How Medicinal Herbs Work: Pharmacokinetics and Pharmacognosy
In this article, we’re going to take a look at two avenues to study the chemistry of plant constituents so you can deepen your understanding of medicinal herbs. One of these studies is about plant constituents and phytochemistry. This is pharmacognosy. The other is about the constituent’s path through the human body. This is pharmacokinetics. Let’s take a look.
In the Beginning…..
Like most people new to herbalism, I began my learning with the “pill mentality.” I coined this term once I realized what I had been doing and how it actually debilitated my herbal expertise. This is when we ask ourselves, “What herb or essential oil should I take or use for “X” condition?”
This is allopathic thinking. It is how doctors and medical professionals tend to think of the human or animal body, in a very reductionistic sense. It’s extremely limiting. Some herbalists think this way, unfortunately, but most of us understand that we need to take a broader view of the human being.
I would venture to guess that 99.9% of modern populations think allopathically, with the pill mentality. And, it’s not our fault.
Big Pharma and other powerful entities have done a fabulous job of educating our traditional healing knowledge out of normal society, leaving us dependent on a medical system, that while helpful at times, also doesn’t often have our best interests (or health) at heart. This is what happens when powerful entities succumb to greed.
But I digress……
The opposite of allopathic thinking is having a holistic view of the body and our health. You may hear some herbalists refer to our “terrain.” This is a view of our being as a whole: mind, body, and spirit. When we apply a holistic viewpoint to our health, we learn to never ask an herbal question so simplistically as “what herb for what condition.”
Instead, we learn to look at the individual body, the needs of the emotions and mind, and the spirit of a person. In this manner, we make better choices for the individual.
This means we must move beyond rote formulas and uses of herbs. We must deepen our knowledge of the glorious plants God created for us! When we start learning more about plant chemistry as well as how plant constituents journey through our body to affect health, we can make better decisions for ourselves, our animals, our families, and our clients if we choose to serve others.
This article is a very beginning guide to pulling two different studies of plant chemistry together, pharmacognosy and pharmacokinetics and why this is important for the herbalist.
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Pharmacognosy and Pharmacokinetics
These are two separate ways of understanding phytochemistry (plant chemistry) and how they work on the body.
First, pharmacognosy is knowing what and how the medicinal components in plants work. This study focuses on the physical, chemical, and biological properties of these substances, their use in medicine and drug discovery, and helps us know which herbs to use and which to avoid.
Next, pharmacokinetics is how we understand what happens to a plant component once it enters the body. In essence, it’s the story of the journey of the plant chemical from entrance to the body until the waste portions are excreted in some manner. There are four stages of the journey, and these are absorption, distribution, metabolism, and excretion (ADME).
Both fields of study are massively huge.
For the herbalist, we need some understanding in order to choose the right plants for the right people and to dose appropriately and safely. This is a very beginning look at the two systems and the high points about what to know.
We’ll start with common plant compounds. I’m only discussing the most common here, and it’s important to know there are many, many others as well as many subcategories of constituents. As you grow as an herbalist, you will deepen your understanding as you continue to read and to take courses. For now, this will give you a glimpse into phytochemistry.
Then, after we cover a few main plant components, we’ll take a look at how these components work in the body.
This is rosemary, and it contains thousands of amazing components such as rosmarinic acid, carnosic acid, menthol and cineole, and many others that support a broad range of body functions. Click here to learn about plants and how they work.
Understanding Common Plant Compounds
When you start learning about herbalism, it can feel overwhelming to sort through all the chemical compounds found in plants. There are broad categories like alkaloids or flavonoids, but within each of those are many subtypes and variations. For example, “alkaloids” or “polysaccharides” aren’t just one thing—these categories and others include dozens of additional distinct families. That’s why it’s not always helpful to rely too heavily on general labels (example, saying all alkaloids are dangerous, which is false).
For now, don’t worry about memorizing every subcategory. As a family herbalist, it’s more important to become familiar with the main groups of plant compounds and how they generally work. Chemists and formulators working in pharmaceutical or advanced botanical medicine will go deeper, but for everyday herbal practice, knowing the basics about these broader phytochemical categories will give you a starting foundation.
🌿 Alkaloids
Alkaloids are nitrogen-containing compounds found in many plants, and they often have a strong effect on the body—sometimes medicinal, sometimes irritating, and sometimes toxic. Scientists believe plants produce them to defend against insects and other threats.
Alkaloids usually taste bitter. That bitterness can actually be a clue—if you taste an unfamiliar herb and it’s quite bitter, it might contain alkaloids. In fact, the bitter taste points to a certain level of toxicity most of the time. Some well-known examples of alkaloids include atropine, ephedrine, quinine, caffeine, nicotine, and even strychnine. There are many others, too.
For general use in herbalism, common alkaloid-containing herbs include black pepper, tobacco, black tea, goldenseal and Oregon grape (and other plants containing berberine), and fenugreek, among many, many others.
Alkaloids can offer benefits like:
Pain relief
Anti-inflammatory effects
Respiratory support
Nervous system calming
Antimicrobial action
But be careful—many of the world’s most dangerous toxic plants contain alkaloids that can severely harm or even kill us. Many toxic plants have “look-alikes” that we must know how to identify properly, too.
🍃 Bitters
Bitters aren’t really a chemical family. However, in your beginning herbalism studies, it’s good to recognize this category as a “taste,” and that taste has clues about actions on the body. Bitter herbs may be bitter due to a wide variety of chemical compounds, including terpenoids, polyphenols, amino acids, and other constituents.
“Bitters” are just what they sound like—herbs that have bitter-tasting compounds (such as alkaloids).
Bitters that are GOOD for you stimulate your digestive system, encouraging the production of saliva, stomach acid, bile, and enzymes.
Their chemical complexity comes from a mix of bitter-tasting substances (including alkaloids), and also glycosides and polyphenols. Plants with bitter compounds may also contain aromatics, which are the volatile essential oils that some plants have in various structures.
They’re usually supportive for liver health and can be helpful if your digestion is sluggish.
Some commonly used bitter herbs include:
Dandelion
Citrus peels
Gentian
Chamomile
Lemon balm
Angelica
Burdock
People have been using bitters for thousands of years—there are even references to bitter herbs in the Bible.
According to Guido Mase’ in his book, The Wild Medicine Solution, bitters should play an important role in your overall health. Bitters support the digestive system like no other component, and many people enjoy taking a sip of a bitter herb formula about 30 minutes before eating and/or an hour or so after eating a meal to help the flow of food, the absorption of nutrients (which we’ll cover in a moment), and reduce bloating and flatulence.
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🫐 Polyphenols
This is a HUGE category of plant chemical compounds, and for this article, we’ll focus on just two of them: flavonoids, the largest group; and tannins, which many herbalists enjoy utilizing in their work with individuals who exhibit lax conditions (too much relaxation such as with varicose veins) or overall constitutions.
Some other common polyphenols are phenolic acids found in vegetables and fruits, lignans (found in flax seed), stilbenes such as resveratrol in grapes, and polyphenolic amides such as capsaicin in cayenne.
I should mention that polyphenols, in general, are often not very bioavailable. This means that in terms of being absorbed and utilized in the body (see below), their use is sometimes problematic. In many cases, the best way to obtain the benefits of some polyphenols is to just ingest them directly. As Hippocrates famously said: “Let thy food be thy medicine.”
Flavonoids:
Flavonoids (also called bioflavonoids) are plant pigments with major health benefits. They’re antioxidants that protect your cells from oxidative stress and help your body manage inflammation.
You’ll find flavonoids in colorful fruits and vegetables—think apples, berries, onions, garlic, kale, red grapes, and for some, red wine.
One of the most well-known flavonoids is quercetin, used for:
Anti-inflammatory support
Fighting free radicals
Supporting immune health
While supplements are available, whole foods are usually better. Herbalists believe it’s best to take specific compounds as part of your diet through whole plants. This is because, as an example, the quercetin interacts synergistically with other compounds and nutrients in the plant, unlike isolated pharmaceutical-style extracts. This points again to the God-given and wonderfully created aspect of medicinal plants.
One special plant many enjoy taking for the anti-histamine benefits through quercetin is stinging nettle leaf and root (Urtica dioica). If you are wondering about taking nettle for seasonal allergies, the most important thing to know is that you must begin taking it daily about two months or so before your seasonal allergies usually begin so the body can best produce anti-histamine when the immune system comes upon an allergen.
Flavonoids can also help:
Protect collagen (important for skin, joints, and connective tissue)
Regulate blood pressure
Support liver function
Strengthen capillaries
And other important functions
Tannins:
Tannins are astringent compounds that bind to proteins and help tighten tissues. If you’ve ever had black tea or bit into a citrus peel and felt that dry, puckery sensation in your mouth—that’s a sign of tannins at work.
Tannins are found in:
Green and black tea
Citrus peels
Red grapes
Blackberry and raspberry leaf
Oak bark
Willow
In herbalism, tannins are helpful for:
Reducing inflammation
Stopping bleeding (especially in small wounds and the gums)
Calming diarrhea or dysentery
Protecting mucous membranes
Tightening mature skin or lax conditions (like varicose veins) in the body
You can see that even with us just reviewing these two polyphenols, and knowing there are many more, that this category of chemical constituents is important.
🌼 Polysaccharides
Polysaccharides are large carbohydrate molecules that are made up of many smaller simple sugar units that are bonded together (monosaccharides). They serve as long-term energy storage in plants (starches) as well as in animals (glycogen form). In plants they also provide structural support in the cell walls (cellulose).
One special polysaccharide that herbalists treasure is mucilage.
Mucilage is the gooey, slippery substance some herbs produce when mixed with water. It’s incredibly soothing and healing, especially for inflamed or irritated tissues like the throat or digestive tract. If you’ve ever cooked okra, you’ve probably noticed the slimy extract. And, it’s SO good for you!
Herbs rich in mucilage include:
Slippery elm
Okra
These are great when you’re dealing with things like sore throats, heartburn, leaky gut, or even skin irritations. To get the full benefit, mucilage usually needs to directly touch the area needing support—whether that’s inside your mouth, throat, stomach, or on your skin.
Luckily, since our GI (gastro-intestinal) tract is simply a long tube from mouth to anus, when we consume mucilage, it affects the entire length in various beneficial ways to heal and soothe.
Mucilage is usually very helpful for those with a dry constitution (dry skin, hair, nails, mouth, eyes, etc.). In Western Herbal Energetics, herbalists use this system to define how an individual may react to various herbs and to determine their individual needs.
This is frankincense resin, and it has some very special powers including supporting skin health, anti-inflammatory actions, and positive effects on the mind and emotions. Find out more about how medicinal plants work inside our premium herbalism community filled with interaction, courses, and live sessions with over a hundred replays at your fingertips. The Confident Herbalist Tribe
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🌲 Polymers (Resins)
Like bitter compounds mentioned above, resins are not a specific plant chemical family, but they are important organic compounds found in many plants. They are generally composed of diverse groups of terpenoids, resinous acids, and polymers. They belong to the polymer chemical family.
Resins are sticky substances produced by plants—especially trees—when they’re injured. They help seal and protect the plant, and they have strong antimicrobial and healing properties for many parts of the body from the skin to the lungs.
Common resins include:
Myrrh
Poplar buds (used to make Balm of Gilead)
Pine (and other evergreens) resin
Calendula (coating on the leaves, flowers)
Resins don’t mix well with water but dissolve better in high proof alcohol, so they’re great in tinctures. They don’t extract well in water infusions (herbal teas). You’ll often see them used in tinctures, salves, incense, or infused oils. They can be found in some capsules, as well, such as Boswellia supplements.
Resins are often:
Antimicrobial
Anti-inflammatory
Expectorant (helpful for clearing mucus)
🫧 Glycosides
Glycosides are another massively huge chemical family, and they may be phenol, alcohol, or sulfur compounds according to Science Direct. Glycosides have sugar proteins that are attached to one or more nonsugar proteins.
Here are a few of the glycoside categories.
Some glycosides have higher levels of toxicity, meaning they may be used as low-dose herbs, which the family herbalist should avoid as these types of plants require specialized training. An example of this is the cardiac glycoside, digoxin which is derived from the foxglove plant. This is a very toxic plant, and even one leaf might kill a person.
Then there are flavonoid glycosides that include rutin and hesperidin, two chemical constituents that are good for us!
We’ve heard of cyanogenic glycosides, which are found in almond and apricot kernels (amygdalin), and also in elderberry leaves and seeds. Once again, these are wonderful examples of constituents that may have toxicity depending on the dosage, but when used correctly can have wonderful effects on the human body.
Another of my favorite examples of a common glycoside we all love is salicin, which is the active constituent found in willow bark. It’s in the phenolic glycoside category.
Need soap? Saponins are special glycosides that foam up when mixed with water—kind of like soap (which is where their name comes from!). The reason these special glycosides work is because that have a hydrophilic (water loving) sugar part and a hydrophobic part (water repelling). This creates a foaming property. This ability to foam also serves to act in some cases as a solubilizer or emulsifier of sorts.
Saponins are found in herbs like licorice root, wild yam, soap nuts, horse chestnut, and others. Saponins are especially good for mucus membranes, much like mucilage.
God created plants perfectly, everywhere on earth, to heal our body, mind, and even help with spirit.
🌬 Volatile Oils (Essential Oils)
If you’ve been in my world any length of time, you know I love my essential oils, being a level two certified aromatherapist and all, as well as an herbalist.
Volatile oils are the aromatic, quickly-evaporating oils found in many herbs. These are the “essential oils” you might be familiar with. In plants, they act as a natural defense system, often protecting against insects or disease. Scientists believe they may have other functions, but do not know much more than this at this time.
Some herbalists use whole plant forms found in aromatic plants like the mints to obtain the chemical advantages of the aromatic compounds, while others may occasionally use potent essential oils extracted through steam distillation. Some herbalists choose to distill plants at home and enjoy the byproduct of the process, which are aromatic hydrosols.
Some herbalists don’t like to use essential oils because they believe they are processed and possibly dangerous. I just want to note that, again, the danger in use is due to a lack of knowledge as well as purchasing cheap, low-quality, possibly adulterated or rectified essential oils.
Here is my personally vetted list (halfway down the page) of high quality legitimate aromatherapy companies. (Please do not purchase from third-party labels or from big box stores or from those who are not aromatherapists with a personal relationship with the small farms. I do not make additional income from sharing these (except for three of them), and you can be sure you’ll obtain great essential oils while doing some price-shopping.
BUT, in terms of essential oils being processed, all of our herbal preparations are processed! That is, unless we are eating the leaves, roots, etc. directly. And, one could argue that the digestive process is a way of processing the plants, too!
We process herbs by making alcohol extracts (tinctures), vinegar extracts (acetums), oxymels (honey and vinegar extracts), etc. Essential oils are extracted by steam distillation, a very natural process—-just as natural as adding herbs to alcohol, in my opinion.
Just keep in mind: essential oils are highly concentrated and should be used with care— diluted when used on the skin and rarely taken internally unless under professional guidance. Hydrosols are very safe, even for infants and small pets. The hydrosol of a plant is the by-product of the steam distillation process, and you can see me make a batch here, right in my kitchen, with simple kitchen equipment. Small amounts of essential oil is extracted along with the hydrosol (or plant water).
Essential oils are commonly found in aromatic herbs like:
Peppermint
Lavender
Eucalyptus
Thyme
Rosemary
Evergreens
Citrus peels
and more…..
Volatile oils work well via inhalation (like steams or diffusers), diluted for topical use, or in tinctures. NOTE: Do not ingest essential oils unless under the guidance of a level 2 or higher aromatherapist with specific training in ingestion.
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Herbal Categories and How They Interact
These plant compounds don’t live in isolation. A single herb might contain multiple types—a plant could be both bitter and astringent, or contain alkaloids and volatile oils. These classifications are just tools to help you begin understanding how herbs work.
The thing I always remember is that God made the plants so perfectly. There is a natural synergy among the plant constituents that science most often can’t explain, try as the scientists like. We know more than we did…but God’s mystery of plant medicine reigns supreme.
Become a Family Herbalist and learn to use both herbs and essential oils safely, effectively, and finally get your unique family’s home apothecary created!
Pharmacokinetics of Herbal Components
Pharmacokinetics is the study of what the body does to a substance once it enters your body. It helps us to understand how plant compounds move through the body once we take them. Understanding pharmacokinetics helps herbalists to:
Choose the best form and route of administration of an herbal preparation
Know approximately how long herbal constituents may stay active in the body
Predict possible interactions with pharmaceuticals (called HDI’s: Herb-Drug Interactions)
Safely adjust dosage amount and frequency for individuals
Be aware of and understand synergy: How plant constituents work together in the body
The process includes four main stages: absorption, distribution, metabolism, and excretion (often remembered as ADME). Sometimes, compounds are also reabsorbed.
Understanding this helps you determine how long an herb works, how it should be administered, and how to adjust dosage once you know more about the specific constituents.
Absorption:
Absorption is how herbal constituents enter the bloodstream from the site of administration. This site might be through the mouth and gut, via the skin, the lungs, etc. There are several factors that influence absorption. These include:
Form of preparation of the herb: tinctures, teas, capsules, syrups. All of these will be absorbed differently and at different speeds. An alcohol tincture is generally absorbed much more quickly than capsules, for example.
Type of solubility of the constituent: Plant components have variable solubilities in either fat (lipid) or water. Some components like essential oils and resins are more soluble in oils and alcohol; while more water soluble components like minerals, flavonoids, and polysaccharides do much better in water infusions such as teas and decoctions.
Digestive health: A healthy gut and gut lining, a body with proper enzyme function, and correct pH levels all will enhance herbal absorption.
Timing and food: Taking herbs on an empty stomach speeds absorption, while a full stomach will slow it down. Taking bitters about 30 minutes before eating a meal, for example, can prepare the digestive system and improve absorption of the nutrients in the food.
Distribution:
Distribution is the process of how the plant constituents move through the bloodstream and affect tissues in the body once they are absorbed. The constituents, once in the bloodstream, travel to different tissues and organs and can influence function. In other words, they are distributed around the body.
Here are some factors and key points to know:
Constituents often have an affinity for certain specific tissues in the body. For example, mucilage has an affinity for supporting mucus membranes throughout the body. Nervine components tend to affect the nervous system function.
The health of a person’s circulation (blood flow), ability to bind proteins, and cell membrane permeability will affect how and where plant compounds are distributed.
The blood-brain barrier factors in as a protector of the brain by restricting access for many constituents and compounds. However, small, lipophilic (fat loving) compounds such as many terpenes in essential oils can cross over.
One important aspect of distribution to understand is that not all constituents are distributed evenly to all parts of the body. This is why learning about medicinal plants deeply and well will help you to know which plants to use for specific conditions.
Metabolism
Also known as biotransformation, metabolism is how the body alters herbal compounds. This takes place mainly in the liver, but also in the gut microbiome and kidneys.
Things to know:
The liver’s enzymes can activate, inactivate, or modify phytochemicals. For example, saponins and glycosides may be broken into more active or absorbable forms.
Gut health plays a role. Gut bacteria can transform many polyphenols and alkaloids into usable metabolites. If the gut is healthy and filled with “good” bacteria, our metabolism is much better.
Some herbal constituents can support or even modulate liver metabolism. For example, both the silymarin in milk thistle and constituents in other liver-loving herbs like dandelion and burdock root can be very supportive of liver function in the process of metabolism. Other constituents can slow liver function down, such as a compound found in grapefruit.
Healthy kidneys play a role in metabolism of plant constituents too. Through processes like oxidation, reduction, and hydrolysis, kidneys can affect the metabolic transformation of some compounds such as flavonoids. Kidneys also regulate the balance of nutrients as well as supporting healthy pH balance in the body.
Excretion (Elimination):
Compounds and metabolites that aren’t useful to our body are eliminated. In fact, they must be removed, or we become ill.
Kidneys help eliminate wastes through the urine.
Bile breaks down compounds, then these wastes are eliminated through fecal matter.
Sweat helps remove toxins through the skin.
Our breath rids our body of toxins via healthy lung and respiratory action.
Breast milk is a valuable form of excretion as some plant compounds are excreted through breast milk. Knowing this, we can skillfully use herbs to help support the infant’s body. An example of this is if mom drinks a cup of chamomile tea about 30 minutes before nursing, a baby with colic may find relief.
Reabsorption:
Sometimes, substances that should be excreted are reabsorbed into the body, especially if digestion is slow (like in constipation) or liver function is impaired. This is less of a concern with herbs than with pharmaceuticals, since herbal compounds are typically more compatible with the body’s natural systems and tend not to be reabsorbed as readily.
Actions we can take to avoid reabsorption include movement (exercise), hydration, proper sleep and rest, getting sunshine, and most other healthy lifestyle habits.
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Final Thoughts on Beginning Understanding of How Medicinal Herbs Work:
Hopefully, this quick introduction to the two P’s of phytochemistry helps you to better understand how plant compounds interact with the body. Having this foundation as a place to further study is a key piece in building your confidence and skill as an herbalist.
IMPORTANT: As you dive further into your herbal education by taking courses and interacting with a vibrant and like-minded herbal community, you'll understand more confidently how they work together, not just independently. We should never make sweeping generalizations about plant chemistry on individuals because people’s bodies are all different, our needs are different, and therefore, we work with individuals holistically.
I hope you enjoyed this overview of two important aspects of learning herbalism.
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Hugs, Health, and Herbs,
Heidi
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