A substance that can cure or heal you is medicinal. Some people swear that chicken soup has medicinal qualities when you have a cold.
Herbalists grow medicinal plants, such as mint and witch hazel, that have healing properties for various ailments. Your mother may believe in the medicinal properties of a hot cup of tea, while other people swear by the medicinal quality of the salty sea air. The adjective medicinal comes from medicine and has a Latin root, medicina, "the healing art, a remedy, or medicine."