VOL.: 73 (1999) (p. 497)Chem. Abstr. No.:
Exposure to quercetin may occur during its production and use in dyes and from its presence in a variety of fruits and vegetables.
5.2 Human carcinogenicity data
No data were available to the Working Group.
5.3 Animal carcinogenicity data
Quercetin was tested in several studies in rats by oral administration in the diet and by topical application in mice. Carcinogenicity was seen in only two studies in rats. Quercetin increased the incidences of intestinal and urinary bladder tumours in one study, but this effect was not seen in subsequent studies. Quercetin produced a low but significant increase in the incidence of renal tubular neoplasms, primarily adenomas in male rats, which was observed only after step-sectioning of renal tissue. When tested in several two-stage models of organ carcinogenesis, quercetin did not significantly enhance tumour incidence, except that of renal tumours induced by oestradiol in a model in hamsters.
5.4 Other relevant data
Although the metabolism of quercetin appears to be similar in humans and rabbits (the same three metabolites were identified in urine), no information on rats or mice was available for comparison. No information was available on the toxicity of quercetin in humans.
Quercetin increased the frequency of DNA damage and lipid peroxidation in liver nuclei of rats in vitro. In long-term studies in rats, there were no treatment-related clinical signs of toxicity, but renal hyperplasia occurred in males.
Quercetin inhibited cytochrome P450 enzymes in both human and rodent microsomes in vitro.
Fetal growth retardation was observed in a study in rats exposed to quercetin by oral gavage.
No data were available on the genetic and related effects of quercetin in humans. It was not genotoxic in experimental systems in vivo. It produced cytogenetic damage in human and rodent cells in vitro, but conflicting results were obtained in assays for gene mutation. It was mutagenic to Drosophila.
There is inadequate evidence in humans for the carcinogenicity of quercetin.
There is limited evidence in experimental animals for the carcinogenicity of quercetin.
Quercetin is not classifiable as to its carcinogenicity to humans (Group 3).For definition of the italicized terms, see Preamble Evaluation.
Previous evaluations: Vol. 31 (1983); Suppl. 7 (1987) (p. 71)
See Also: Toxicological Abbreviations Quercetin (IARC Summary & Evaluation, Volume 31, 1983)