I wish I could remember the name of a mystery series that aired several years ago about a medieval monk who was knowledgeable in herbal medicine. If I recall correctly some of the herbs were involved in crimes which he solved.
Edith Pargeter, the author of the Cadfael series, said of her experience as a chemist's assistant: "We used to make bottled medicine that we compounded specially, with ingredients like gentian, rosemary, horehound. You never see that nowadays; those tinctures are never prescribed. They often had bitters of some sort in them, a taste I rather liked. Some of Cadfael’s prescriptions come out of those years."