduced electron carriers (flavins or hydroquinones) and azo dyes, either the reduced electron carrier or the azo compound should pass the cell plasma membrane barrier. Highly polar azo dyes, such as sulfonated compounds, cannot pass the plasma membrane barrier, as sulfonic acid substitution of the azo dye structure apparently blocks effective dye permeation [28], The removal of the block to the dye permeation by treatment with toluene of Bacillus cereus cells induced a significant increase of the uptake of sulfonated azo dyes and of their reduction rate [29]. Moreover, cell extracts usually show to be more active in anaerobic reduction of azo dyes than whole cells. Therefore, intracellular reductases activities are not the best way to reach sulfonated azo dyes reduction the biological systems in which the transport of redox mediators or of azo dye through the plasma membrane is not required are preferable to achieve their degradation [13]. 

Transfer of calcium cations (Ca2 + ) across membranes and against a thermodynamic gradient is important to biological processes, such as muscle contraction, release of neurotransmitters or biological signal transduction and immune response. The active transport can be artificially driven (switched) by photoinduced electron transfer processes (Section 6.4.4) between a photoactivatable molecule and a hydroquinone Ca2 + chelator (405) (Scheme 6.194).1210 In this example, oxidation of hydroquinone generates a quinone to release Ca2+ to the aqueous phase inside the bilayer of a liposome, followed by reduction of the quinone back to hydroquinone to complete the redox loop, which results in cyclic transport of Ca2 +. The electron donor/acceptor moiety is a carotenoid porphyrin naphthoquinone molecular triad (see Special Topic 6.26). 

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