Safety evaluation of phytosterol esters. Part 7. Assessment of mutagenic activity of phytosterols, phytosterol esters and the cholesterol derivative, 4-cholesten-3-one

Abstract

Phytosterol esters are phytosterols derived from vegetable oils following esterification to fatty acids. When phytosterols are added to foods, they inhibit the absorption of dietary and endogenous cholesterol and thereby reduce blood cholesterol concentrations. As part of a comprehensive programme of safety assessment, the mutagenic potential of phytosterols and phytosterol esters has been assessed in a bacterial mutation assay and an in vitro chromosome aberration assay. In addition, an in vitro mammalian cell gene mutation assay and two in vivo mutagenicity studies, namely rat bone marrow micronucleus and liver unscheduled DNA synthesis (UDS) assays, were conducted on phytosterol esters only. Phytosterols and phytosterol esters did not show any evidence of mutagenic activity in any of these assays. A breakdown product of cholesterol is 4-cholesten-3-one and thus the amount of 4-cholesten-3-one in the gut may increase following supplementation of foods with phytosterol-esters. 4-cholesten-3-one had been previously reported as mutagenic but, due to various shortcomings, these data could not be used to assess the mutagenic activity of 4-cholesten-3-one. The mutagenic activity of 4-cholesten-3-one and its major faecal by-products, 5β-cholestan-3-one, was assessed in two in vitro assays, a bacterial mutation assay and an in vitro chromosome aberration assay. Neither 4-cholesten-3-one nor 5β-cholestan-3-one showed evidence of mutagenic activity in these assays.