Evaluation of the effect of steviol on chromosomal damage using micronucleus test in three laboratory animal species.

The chromosomal damage activity of steviol, a product of enzymatic alteration of stevioside, a natural non-caloric sweetener was reevaluated by using a bone marrow micronucleus test in both male and female hamsters, rats and mice. The micronucleus test is used widely as a rapid and efficient alternative in chromosome analysis for detecting in vivo cytogenetic damage. Steviol at the dose of 4 g/kg body weight for hamsters and 8 g/kg body weight for rats and mice showed no effect on the frequencies of micronucleus formation in bone marrow erythrocytes of both male and female hamsters, rats and mice. Moreover, there was also no apparent change in the PCEs:NCEs (polychromatic erythrocytes:normochromatic erythrocytes) ratio of the male animals of all three treated species at 24, 30, 48 and 72 hour intervals. However, steviol at the given dose can cause significant reduction of PCEs to NCEs ratio of the female hamsters at 72 hours and female rats and mice at 48 and 72 hours after receiving steviol orally. From these results, it could be proposed that steviol at the given dose to the treated animals produced adverse metabolites and these metabolites could reach the bone marrow, the target organ for micronucleus test. These metabolites also exhibited a slightly cytotoxic effect but not clastogenic effect to the bone marrow erythrocytes.

Lack of mutagenicity of stevioside and steviol in Salmonella typhimurium TA 98 and TA 100.

Stevioside, a sweet-tasting diterpene glycoside derived from Stevia rebaudiana, and steviol, a product from enzymatic hydrolysis of stevioside, were tested for mutagenic activity by the in vitro Ames test, a preincubation method, using Salmonella typhimurium TA 98 and TA 100 as the tester strains, either in the presence or absence of metabolic activating system derived from the sodium phenobarbital and 5,6-benzoflavone pretreated liver S9 fractions from various animal species including rat, mouse, hamster and guinea pig. Stevioside and steviol at the concentrations up to 50 mg and 2 mg per plate, respectively showed no mutagenic effect on both tester strains either in the presence or absence of metabolic activating system. However, at the high concentration both stevioside and steviol showed some toxic effects on both tester strains. The toxic effect was decreased in the presence of the metabolic activating system.