Mutagens in coffee and tea.

Coffee prepared in the usual way for drinking contains a substance(s) that is mutagenic to Salmonella typhimurium TA100 without mammalian microsomal enzymes. One cup of coffee (200 ml) contains mutagen(s) inducing 1.4-4.6 X 10(5) revertants under standard conditions. Instant coffee too is mutagenic to TA100 and one cup of instant coffee prepared from 1 g of coffee powder and 200 ml of water induced 5.6-5.8 X 10(4) revertants of TA100. Caffeine-free instant coffee also has similar mutagenicity. Addition of microsomal enzymes abolished the mutagenicity. Black tea, green tea and Japanese roasted tea were also mutagenic to TA100 without S9 mix and one cup of these teas prepared in the ordinary way produced 1.7-3.8 X 10(4) revertants of TA100. Black tea and green tea were also mutagenic to TA98 in the presence of S9 mix after treatment with a glycosidase from Aspergillus niger, hesperidinase. This type of mutagen in one cup of black tea induced 2.4 X 10(5) revertants of TA98.