Introduction to Plant Constituents
Plants depend on chemistry for nearly all of their interactions–sensing the world, responding to the world, adjusting their metabolism, and protecting themselves.
It all starts with green plants developing the ability to capture tiny packets of energy from the sun, which is 93 million miles away. These photons from the sun upgrade electrons to a slightly higher energy level in the chlorophyl molecules, and that minute amount of energy is captured and ultimately stored in the form of sugars. From the basic building blocks of water, CO2, and sunlight they are able to build up the vast array of secondary chemicals for all their functions. The really astounding thing is that this ability of plants to capture energy from the sun in a profoundly efficient way is the basis of most of the life on planet Earth. Scientists keep trying to hack photosynthesis, but so far have not been able to do so, only parts of it. Plants are really smart in the sense they are wonderfully adapted to their life here and able to fulfill their needs with only the few resources that are available. Yet it has taken them many millions of years in order to bring it to this level of efficiency.
Before you really get into the chemistry of plants and how it relates to herbalism, remember that plants have basically two major types of compounds they produce for their needs.
1. Primary constituents which make up most of the biomass of the plants–these include proteins made up of amino acids, fatty acids, and carbohydrates. Carbohydrates are made up of sugar molecules, including long chains of them, the polysaccharides. The major polysaccharides are cellulose (glucose polymers) which is structural and put together so we cannot digest them efficiently, and starch (also glucose polymers attached a little differently than cellulose) which we can digest.
2. Secondary, or Low molecular weight constituents which makes up only 3 to 10% of the total dry plant biomass. These are small and large, and are more biologically active than the structural (cellulose, lignan), energy-storing (starch and smaller sugars), and information-storing (amino acids, DNA) molecules. These are of several types, produced by the plants through very specific pathways that use enzymes to facilitate the production of a vast array of chemical compounds that have evolved and been refined by millions of years of living in the world. These include:
Terpenes, which comprise the building blocks of essential oils, carotenes, and rubber, among others.
Phenolics (containg a phenolic ring, which is a resonant structure with alternating double-bonds and single bonds, typically in a 6-carbon ring) These include constituents like coumarin, salicylic acid, flavonoids (yellow colors of leaves), anthocyanidins (purple colors of flowers, leaves), and tannins among others.
Somewhat related to, and produced by the same pathway at the beginning in their biosynthetic journey, are the alkaloids, which are basic (rather than acidic) compounds, and contain nitrogen and typically affect our nervous system in some way.
Fatty acids in seeds and other parts of plants, some of which are biologically active.
These are the 4 high-level categories of small molecular weight compounds. Many of these are used by plants for defense, but some for signaling and metabolic functions.
In this short course within the larger course of herbal medicine, I will go through some of the basic principles and constituent groups and talk about their activity and occurrence in plants. You can listen to the various parts of the larger presentation that you are interested in and use the workbook as well. After a presentation of the constituents, I will get into the pharmacology of plants and talk about some of the major biological activities of the major constituent groups, like antispasmodic, antiinflammatory, analgesic, sedative, calmatives, and expectorants to name only a few.
Again, I’m not going to make a study of these topics a crucial part of your grade and I’m presenting the material because I have found it can greatly expand our view of healing with plants, and since plants are dependent on chemistry for sensing and responding to the world to a large degree, we can learn much about the behavior and being of the plants.
Many thanks! CH
