Absinthol

A monoterpene ketone found in wormwood (Artemisia absinthium). Also called thujone. Responsible for the bitter taste and traditional medicinal use as an anthelmintic and digestive bitter. Toxic in large doses; the term absinthol is sometimes used to describe the thujone-rich fraction of wormwood essential oil. See also: thujone.

Acetylcholine

A neurotransmitter involved in memory, muscle function, and the parasympathetic nervous system. Some herbs, including bacopa and lion's mane, are studied for their ability to support acetylcholine levels or activity in the brain.

Achilleine

An alkaloid found in yarrow (Achillea millefolium). Associated with hemostatic (blood-stopping) activity. Contributes to yarrow's traditional use for wounds and heavy menstrual bleeding.

Actaeine

A triterpene glycoside found in black cohosh (Actaea racemosa). Contributes to the herb's antispasmodic and estrogenic activity studied in menopausal symptom research.

Alkaloids

Nitrogen-containing organic compounds produced by plants, often with significant physiological effects on humans. Alkaloids include a wide range of compounds such as berberine (goldenseal), caffeine (green tea), morphine (poppy), and capsaicin-related compounds. They are often the primary active constituents responsible for an herb's medicinal strength. Dosage matters significantly with alkaloid-rich herbs.

Allantoin

A compound found in comfrey and other plants. Promotes cell proliferation and wound healing. Used topically in creams and salves for skin repair and soothing inflamed tissue.

Amino Acids

The building blocks of proteins. Some herbs contain significant concentrations of specific amino acids that contribute to their nutritive and therapeutic actions. Spirulina and moringa are notable examples.

Anthraquinone Glycosides

Compounds found in senna, cascara, and yellow dock that stimulate intestinal motility, producing a laxative effect. Should be used short-term only; long-term use can cause dependence and electrolyte imbalance.

Asparagine

An amino acid found in asparagus and related plants, including shatavari. Contributes to diuretic effects and supports kidney function in traditional use.

Astragalin

A flavonoid glycoside (kaempferol-3-glucoside) found in several plants including astragalus. Associated with anti-inflammatory, antioxidant, and immune-supporting activity.

Aucubin

An iridoid glycoside found in plantain and other plants. Associated with anti-inflammatory and liver-protective effects. Contributes to plantain's traditional use for wound healing and digestive support.

Azulene

A blue-colored sesquiterpene hydrocarbon formed during steam distillation of chamomile and yarrow. Not present in the fresh plant but develops from matricine or achillicin during processing. A potent anti-inflammatory compound responsible in part for the blue color of German chamomile essential oil.

Benzene (Benzene Derivatives)

In herbal chemistry, benzene refers to the aromatic ring structure found in many plant phenols, including flavonoids, coumarins, and lignans. These derivative structures contribute significantly to antimicrobial and antioxidant properties.

Berberine

A bright yellow isoquinoline alkaloid found in goldenseal, Oregon grape, barberry, and coptis. Has demonstrated antimicrobial, anti-inflammatory, blood sugar-lowering, and cholesterol-lowering effects in clinical studies. One of the more researched herbal compounds with a broad therapeutic profile.

Beta-Carotene

A carotenoid pigment that the body converts to vitamin A. Found in orange and red plant foods and herbs. A potent antioxidant; excess consumption from supplements can be harmful in smokers. Dietary sources are considered safe. See also: carotenoids.

Betaine

A methyl donor compound found in beets, nettles, and other plants. Supports liver function, homocysteine metabolism, and digestive acid production (as betaine HCl).

Bilobalide

A sesquiterpene trilactone found in ginkgo biloba leaves. Studied for neuroprotective effects, including protection against ischemia-induced nerve damage and support of mitochondrial function in brain cells.

Bitter Glycoside

Glycoside compounds with a bitter taste that stimulate the digestive system by triggering bitter taste receptors. They promote gastric secretion, bile flow, and appetite. Found in gentian, dandelion, and artichoke. See also: bitter principles.

Bitter Principles

A collective term for compounds that produce a bitter taste and stimulate digestive function. Includes bitter glycosides, sesquiterpene lactones, iridoids, and alkaloids depending on the plant. Used broadly to describe the bitters class of herbal action.

Bitter Sesquiterpenes

Sesquiterpene compounds with a bitter flavor profile. Found in wormwood and artichoke. Contribute to digestive stimulant and appetite-stimulating effects through bitter receptor activation.

Bitters

A general term for compounds or preparations that produce bitterness and stimulate digestive secretions. See: bitter principles, bitter glycosides, bitter sesquiterpenes.

Bromine

A trace mineral found in some marine plants. Historically used in sedative preparations. Present in seaweeds and some herbs in small amounts.

B Vitamins

A group of eight water-soluble vitamins including B1 (thiamine), B2 (riboflavin), B3 (niacin), B5 (pantothenic acid), B6, B7 (biotin), B9 (folate), and B12. Support energy metabolism, nervous system function, and red blood cell production. Found in nutritive herbs such as nettles, oatstraw, and moringa.

Caffeic Acid

A hydroxycinnamic acid found in many plants including echinacea, rosemary, and dandelion. Has antioxidant, anti-inflammatory, and immune-supporting properties. Often found alongside chlorogenic acid as an ester (caffeoylquinic acid).

Calcium

An essential mineral found in significant quantities in nutritive herbs such as nettles, oatstraw, and horsetail. Required for bone density, muscle contraction, nerve transmission, and blood clotting.

Camphor

A bicyclic monoterpene ketone found in camphor tree, rosemary, sage, and some other aromatics. Used topically as a counterirritant for muscle pain and congestion. Toxic when ingested in concentrated form; the small amounts in herbal preparations are generally safe.

Capsaicin

The primary active compound in cayenne pepper (Capsicum annuum), responsible for its heat. Binds to TRPV1 pain receptors, initially stimulating then depleting substance P, which reduces pain signals. Used topically in creams for neuropathic pain, arthritis, and muscle soreness. Internally it stimulates circulation and digestion.

Carotene

Orange-yellow pigments in the carotenoid family. Precursors to vitamin A. Found in carrots, calendula, and many orange and yellow herbs. See also: carotenoids, beta-carotene.

Carotenoids

A class of fat-soluble plant pigments including beta-carotene, lycopene, lutein, and zeaxanthin. Act as antioxidants and some convert to vitamin A in the body. Found in orange, red, and yellow herbs and plant foods. Cayenne, calendula, and rose hips are good sources.

Carvacrol

A phenolic monoterpene found at high concentrations in oregano and thyme essential oils. Has well-documented antimicrobial, antifungal, and anti-inflammatory activity. One of the primary compounds responsible for oregano oil's use against pathogens.

Catechin

A type of flavonoid found in green tea, hawthorn, and other plants. Catechins are potent antioxidants that support cardiovascular health and have anti-inflammatory properties. EGCG (epigallocatechin gallate) from green tea is the most studied catechin.

Chlorogenic Acid

A polyphenol ester of caffeic acid found in artichoke, dandelion, and coffee. Antioxidant with studied effects on blood sugar regulation and blood pressure.

Choline

An essential nutrient involved in neurotransmitter synthesis (acetylcholine), cell membrane structure, and liver fat metabolism. Found in dandelion, oatstraw, and other nutritive herbs. Important for cognitive function and fetal brain development.

Chrysarobin

An anthraquinone derivative found in pau d'arco and araroba. Has antifungal properties. Used historically for skin conditions.

Cimicifugin

A resin compound found in black cohosh (Actaea racemosa). Contributes to the herb's antispasmodic and sedative properties. Named from the plant's former genus name Cimicifuga.

Cynarin (Cinarin)

A caffeoylquinic acid found in artichoke leaf. Promotes bile production and flow, supporting liver and gallbladder function. A primary active compound behind artichoke's use as a liver and digestive tonic.

Cineol

See: cineole.

Cineole (1,8-Cineole / Eucalyptol)

A monoterpene oxide found in eucalyptus, rosemary, cardamom, and sage. The primary active compound in eucalyptus oil. Has expectorant, antimicrobial, and anti-inflammatory effects. Used in cough preparations and topical rubs for respiratory congestion.

Citral

A mixture of two monoterpene aldehydes (geranial and neral) responsible for the lemon scent in lemongrass, lemon balm, and lemon verbena. Has antimicrobial and anti-inflammatory properties.

Citronellal

A monoterpene aldehyde found in citronella, lemon balm, and lemon eucalyptus. Responsible for citronella's insect-repelling properties. Also contributes to the calming aroma of lemon balm.

Citronellol

A monoterpene alcohol found in rose, geranium, and citronella oils. Contributes to floral fragrance and has antimicrobial properties.

Coumarin

See: coumarins.

Coumarins

Polyphenolic compounds with antimicrobial, antiviral, anti-inflammatory, antidiabetic, and antioxidant properties. Also capable of inhibiting certain enzyme activity. Found in sweet clover, cinnamon, celery, and parsley. Warfarin, the pharmaceutical blood thinner, is derived from a coumarin compound. High-dose coumarin-containing herbs may interact with anticoagulant medications.

Cratelegin

A flavonoid compound found in hawthorn (Crataegus species). Contributes to hawthorn's cardiovascular effects including improved coronary blood flow and cardiac efficiency.

Curcumin

The primary bioactive polyphenol in turmeric (Curcuma longa), responsible for its golden color. Extensively studied for anti-inflammatory, antioxidant, and neuroprotective properties. Poor oral bioavailability on its own; absorption is enhanced by piperine (black pepper) or fat-based preparations. One of the most researched plant compounds in modern herbal science.

Diosmin

A flavonoid glycoside found in citrus peel and some herbs. Used clinically in Europe for venous insufficiency and hemorrhoids. Supports blood vessel tone and reduces inflammation in vascular tissue.

Enzymes

Proteins that catalyze biochemical reactions. Some herbs contain digestive enzymes that support food breakdown. Papain (papaya) and bromelain (pineapple) are the most studied herbal enzymes.

Essential Oil

Also called volatile oils. Concentrated, aromatic compounds responsible for a plant's distinctive scent. They evaporate when exposed to heat, light, or oxygen and are composed primarily of terpenoid and phenylpropanoid compounds. Responsible for much of an herb's antimicrobial, antispasmodic, and aromatic digestive activity. See also: volatile oils.

Farnesol

A sesquiterpene alcohol found in flowers including chamomile and rose. Has antimicrobial properties, particularly against Candida species and some bacteria.

Fats

See: fatty acids, lipids.

Fatty Acids

Products of fat breakdown during digestion. Assist in body insulation, energy storage, and vital organ protection. Omega-3 and Omega-6 fatty acids cannot be synthesized internally and require dietary sources. Found in saw palmetto, evening primrose, and seed-bearing herbs. Essential for cell membrane integrity and hormone production.

Flavone Glycosides

Flavonoids bound to sugar molecules. The glycoside form improves water solubility but may reduce direct absorption compared to aglycone forms. Ginkgo biloba's standardized extracts are typically measured for flavone glycoside content (24%).

Flavonoids

A large class of plant pigments found alongside chlorophyll and carotenoids. They strengthen capillaries and provide antioxidant, antiviral, hepatoprotective, anti-inflammatory, and antihypertensive properties. They bind to enzyme surfaces, inhibit enzyme systems, stabilize membranes, and protect plants from environmental stress. Over 6,000 flavonoids are known. Major subclasses include flavones, flavonols, flavanones, catechins, and isoflavones.

Formic Acid

A simple organic acid found in nettles and ants. Responsible for the stinging sensation of nettle leaves. Lost during drying or cooking. In small concentrations it has antimicrobial properties.

Furanosesquiterpenoids

A class of sesquiterpene compounds with a furan ring, found in myrrh and other resins. Contribute to myrrh's antimicrobial and anti-inflammatory properties.

Geraniol

A monoterpene alcohol found in rose, palmarosa, and lemon balm. Has antimicrobial properties and contributes to the floral aroma of several herbs.

Ginkgolides

Diterpene trilactones unique to ginkgo biloba. They are potent platelet-activating factor (PAF) antagonists, reducing platelet aggregation and improving circulation. Key compounds behind ginkgo's use for cognitive support and peripheral circulation. Ginkgolide B is the most studied.

Ginsenosides

Triterpene saponins found specifically in Panax ginseng and closely related species. The primary active compounds responsible for ginseng's adaptogenic, energy-supporting, and cognitive effects. Over 100 individual ginsenosides have been identified. Not present in Siberian ginseng (eleuthero), which is a different plant family.

Gitonin

A steroidal saponin found in sarsaparilla and related plants. Contributes to the herb's traditional use for skin conditions and joint inflammation.

Glucosinolates

Sulfur-containing glycosides found primarily in brassica plants (horseradish, mustard, watercress). When the plant is damaged, glucosinolates break down to form isothiocyanates, which have antimicrobial and studied chemoprotective properties.

Glutathione

The body's primary intracellular antioxidant. Some herbs support glutathione production rather than supplying it directly (it is poorly absorbed orally). Milk thistle, turmeric, and garlic are studied for their ability to raise glutathione levels in liver cells.

Glycoside

See: glycosides.

Glycosides

Compounds in which a sugar molecule is bound to a non-sugar active component (the aglycone). The sugar portion typically improves water solubility and may affect absorption. Many classes of active plant compounds are glycosides, including flavonoid glycosides, cardiac glycosides, and bitter glycosides. Hydrolysis by gut bacteria or digestive enzymes often releases the active aglycone.

Glycyrrhizic Acid

A triterpene saponin found in licorice root (Glycyrrhiza glabra). About 50 times sweeter than sugar. Has anti-inflammatory, antiviral, and adrenal-supporting properties through inhibition of cortisol breakdown. High doses or long-term use can cause sodium retention, potassium loss, and elevated blood pressure. Deglycyrrhizinated licorice (DGL) preparations remove this compound for safer use.

Gums

Polysaccharide exudates produced by plants as protective responses to injury. Includes gum arabic and gum tragacanth. Used as demulcent and soothing agents in herbal preparations. Contribute to bulk-forming laxative action in some herbs.

Hesperidin

A flavanone glycoside found in citrus peel. Supports capillary integrity, reduces inflammation, and has antioxidant properties. Often combined with vitamin C in studies of vascular health.

Hydrastine

An alkaloid found in goldenseal (Hydrastis canadensis), alongside berberine. Has vasoconstricting and astringent properties. Contributes to goldenseal's traditional use for mucous membrane conditions and wound healing.

Hyperforin

A phloroglucinol derivative found in St. John's Wort (Hypericum perforatum). A primary active compound responsible for antidepressant effects through inhibition of serotonin, dopamine, and norepinephrine reuptake. Also responsible for significant drug interactions with CYP3A4-metabolized medications including contraceptives and antiretrovirals.

Hypericin

A naphthodianthrone pigment found in St. John's Wort (Hypericum perforatum). The dark red compound visible in the plant's oil glands. Historically thought to be the primary antidepressant compound; current research indicates hyperforin plays a larger role, but hypericin has antiviral and photoactive properties.

Icariin

A flavonoid glycoside found in horny goat weed (Epimedium species). Has studied effects on libido, erectile function, and bone density. Acts as a weak PDE5 inhibitor (similar mechanism to sildenafil) and supports testosterone metabolism in some models.

Imidazole Alkaloids

A class of alkaloids containing an imidazole ring. Found in pilocarpus and some other plants. Contribute to parasympathetic nervous system stimulation.

Inulin

A soluble dietary fiber and prebiotic fructan found in chicory root, dandelion root, artichoke, and burdock. Feeds beneficial gut bacteria (particularly Bifidobacterium), supports bowel regularity, and may help stabilize blood sugar. Can cause gas and bloating in sensitive individuals.

Invert Sugar

A mixture of glucose and fructose formed by hydrolysis of sucrose. Found in some herbal preparations and plant extracts. Contributes to sweetness and acts as a preservative in syrups.

Iodine

An essential mineral required for thyroid hormone production. Found in significant amounts in seaweeds and some land plants grown in iodine-rich soil. Both deficiency and excess iodine can disrupt thyroid function.

Iron

An essential mineral required for red blood cell production and oxygen transport. Found in significant quantities in nettles, yellow dock, dandelion, and other nutritive herbs. Non-heme iron from plants absorbs better when taken with vitamin C. Yellow dock is traditionally used to support iron absorption specifically.

Isoferulic Acid

A hydroxycinnamic acid found in cimicifuga and other plants. Has anti-inflammatory and antidiabetic properties in preclinical research.

Isoflavones

A subclass of flavonoids with phytoestrogenic activity, meaning they can weakly bind to estrogen receptors. Found primarily in legumes including red clover and soy. Studied for menopausal symptom relief, bone density support, and cardiovascular effects. Caution in hormone-sensitive conditions.

Isovaleric Acid

A short-chain fatty acid found in valerian root and hops. Contributes to the characteristic unpleasant odor of valerian. Has some sedative activity and contributes to the herb's calming properties alongside valerenic acid.

Isorhamnetin

A flavonol found in sea buckthorn, calendula, and other plants. Has anti-inflammatory, antioxidant, and studied cardiovascular-protective properties.

Kaempferol

A flavonol found in many herbs including calendula, ginkgo, and elder. Has antioxidant, anti-inflammatory, and studied anti-cancer properties in laboratory research. One of the most common dietary flavonoids.

Lapachol

A naphthoquinone found in pau d'arco (Tabebuia impetiginosa) inner bark. Has demonstrated antifungal, antibacterial, and antiviral activity in laboratory studies. High doses are toxic; therapeutic use relies on the whole bark extract which contains multiple synergistic compounds.

Lignans

Polyphenolic compounds found in seeds, flaxseed, and some herbs including schisandra. Have phytoestrogenic and antioxidant properties. Gut bacteria convert dietary lignans into enterolactone and enterodiol, which have hormonal activity. Flaxseed is the richest dietary source.

Limonene

A cyclic monoterpene responsible for the citrus scent in lemon, orange, and many herbs including lemongrass. Has antimicrobial, anti-inflammatory, and studied anti-cancer properties. Found in the essential oils of many aromatic herbs.

Linalool

A monoterpene alcohol responsible for the characteristic floral scent of lavender and many other herbs. Has sedative, anxiolytic, and analgesic properties. Studies suggest it acts on GABA receptors in the central nervous system, supporting lavender's traditional use for anxiety and insomnia.

Linolenic Acid

An essential omega-3 fatty acid (ALA) found in flaxseed, hemp, and some medicinal plants. The body uses it to produce EPA and DHA, though conversion rates are limited. Important for cardiovascular and inflammatory balance.

Lupulin

A yellow resinous powder found in the glands of hops (Humulus lupulus) strobiles. Contains the bitter acids (humulone, lupulone) and essential oils responsible for hops' sedative and bitter properties. 2-Methyl-3-buten-2-ol, formed from lupulin degradation, has direct sedative activity.

Macamides

Unique fatty acid amides found in maca root (Lepidium meyenii). Specific to the maca plant and studied for their role in the herb's energy-boosting and libido-supporting effects. May interact with the endocannabinoid system.

Magnesium

An essential mineral involved in over 300 enzymatic reactions. Supports muscle relaxation, nerve function, sleep, and energy production. Found in nettles, oatstraw, and dark leafy herbal preparations. Deficiency is common and associated with muscle cramps, anxiety, and insomnia.

Manganese

A trace mineral essential for bone formation, wound healing, and enzyme function. Found in nettles, oatstraw, and horsetail. Supports antioxidant enzyme superoxide dismutase (MnSOD).

Menthol

A cyclic terpene alcohol found in peppermint and spearmint. Activates cold-sensitive receptors (TRPM8), producing a cooling sensation without actually lowering temperature. Has antispasmodic effects on smooth muscle, making it useful for IBS and tension headaches. Topically applied for pain relief and nasal congestion.

Menthone

A ketone found alongside menthol in peppermint oil. Has a strong mint odor and contributes to the herb's antispasmodic and antimicrobial properties.

Monoterpenes

The smallest class of terpenes, composed of two isoprene units (10 carbons). They make up the majority of most essential oils and are responsible for the characteristic aromas of herbs like lavender, peppermint, and rosemary. Examples include limonene, linalool, camphor, and menthol. Generally have antimicrobial and antispasmodic properties.

Mucilage

A gelatinous, slippery polysaccharide substance produced by many plants. When hydrated, it forms a protective coating over inflamed mucous membranes. Used internally for sore throats, gastritis, ulcers, and urinary tract irritation. Found in marshmallow root, slippery elm, and Irish moss.

Mucins

Glycoproteins produced by the body's mucous membranes. Some demulcent herbs support mucin production and protection of the mucosal lining. Distinct from plant mucilage but with similar protective function in the body.

Myrcene

A monoterpene found in hops, lemongrass, and thyme. Has sedative, analgesic, and anti-inflammatory properties. In hops, it contributes to the calming effect alongside lupulin.

NDGA (Nordihydroguaiaretic Acid)

A potent antioxidant lignan found in chaparral (Larrea tridentata). Has antioxidant and antimicrobial properties. Associated with hepatotoxicity and kidney damage at high doses, which limits chaparral's therapeutic use.

Nerol

A monoterpene alcohol found in neroli (bitter orange blossom) and lemongrass. Has a fresh floral scent and antimicrobial properties.

Oleanolic Acid

A pentacyclic triterpene found in olive leaf, calendula, and many other plants. Has anti-inflammatory, hepatoprotective, and antiviral properties. Studied for cardiovascular and metabolic effects.

Oleic Acid

A monounsaturated omega-9 fatty acid found in olive oil and many seed oils. Anti-inflammatory; supports cardiovascular health and cellular membrane integrity.

Oligosaccharides

Short-chain carbohydrates with prebiotic activity that feed beneficial gut bacteria. Found in medicinal mushrooms and several root herbs. Contribute to immune-modulating effects of mushrooms like reishi and chaga.

Organic Acids

A broad category including citric, malic, tartaric, and other plant acids. Contribute to flavor (tartness) and some therapeutic effects including mild antibacterial action and support of mineral absorption.

Origanene

A terpene compound found in oregano. Contributes to the herb's antimicrobial properties alongside carvacrol and thymol.

Oxalates

Organic acid salts found in spinach, sorrel, yellow dock, and some other herbs. Bind to calcium and other minerals, potentially reducing their absorption. High oxalate intake is associated with kidney stone formation in susceptible individuals. A concern with long-term, high-dose use of oxalate-rich herbs.

Palmitic Acid

A saturated fatty acid found in saw palmetto and many plant oils. A key component of saw palmetto's lipophilic extract that supports prostate health.

Parillin

A steroidal saponin found in sarsaparilla. Associated with the herb's traditionally used for wellness and anti-inflammatory properties.

Phenolic Acid

See: phenolic acids.

Phenolic Acids

A subclass of polyphenols including caffeic acid, rosmarinic acid, chlorogenic acid, and others. Have antioxidant, anti-inflammatory, and antimicrobial properties. Widely distributed across medicinal herbs. Water-soluble and readily absorbed from herbal teas and extracts.

Phenols

Aromatic alcohols possessing bactericidal, antiseptic, and anthelmintic properties. Amino acids, phenylpropanoids, salicylates, salicins, lignans, and coumarins derive from phenols. Compounds with the suffix "-ol" frequently belong to this category. A broad and important class in medicinal herb chemistry.

Phytoestrogens

Plant compounds that weakly mimic or modulate estrogen in the body by binding to estrogen receptors. Include isoflavones (red clover, soy), lignans (flaxseed), and coumestans. Effects are complex and context-dependent. May help with menopausal symptoms but should be used with caution in hormone-sensitive conditions including estrogen-receptor-positive cancers.

Phytosterols

Plant-derived sterols structurally similar to cholesterol. Compete with cholesterol for absorption in the gut, potentially reducing blood cholesterol levels. Found in saw palmetto, nettle root, and many seeds. Saw palmetto's phytosterols contribute to its prostate-supportive effects.

Polyphenols

Compounds containing multiple phenol units with high antioxidant activity. Flavonoids and tannins represent the two largest polyphenol groups. Polyphenols protect plants from UV radiation and pathogens; in humans they reduce oxidative stress, modulate inflammation, and support cardiovascular health.

Polysaccharide Glycans

Complex carbohydrate chains found in medicinal mushrooms including reishi, chaga, and turkey tail. Beta-glucan polysaccharides are the primary immune-modulating compounds in these mushrooms, interacting with immune cell receptors to support immune surveillance and activity.

Polysaccharides

Long-chain carbohydrate polymers. In herbs, polysaccharides include starches, mucilage, and immune-active beta-glucans. Echinacea's polysaccharides are studied for immune-stimulating properties. Medicinal mushroom polysaccharides are among the most researched immunomodulatory compounds in herbal medicine.

Potassium

An essential mineral electrolyte found in high amounts in dandelion leaf, nettles, and other nutritive herbs. Critical for heart rhythm, blood pressure regulation, muscle function, and fluid balance. Diuretic herbs that also supply potassium, like dandelion leaf, are preferred over those that deplete it.

Proazulene

Precursor compounds in chamomile and yarrow that convert to azulene during steam distillation. Matricine and achillicin are proazulenes. See also: azulene.

Procyanidins

Oligomeric proanthocyanidins, a type of condensed tannin. Found in hawthorn, grape seed, and pine bark. Support vascular integrity, have potent antioxidant activity, and are among the most studied flavonoid compounds for cardiovascular health.

Protein

See: proteins.

Proteins

Large molecules made of amino acid chains. Some herbs such as moringa and spirulina contain significant complete or near-complete protein profiles. Enzymes are specialized proteins. Lectins are another protein class found in some plants with immune-stimulating effects.

Protodioscin

A steroidal saponin found in tribulus and fenugreek. Studied for its role in supporting testosterone precursor metabolism and libido. Evidence in humans is limited; effects are more consistently demonstrated in animal models.

Pseudohypericin

A naphthodianthrone compound found alongside hypericin in St. John's Wort. Has antiviral properties and contributes to the photoactive profile of the plant.

Quercetin

One of the most abundant dietary flavonoids. Found in elderberry, calendula, nettles, and many other herbs. Has anti-inflammatory, antihistamine, antiviral, and antioxidant properties. Inhibits release of histamine from mast cells, supporting its use for seasonal allergies. Bioavailability improves with lipid-based delivery or quercetin phytosome preparations.

Quinones

Aromatic compounds with antimicrobial and antioxidant properties. Lapachol from pau d'arco is a naphthoquinone. Hypericin from St. John's Wort is a naphthodianthrone. Anthraquinones from senna and cascara have strong laxative effects.

Racemosin

A compound found in black cohosh (Actaea racemosa). Contributes to the herb's anti-inflammatory and antispasmodic properties.

Resin

See: resins.

Resins

Sticky, solid or semi-solid plant exudates insoluble in water but soluble in alcohol. Often have antimicrobial, anti-inflammatory, and protective properties. Myrrh, frankincense, and propolis are resin-based herbal preparations. Resins are typically extracted into tinctures using high-proof alcohol.

Rosmarinic Acid

A polyphenolic ester of caffeic acid and hydroxyphenyllactic acid. Found in rosemary, lemon balm, sage, and other lamiaceae herbs. Has antioxidant, anti-inflammatory, antiviral, and neuroprotective properties. Inhibits histamine release, supporting use in allergy management. Also studied for cognitive protection.

Rumicin

A chrysophanic acid derivative found in yellow dock (Rumex crispus). Contributes to the herb's mild laxative action. Related to anthraquinone compounds.

Rutin

A flavonoid glycoside (quercetin-3-rutinoside) found in rue, buckwheat, elderberry, and many other plants. Supports capillary integrity, reduces inflammation, and acts as an antioxidant. Studied for effects on varicose veins and hemorrhoids. Gut bacteria convert rutin to quercetin, the active aglycone, after ingestion.

Salicylates

Esters and salts of salicylic acid. Found in meadowsweet, willow bark, and birch. Have anti-inflammatory, analgesic, and antipyretic properties. Aspirin is a synthetic salicylate derived from salicylic acid. People sensitive to aspirin or with bleeding disorders should use salicylate-rich herbs with caution.

Salicylic Acid

A beta-hydroxy acid found in willow bark and meadowsweet. Anti-inflammatory and keratolytic (exfoliating) when applied topically. The parent compound from which aspirin is derived. See also: salicylates.

Saponins

Glycosides with a soap-like quality, forming stable foams in water. Have a wide range of effects depending on the specific type: steroidal saponins may have hormonal activity (wild yam, tribulus), triterpenoid saponins affect immune and cholesterol metabolism (licorice, astragalus, reishi). Some saponins are hemolytic in isolated form but safe in whole-herb preparations at normal doses.

Sarsaponin

A steroidal saponin found in sarsaparilla (Smilax species). Along with parillin and gitonin, contributes to the herb's traditionally used anti-inflammatory and skin-supporting properties.

Scutellarin

A flavonoid glycoside found in skullcap (Scutellaria lateriflora). Studied for anxiolytic, neuroprotective, and anti-inflammatory effects. Contributes to skullcap's use for nervous tension and anxiety.

Sesquiterpene Lactones

A class of sesquiterpenes with a lactone ring, responsible for the bitter taste in many plants of the Compositae (daisy) family. Found in feverfew, wormwood, chamomile, and artichoke. Have anti-inflammatory properties through NF-kB pathway inhibition. Parthenolide (from feverfew) is a well-studied example for migraine prevention.

Sesquiterpenes

Terpenes composed of three isoprene units (15 carbons). A major class of plant constituents including azulene, bisabolol, and farnesene. Found in chamomile, ginger, and valerian. Have anti-inflammatory, sedative, and antimicrobial properties. Valerian's valerenic acid is a sesquiterpene.

Silica

Silicon dioxide and related silicic acid compounds. Found in high concentrations in horsetail (Equisetum arvense). Supports connective tissue, bone, hair, skin, and nail integrity. Important for collagen synthesis. Horsetail is the primary herbal source for therapeutic silica.

Silicon

The mineral form of silica. See: silica.

Silymarin

A complex of flavonolignan compounds (primarily silybin, silydianin, and silychristin) extracted from milk thistle (Silybum marianum) seeds. The primary active complex responsible for liver-protective effects. Stabilizes liver cell membranes against toxin entry, promotes protein synthesis in liver cells, and acts as an antioxidant in liver tissue. One of the most clinically studied herbal compounds for liver disease.

Sitosterol

A phytosterol (beta-sitosterol) found in saw palmetto, nettle root, and many plant foods. Structurally similar to cholesterol. Studied for effects on prostate health, cholesterol levels, and immune function.

Starch

A complex carbohydrate energy storage compound found in roots and tubers. Some medicinal roots contain significant starch content (slippery elm, marshmallow root). Contributes to mucilaginous properties when hydrated.

Steroidal Lactones

Withanolides and related steroid-based lactone compounds found in ashwagandha (Withania somnifera). The primary active compounds behind ashwagandha's adaptogenic, anti-inflammatory, and thyroid-modulating effects. Withaferin A is the most studied withanolide.

Steroidal Saponins

Saponins with a steroid-based aglycone structure. Found in wild yam, fenugreek, tribulus, and sarsaparilla. Some have weak hormonal activity or serve as precursors to steroidal synthesis in the laboratory (diosgenin from wild yam is used industrially for steroid production, though the body cannot make this conversion directly).

Steroids (Plant Steroids)

Naturally occurring steroid-skeleton compounds found in plants, including phytosterols and steroidal saponins. Distinct from synthetic anabolic steroids. Some plant steroids modulate hormonal activity weakly; others serve structural functions in the plant cell membrane.

Sterols

See: phytosterols, sitosterol. Sterols are a subgroup of steroids. Plant sterols and stanols are studied for cholesterol-lowering effects.

Stigmasterin

A phytosterol found in chaparral, sarsaparilla, and other herbs. Related to stigmasterol; contributes to the herb's anti-inflammatory and membrane-stabilizing properties.

Sugars

Simple and complex carbohydrates. In medicinal herb context, naturally occurring sugars in roots and fruits contribute to palatability and the glycoside structure of many active compounds. Invert sugar in honey-based preparations serves as a preservative.

Sulfur

A non-metallic mineral essential for protein synthesis and found in sulfur-containing amino acids (methionine, cysteine). Garlic and onion's characteristic odor comes from organosulfur compounds (allicin, diallyl disulfide) responsible for their antimicrobial and cardiovascular effects.

Tannin

See: tannins.

Tannins

A polyphenol subgroup containing non-crystalline compounds that create mildly acidic reactions when combined with water. Responsible for astringency and sour taste in herbs and foods. They inhibit pathogenic bacterial biofilm formation. Actions include drying mucous membranes, constricting blood vessels, and producing binding effects in the digestive tract while protecting mucous membranes from irritation. High tannin content is found in oak bark, black tea, witch hazel, and raspberry leaf.

Terpenoids

The largest and most diverse class of plant natural products, derived from the same basic isoprene unit as terpenes but with additional functional groups. Include monoterpenoids, sesquiterpenoids, diterpenoids, and triterpenoids. Many vitamins (A, D, E, K), steroids, and essential oil constituents are terpenoids. Responsible for much of an herb's therapeutic activity.

Terpenes

Constituents primarily responsible for the essential oil and aroma of a plant. Thousands exist, classified by chemical structure into Monoterpenes (10C), Sesquiterpenes (15C), Diterpenes (20C), and Triterpenes (30C). The most abundant class of plant secondary metabolites.

Thujone

A monoterpene ketone found in wormwood, sage, and thuja. Has bitter and antimicrobial properties. Acts as a GABA receptor antagonist, which can cause convulsions at high doses. The psychoactive reputation of absinthe (distilled wormwood) was historically attributed to thujone. Properly prepared herbal extracts contain safe levels. Avoid concentrated thujone-rich preparations during pregnancy.

Thujyl Alcohol

An alcohol related to thujone found in some Artemisia species. Contributes to antimicrobial properties of the essential oil fraction.

Thymol

A phenolic monoterpene found in thyme (Thymus vulgaris) and oregano essential oils. One of the most potent natural antimicrobial compounds. Used as an antiseptic in dental preparations (Listerine uses thymol). Also an expectorant and antispasmodic in the respiratory tract. The basis for thyme's well-documented use in cough and bronchitis preparations.

Tribulosaponins

Steroidal saponins specific to tribulus (Tribulus terrestris). Include protodioscin and other compounds studied for their effects on testosterone precursor metabolism and sexual function. Evidence in human trials is mixed.

Triterpene Acids

Triterpenoid compounds with acidic functional groups, including ursolic acid and oleanolic acid. Found in rosemary, lavender, and many other herbs. Have anti-inflammatory, antitumor, and liver-protective properties.

Triterpenes

Terpenes composed of six isoprene units (30 carbons). Include triterpenoid saponins (ginsenosides, glycyrrhizin), sterols, and other compounds. Found in reishi mushroom, ginseng, licorice, and calendula. Have immune-modulating, adaptogenic, hepatoprotective, and anti-inflammatory properties.

Triterpenoids

See: triterpenes. Triterpenoids are triterpenes with oxygen-containing functional groups. Reishi's ganoderic acids are lanostane-type triterpenoids with liver-protective and immune-modulating properties.

Turmerones

Sesquiterpene ketones found in turmeric essential oil, including ar-turmerone, alpha-turmerone, and beta-turmerone. Studied for neuroprotective effects and for enhancing curcumin absorption. May also have their own anti-inflammatory properties independent of curcumin.

Ursolic Acid

A pentacyclic triterpene found in rosemary, lavender, thyme, and elder flowers. Has anti-inflammatory, antioxidant, and studied anticancer and muscle-building properties. One of the most studied triterpenes in modern herbal research.

Valerenic Acid

A sesquiterpene carboxylic acid found in valerian root (Valeriana officinalis). A primary active compound responsible for valerian's sedative effects. Acts as a positive allosteric modulator of GABA-A receptors, similar in mechanism to benzodiazepines but much weaker. Also inhibits breakdown of GABA.

Vitamin C

An essential water-soluble antioxidant vitamin. Found in high concentrations in rose hips, elderberry, cayenne, and other herbs. Supports immune function, collagen synthesis, iron absorption, and antioxidant defense. The body does not synthesize it; dietary intake is required.

Vitamin E

A fat-soluble antioxidant vitamin. Found in seed and nut oils, red clover, and other herbs. Protects cell membranes from oxidative damage. Important for cardiovascular and skin health.

Vitamin K

A fat-soluble vitamin essential for blood clotting and bone health. Found in nettle, dandelion, and other green leafy herbs. K1 (phylloquinone) from plants supports clotting; K2 (menaquinone) from fermented foods supports bone and cardiovascular health. High vitamin K herb intake can interact with warfarin therapy.

Vitamins

Essential organic compounds required in small amounts for normal bodily function. Many nutritive herbs are notable sources of specific vitamins. Nettles supply vitamins A, C, D, and K; moringa is particularly rich in multiple vitamins. See also: vitamin-c, vitamin-e, vitamin-k, b-vitamins.

Volatile Oil

See: volatile oils.

Volatile Oils

The same as essential oils. Responsible for the distinctive odors of aromatic plants; they evaporate readily when exposed to light, oxygen, or heat. Composed primarily of terpenoid and phenylpropanoid compounds. Responsible for the antimicrobial, antispasmodic, carminative, and aromatic actions of many medicinal herbs. Best preserved by using airtight storage and moderate temperature preparations.

Waxes

Esters of fatty acids and long-chain alcohols found on plant surfaces. In herbs, waxes serve as protective coatings. Medicinally, plant waxes are used in topical preparations for their emollient and protective properties. Carnauba wax and beeswax are common in herbal salves and lip balms.