The daily dose for individual non-toxic herbs in traditional Chinese medicine is usually in the range of 3 to 10 g, given as a decoction or in pill or powder form.¹ Often higher doses are prescribed by decoction than for pills, as might be expected since not all active components readily dissolve in hot water.² (Pills generally consist of the powdered herb incorporated into a suitable base.) Herbs are invariably prescribed in formulations. Doses for such formulations are about 3 to 9 g taken three times daily but can be higher in the case of decoctions.

For each individual herb, a wide dosage range is usually given in texts. (This applies for all herbal systems.) One reason for this is that if a herb is used by itself or with just a few other herbs, a larger dose is used than when it is combined with many other herbs.² Dose also varies according to the weight and age of patients and the severity or acuteness of their condition.

Recently, a more processed form of dosage has become popular among practitioners of Chinese medicine. This involves the prescription of formulas in a granulated form. The granules are prepared by drying or freeze-drying decoctions, that is aqueous extracts, of herbal formulas. Usually 2 g of granules is prescribed three times daily, which corresponds to about 6 to 10 g of original dried herbs per dose.

Some herbs, or closely related species, are used in both Chinese and Western herbal medicine. Table 6.1^1,3,4 compares dosages for a few of these herbs.

Table 6.1 Comparison of dosages used in Chinese and Western herbal medicine

Note: For dosages of tinctures and extracts given three times daily, the corresponding amount of dried herb per day has been calculated.

In general, the similarity in the dosage range between the different systems is striking. Discrepancies do exist for Zingiber and Taraxacum, which in the case of Zingiber can be explained by a higher content of the active components in the alcoholic tincture compared to the decoction, and, in the case of Taraxacum may be a reflection on the different species used.

Ayurveda often involves complex formulations which are prepared over several days and can contain many herbal and mineral components. Consequently, there is more dosage diversity than for Chinese medicine. Dosage ranges for individual non-toxic herbs are generally in the region of 1 to 6 g/day as powders or tinctures, with higher doses often recommended for decoctions.⁵

Eclectic medicine was a largely empirical school of medicine which developed in America during the 19th century.⁶ The movement was most prominent for a brief period from the late 19th to the early 20th centuries, when there were several teaching universities and many eminent scholars in the USA. Although the Eclectics used simple chemical medicines such as phosphoric acid, they mainly prescribed herbal medicines. Their knowledge of materia medica was their greatest contribution to Western herbal medicine; for example, herbs such as Echinacea and golden seal were made popular by them after observation of their use by the Native Americans.

The Eclectics tended to use higher doses than those recommended in current texts and pharmacopoeias, although the ranges tend to overlap. Table 6.2 compares dosages currently used^3,4 with those found in Eclectic texts^7,8 for alcoholic extracts of herbs.

Table 6.2 Comparison of dosages used by the Eclectics and modern dosages

Note: The corresponding amount of dried herb per day has been calculated from recommended dosages for fluid extracts.

The British Herbal Pharmacopoeia 1983 (BHP) carries extensive dosage information for individual herbs and is generally regarded as an important traditional reference on this subject for Western herbal practitioners. Dosages given in the BHP were derived from earlier texts such as the British Pharmacopoeia (BP) and the British Pharmaceutical Codex (BPC) but also resulted from a survey of herbal practitioners. More recently, the British Herbal Compendium (BHC) has been published in two volumes, with dosage information for the practitioner.^9,10

The doses given by the BHP 1983 contain some inconsistencies. The main problem is that doses for tinctures often do not correlate to corresponding doses for liquid extracts. For a 1:1 extract and a 1:5 tincture of a particular herb to correlate in terms of dose, the dose range for the tincture should be five times that of the extract, since it is theoretically five times weaker. This problem contrasts with other pharmacopoeias such as the BPC 1934 where the correlation is generally, but not exactly, observed. Some examples that highlight this problem are provided in Table 6.3.

The poor correlation demonstrated in Table 6.3, where in the case of Eupatorium purpureum the tincture dose is actually less than the extract dose, probably arises for two reasons:

Since tinctures better preserve the chemical profile of the dried herb, more credibility should be given to the tincture doses when using the dosage ranges in the BHP 1983.

Under the direction of the German Health Department, the Commission E prepared a series of monographs on commonly used medicinal herbs during the 1980s. The Commission E was an expert committee consisting of doctors, pharmacologists, pharmacognocists and toxicologists from both academia and industry. If a herb did not receive a positive monograph from the Commission E, it could not be readily registered as a medicine in Germany. In the preparation of a monograph, the Commission E took into account relevant traditional use as well as scientific research.

A positive monograph for a herb also included dosage information. Many of the monograph doses are for infusions or decoctions since this reflects the common use of teas in the German marketplace.¹¹ Such daily doses are usually in the range of 2 to 10 g. Occasionally a monograph will specify a dose for a herb in terms of major active constituents; for example, for Ephedra the daily dose is 45 to 90 mg of alkaloids (about 4 to 8 g of herb) which is similar to the range in Table 6.1. Occasionally, where tincture and extract doses are given by the Commission E, there is not always a good correlation. For example, the single dose for valerian tincture is 1 to 3 mL and yet the single dose for a fluid extract is 2 to 3 mL. The reasons for this may be the same as those discussed above for the BHP 1983.

The Scientific Committee of ESCOP (European Scientific Cooperative of Phytotherapy) has published a series of herbal monographs.^12,13 These were compiled by an international team of expert authors and represent a major contribution to the harmonisation of standards for herbal medicines across the European Union. These monographs contain useful dosage information reflecting the European situation and have been taken into account for the dosage recommendations in this text.

The clinical trial is arguably the best way to determine the effective dose of either a single herb or a herbal formulation. This will not always be applicable to traditional medicine, however, since prescriptions are usually prepared on an individual basis. Also, a clinical trial does not necessarily determine the optimum dose. However, it does confer a relative certainty to the clinical results. That is, at a given dose of a given preparation a certain percentage of patients are likely to respond; for example, Ginkgo biloba standardised extract at 120 mg/day (which corresponds to about 6 g/day of dry leaves), given for 2 months, will improve intermittent claudication in 60% of patients.¹⁴

Sometimes the clinical trial has used a standardised extract of the herb which can then be correlated to the whole herb; for example, silymarin in liver disorders at 240 mg/day corresponds to 8 to 16 g/day of Silybum marianum seeds.¹⁵

Currently in the USA, New Zealand, parts of Europe (especially among homeopaths) and to some extent Australia, there are practitioners who prefer to prescribe drop doses of 1:5 or even more dilute tinctures. It is useful to examine the possible origins of this approach.

In Europe, homeopaths often use combinations of herbal mother tinctures in drop dosage, for example, ‘drainage’. This approach is sometimes incorrectly labelled as ‘phytotherapy’.

In the USA a more direct influence comes, ironically, from a development of Eclectic medicine. In 1869, the Eclectic physician John Scudder proposed the concept of ‘specific medication’.⁷ With this concept, medicines were matched specifically to the symptom picture of the patient and then given in the minimum dose required. Although this system may seem similar to homeopathy, there were important differences.¹⁶ Material doses were always used, albeit lower than those prescribed by other Eclectics, and the prescription was not based on the law of similars. However, like classical homeopathy, there was a tendency to use only one medicine at a time.

Scudder initially proposed that ‘specific medicines’ should be tinctures prepared from the fresh plant.¹⁶ A fresh plant tincture is sometimes still called a ‘specific tincture’. Hence, the approach of using drop doses of tinctures, especially fresh plant tinctures, also comes from Scudder.

Although Scudder’s system of specific medication was seen as an important development in Eclectic medicine, it was considerably modified by Lloyd.¹⁷ Lloyd felt that drop doses of tinctures were too low and described the preparations proposed by Scudder as ‘superficial’. Lloyd proceeded to develop elaborate herbal preparations which were concentrated, semi-purified liquids. He also called these ‘specific medicines’ and they were widely adopted by Eclectic practitioners. However, in the early 20th century English herbalists aligned themselves with the American physiomedicalists in using simpler formulations, because Lloyd’s specific medicines proved too costly to import.

Lloyd sometimes used solvents other than ethanol and water in the preparation of his specific medicines.¹⁷ His methods were kept secret and even today are not widely known. Lloyd writes: ‘The aim has been to exclude colouring matters … and inert extractive substances also from these preparations …’. In this sense, he was tending towards the concept of orthodox drugs. However, his preparations were still chemically complex and ‘very characteristic’ of the original herb.¹⁷ According to Felter, the specific medicines developed by Lloyd were at least eight times stronger than 1:5 tinctures.⁷ It is these highly concentrated preparations which were generally used by Eclectic physicians in drop doses, and even then doses could be quite high – up to 60 drops (3 mL) three times daily.⁷

In conclusion, the use of drop doses of tinctures, especially fresh plant tinctures, originated in response to the availability of more concentrated specific medications and was not representative of the general practice of Eclectic medicine, nor initially a challenge to traditional dosages.

In the UK in the past herbalists used fluid extracts, usually prepared using heat or from concentrates. However, among newer practitioners in the 1980s there was disenchantment with these preparations because of their inconsistent quality. These practitioners instead adopted the use of 1:5 tinctures. Usually, formulations of tinctures are prescribed at doses of 2.5 to 5 mL three times daily. However, BHP 1983 doses for tinctures can only be achieved by this approach if the formulation contains one to three herbs (see Table 6.3 for examples). Unfortunately, this restriction is usually not followed and it can be concluded that the move to tinctures has resulted in the use of lower doses.

The dosages used by the traditional systems of India and China, by most of the Eclectics and those established by clinical trials or recommended by expert committees or in pharmaceutical texts all tend towards the higher end of the dosage spectrum. Such an agreement should not be ignored if there is to be consistency in modern phytotherapy.

If liquid preparations are to be used, then the BHP 1983 is an appropriate guide. However, as discussed above, more credibility should be given to the tincture doses. The difficulty in using 1:5 tinctures is the large volumes which are required to achieve BHP doses for multi-herb formulations. One way to overcome this problem is to make a more concentrated preparation but without the use of heat or vacuum. Such a preparation would be more akin to a 1:5 tincture than a fluid extract, since it would better reflect the chemical characteristics of the starting herb. The most concentrated preparation which can be achieved from a dried herb without using heat or vacuum concentration, and yet achieving high extraction efficiency, is a 1:2. A process of cold percolation is necessary to achieve a 1:2 extract. Dosages for 1:2 extracts can be calculated as 0.4 of the dose for 1:5 tinctures, since they are 2.5 times stronger.

This approach enables the use of multi-herb formulations consistent with BHP and BHC dosage guidelines. For special preparations, such as herbal extracts standardised for active components, dosages established by clinical trials should be followed.

Liquid preparations have considerable advantages and are widely used. The main advantage is the easy preparation of formulations for each individual patient (extemporaneous dispensing). The other considerable advantage of liquids is that, if properly prepared, they involve minimal processing and truly reflect the chemical characteristics of the herb in a compact, convenient form. They also confer considerable dosage flexibility, which is especially relevant when prescribing low doses for small children. Liquids are readily absorbed and are convenient to take.

Superior bioavailability is also an under-researched advantage of herbal liquids. When a solid dosage preparation is ingested, it must first disintegrate. The plant’s phytochemicals need to dissolve in digestive juices (and the water simultaneously imbibed with the tablet or capsule) in order to be absorbed by the body. Research has demonstrated that there is a relationship between the rate and degree of dissolution of the phytochemicals in a solid dosage preparation and their ultimate absorption into the bloodstream. The advantage of herbal liquids is that the all-important phytochemical constituents are already in solution.

The main disadvantage of liquids is taste, although in the case of bitters the taste is an essential part of the therapy. The taste problem is somewhat exaggerated by some patients. Most patients get used to the taste of their mixture and some even grow to like it. If taste becomes a problem, there are flavouring preparations available and these are particularly useful for children.

It is helpful to ask patients before prescribing if they mind taking strong-tasting liquids. This will draw a commitment from those who say it is not a problem and guide the clinician to solid dose alternatives if the answer is otherwise.

The way a herbal liquid is taken can minimise the experience of any unpleasant taste. The most important factors are the contact time of the remedy in the mouth and the intensity of the contact. Some practitioners claim that absorption from the oral cavity is often part of the activity of herbal preparations. So it may in fact be preferable to prolong the contact time. But from the point of view of taste, it should be minimised.

To reduce the intensity of the contact, the herbal liquid must be diluted. However, if it is diluted too much the contact time will be too long. So there is a trade-off between intensity and contact time. It is recommended that a 5 mL dose is diluted with around 10 mL of water or fruit juice. This can easily be swallowed in one go, making the contact time minimal. Another way to reduce further the intensity of the contact is to suck on some ice beforehand. This deadens the taste buds and the olfactory nerve. Chilling the medicine beforehand and adding chilled water is another way to reduce the taste intensity.

Contact time can be further reduced by immediately rinsing the mouth with water or fruit juice. About 50 mL can be quickly consumed immediately after the liquid is taken. To best achieve this, the diluted liquid should be in one hand and the rinse in the other. They are then consumed in a one–two action, as quickly as possible. Using this technique, taste can be dramatically minimised and few patients complain of any problem. For herbs with a lingering aftertaste, eating something afterwards will help.

Another option to avoid the taste of a herbal liquid is to put the liquid (undiluted) into a hard gelatin capsule using a dropper. The capsule will soften slowly over the next hour, so it can be conveniently consumed well before this happens.

Another disadvantage of liquids that applies in a few cases is the alcohol content. This is if the patient is allergic to alcohol or is an ex-alcoholic who does not wish to take alcohol in any form. Also, some strict Muslims will also not take alcohol, even in medicines. Only a very small minority of patients are genuinely sensitive to alcohol. In others, a presumed sensitivity is only an exaggerated reflex response to the medicine. This can usually be alleviated by lower doses at greater frequency, taken with copious water or food. Usually the small quantities of alcohol involved will not affect a mildly damaged liver – a 5 mL dose contains as much alcohol as about one-sixth of a glass of beer or wine. The alcohol content of liquids is not a problem for children since correspondingly lower amounts of liquids, and hence alcohol, are prescribed.

Use of alcohol in herbal liquid preparations is important since it is a good solvent for herbal active components and an excellent preservative. This is discussed in more detail later in this chapter, together with a brief review of the history and context of ethanol use in herbal preparations.

Herbal tablets are a convenient dosage form and no problems with taste or alcohol are associated with their use. However, tablets contain fixed formulations which cannot be exactly adapted to the needs of the individual patient. Therefore, it is critical that the herbs contained in a tablet are carefully chosen for the disorder they are intended to treat. Even then, the degree of treatment flexibility is limited.

A major potential problem with tablets is the degree of processing required. Processing is minimal for tablets containing the powdered herb, but the amount of herb which can be incorporated into such tablets is limited (without making them excessively large). Tablets are therefore usually made from extracts, which are more concentrated than the original dried herb. In order to achieve this, the herb is first extracted with a solvent. Often water is used to keep costs down. The resultant liquid is then dried to either a soft or a powdered concentrate using processes such as vacuum concentration or spray drying. Heat-sensitive or volatile components can be damaged or lost by this process. Heat is also sometimes used in the tablet-making process via a granulation step: the tablet mixture may be wetted and then dried in an oven before the final pressing. This risks further damage to the active components. Hence, when manufacturing tablets, quality may be sacrificed for the sake of quantity. One way to compensate for this problem with concentrates is to standardise each herbal ingredient for key active components. However, the components chosen for standardisation must be meaningful in terms of the desired activity of the herb (see later). In other words, they must be meaningful indicators of quality.

Another problem with tablets is that, despite the use of concentrates, they are sometimes formulated to contain low amounts of herbs. Many tablets contain herbs in equivalent dried herb doses of 1 to 50 mg (that is, the herb is there as a concentrate and the equivalent amount of dried herb is calculated from the known strength of the concentrate). It is difficult to see how therapeutic doses can be achieved from such small quantities.

For many patients one liquid formulation may not be enough to treat adequately their complex and varied medical conditions. This is where tablets can be extremely useful. For these patients a herbal formulation can be combined with one or more tablet formulations.

Sometimes only tablets can confer clinically effective doses. Some herbal products have been shown in clinical trials to be only effective at high doses. If these herbs were given in liquid form, the doses of liquid needed would be impractically high. A good example of this is the willow bark tablet that contains around 8 g of willow bark. This means that each tablet is equivalent to 16 mL of a 1:2 liquid extract. The only practical way to give such clinically effective doses of willow bark, based on clinical trials, is to use a herbal tablet.

Boswellia is a highly resinous herb which needs to be extracted in 90% alcohol. Hence, if Boswellia was used as a liquid and administered at clinically effective doses, the amount of alcohol the patient would need to consume would be too high. So the best way to give Boswellia is therefore in tablet form (or as a capsule).

By using herbal tablets, the herbalist does not need to carry an overly large range of herbal liquids in their dispensary. For example, for a condition such as a urinary tract infection, rather than carrying three or four herbs to treat this issue, only one tablet product needs to be stocked. Tablets are also far more easily transported both from the supplier and to patients in remote locations, and for use during travel.

A well-developed tablet formulation, put together by experienced and knowledgeable herbalists, represents a valuable tool, especially for the young and inexperienced practitioner. In a sense, the practitioner who uses such a formulation is drawing on the wealth of clinical experience of the formulators and is more likely to achieve a better clinical result and to learn through that process.

Sometimes the best way to prescribe a herb is as a powder. This particularly applies to mucilage-containing herbs. When these herbs are mixed with water, the mucilage reacts with the water to form a gel and the wet herb swells to many times its original volume. Mucilage is not very soluble in alcohol-water mixtures, hence it is difficult to use mucilaginous herbs effectively as liquids. In any case, if fluid extracts of, say, slippery elm and marshmallow were properly made, they would be so gelatinous that they could not be poured.

When giving mucilaginous herbs as powders it is best to advise the patient to mix them quickly with water and to take the mixture immediately before it swells. Otherwise, the patient often experiences difficulty negotiating the gelatinous mass which results. A copious amount of water should then be consumed to allow swelling in the stomach. Other herbs given as powders are also best taken slurried with water and rinsed down by additional water.

Tannin-containing herbs for the treatment of colon problems should also be given as powders. This is because the tannins are only slowly dissolved from the herb matrix and, therefore, are still being released in an active form when the powdered herb reaches the colon.

A big advantage of powders is that the total constituents of a herb are presented to the patient’s digestive tract, rather than those constituents which only dissolve in alcohol or water. This can also be a disadvantage if the patient has compromised digestion. Where the fat-soluble components are an important part of the activity of a herb, the powder should be followed by a dose of vegetable oil or lecithin to assist absorption.

Capsules are a convenient way to give powdered herbs because they conceal unpleasant tastes or textures. A drawback is that even large capsules can only hold 300 to 600 mg of powdered herb, which means that sometimes many capsules need to be taken to achieve adequate doses. Capsules containing herbal formulations are subject to the same limitation of flexibility as tablet formulations. Single herbs in capsules do confer prescription flexibility, since one merely prescribes each of the required herbs in capsule form. The disadvantage is that the patient may need to take a large number of capsules in order to achieve adequate doses for several herbs.

Concentrated extracts can be used in capsules instead of the powdered herb. In this instance, the same advantages and disadvantages discussed above for tablets apply.

Infusions and decoctions are time-honoured methods for delivering oral doses of herbs. In modern phytotherapy, they are mainly used where the active components of the herb are water soluble, for example, for herbs containing polysaccharides, tannins or mucilage or some glycosides. They also can be advantageous for the treatment of urinary tract problems and for the administration of alterative (depurative) herbs. Diaphoretics should be given hot to maximise their effectiveness, hence they are often administered as infusions or decoctions.

The major disadvantage of infusions or decoctions is that water is not a good solvent for many of the active components in herbs. This problem is compounded by the relatively short extraction time used in their preparation (usually 5 to 10 minutes). In addition, the large volume of hot liquid usually means that exposure to any unpleasant taste is considerably prolonged. The higher doses of herb often used in infusions and decoctions can sometimes compensate for the limitations of hot water as a solvent.

The strength of a liquid preparation is usually expressed as a ratio. For example, 1:5 means that 5 mL of the final preparation is equivalent to 1 g of the dried herb from which the preparation was made. Liquid preparations weaker than 1:2 are usually called ‘tinctures’ whereas 1:1 and 1:2 preparations are typically called ‘extracts’. Tinctures are usually made by a soaking process known as maceration, whereas extracts are best made using percolation. However, tinctures can also be adequately manufactured by a percolation process. These days, 1:1 liquid extracts can be made by reconstituting soft or powdered concentrates (not recommended).

It has been argued that 1:2 extracts are relatively new, are not mentioned in the BHP 1983 or other pharmacopoeias and therefore should not be used. In fact, 1:2 extracts are mentioned in 19th century texts^16,18 and were described in the German Pharmacopoeia (DAB). The seventh edition of the DAB actually defines a liquid extract as a 1:2 extract.¹⁹

The dominant historical use of 1:1 extracts may not have been the wisest choice because of the extra processing required. In 1953, a Dutch PhD student studied the impact of pharmaceutical processing on some active components of thyme (Thymus vulgaris).²⁰ The components tested were the phenols (thymol and carvacrol), which are responsible for the antiseptic activity of thyme. Thymol and carvacrol are found in the essential (volatile) oil of thyme and could conceivably be lost under conditions of vacuum or heat. The following preparations were made:

The phenol content in all four preparations and in the original herb was measured and the results are summarised in Table 6.4. The table also provides the essential oil content of some of the preparations.

As can be seen from Table 6.4, the 1:2 extract contains only marginally less phenol content than the 1:1. This is presumably because the phenols were largely lost during the heating of the second percolate which occurs in reserved percolation. Hence, on the basis of the active components tested, the 1:2 is almost as strong as the 1:1. It should be noted from Table 6.4 that neither the 1:1 nor the 1:2 quantitatively extracted all the phenols from the dried herb, presumably because these components were not completely soluble at the ethanol percentage chosen. The 1:2 contained 37% of the original phenol content in the dried herb, compared to 22% for the 1:1.

The results for the soft and powdered extracts are disturbing. For the soft extract, 82% of the phenols were lost in processing, and for the powdered extract the loss was 48%. Compared to spray drying, conditions of vacuum therefore seem more likely to cause the loss of essential oil components, although the losses in both cases are considerable. A Swiss study found that concentration of a chamomile extract under vacuum caused the loss of about half of the essential oil.²¹

The content of essential oil and phenols in the corresponding amount of dried herb are also provided for the various preparations in the right-hand columns of Table 6.4. As can be seen from the table, the soft and powdered extracts only contain a fraction of the essential oil and phenol content of the dried herb. Hence, for this example, the use of these concentrates in the manufacture of liquids, tablets or capsules would clearly represent a substantial sacrifice of quality for the sake of an increase in quantity. If the soft extract was reconstituted to a 1:1 which is a common practice, it would contain about 30% of the phenol content of the 1:2 (0.04% versus 0.11%).

Ethanol (or alcohol) has been used for hundreds of years to prepare liquid herbal preparations and indeed ethanol-water mixtures do appear to be quite efficient for the extraction of a wide variety of compounds found in medicinal plants. Chemical analyses of organic substances absorbed into pottery jars have recently confirmed the use of medicinal wines in ancient Egypt (about 3150 bc and millennia thereafter) and ancient China (seventh millennium bc). The ancient Egyptian wine contained herbs and tree resins dispensed in wine made from grapes. The jar from ancient China contained a mixed fermented beverage of rice, honey and fruit (hawthorn (Crataegus spp.) fruit and/or grape). The medicinal use of wines has been described in ancient documents, and the early Chinese history of fermented beverages is suggested from the shapes and styles of Neolithic pottery vessels.^22,23 Ancient Egyptian papyri describe water, milk, oil (presumably olive oil), honey, beer and wine as carriers for medicinal herbs. Jewish medicine, described in the second-century Talmud, refers to a ‘potion of herbs’ mixed with beer or wine.²⁴

Although the principle of distillation was known to the ancient Greeks, the Arabs adapted the process to produce alcohol, which they then used for medicinal purposes. (The word alcohol, which first appeared in most modern languages in the 16th century, was derived from Arabic (al-koh’l).)²⁵

The first official British Pharmacopoeia, the London Pharmacopoeia, was issued in 1618. It contained a section outlining ethanolic fluid extracts and drew heavily on the classics.²⁶

Nicholas Culpeper, the 17th century English herbalist and one of the best-known advocates of Western herbal medicine, described the distillation of one or more herbs in wine, and the maceration of spices in alcohol. Single herbs, such as dried wormwood (Artemisia absinthium), rosemary (Rosmarinus officinalis) and eyebright (Euphrasia officinalis), were steeped in wine and set in the sun for 30–40 days to make a physical wine.²⁷

A number of studies have highlighted the importance of the correct choice of the ethanol percentage in terms of maximising the quality of liquid preparations. The Swiss study mentioned above found that 55% ethanol was the optimum percentage for the extraction of the essential oil from chamomile (Matricaria chamomilla).²¹ Higher percentages of ethanol did not extract any additional oil and there was a decrease in the solids content of the extract, which indicates that other components were being less efficiently extracted. More recently, Meier found that 40–60% ethanol was the optimum range for achieving the highest extraction efficiency for the active components of a variety of herbs.²⁸ For example, at 25% ethanol, none of the saponins in ivy leaves (Hedera helix) was extracted, but at 60% ethanol they were maximally extracted.

Higher ethanol percentages do not always confer higher activity. French researchers found that Viburnum prunifolium bark extracted at 30% ethanol was five times more spasmolytic than a 60% extract.²⁹

The basic guidelines for the choice of the ethanol percentage to optimise the activity of the final liquid are as shown in Table 6.5.

Table 6.5 Choice of ethanol percentage to optimise the activity of final liquid

Some educators have suggested that herbal liquids are a less desirable dosage form because they are less stable than solid dosage preparations. However, there is little objective evidence to back up this assertion. Some companies now undertake stability studies on their herbal liquids as a requirement of pharmaceutical GMP, and experience in this field is that most liquids maintain their phytochemical profiles within the normal shelf-life requirements of 2 to 3 years.

Provided herbal liquids are purchased through a herbal manufacturer which operates to pharmaceutical GMP standards and has a comprehensive stability programme in place, keeping to within expiry dates is sufficient to ensure retained activity. This is, of course, if the manufacturer’s recommended storage conditions are observed. Sunlight is particularly damaging to the phytochemicals in a herbal liquid, so they must be stored in amber glass bottles away from direct sunlight. Temperature is also an important factor. Generally storage below 30°C (86°F) is recommended (temperatures occasionally above 30°C (86°F) will not cause a problem, if the average is below this level). Also a minimum storage temperature of 10°C (50°F) should be maintained. Some herbal liquids such as celery and wild yam will form into a gel if they become too cold. While gentle reheating will generally make them liquid again, irreversible changes may occur if the cold conditions are prolonged.

Many herbal liquids develop a sediment over time. If the extract has not been heated during its manufacture this is a natural occurrence which generally has only a minor impact on quality. A common question among practitioners is whether this sediment should be rejected or redispersed into the liquid. There are no hard and fast rules here, but a general guide is that if the sediment has tended to aggregate or concrete into a hard mass, then it should be rejected. If, however, the sediment is fine and easily redispersed, then the bottle should be shaken to do this before dispensing. For mixtures of several herbal liquids the sediment should always be redispersed

Glycetracts or glycerites are liquid preparations made using glycerol and water instead of ethanol and water. They are useful preparations where the active components are water-soluble, for example, marshmallow root (Althaea officinalis), since they do not contain alcohol and the sweetness of the glycerol gives them a better taste. However, their importance should not be overrated. Glycerol is a poor solvent for many of the active components found in herbs and glycetracts are less stable than alcoholic extracts. Moreover, because of the viscosity of glycerol, concentrated preparations are difficult to make by percolation. The manufacture of 1:1 or 1:2 glycetracts therefore invariably requires the use of a concentration step involving heat or vacuum.

In recent times the use of tinctures made from the fresh plant has become popular among some herbalists. The belief is often that a fresh plant tincture better reflects the plant’s ‘vitality’ or ‘energy’ and therefore will be a more therapeutic preparation. Other practitioners believe that a fresh plant tincture will better preserve the delicate active components of the plant.

On the other hand, the following observations need to be considered:

Based on how they are made, standardised extracts can be classified into three basic types. These are:

These types of extracts progressively represent a transition from a more traditional herbal product through to more modern types of products, which can be called phytopharmaceuticals. Phytopharmaceuticals are not like conventional drugs, but they are also very different from galenical extracts. Practitioners will wish to choose, based on their philosophical perspective, whether the use of phytopharmaceuticals is acceptable to them. However, as part of this process they should consider that phytopharmaceuticals are often chemically complex (an important criterion for phytotherapy), clinically proven and very safe. Probably, as suggested earlier, the decision is best based on a case-by-case basis.

Standardised extracts are not a guarantee of quality, as they are often represented. Inappropriate choice of marker compounds, poor design or execution of analytical methods, spiking with pure phytochemicals (which is actually quite rare except for examples where the pure phytochemical is relatively cheap, such as caffeine or rutin) or failure to demonstrate phytoequivalence can mean that the standardised extract is poorer in quality or less effective than a well-made galenical extract. Only those manufacturers who practise good science and have a comprehensive understanding of the many complex issues that impact on herbal quality will be able to produce meaningful standardised extracts.