Contains the full lesson along with a supporting toolkit, including teachers’ notes.
Many people believe that natural substances are better and safer than manmade medicines. This idea has to be treated with caution, because there are some very toxicnatural substances contained in plants, e.g. hemlock, ricin and ergot. It has been estimated that 25% of modern prescription drugs contain at least one compound derived directly or indirectly from higher plants1. Many others are derived directly or indirectly from fungi or micro-organisms. There is a continuing search for other substances to add to these and folk medicine can often provide a lead. One of the frequently quoted reasons for preserving the tropical rainforests is that they contain many plants of potential medicinal value. Numerous books have been written on the medicinal uses of plants, and Culpepper’s Complete Herbal (written in the 16th century) is perhaps one of the most famous. Such books were written with self-medication in mind; however, this should be done with caution, except for the most minor of ailments, and only for short periods of time.
Plants have been used medicinally for thousands of years. China and India have a particularly long tradition in herbal medicine and large quantities of herbal medicines are imported from there. How do we know that these will work and will not do us any harm? Before we answer these questions we will take a closer look at a few medicines derived from plants and how they were discovered and developed.
Indians discovered hundreds of years ago that foxglove [Digitalis], from which the drug digoxin is derived, could be used to control rapid heartbeat. How might this discovery have been made? It would seem reasonable to suppose that they observed that when peopleingested foxglove seeds they often died because their heart slowed down and eventually stopped beating. The medicine men, who were acutely aware of the value of many plants, considered that if one gave a tiny amount of the plant to someone with rapid heartbeat, then perhaps it would slow down theheartbeat without killing them.