Fd Chem. Toxic. Vol. 30, No. 6, pp. 483489, 1992 0278-6915/92 $5.00+ 0.00 Printed in Great Britain. All rightsreserved Copyright© 1992Pergamon Press Ltd PROTECTION BY ALBUMIN AGAINST THE PRO-OXIDANT ACTIONS OF PHENOLIC DIETARY COMPONENTS C. SMITH, B. HALLIWELL*and O. I. ARUOMAt Department of Biochemistry, University of London King's College, Strand, London WC2R 2LS, UK and *Pulmonary Critical-Care Medicine, UC Davis Medical Center, 4301 X Street, Sacramento, CA 95817, USA (Accepted 20 January 1992) Abstract--Syntheticand natural phenolic compounds are increasingly used in food preservation. Carnosol and carnosic acid (active components of rosemary extract), flavonoids (morin, quercetin, fisetin, myricetin), other plant phenolics (gossypol) and propyl gallate may protect lipids against oxidative damage but have the potential to increase damage to non-lipid constituents of foods, such as carbohydrates and DNA. Thus, in the presence of ferric EDTA and H202, they can form highly reactive hydroxyl radicals that can degrade the sugar deoxyribose and/or accelerate DNA degradation by means of a ferric- bleomycin complex. Human and bovine serum albumin afford considerable protection against damage to deoxyribose and DNA mediated by the above reactions. It is suggested that, given the fortification of foods with iron and EDTA and the use of phenolic substances as 'antioxidant' food additives, the addition of albumin might afford some protection. INTRODUCTION Free-radical reactions are recognized to play some role in the pathogenesis of certain human diseases including rheumatoid arthritis, cancer, athero- sclerosis, ischaemia/reperfusion injury and some neurological disorders (reviewed in Halliwell and Gutteridge 1989; Sies, 1991). Interest is also growing in the role played by free radicals in food deterio- ration and preservation (Addis, 1986; Aruoma and Halliwell, 1991; Champagne et al., 1990; Ericksson, 1987; Whang et al., 1988). Free-radical reactions can lead to deterioration in food flavour and loss of food quality (for example, rancid flavours of fats and the 'stale' flavour of beer), but in some cases the products arising from such reactions appear to be an important part of the flavour (for example, the contribution of volatile compounds to the flavour of cheese) (Grosch, 1987). Free-radical oxidation of food lipids by the chain reaction of lipid peroxidation is a major problem for food manufacturers (Ericksson, 1987). The formation and decomposition of lipid hydro- peroxides results in the degradation of fats to un- pleasant end products. Such deterioration can be minimized by the use of antioxidants (Ericksson, 1987; Hudson, 1990; Loliger, 1991). An antioxidant tTo whom correspondence should be addressed. Abbreviations: BSA = bovine serum albumin; HSA ---human serum albumin; "OH = hydroxyl radical; TBA = thiobarbituric acid; TCA = trichloroacetic acid. may be defined as a substance that, when present at low concentrations compared with that of an oxidizable substrate, significantly delays or prevents the oxidation of that substrate (Halliwell and Gutteridge, 1989). Lipids, DNA, carbohydrates and proteins are examples of oxidizable substrates. How- ever, toxicity problems (real or imagined) have arisen from the use of synthetic phenolic antioxidants such as butylated hydroxyanisole and butylated hydroxy- toluene (Ito et al., 1985; Stich, 1991) added to foods to inhibit free-radical damage to lipids. Hence, there is increasing interest in the use of 'natural' anti- oxidants such as tocopherols, flavonoids or rosemary extracts in the preservation of food materials (Aruoma et al., 1992; Aruoma and Halliwell, 1991; Loliger, 1991; Stich, 1991). Food antioxidants might also be absorbed into the human body and help to protect against atherosclerosis by inhibiting per- oxidation of circulating lipoproteins (Esterbauer et al., 1989). The antioxidant activity of food additives is fre- quently assessed only in lipid systems. Unfortunately, some lipid antioxidants may accelerate free-radical damage to non-lipids such as DNA or carbohydrates (Aruoma et al., 1990 and 1992; Halliwell, 1990; Laughton et al., 1989 and 1991). Thus phenolic lipid 'antioxidants' (Fig. 1) such as propyl gallate, buty- lated hydroxyanisole, butylated hydroxytoluene, flavonoids and gossypol can reduce Fe 3÷ to Fe 2÷ and stimulate free-radical damage to carbohydrates and DNA (Aruoma, et al., 1990; Halliwell, 1990; Laughton et al., 1989). End products of such damage 483