This article was written by Serge, MSc. Plant Biologist and Environmental Scientist with a BSc in Plant Biology and an MSc in Environmental Biology and Biogeochemistry. My background covers plant biochemistry, botany, and field research in forest and soil ecosystems. I write from real experience, not just literature.
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The first herbal tea I ever paid serious attention to was nettle. I had studied Urtica dioica in plant classification, knew its flavonoid profile and understood the biosynthetic pathway behind quercetin and kaempferol. Then I actually brewed a cup and drank it. The gap between knowing the chemistry and experiencing the plant directly is something no textbook covers.
I have been drinking herbal teas seriously ever since: green tea (Camellia sinensis) most mornings, hibiscus (Hibiscus sabdariffa) regularly, and nettle (Urtica dioica) when I want something grounding and mineral-rich. Each one tastes different, behaves differently in water, and carries a different compound profile depending on brewing temperature, steeping time and the plant part used.
Most people drink herbal teas without thinking much about what is actually moving into the water. That is a shame, because herbal tea chemistry is genuinely interesting.
What Happens When You Brew a Herbal Tea
Hot water is a solvent. When you pour it over dried or fresh plant material, it begins pulling water-soluble compounds out of the plant tissue: phenolic acids, flavonoids, some alkaloids, volatile aromatic compounds and minerals. What ends up in your cup depends on which compounds are present in that plant, how well they dissolve in water, and how long and how hot you brew.
This is why preparation matters more than most people realise. Green tea brewed at 80 degrees Celsius produces a different flavour and compound profile from the same leaves brewed at 100 degrees.
The hotter water pulls out more of the bitter catechins and caffeine, and pulls them out faster, while the cooler water gives a smoother, more balanced cup.
My plant biochemistry studies covered extraction chemistry in the context of secondary metabolite analysis. The same principles that apply in a laboratory extraction apply in your kitchen: temperature, solvent polarity, contact time and plant particle size all affect what you end up with. I compare water with other solvents in the extraction chemistry of teas, tinctures and capsules.
Green Tea (Camellia sinensis)
Camellia sinensis is probably the most chemically studied plant in the tea world, and the only true tea plant. Its leaves contain catechins, a subclass of flavonoids, with epigallocatechin gallate being the most abundant and most studied.
These compounds accumulate in the leaf as UV-screening and antimicrobial defence chemistry, as I explain in more depth in the plant chemistry of green tea.
The plant also contains caffeine and theanine, an unusual amino acid that affects neurotransmitter activity. Studies suggest that theanine and caffeine together produce a different alertness profile from caffeine alone. Many regular green tea drinkers describe a calm, focused state rather than the jittery effect of coffee, and the chemistry fits that observation.
I drink green tea most mornings. The flavour varies considerably between varieties and growing regions. A Japanese sencha tastes completely different from a Chinese green tea, even though both come from Camellia sinensis, because growing conditions, processing method and harvest timing all shift the compound profile.
Brew at around 75 to 80 degrees Celsius for two to three minutes. Boiling water makes it bitter.
Hibiscus (Hibiscus sabdariffa)
Hibiscus sabdariffa produces one of the most visually striking teas available. The deep crimson colour comes from anthocyanins, specifically delphinidin and cyanidin glycosides, which the plant makes through the phenylpropanoid pathway as pigmentation and antioxidant chemistry in the calyx tissue.
I drink hibiscus regularly. The flavour is tart and fruity, with a pronounced acidity from organic acids including citric and malic acid. It works well hot or cold, and the colour alone tells you the anthocyanin concentration is substantial.
The calyx, the fleshy red part used for tea, is the part of the flower that surrounds the seed pod. It is unusually rich in organic acids and anthocyanins compared with most plant tissues.
Traditional use of hibiscus tea spans West Africa, the Caribbean, Central America, and parts of Asia and the Middle East, which shows how widely this plant has been valued. I go into its chemistry and blood pressure research in hibiscus tea and its anthocyanin chemistry.
Brew in hot but not boiling water for five minutes. The colour extracts quickly, and longer steeping increases the acidity noticeably.
Looking for a Complete Guide to Herbal Tea?
I’ve put together a complete guide on picking good herbs, storing them so they stay fresh, and brewing each type the right way.
Covers choosing, storing, and brewing, so you get the most out of every cup.
Nettle (Urtica dioica)
I have written about nettle elsewhere, and I keep coming back to it because the chemistry deserves attention. The leaves contain the flavonoids quercetin and kaempferol, vitamins A, C and K, and a mineral profile including iron, calcium and magnesium that is unusually dense for a leafy plant.
Brewing neutralises the sting completely. What you get in the cup is mild, slightly green and warming. I have also steeped nettles in vodka to make a tincture, which pulls out a broader range of compounds than water, including some of the more fat-soluble constituents, although it extracts less of the minerals that make nettle tea so useful. I explain that trade-off in how herbal tinctures work.
Young spring leaves picked before flowering give the best flavour and the highest nutrient content. The chemistry shifts after flowering, and the leaves become tougher and more bitter. My free herb harvest calendar shows the best picking windows for nettle and other common herbs.
Chamomile (Matricaria chamomilla)
Matricaria chamomilla flowers contain apigenin, a flavone that has received attention for its interaction with GABA-A receptors, the same receptor complex involved in the calming effects of several well-studied herbs. Apigenin is made through the phenylpropanoid pathway alongside other flavonoids concentrated in the flower heads.
Chamomile’s characteristic apple-like aroma comes from a mix of volatile compounds in the flower heads, and the terpenoid alpha-bisabolol is present in the fresh flower too.
Chamazulene, the compound that turns chamomile essential oil blue, is different. It does not exist in the flower at all and forms only during steam distillation, which is why you will not find much of it in a cup of tea.
Chamomile tea has one of the longest documented histories of use in European herbal medicine. The flower head is the part used. Steeping for five to ten minutes in just-boiled water extracts its flavonoid and terpenoid profile effectively, and I explain how it pairs with other calming herbs in the chemistry of herbal tea combinations.
Ginger (Zingiber officinale)
Zingiber officinale rhizomes contain gingerols and shogaols, pungent phenolic compounds responsible for the characteristic heat and aroma. Shogaols form from gingerols during drying, which is why dried ginger tastes sharper and more pungent than fresh ginger.
Both compound classes interact with digestive physiology through several mechanisms. Ginger tea has one of the strongest traditional records for nausea and digestive discomfort across Asian, European and Middle Eastern herbal traditions, and the chemistry offers plausible mechanisms for those uses.
Fresh ginger, sliced and steeped in hot water for ten minutes, produces a clean, spicy tea. Dried ginger produces a more concentrated, pungent brew.
Peppermint (Mentha × piperita)
Mentha × piperita leaves are dominated by menthol and menthone, monoterpenoid compounds made through the terpenoid pathway and stored in glandular trichomes on the leaf surface. When you crush a peppermint leaf, the trichomes rupture and release menthol immediately.
Hot water extracts menthol and related volatile compounds effectively, though some evaporate quickly at high heat. Covering the cup while steeping reduces this aromatic loss. The cooling sensation in peppermint tea comes from menthol activating cold-sensitive receptors in the mouth and throat.
Peppermint has a long traditional record for digestive support, and its chemistry gives a clear mechanism: menthol relaxes the smooth muscle of the gut, mainly by blocking calcium channels in the muscle cells.
Lemon Balm (Melissa officinalis)
Melissa officinalis leaves contain rosmarinic acid, a phenolic compound made through the phenylpropanoid pathway, alongside volatile aromatic compounds including citral, which gives the plant its lemon scent.
In laboratory studies, rosmarinic acid inhibits GABA transaminase, an enzyme that breaks down GABA. This gives a biochemical basis for the traditional use of lemon balm as a calming herb, which I explore in lemon balm, rosmarinic acid and GABA.
The volatile compounds extract well in hot water but dissipate quickly, so fresh lemon balm makes a more aromatic cup than dried.
Raspberry Leaf (Rubus idaeus)
Rubus idaeus leaves contain tannins and flavonoids including quercetin and kaempferol, along with a compound traditionally called fragarine that has been linked to uterine muscle tone but has never been well characterised. The leaves have a long history of use in European herbal medicine, particularly in women’s health.
I have no personal experience with raspberry leaf tea. The traditional use record is extensive and the tannin and flavonoid chemistry is well documented.
It makes a mild, slightly astringent tea with a flavour closer to black tea than most herbal infusions. Because of its traditional link to the uterus, it is usually only taken in late pregnancy and under the guidance of a midwife or doctor.
Choosing Quality Herbal Teas
Plant part, growing conditions, harvest timing and processing all affect the compound profile of what ends up in a tea bag or loose-leaf blend. Organic certification reduces the risk of pesticide residues.
Standardised or pharmacopoeial-grade herbs carry more consistent compound profiles than commodity-grade material. For water temperatures and steeping times for each herb, my free herbal tea steeping guide does the work for you.
Jmacbotanicals and Traditional Medicinals both say they source certified organic herbs and publish information about their sourcing and quality standards.
For anyone wanting reliable herbal tea preparations without sourcing each herb individually, their ranges cover most of the species discussed here.
FAQs
What compounds does green tea contain?
Green tea from Camellia sinensis contains catechins, including epigallocatechin gallate, along with caffeine and theanine. The catechins are flavonoid compounds that the leaf makes as UV-screening and antimicrobial defence chemistry, part of the wider story of why plants produce secondary metabolites.
Why does hibiscus tea turn red?
The deep crimson colour comes from anthocyanins, specifically delphinidin and cyanidin glycosides, concentrated in the calyx tissue of Hibiscus sabdariffa. These pigments are made through the phenylpropanoid pathway and act as antioxidant defence chemistry.
What temperature should you brew green tea?
Around 75 to 80 degrees Celsius for two to three minutes. Hotter water extracts the bitter catechins and caffeine faster and in larger amounts, making the cup harsh.
What gives peppermint tea its cooling sensation?
Menthol, a monoterpenoid stored in glandular trichomes on Mentha × piperita leaves, activates cold-sensitive receptors in the mouth and throat, producing the characteristic cooling effect.
What compounds are in chamomile tea?
Matricaria chamomilla flowers contain apigenin, a flavone with documented GABA-A receptor activity, alongside the terpenoid alpha-bisabolol and a mix of volatile compounds that give the tea its apple-like aroma. Chamazulene, often listed for chamomile, forms only when the essential oil is distilled.
Why does dried ginger taste stronger than fresh?
Shogaols form from gingerols during drying. Shogaols are more pungent than gingerols, which is why dried Zingiber officinale has a sharper, more intense flavour than fresh ginger.
What is rosmarinic acid in lemon balm?
Rosmarinic acid is a phenolic compound in Melissa officinalis leaves, made through the phenylpropanoid pathway. In laboratory studies it inhibits GABA transaminase, an enzyme involved in breaking down GABA, which gives a biochemical basis for lemon balm’s traditional calming use.
Does steeping time affect herbal tea chemistry?
Yes, significantly. Longer steeping extracts more compounds, including tannins, which increase astringency and bitterness. Most herbal teas do well with five to ten minutes of steeping. Green tea is more sensitive and should not be steeped beyond about three minutes if you want to avoid bitterness.
What part of the nettle plant is used for tea?
Young leaves of Urtica dioica, harvested before flowering. Hot water neutralises the sting completely during brewing. After flowering, the leaves become tougher and their flavour and chemistry shift.
Why does covering your cup while steeping matter?
Volatile aromatic compounds, including the terpenoids responsible for the aroma of peppermint and lemon balm, evaporate quickly with heat. Covering the cup while steeping reduces this loss and keeps more of the aroma in the final brew.
