Understanding Tinctures: The Science of Herbal Extraction

Glossary of Key Terms

ABV (% Alcohol by Volume) - The percentage of alcohol in a liquid, indicating how strong the alcohol content is.

Amphiphilic molecule - A molecule that has both a water-loving (hydrophilic) end and a fat-loving (lipophilic) end. Ethanol (the alcohol used in tinctures) is amphiphilic, allowing it to dissolve both polar (water-soluble) and non-polar (oil-soluble) compounds.

Constituents - The naturally occurring chemical compounds found in plants (e.g. alkaloids, flavonoids, resins, polysaccharides).

Double Extraction - Combining a water-based decoction and an alcohol-based tincture to extract both water- and alcohol-soluble compounds.

Extraction - The process of pulling the chemical constituents from plant material into a liquid.

Maceration - The method of steeping plant material in a solvent for a set period (usually 2–4 weeks) to extract its constituents.

Marc - The solid plant material left behind after extraction.

Menstruum - The liquid used to extract the plant constituents (usually a mix of alcohol and water).

Percolation - A continuous extraction process where solvent slowly passes through the herb, creating a stronger tincture.

Polarity - A measure of how evenly electrical charge is distributed in a molecule. Determines solubility, whether a substance dissolves in water or alcohol.

Ratio (e.g. 1:3) - The weight-to-volume relationship between herb and solvent (e.g. 1 part herb to 3 parts solvent).

Solubility - The ability of a substance to dissolve in a solvent.

Solvent - The liquid that dissolves another substance (the solute). In tincture making, the solvent is referred to as the menstruum.

Tincture - A concentrated liquid extract of a herb, typically made using alcohol and water as solvents.

1. Understanding the Chemistry Behind Tinctures

If you’ve ever stirred sugar into tea or oil into salad dressing, you’ve already seen chemistry in action. Some things dissolve easily in water, while others don’t, and this same principle explains how tinctures work.

At its simplest, a tincture is a mixture of plants and liquid. The liquid (called the menstruum) draws out the plant’s natural chemical compounds, known as constituents. Whether those molecules dissolve depends on their polarity, a concept that describes how molecules interact with water and other polar solvents, such as alcohol.

What Polarity Means

To understand tincture chemistry, we need to understand why some molecules mix easily with water while others repel it.
This comes down to a property called polarity, the distribution of electrical charge within a molecule.

Every molecule is made of atoms held together by chemical bonds. In these bonds, electrons aren’t always shared evenly. Some atoms, such as oxygen, are more electronegative, meaning they attract electrons more strongly than others, like hydrogen or carbon.

When atoms with different electronegativities bond, one side of the molecule becomes slightly negative (where the electrons spend more time) and the other side becomes slightly positive (where electrons are pulled away).
This separation of charge creates a dipole, a molecule with two poles, like a microscopic magnet.

• Polar molecules have permanent dipoles. Water (H₂O) is the classic example: the oxygen atom holds electrons more tightly than the hydrogens, giving the oxygen a partial negative charge (δ–) and the hydrogens a partial positive charge (δ+). The molecule’s bent shape means these charges don’t cancel out, creating a strong overall polarity.

• Non-polar molecules, by contrast, either share electrons equally or have symmetrical shapes that cancel out any charge separation. Oils, fats, and many plant resins fall into this category.

Because of these charge differences, polar molecules attract and mix with other polar molecules, while non-polar molecules cluster together and exclude polar ones. This is why oil separates and floats on water; the two liquids are chemically incompatible.

Why This Matters for Tinctures

In herbal extraction, the concept of polarity determines which plant compounds dissolve in which solvent.
Water is a strongly polar solvent and therefore pulls out polar constituents, compounds with oxygen-rich or sugar-like structures that can form hydrogen bonds. These include:

• Polysaccharides and mucilage (e.g. Althaea officinalis),

• Tannins, glycosides, and organic acids (e.g. Taraxacum officinale, Plantago spp.),

• Minerals and vitamin C, which exist as charged ions or polar molecules.

Alcohol (ethanol), on the other hand, is less polar. It has both a polar hydroxyl group (–OH) and a non-polar ethyl chain (–CH₂CH₃). This makes it amphiphilic, meaning it can interact with both polar and non-polar substances. It can dissolve:

• Moderately polar compounds such as flavonoids and alkaloids,

• Weakly polar or non-polar compounds like essential oils, resins, sterols, and fats.

In other words:

• Water-loving (hydrophilic) molecules dissolve into the water portion of the tincture.

• Oil-loving (lipophilic) molecules dissolve into the alcohol portion.

The Science in Numbers

Chemists often describe solvent polarity using a dielectric constant, a measure of how well a liquid can separate positive and negative charges.

• Water has a very high dielectric constant (≈78 at 25 °C), meaning it strongly stabilises charged or polar molecules.

• Ethanol’s dielectric constant is much lower (≈24), which means it favours molecules that are less polar.

When you mix alcohol and water together, you create a continuum of polarity, a solvent that can dissolve an enormous range of herbal constituents. By adjusting the percentage of alcohol, you control the solvent’s effective polarity:

• Lower alcohol (more water) means higher polarity = extracts sugars, tannins, and mucilage.

• Higher alcohol (less water) means lower polarity = extracts resins, oils, and alkaloids.

“Like Dissolves Like”

One of the most fundamental rules in both chemistry and herbal extraction is “like dissolves like.”
It means that a compound dissolves best in a solvent that shares similar chemical properties and polarity.

At the molecular level, dissolving happens when the attractive forces between solvent and solute molecules are strong enough to overcome the cohesive forces holding the solute together. For extraction to occur efficiently, the solvent must form comparable intermolecular interactions, hydrogen bonds, dipole–dipole attractions, or van der Waals dispersion forces with the solute.

• Polar solvents (like water) stabilise polar compounds by surrounding them with partial charges that offset their own charges. Water’s bent shape and strong hydrogen-bonding ability let it form hydration shells around ions and polar molecules, drawing them into solution. This is why it extracts sugars, glycosides, tannins, and organic acids so effectively.

• Non-polar solvents (like oils or hydrocarbons) stabilise non-polar compounds through weak London dispersion forces, allowing lipophilic substances such as resins, fats, and waxes to dissolve.

• Ethanol, sitting between the two, is amphiphilic. Its hydroxyl group (–OH) forms hydrogen bonds with polar molecules, while its ethyl tail (–CH₂CH₃) interacts with non-polar molecules via dispersion forces.

When water and ethanol are mixed, they form a hydrogen-bonded network that adapts to the solutes present. A water-rich mixture behaves more polar; an alcohol-rich one behaves more non-polar. This flexibility gives tincture makers a continuum of solvent polarity to target specific chemical groups by simply adjusting the alcohol percentage.

From a practical herbal perspective:

• Low-alcohol tinctures (20–30 %) behave more like water and extract hydrophilic constituents such as mucilage, polysaccharides, tannins, and minerals.

• Medium-alcohol tinctures (40–60 %) achieve a balanced extraction, drawing both flavonoids, glycosides, and alkaloids.

• High-alcohol tinctures (70–90 %) behave more like pure ethanol and are required to dissolve resins, essential oils, sterols, and alkaloid bases.

This rule also explains why some herbs are better suited to high- or low-alcohol extractions. For example, Commiphora myrrha and Boswellia spp. are resinous and require 90% ethanol, while Althaea officinalis (rich in mucilage) extracts best in water or 25% alcohol; too much ethanol would actually cause those polysaccharides to precipitate. When I first learnt this, it changed how I looked at every tincture recipe. Not just drowning herbs in vodka and hoping for the best, but now understanding the intentional chemistry of each medicine.

The Molecular Picture

At the microscopic level, when a plant is submerged in the menstruum, water and alcohol molecules move between its cells. Polar water molecules form hydrogen bonds with oxygen- and nitrogen-containing groups in the plant compounds, while ethanol molecules orient their –OH group toward polar regions and their ethyl tail toward hydrophobic regions. This dual action allows the solvent to “wrap around” and dissolve a vast array of chemical structures.

Why We Use Alcohol and Water Together

Water and ethanol are the two most effective and widely used solvents in herbal extraction because, together, they span a broad range of polarity.

Water (H₂O) is a highly polar protic solvent. Its bent molecular shape and strong hydrogen bonding capacity make it excellent at dissolving other polar compounds, molecules that contain hydroxyl (–OH), carboxyl (–COOH), or glycosidic (–O–) groups. These include polysaccharides, mucilage, glycosides, organic acids, and minerals. Water’s dielectric constant (≈78 at 25 °C) indicates its strong ability to stabilise ions and charged species, which is why it excels at extracting water-soluble salts and ionic compounds from plant material.

Ethanol (C₂H₅OH), the alcohol used in tinctures, is a weaker hydrogen-bond donor and acceptor than water, giving it a lower dielectric constant (≈24 at 25 °C). This means it can solubilise less polar and even non-polar compounds, such as essential oils, alkaloids, resins, sterols, and some lipophilic flavonoids, that water alone cannot dissolve.

What makes ethanol particularly valuable is that it is amphiphilic. The molecule has:

• a hydroxyl group (–OH) that interacts with water and polar solutes via hydrogen bonding; and

• a hydrophobic ethyl chain (–CH₂CH₃) that interacts with lipophilic, non-polar solutes via dispersion (London) forces.

Due to its dual nature, ethanol bridges the gap between polar and nonpolar solvation environments.

When we mix ethanol and water, their molecules form hydrogen-bonded networks, creating a continuum of polarity rather than a simple average of the two. This mixture allows for the fine-tuning of solvent strength; the lower the ethanol concentration, the higher the effective polarity; conversely, the higher the ethanol concentration, the more non-polar the solvent becomes.

Diffusion and Solvation (How Extraction Happens)

Once the herb is submerged in the menstruum, diffusion begins. Molecules naturally move from regions of high concentration (inside plant cells) to regions of low concentration (in the solvent) until equilibrium is reached.

Extraction rate is influenced by:

• Temperature - moderate warmth increases molecular motion and extraction speed.

• Surface area - finely chopped or powdered herbs expose more cell surfaces.

• Agitation - shaking the tincture renews the solvent boundary layer, maintaining concentration gradients.

During this process, solvation occurs as water and ethanol molecules surround solute molecules, pulling them into the solvent. Water interacts strongly with polar functional groups, while ethanol’s dual polarity allows it to solvate both polar and non-polar regions, producing a rich, complex extract.

Preservation and Stability

Beyond extraction, alcohol provides long-term preservation. Ethanol denatures microbial proteins, disrupts cell membranes, and lowers water activity, creating conditions unsuitable for bacterial or fungal growth.

Tinctures containing ≥ 20 % ABV are self-preserving, while those above 40 % ABV often remain stable for five years or more when stored in a cool, dark place. Water-only extracts, by contrast, are perishable and require refrigeration or additional preservatives.

Bringing the Chemistry Together

Polarity, solvation, and diffusion are key factors that explain the effectiveness of tinctures.

• Water extracts hydrophilic compounds = carbohydrates, minerals, organic acids.

• Alcohol extracts lipophilic compounds = resins, alkaloids, volatile oils.

• The combination captures the full spectrum of a plant’s chemistry, producing a stable, potent extract.

...to be continued in Section 2. The Role of Alcohol Percentage and Solubility.