Calamus (Acorus calamus L.)
Acorus calamus L. (common names: calamus or sweet flag) is originally an Indian plant that was brought to the United States via Europe. It can now be found in numerous states, where it prefers temperate and sub-temperate climates and wetlands for optimal growth, often bordering on swamps, marshes, and riverbeds. Calamus is a basal monocot from the Acoraceae family, where it was placed upon removal from the Araceae family based on molecular data. It is a sterile triploid that only seldomly flowers and commonly spreads through rhizomes.
Calamus looks back at a long history of traditional medicinal use, both in Chinese and Indian, as well as European, medicine. Its oil is also a popular perfume component. For medicinal purposes, rhizomes are collected in early spring, or in late fall. They contain varying amounts of essential oil rich in mono- and sesquiterpenes such as acorone. A bitter aromatic plant, calamus is mostly used as a carminative in herbal remedies. In the US, use of calamus and its products was banned in 1968 following demonstration of carcinogenic effects of long-term, high-dosage application in an animal model. An essential oil component β-asarone was identified as the responsible procarcinogenic agent. Even though the relevance of these tumor-inducing effects for dosage commonly used by humans is unknown, its consumption is still not recommended.
Several morphological features as well as the composition of essential oil distinguish it from the indigenous American variety Acorus americanus, which is diploid, and whose essential oil does not contain the procarcinogenic β-asarone. The rhizome of Acorus americanus is traditionally candied and used as condiment.