The chaste tree (also known as monk's pepper tree or wild lavender) is a small deciduous tree native to the Mediterranean region. Growing from 1 to 6 meters in height, the chaste tree has long-petioled leaves with five to seven spear-shaped leaflets, up to 10 centimeters long. The tree blossoms from September to October, producing whorls of blue or pink blossoms which eventually give way to small (3 to 4 millimeters in diameter), glubular, reddish-black berries, each containing four seeds. The dried fruits are used for health purposes.
Chasteberries contain iridoid glycosides, flavonoids, and volatile oils, including alpha-pinenes and beta-pinenes.
Germany's Commission E lists chasteberries as an approved herb for treatment of premenstrual syndrome (PMS) and irregularities of the menstrual cycle. One uncontrolled study conducted on 1,634 women found chasteberry to improve PMS symptoms in 93 percent of the patients. A double-blind, placebo-controlled study conducted on 97 women found chasteberry extract to be useful in the treatment of breast pain associated with PMS. In vitro studies suggest that compounds found in chasteberries may affect PMS symptoms by blocking receptors of neurochemicals that stimulate the production of the hormone prolactin. A double-blind, placebo-controlled study involving 52 women with elevated prolactin levels found that chasteberries reduced prolactin levels and eliminated deficits in progesterone synthesis, which may benefit women with PMS
The daily dosage approved by Commission E is aqueous-alcoholic extracts providing the equivalent of 30 to 40 mg of dried chasteberries. Chasteberry appears to be safe at this dosage range, although side effects such as itching and rashes have been reported in some individuals. Chasteberry is not recommended for use during pregnancy or nursing.