Isaac Swainson

Isaac Swainson (1746–1812) was famous for his botanical garden, which was largely funded from the profits of a herbal remedy for venereal disease. For his commercial activities in the latter field, he has been called a "radical quack". He was a relative of William John Swainson, the zoologist, and of Charles Swainson (naturalist). A plant genus is named after him. A biography has been recently produced 
Velno's Vegetable Syrup.
Swainson moved to London where he served as assistant to a Dr. Mercier in Frith Street, Soho, where he settled. Later, he purchased from Dr Mercier the recipe of a patent medicine called "Velnos’ Vegetable Syrup", named after Vergery de Velnos. This was one of many cures for venereal diseases based on vegetables rather than mercury, which is extremely toxic. This brand became well-known and Swainson reputedly made as much as £5,000 a year from its sales. In addition to curing various venereal diseases, including “the pox” and the “French disease”, it was claimed to cure leprosy, gout, scrophula, dropsy, small pox, consumption, tape worms, cancer, scurvy, and diarrhea 
Whether he believed in the efficacy of his remedy or not, he did study the conventional medicine of the era and gained an MD in 1785, although there is no record of his subsequent election to the Royal College of Physicians.
Sturt's Desert Pea.
Swainson, who was less noted for botany, is honoured by the genus name Swainsona, which is now known as the emblem of South Australia. Its common name is Sturt's desert pea. 