Vitex agnus-castus, commonly called chaste tree, chasteberry, or monk’s pepper, is a shrub of the Lamiaceae family native to the Mediterranean region and Western Asia. The name comes from Latin agnus (“lamb,” symbolizing chastity) and castus (“pure”), reflecting its long association with celibacy. The plant produces aromatic leaves and small purple flowers, but it is primarily cultivated for its pepper-like fruits (chasteberries), which have been used since antiquity.

In ancient Greece and Rome, chasteberry was linked to rituals of chastity and was used by women during religious festivals such as the Thesmophoria. Medieval monks chewed the dried berries or sprinkled them on food as a supposed aid to suppress libido, hence the English name “monk’s pepper.” It was also employed in folk medicine for gynecological conditions and as a digestive spice. Today, Vitex agnus-castus is most widely used in herbal medicine, particularly in Europe. Standardized extracts are taken for premenstrual syndrome (PMS), mastalgia (breast pain), and menstrual cycle irregularities. Some evidence suggests that the plant may act through dopaminergic effects, influencing prolactin levels. The berries are sometimes used as a seasoning in place of black pepper, though this is less common now.