Preparation of herbal extracts

Dried herbs are traditionally consumed as tea. Either by pouring boiling water over the dried drug, or by boiling it for 10 min. which is necessary for hard plant parts such as bark or roots. The dosage is typically quite high, – a whole handful of each herb, to ensure just a minimum of active substances.

So herbal teas in everyday life should be considered more as a pleasant, valuable supplement to a healthy diet rather than as therapy, where they are almost useless. Without a guarantee of which active substances you get in the herbal tea, they are thus not sufficient to make a big difference in e.g. chronic diseases. Some essential oils are released when the boiling water is poured over, and the oils may contain some volatile substances which can be used for e.g. acute respiratory problems. But as actual therapy, herbal teas are generally not strong enough.

Tinctures and liquid extracts

Tinctures, and especially extracts, are much stronger, as the added alcohol is a better solvent than water and because they are usually produced via percolation (see later section), which produces a more concentrated extract. Herbs usually work better in combination with several different herbs, and physiotherapists and other practitioners are known to use liquid herbal extracts, which are typically a mixture of several herbs. An example is a cough mixture, which may contain cough-relieving, expectorant herbs, but also immune-stimulating and disinfecting herbs. The dosage is often up to 15 ml daily of a mixture of 4-5 herbs.

Liquid extracts are available as premixed supplements and herbal remedies and in larger bottles that practitioners use when creating individual blends for their clients. The advantage of liquid extracts is that they are easy to mix, last a long time and the dosage is very flexible. The problem is that they are alcohol based, taste terrible and are generally quite expensive. It is possible to remove the alcohol after extracting the active substances and add glucose syrup or glycerol instead. It enhances the taste of the product, but also requires the addition of preservatives.

Dry extracts

Dry extracts are liquid alcohol extracts that have been dried into a powder. This means that all water and alcohol have been removed. The dry extracts can then be used in tablets, capsules and powder mixtures. The advantage is that three 1000 gram tablets can contain as much as 15 ml of a mixture of liquid extracts. The disadvantages are that a practitioner cannot determine the composition themselves and that the dosage is not flexible. And many consumers find the large tablets or capsules too difficult to swallow. Dry extracts are also available in powder form. The products appear either as ready-mixed preparations, where several different dry extracts are mixed with other ingredients, often vitamins and minerals or protein powders.

Other dry extracts are available as single herbs in cans. They can be used individually or combined in the same way as liquid extracts. The advantage is that one extract can easily be mixed as needed with others, it contains no alcohol and also makes the taste more tolerable than liquid alcohol extracts. Dry extracts in powder form make the dosage flexible for both children and adults. If one measuring spoon of the product is a full adult dosage, a quarter to half a measuring spoon can be used for children or as a maintenance dosage. Different drugs can be easily mixed as needed and mixed into a little juice or yogurt. You can typically see if a product is a dry extract on the declaration, where it is stated which strength the drug is in. A 5:1 dry extract indicates that five kilos of dried drugs have been used to produce one kilo of dry extract. More on that later.

Preparation of herbal medicine

Raw materials
First, you have to make sure that it is the right plant. It sounds a bit silly, but irresponsible counterfeiting often happens. Once an herb is dried and chopped into small pieces, it is not entirely easy to recognize it. But with experience you can learn to recognize the colour, taste and smell of the individual herbs. The plant material must have the right color, be free of dust and counterfeits. The herb must smell fresh and clean, and especially herbs with aromatic substances must smell strongly.

The next study is called macromorphology, where people trained in structural botany examine the unique structures of herbs. How the edge of the plant material looks when it is broken over, whether it is a fine, straight or uneven edge, with or without fibers. All together a clue about the plant's identity. Some leaves are hairy, others completely smooth. The color can change from the upper side to the lower side, stems can have special shapes, e.g. be square and the seeds may have a special texture and color.

The next step is to examine the plant material under a microscope. This study is called micromorphology. The powdered herb dissolved in various solvents is examined under the microscope and compared to a recognized standard such as described in The Atlas of Microscopy of Medicinal Plants, Culinary Herbs and Spices by Jackson and Snowdon. The British Herbal Pharmacopoiea contains the micro- and macro-morphological details of the herbs.

Thin Layer Chromatography (TLC) is a method in which two or more substances in an herb are separated out on a glass plate, so that the content of active substances can be assessed. A glass plate is dipped in silica gel and dried. The plant material is dissolved in a solvent and painted as small spots at the bottom of the glass plate. The solvent is evaporated with a heating fan and the glass plate is placed upright in a glass dish containing the developer liquid. The choice of the chemical composition of the developer depends on which substances are being investigated. The liquid covers just the bottom of the silica plate, but is pulled by hair tube action 10 to 15 cm up the plate over the course of half an hour to a full hour, leaving the active substances at different levels. The silica plate is removed from the glass dish, dried, and can then be examined and photographed under ultraviolet light. TLC gives some nice color strips, where the location of the color spots and their intensity determine the presence of active substances in the dried herb, in herbal extracts or in tablets. When using HPTLC (High Performance TLC), the amount of active substances can be determined from the intensity of the colors, while ordinary TLC only indicates the presence of the active substances. By comparing a TLC of a dried herbal material with an authorized standard, you can determine the quality of the starting material as well as the finished product. But can also do TLC with finished herbal extracts to compare the quality of different batch units or different companies' products. New shipments must always be stored in a so-called "dirty area" until the laboratory has approved the drug.

Chemical analyses
It is also possible to examine the plant material or the finished product for specific substances. These analyzes are specific to the substance to be measured and often require advanced laboratory equipment. HPLC is a three-dimensional graph that can create a picture of any plant and ensure that the active substances are present - and in what quantity. The individual graphs are called "peaks" and tell about the amount of the active substance in question. It is also with this method that you can make standardized extracts (abbreviated in everyday life to STA). Here it is ensured that the finished product contains a minimum content of exactly the active substances that research shows are the most important.

The solvent used in the production of herbal extracts is called "menstruum". Since you want an extract of all the drug's active substances, it is important that the selected menstruum is able to extract all the active substances, retain them in the solution and at the same time leave the inactive substances in the plant material. Menstruum must also be able to preserve the extract, prevent enzyme degradation of the active substances and thereby give the product an extended shelf life. Menstruum can consist of:

  • Water alone
  • A mixture of water and alcohol
  • Of water and glycerin
  • Pure glycerin
  • Wine
  • Vinegar and water
  • A fat oil
  • Various stronger solvents, e.g. hexane, butanol or acetone

In the vast majority of cases, a mixture of water and ethanol (alcohol) is the preferred menstruum in the preparation of herbal extracts and tinctures.

Water as a universal solvent
Water molecules are able to bind to many different elements and molecules and are therefore perceived as a universal solvent. Water dissolves proteins, alkaloid salts, dyes, glycosides, mucilage substances, sugars, anthraquinones, tanning substances, mineral salts, vegetable acids and enzymes. Water is not effective in dissolving waxes, fats, oils and alkaloids. Water is cheap, non-toxic, non-flammable and can dissolve many substances. But water can also dissolve inactive substances, and will not prevent mold and bacteria from forming in the extract. Water also promotes hydrolysis and enzymatic activity.

Alcohol as a solvent
Ethanol dissolves alkaloids and their salts, essential oils, resin substances, glycosides, tannins, anthraquinones, plant acids and salts. Ethanol does not dissolve proteins, mucous substances, fats, waxes and fatty oils. Ethanol inhibits bacteria and mold formation. Ethanol is not toxic in small quantities, inhibits the hydrolysis of glycosides and saponins and inhibits enzyme activity which can break down alkaloids and glycosides.

  • 25% ethanol is used for water-soluble substances such as slimes, tanning substances and certain glycosides, e.g. flavonoids and some saponins.
  • 45-60% ethanol is used for essential oils, alkaloids, most saponins and some glycosides.
  • 90% ethanol is used for resin substances.

Water and ethanol can thus extract some of the same ingredients, but must be used in combination to get all the active ingredients in the finished extract. The small amount of alcohol in the daily dosage of herbal medicine is of no importance to most people and will not show up in the blood at all, as the liver will break down the alcohol before. This also applies to children, where the dosage is significantly reduced. For people with severe liver disease and for patients who do not drink alcohol for religious reasons, there are now alternatives in the form of high-quality glycerol extracts, herbal teas and herbal tablets. But the strongest and most economical preparations are dry extracts.

Glycerin as solvent
Glycerin is a viscous, sweet-tasting, colorless alcohol (which does not have an alcoholic effect like ethanol and can therefore be used by patients on antabuse), especially used for plants containing tannins and mucilages. Glycerin is non-toxic, enhances the taste, promotes the soothing effect of the mucilaginous substances on the mucous membranes and inhibits the formation of fungi and bacteria. However, glycerol extracts will not have the same shelf life as extracts made in ethanol.

Vinegar and wine as a solvent
The production of extracts in vinegar and wine is mostly used in home production.

Preparation of extracts

When a plant is dried, the sap evaporates and the cell walls shrink. When the dried herb is soaked in menstruum, the plant tissue swells and softens again and the soluble parts inside the cells dissolve and are drawn out into the liquid by osmosis. This process is called maceration. The four most commonly used methods used in the preparation of herbal preparations are extraction, decoction, maceration and percolation.

Pull out
In a regular extraction, boiling water is poured over the desired amount of chopped herb and covered with a lid. The herbal tea must steep for 5-15 minutes, stirring occasionally. The tea is usually drunk hot. The dosage for most non-toxic herbs is one teaspoon of the herb to a cup of boiling water, three times daily. As previously mentioned, herbal teas are most suitable for prevention in everyday life.

Where leaves and flowers are extracted by the above method, it is recommended that harder plant parts, such as bark and roots, are extracted by a decoction. Place a teaspoon of the herb in a cup of water, bring to a boil and simmer for 5-15 minutes, covered. Drink hot.

Preparation of a tincture can be done by maceration followed by pressing. The plant parts are soaked for two to four weeks with daily shaking. The liquid is then poured off and the softened herb, called the marcen, is pressed with a mechanical or hydraulic press. The two liquids are then mixed together. One kilo of herb dissolved in five liters of menstruum (alcohol/water) will produce a tincture of the strength 1:5 using this method.

The dried herb is wetted and soaked in alcohol/water for four to six hours, after which it is packed into a cylindrical container called a percolator. The extraction fluid (menstruation) is poured over the herb and it is allowed to macerate for 24 hours. The cock is then opened at the bottom and the menstruum is allowed to seep through the herb. This process extracts all the active substances from the plant tissue. By this simple process, called percolation, you can make a tincture in the ratio 1:2, where one part herb is extracted into two parts menstruum. These tinctures are often called extracts to illustrate that they have been made by percolation and not just maceration, and that they are stronger than a normal 1:5 tincture. By measuring the content of active substances before and after percolation, it can be clearly demonstrated that the right technique can extract far more active substances than with other methods. Extracts of the 1:1 ratio can only be made by continuing the extraction process with fresh menstruum and then evaporating and concentrating the liquid back to the correct ratio.

Different strengths of herbal products
1:2 is one of the strongest extracts that can be prepared without the use of evaporation under vacuum. A 1:2 extract is like a virgin olive oil: the pure product produced as gently as possible. A 1:5 is also gently produced, but a 1:2 is 2.5 times as strong, at the same time that it is often only slightly more expensive to produce than a 1:5 tincture. A fresh plant tincture is made from the fresh plant, but since a fresh plant can contain up to 80% water, these tinctures can be five times weaker than a tincture made from the dried herb. Another type of fresh plant tincture is the so-called stabilized plant juices, called succus. The fresh plant is pressed and the juice is stabilized by adding 25% alcohol. Galium aparine is an herb that is particularly suitable for making succus.

Dry extracts
A dry extract is, as the name indicates, an extract that has been dried. There is therefore a big difference between a dry extract and a dried drug (medicinal plant). Medicinal plants are air-dried in special drying rooms where hot air is blown through layers of herbs placed on shelves of chicken wire. The dried herb is then finely chopped and is ready for packaging as herbal tea or further processing. The production of dry extracts consists of 3 phases:

  1. drying and pulverizing the active plant part
  2. extraction of the active substances in liquid form (liquid extract)
  3. concentration and spray drying of the liquid extract into powder form

Dandelion leaves – example 1
Let's start with 1.25 kg of fresh dandelion leaves. Since fresh leaves contain about 80% water, this corresponds to only 250 g of dried leaves. The next step is to produce a liquid extract. You typically produce a 1:2 tincture with a mixture of water and alcohol as the extraction liquid. In other words, the 250 g of dried leaves become 500 ml of liquid extract. The final step is to concentrate this liquid extract, i.e. remove most of the water and alcohol and then spray dry the extract to a fine powder. The process is very similar to the production of milk powder from ordinary milk. In the production of dry extracts, it is necessary to add a filler powder during the process to keep the active substances in the plant together. The filling powder is often maltodextrin – a carbohydrate (polysaccharide) extracted from corn. The final product is a dry extract in powder form. The concentration of the active substances in the dry extract depends on the individual plant and the specific extraction method used and can range from a 5:1 all the way up to 100:1 or more. A dandelion dry extract is often around 5:1. This means that our 250 g of dried dandelion leaves produces 50 g of dry extract. So 1.25 kg (1250 g) of fresh dandelion leaves produces 50 g of dry extract. In other words, the quantity (weight) is reduced 25 times. Or in other words, 50 g of a 5:1 dry extract can contain the same as a 500 ml 1:2 extract.

Horse chestnut – example 2
Horse chestnut is used in the treatment of poor venous circulation. The active substance is escin. Escin is effective against symptoms from varicose veins, shin ulcers and haemorrhoids. Several scientific trials have shown that the effective dosage is a minimum of 100 mg of escin daily. The dried horse chestnut contains approximately 3% escin, i.e. 3300 mg contains approximately 100 mg of escin. If we want to use a 1:2 liquid extract, the dosage must be a minimum of 6.6 ml daily or over 46 ml per week. And this dosage assumes that the dried drug contains the full 3% escin and that the extraction is complete. The saponins in horse chestnut make horse chestnuts difficult to eat and horse chestnut tea is no pleasure either. Liquid extract is also not easy to drink, especially not nearly 50 ml per week. It is easier and more accurate to use a dry extract.

Production of horse chestnut dry extract

• Dried horse chestnut is finely chopped and ground into a powder

• The herbal powder is extracted in 60% alcohol below 40º−50º degrees C

• The liquid extract is concentrated under vacuum and around 60º degrees until the extract contains 45-55% moisture

• The extract is spray-dried into a powder

• Maltodextrin is added to the powder until the finished product contains 20% escin

Since experiments have shown that the optimal dosage is around 100 mg of escin daily, we can calculate that the optimal daily dosage is 500 mg of dry extract daily. How many kilos of dried horse chestnuts are needed depends on their escin content. And there is a very large difference in the content of the active substances, as climate, soil conditions, geographical location and many other parameters determine whether a drug produces enough active substances. When you know that 100 mg of escin is to be used daily and you know that you have achieved this goal in the finished product, you are allowed to write that the drug is standardized, in this case for escin. A standardized drug assures the consumer that the product has the quality that one wants or that research says is necessary to achieve a specific effect.