Formation and inhibition of the heterocyclic amine 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in a model system

Abstract

Heterocyclic amines (HCAs) are a class of mutagenic and carcinogenic chemical compounds formed on the outside of meat and fish when cooked at high temperatures. 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is the most abundantly formed HCA. HCAs have been found to cause cancer in mice and rats; PhIP specifically has been found to cause breast, rectal, prostate, and colon cancers. Model systems are often used to replicate the HCA chemical reactions in meat products without causing the many side reactions when meat is cooked at high temperatures. Model systems are also a useful way to study the effects of different variables and compounds on the formation of HCAs without using meat. A model system using amounts of 0.2 mmol glucose, 0.4 mmol creatinine, and 0.4 mmol phenylalanine in 10:90 water/diethylene glycol (v/v) was used to study the formation of PhIP. Differing levels of black pepper oil, black pepper extract, and rosemary extract (36, 71, 142, 285, 550 μL), synthetic antioxidants BHT and TBHQ (0.05 mmol, 0.1 mmol, 0.2 mmol, 0.4 mmol), and piperine (4.02 mg, 8.04 mg, 16.14 mg, 31.14 mg) were added to the model system to study their effect on PhIP formation. PhIP formation with added BHT (0.2 and 0.4 mmol) and TBHQ (0.4 mmol) were not significantly different from the control. All other added compounds decreased PhIP formation significantly from the control at p < 0.05. Solid phase micro extraction (SPME) headspace analysis was conducted on ground black pepper, black pepper oil, and black pepper extract to determine possible components responsible for PhIP inhibition. Six volatile compounds were found in common between ground black pepper, black pepper oil, and black pepper extract: 1R-α-pinene, 3-carene, caryophyllene, α-caryophyllene, cyclohexene, and D-limonene. D-limonene and caryophyllene had the largest peak areas, suggesting those compounds may play a part in PhIP inhibition in model systems.