Introduction
In traditional herbal medicine systems, herbal remedies are prepared in several rather standardized ways which usually vary based upon the plant utilized, and sometimes, what condition is being treated. Some of these methods include infusions (hot teas), decoctions (boiled teas), tinctures (alcohol and water extracts), and maceration (cold soaking) which are detailed more fully herein. In indigenous Indian medicine systems, medicine men or shamans generally use these same methods in addition to others. Others include preparing plants in hot baths (in which the patient is soaked in it or bathed with it), inhalation of powdered plants (like snuff), steam inhalation of various aromatic plants boiled in hot water, and even aromatherapy (Taylor, 2005).
Methods of Preparing Herbal Medicines
1. Concoctions
These are aqueous preparations of different plant parts soaked or boiled in water for particular period of time. If boiled, it is done for 15–20 min, but if soaked, it is soaked for 3 days before consumption to ensure thorough extraction. Concoction can also be prepared using plant parts as soup popularly called “aseje” in Yoruba traditional system of medicine. These soups can be prepared by adding several other materials such as dried chameleon, snail, and dried toads among others. The soup is prepared for a day’s consumption.
2. Decoctions
Decoctions are aqueous preparations of plant parts boiled in water for 15–20 min until the water volume is halved. Decoctions are prepared by breaking the plant parts into small pieces before soaking in a given amount of water in an earthenware container (Palayok). The water should cover the plant parts, then the container is covered, and the preparation is boiled until the water volume is halved. The boiled preparation is strained, cooled, and refrigerated which can be kept for 2 or 3 days.
3. Strong decoctions
Depending on the type of plant material used, strong decoctions are prepared in two general ways. The first involves boiling the mixture for a longer time. This is usually indicated when working with larger woody pieces of bark. Longer boiling time, up to 2 h or more, is sometimes necessary to break down, soften, and extract the larger pieces. Alternatively, when smaller woody pieces are used yet a stronger remedy is required, the decoction is prepared as above (boiling for 20 min), then it is allowed to sit/soak overnight before straining out the herb. When straining, it is ensured that the cut herb pieces are pressed in the strainer to get as much moisture/decoction out of the herb pieces (Taylor, 2005).
4. Dried decoctions
Dried decoctions were developed in Japan in the 1950s and have become a major meth¬od of providing herbs in Japan, Taiwan, the United States, and Europe. The dried decoctions are produced by making very large batches of the herb formulas as decoctions (in large tanks), and then draining the liquid from the dregs. The liquid is then evaporated (using heat and vacuum) to form a syrup. The syrup is then put into a spray drier along with a powder carrier (usually starch or the dried, powdered, herb dregs), and the remaining water is evaporated, leaving a dry powder (Dharmananda, 1997).
5. Infusions
As in preparing tea, infusions are prepared using dried or fresh herbs. The plant materials are soaked in hot water and allowed to stand for 10 min. Then strain the tea and drink it hot or ice cold. It’s just for a day’s use.
6. Pills
This preparation is also called honey pills. Pills can be made by mixing thoroughly the dried and powdered herbal materials with equal quantity of honey cooked to bright red syrup. The mixture is allowed to cool off after which it would be rolled to desired tubular strands and cut into small pieces. The pieces are air dried in clean place and bottled neatly. If honey is not available, concentrated syrup of cane sugar can be substituted.
7. Powder
This is the most common and easiest way of preparing herbal materials. With mortar and pestle, the well dried plant materials are crushed and ground into a fine uniform powder. The powder is stored in clean bottles, and should be as fine as possible to ensure faster solubility. Although the local healers of Oromo, Gambi district of Southwest Ethiopia employed several methods of preparation of traditional medicines from plants, powdering and pounding were the most frequently used methods of traditional medicine preparation (Abera, 2014).
8. Tinctures
This preparation is also called alcoholic decoction. To prepare tinctures, the herbal materials either fresh or dried are placed in 40–60% proof alcohol. It is prepared by placing one part of herb to five parts of distilled spirit and is kept in an airtight container. The mixture is shaken or stirred at least once daily. Alcoholic decoction extracts preserve the essential ingredients for the longest possible time. The extract is strained and stored in an airtight glass jar. Dosages are usually five to twenty drops taken directly or added to water. Also, this can be prepared by boiling the alcohol alongside the desired herbs in water. Then the solution would be poured into container and tightly sealed. After 2 weeks of usage, the residue of the solution can be used to prepare ointment.
9. Tablets
The herbs of interest are powdered and thoroughly mixed. If small sized tablets with high drug concentration are desired, a portion of the dried drug material may be decocted into a thick concentrated solution and then mixed with the other powdered materials. In making the tablet, a sufficient amount of starch or rice paste is added to the mixture and is forcefully mixed and kneaded by hands. Small globular tablets are made of the kneaded paste-like material with the aid of improvised tablet making devices which may be constructed from wood or metal.
10. Syrup
This preparation is applicable for children and infants. This is prepared by dissolving certain amount of cane sugar in certain volume of boiling water until the sugar thoroughly dissolves in the water. The desired herb is placed in water, boiled, and decanted. The resulting extract (generally every 1 mL of the decoction fluid contains 1 g of the concentrated drug) is added to the prepared cane sugar syrup in 1:1 proportion. The decoction should be treated with sufficient amount of fungicide like benzoic acid for long storage if the syrup is not to be added.
11. Poultice
Poultice, sometimes referred to as paste, is prepared by grinding and crushing the desired plant materials either dried or fresh (preferable) with a little water, oil, or honey. The resulting paste is then spread on a square of a clean cloth or banana trunk and applied or tied to the affected area. However the crushed plant can also be boiled to achieve a pulp.
12. Compresses
These are usually milder than poultice. An infusion or decoction is used to soak a clean cloth or a banana trunk and placed on the affected areas.
13. Juices
Juices are prepared by pounding fresh plant materials and filtering through a fine piece of cloth or by squeezing the plant parts to extract the juice.
14. Oxymels
An oxymel is a specialized sweet and sour herbal honey preparation, a sweet honey mixed with a little sour vinegar. This combination may be used as a carrier for herbal infusions, decoctions, concentrates, tinctures, and other herbal extracts. Oxymels are used as a gargle or as a vehicle for intense herbal aids such as Garlic, Cayenne, and Lobelia (Green, 2002). The stability of oxymels may depend on the content of honey, vinegar as well as the preparation for which it is being used as a carrier (Bascom, 2002).
15. Herbal capsules
Capsules are solid dosage forms containing drug and usually, appropriate filler (s) enclosed in a gelatin container (Winfield et al., 2009). Capsules may be available in hard gelatin for dry powdered herbal ingredients or granules (Bayor et al., 2011), or soft gelatin shells for herbal oils and for herbal ingredients that are dissolved or suspended in oil. The gelatin shell readily ruptures and dissolves following oral administration.
Drugs are normally more readily released from capsules compared to tablets (Hoffman, 2003). Capsules may help mask the unpleasant taste of its contents and uniformity of dosage can be relatively readily achieved (Aulton, 2007). Herbal capsules normally consist of hard shelled gelatin capsules with the plant material finely milled and sifted and filled into shell or extracts of the herbal material(s) with appropriate excipients such as fillers (Johnson et al., 2010). The stability of herbal capsule preparations is relatively better when compared to aqueous preparations such as decoctions and infusions. Stability and shelf life of capsule preparations should be determined to provide appropriate instructions for storage of the product (Aulton, 2003). An accelerated stability study of herbal capsules indicated for immunomodulation and stress in India found the change in quantifiable active components to be within 90% of the initial amount showing the stability of the product at room temperature for 2 y (Bankoti et al., 2012).
Herbal capsules filled with pellets showed a uniform and stable release of phenolic compounds in various long-term storage conditions, indicating that the method of preparation of dry herbal extracts affects the stability of the active ingredients (Pranskuniene et al., 2013). The carotene content of most pilot batches of soft gelatin capsules containing thick extracts of pine needles during long-term (3-24 mo) and accelerated (3-12 mo) stability studies at 25 °C}2 °C/60%}5% RH and 30 °C}2 °C/65%}5% RH was found to be satisfactory (≥30 mg%) (Daberte et al., 2011).
16. Herbal suppositories
Suppositories are solid dosage forms meant for insertion into the rectum. They are prepared by moulding with the incorporation of the medicinal agent into a suitable base which should melt or dissolve at body temperature to exert the therapeutic effect. Suppositories may be used for local or systemic effects (Winfield et al., 2009). Herbal suppositories are normally prepared by mixing powdered and finely sited herbs or extracts with cocoa butter as the base (Green, 2002). They are normally used to soothe inflamed surfaces of the nasal mucosa and aid the healing process; reduce swollen membranes and overcome pus filled discharge or to act as a laxative to treat constipation (Page, 2004). The stability of suppositories, amongst other factors, depends on the temperature of storage and packaging. They are relatively stable at low temperatures of storage. Unless other information on stability is provided from a study, a shelf life of one month may be appropriate (Winfield et al., 2009).
17. Herbal glycerites
Glycerites are made like tinctures but in this instance, glycerine is used in the extraction process instead of a mixture of alcohol and water. A glycerite will keep well as long as the concentration of glycerine is at least 50 % to 60 % in the finished product. The shelf life is only about six months to two years. Glycerine should not be the solvent of choice for herbs that contain resins and gums; alcohol is needed to properly extract the active constituents of these herbs.
Glycerites should be refrigerated for best effects (Bascom, 2002). Glycerine is a good preservative for fresh plant juices, in which half fresh plant juice and half glycerine are mixed, as it keeps the juice green and in suspension better than alcohol. This sort of preparation is called a succus. Glycerine is particularly good in making medicines for children, and for soothing preparations intended for the throat and digestive tract, or coughs (Bruton-Seal, 2009). Glycerites are normally less potent than alcoholic extracts and have a shorter shelf Medicinal Plants Uses in Traditional Medicine