It is found in many plants and foods, such as red wine, onions, green tea, apples, berries, Ginkgo biloba, St. John's wort, American elder, and others.
Ọ na-achọta ọtụtụ osisi na ihe oriri, dị ka red wine, eyịm, green tii, apụl, tomato, Ginkgo biloba, St. Jọn wort, American okenye, na ndị ọzọ.