Abstract
Compounds with two phenolic OH groups like curcumin possess efficient antioxidant and anti-inflammatory activity. We synthesized p-cresol dimer (2,2'-dihydroxy-5,5'-dimethylbiphenol, 2a) and p-methoxyphenol dimer (2,2'-dihydroxy-5,5'-dimethoxybiphenol, 2b) by ortho-ortho coupling reactions of the parent monomers, p-cresol (1a) and p-methoxyphenol (1b), respectively. Their antioxidant activity was determined using the induction period method, and their cytotoxicity towards RAW 264.7 cells was also investigated using a cell counting kit. The stoichiometric factors n (number of free radicals trapped by one mole of antioxidant moiety) for 2a and 2b were 3 and 2.8, respectively, being greater than those for 1a and 1b. The ratio of the rate constant of inhibition to that of propagation (kinh/kp) for 2a and 2b was similar to that for 2-t-butyl-4-methoxyphenol (BHA), a conventional food antioxidant. The 50% inhibitory dose (ID50) declined in the order 1b > 1a >> 2b > 2a > BHA. The cytotoxicity for 2a and 2b was significantly greater than that for the parent monomers (p < 0.001), but smaller than that for BHA (p < 0.01). Compounds 2a and 2b may be useful as food antioxidants.
Highlights
Introduction pCresol (1a, Figure 1) is a natural product present in many foods, crude oil, and coal tar, and detectable in animal and human urine
That for the benzoyl peroxide (BPO) system declined in the order 2a > 2b > 1b > BHA > BHT > BMP > 1a
We previously reported that bis-BHA shows an anti-inflammatory activity [18]
Summary
Cresol (1a, Figure 1) is a natural product present in many foods, crude oil, and coal tar, and detectable in animal and human urine. In addition to its industrial uses, 1a is used as an antiseptic and disinfectant because of its bactericidal and fungicidal properties, but available data to support the safety of p-cresol for use in cosmetic were insufficient [1]. P-Methoxyphenol (1b, Figure 1) is an acceptable antioxidant, but is known to be carcinogenic, being structurally similar to the known forestomach carcinogen, BHA [3,4]. The adverse toxicological effects of 1b and BHA may be related to their prooxidative properties. Dimers derived from 1b and BHA are expected to have enhanced antioxidative activity, because dimerization reduces the prooxidative activity of the parent monomers
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