Oxidation in vitro

Ethanol also inhibits ADH-catalyzed retinol oxidation in vitro, and ethanol treatment of mouse embtyos has been demonstrated to reduce endogenous RA levels. The inhibition of cytosolic RolDH activity and stimulation of microsomal RolDH activity could explain ethanol-mediated vitamin A depletion, separate from ADH isoenzymes. Although the exact mechanism of inhibition of retinoid metabolism by ethanol is unclear, these observations are consistent with the finding that patients with alcoholic liver disease have depletedhepatic vitamin A reserves [review see [2]. 

In recent years a number of in vitro studies have shown that the presence of Met(O) residues in a wide variety of proteins causes loss of biological activity. Table 2 lists some proteins which have been demonstrated to lose activity when specific Met residues are oxidized in vitro. Two of these proteins, E. coli ribosomal protein LI 2 and mammalian a-1-PI, have been studied extensively and will be discussed in detail. 

KERRY N and ABBEY M (1998) The isoflavone genistein inhibits copper and peroxyl radical mediated low density lipoprotein oxidation in vitro. Atherosclerosis. 140 (2) 341-7. 

Haila, K., Effects of carotenoids and carotenoid-tocopherol interaction on hpid oxidation in vitro, etc.. University of Helsinki, Department of Applied Chemistry and Microbiology, Helsinki, 1999. 

Antioxidants that inhibit LDL oxidation in vitro prevent fetty streak formation in animal models (Carew etal., 1987 Kita etal., 1987 Bjorkhem etal., 1991) and others are associated with protection against coronary artery disease in population studies (Gey et al., 1991 Stampfer etal., 1993 Rimm etal., 1993). 

Frenkel, K., Zhong, Z., Wei, H., Karkoszka, J., Patel, U., Rashid, K., Georgescu, M. and Solomon, J.J. (1991). Quantitative high-performance liquid chromatography analysis of DNA oxidized in vitro and in vivo. Anal. Biochem. 196, 126-136. 

Adler, K.B., Akiey, N.J. and Holdenstaufier, W.J. (1989). Exposure of airway epithelium to extracellular oxidants in vitro stimulates arachidonic acid metabolism and mucin secretion. Am. Rev. Resp. Dis. 139, A403. 

Siems, WG, Sommerburg, O, and van Kuijk, F, 1999. Lycopene and beta-carotene decompose more rapidly than lutein and zeaxanthin upon exposure to various pro-oxidants in vitro. Biofactors 10, 105-113. 

Katz, M., Chan, C., Tosine, H., Sakuma, T. (1979) Relative rates of photochemical and biological oxidation (in vitro) of polynuclear aromatic hydrocarbons. In Polynuclear Aromatic Hydrocarbons. Jones, P.W., Leher, P., Eds., pp. 171-189, Ann Arbor Science Publishers, Ann Arbor, MI. 

This method is also used to measure ex vivo low-density lipoprotein (LDL) oxidation. LDL is isolated fresh from blood samples, oxidation is initiated by Cu(II) or AAPH, and peroxidation of the lipid components is followed at 234 nm for conjugated dienes (Prior and others 2005). In this specific case the procedure can be used to assess the interaction of certain antioxidant compounds, such as vitamin E, carotenoids, and retinyl stearate, exerting a protective effect on LDL (Esterbauer and others 1989). Hence, Viana and others (1996) studied the in vitro antioxidative effects of an extract rich in flavonoids. Similarly, Pearson and others (1999) assessed the ability of compounds in apple juices and extracts from fresh apple to protect LDL. Wang and Goodman (1999) examined the antioxidant properties of 26 common dietary phenolic agents in an ex vivo LDL oxidation model. Salleh and others (2002) screened 12 edible plant extracts rich in polyphenols for their potential to inhibit oxidation of LDL in vitro. Gongalves and others (2004) observed that phenolic extracts from cherry inhibited LDL oxidation in vitro in a dose-dependent manner. Yildirin and others (2007) demonstrated that grapes inhibited oxidation of human LDL at a level comparable to wine. Coinu and others (2007) studied the antioxidant properties of extracts obtained from artichoke leaves and outer bracts measured on human oxidized LDL. Milde and others (2007) showed that many phenolics, as well as carotenoids, enhance resistance to LDL oxidation. 

Figure 17 Time course of the antiradical parameters ACL0 and ACW of LDL measured by the PCL method its a-tocopherol content (AT) measured by the HPLC technique and conjugated dienes (LDL-abs. at 234 nm) during Cu2+-initiated oxidation in vitro. (From Ref. 36.)...

Yin, J., Chaufour, X., McLachlan, C., McGuire, M., White, G., King, N., and Hambly, B., 2000, Apoptosis of vascular smooth muscle ceUs induced by cholesterol and its oxides in vitro and in vivo, Atherosclerosis 148 365-374. 

The main route of nicotine metabolism is through hepatic oxidation. In vitro, nicotine is oxidized by CYPs at the 5 carbon (C-oxidation) of the pyrrolidine ring. 

The periodontal pocket is another site for drug delivery in the oral cavity. Needleman et al. [46] investigated three mucoadhesive polymers (cationic chitosan, anionic xanthan gum, neutral polyethylene oxide) in vitro, using organ cultures, and in vivo in patients on their periodontal and oral mucosa. Of the polymers studied, chitosan displayed the longest adhesion in vitro and on the periodontal pockets, and the shortest adhesion on oral mucosa. 

Relative Rates of Photochemical and Biological Oxidation (in vitro) of Polynuclear Aromatic Hydrocarbons," in POLYNUCLEAR AROMATIC HYDROCARBONS, P.W. Jones and P. Leber (Editors), Ann Arbor Science Publishers, Inc., Ann Arbor, MI, 171-89. 

Destruction of nitric oxide by superoxide in the buffers is more likely to account for the short half-life of nitric oxide in vitro. Superoxide dismutase (15-100 U/ml) substantially increased the apparent half-life of EDRF, strongly suggesting that superoxide contributes to the short biological half-life of nitric oxide. In the perfusion cascade bioassay system, the buffers are bubbled with 95% oxygen, contain 11 mM glucose as well as trace iron plus copper contamination and are incubated under the weak ultraviolet (UV) radiation of fluorescent lights. These are prime conditions for the autoxidation of glucose to form small amounts of superoxide in sufficient amounts to account for the short half-life of nitric oxide in nanomolar concentrations. The rate of reaction between superoxide and nitric oxide is 6.7 X 10 M sec L The shortest half-life of nitric oxide measured is approximately 6 sec. To achieve a half-life of 6 sec, the steady state concentration of superoxide would only need to be 17 pM, calculated as ln(2)/ (6 sec X 6.7 X 10 M" sec )-... 

Table 7. Antioxidant Potency of Vitamins and Phenolics Based on LDL Oxidation In Vitro...

An antioxidant is a product that inhibits the oxidation in vitro... 

Brown, J.E. and Rice-Evans, C.A. 1998. Luteolin rich artichoke extract protects low density lipoprotein from oxidation in vitro. Free Radio. Res. 29, 247-255. 

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