These belly benefits are attributed to the fenchone, anethole, and estragole found in fennel seeds. (dietselfhelp.com)
Women who are pregnant or breastfeeding should also limit their basil intake due to the presence of estragole. (herbazest.com)
Among these are trans - anethole (a flavor component of anise and fennel), estragole (found in basil), eugenol (which occurs in clove bud oil) and isoeugenol (contained in ylang ylang). (groundedorganic.com)