Abstract
Although much attention has focused on environmental contamination by heavy metals,
pesticides, and polychlorinated biphenyls, potential deleterious effects of naturally
occurring organic compounds have received much less consideration. Saponins, which
are glycosides found in many plants, are important, environmentally ubiquitous
organic compounds. Saponins have both beneficial and deleterious effects in adults,
but little is known about how saponins effect early vertebrate embryonic development.
The authors tested the toxicity of quillaja saponin using a zebrafish embryo assay.
Quillaja saponin, extracted from bark of the tree, Quillaja
saponaria, is a common foaming agent used in foods and beverages. At 6 h
post fertilization, zebrafish embryos were exposed to five concentrations (0
[negative control], 1, 5, 10 or 20 μg) of quillaja saponin per
milliliter of medium. Zebrafish embryos exposed to 2% ethanol were positive controls
(100% embryonic death). Embryos were assessed at 30, 54, and 72 h post fertilization
for changes in embryonic development, mortality, time of hatching, and morphological
deformities. Embryos exposed to 1 and 5 μg saponin were healthy,
showed no obvious deformities, but exhibited shrinkage of the chorion. Hatching time
for zebrafish embryos exposed to 1 and 5 μg/ml saponin decreased by
18 h compared to unexposed embryos. Zebrafish embryos treated with 5
μg/ml saponin responded less to touch than embryos treated with 1
μg/ml saponin or controls. Zebrafish embryos exposed to more than
5 μg/ml saponin exhibited 100% embryonic mortality. These results
indicate that exposure to 5 μg/ml or less of quillaja saponin acts
as a growth promoter, whereas concentrations of 10 μg/ml or greater
are lethal.