Inhibition of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone carcinogenesis in mice by D-limonene and citrus fruit oils.

The effects of D-limonene and citrus fruit oils, i.e. orange oil and lemon oil, on 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced neoplasia of the lungs and forestomach of female A/J mice were investigated. D-Limonene and the citrus fruit oils given p.o. 1 h prior to NNK, also administered p.o., inhibited pulmonary adenoma formation and the occurrence of forestomach tumors. In an additional experiment, D-limonene given p.o. 1 h prior to NNK administered i.p. again showed pronounced inhibition of pulmonary adenoma formation. This study provides additional data demonstrating that non-nutrient constituents of the diet can inhibit carcinogen-induced neoplasia when administered at a short time interval prior to carcinogen challenge.