Table 4.

Major plant ingredients used for medicinal purposes.

Group	Description
Alkaloids	Nitrogen-bearing molecules found in a variety of plants. Used in drugs like vincristine (from Madagascar periwinkle) and sinomenine (from Sinomenium acutum) [325] for cancer treatment; atropine (from deadly nightshade) for emergency medicine, anesthesia, cardiology, and other specialties as well as reversing bradycardia and managing organophosphate poisoning [326]; and morphine (from the poppy plant, Papaver somniferum) for pain relief in cancer patients [327].
Bitters	Plants with a bitter taste that stimulate salivary glands and digestive organs. Examples include hop acids from the hop plant (Humulus lupulus) exhibiting anticancer activity [328], and amarogentin (Gentiana lutea radix, L.), a bitter taste receptor activator regulating a variety of cell signaling including AMP-activated protein kinase (AMPK), STAT3, Akt, ERK, and p53 [329]
Cardiac glycosides	Compounds (digitoxin, digoxin, and convallotoxin) in medicinal plants like Foxglove and Lily of the Valley that support heart strength and stimulate urine production.
Cyanogenic glycosides	Glycosides based on toxic cyanide found in plants like wild cherry and elderberry. Used in small doses as a muscle relaxant and to soothe dry coughs.
Flavonoids	Compounds found in many plants that often act as pigments and have antiviral and anti-inflammatory properties. They generally have a 15-carbon skeleton and are known to strengthen capillaries and prevent leakage into tissues. Examples include lemon and buckwheat.
Minerals	Many plants draw minerals from the soil and convert them into a form easily used by the human body. Example: horsetail, which is high in silica and used for arthritis because it supports the repair of connective tissue.
Phenols	Plant compounds thought to protect against infection and herbivory. Often anti-inflammatory and antiseptic. Phenols vary in structure and range from salicylic acid to complex sugar-containing phenolic acids. Examples include wintergreen, willow, and mint family.
Polysaccharides	Sugar molecules found in all plants that can form jelly-like masses used to treat dry or irritated tissues.
Proanthocyanins	Pigments related to tannins and flavonoids that protect circulation. Found in red grapes, blackberries, and hawthorn berries.
Saponins	Active compounds that produce lather in water. Found in plants like agave and wild yam. Steroidal saponins are very similar to the chemical structures of many of the human body’s hormones including estrogen and cortisol. Some of them are used to produce synthetic hormones.
Tannins	Compounds produced by most plants that deter herbivory and are useful in curing leather. Found in plants like oak bark and black catechu.
Vitamins	Many plants contain high levels of useful vitamins. Examples include watercress, rose hips, and sea buckthorn, which have high levels of vitamins B, C, and E.
Terpenes/terpenoids	Terpenes and terpenoids are the main bioactive compounds of essential oils, volatile and concentrated liquids extracted from different parts of plants. Example: tea tree oil, a strong antiseptic. Carvacrol, carvone, eugenol, geraniol, and thymol for antimicrobial activity [330]. Paclitaxel (taxol from Taxus brevifolia tree) for cancer treatment [331]
Fatty acids	Omega-3 fatty acids play an important role in regulating brain function and lowering cardiovascular disease risk; alpha-linolenic acid from nuts and seeds, flaxseed oil, soybean oil, and canola oil [332]; eicosapentaenoic and docosahexaenoic acid from microalgae [333]

The table was adapted from the webpage (source: U.S. Department of Agriculture; U.S. Forest Service: Active plant ingredients used for medicinal purposes) [334].