CHAPTER 23: Khat, Betel, Coca and Tobacco Chewing: Genotoxic Effects in Micronucleus Assays

Epidemiological findings indicate that the chewing of tobacco, betel (with and without tobacco) and khat leaves causes cancer and preneoplastic lesions (leukoplakia) in the oral cavity, while no data are available concerning the effects of coca leaves. The results of human studies show that these habits (except the consumption of coca leaves) cause the formation of micronuclei (MN) in exfoliated buccal mucosa cells. Taken together, the results show that MN reflect the cancer risks of this widespread chewing habit. In vitro and animal experiments with extracts of betel quid and tobacco support the assumption that chewing causes damage of the genetic material. It is likely that alkaloids that are contained in these plants, such as cathinione in khat, arecoline and structurally related compounds in betel quid, account for their genotoxic properties. Furthermore, specific nitrosamines were identified in betel quid and also in chewing tobacco which may play a role in regard to MN formation in the buccal cavity.