The chemicals in a plant responsible for having its medicinal effects is call its active constituents. These chemicals are what pharmaceutical companies isolate and made into drugs. For example, Aspirin (acetylsalicylic acid) was derived from the bark extracts of a Salix willow tree.
Active constituents are broken in to the following 16 groups. I noted some of them in the blogs for each herb.
polyphenols - are groups of phenols and are subdivided into several major subclasses: phenolic acids, stilbenes, tannins, diferuloylmethanes and flavonoids.