Herbs in Africa Part 6 Skin Care lotions and Medicinal Balms

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Herbs in Africa Part 6

Skin Care lotions and Medicinal Balms

By Ivor Hughes. www.herbdatanz.com

See below for links to earlier articles in this series

Given the antiquity of such preparations, it is possible to manufacture a satisfactory product without recourse to theory, simply by following a recipe which uses only natural substances. However today we will find those substances are obtained from many different parts of the world. So there will be some variation in the physical behaviour displayed. Therefore some theoretical grounding will be useful if one encounters a production problem.

The Emulsions

Emulsions may be used internally or topically for medicinal or cosmetic purposes. If the remedy is to be used internally, then the purpose of the emulsion is to disguise any unpleasant taste, or circumvent any nauseating effect, for example, Emulsion of Asafetida. Emulsions for internal use are rarely encountered today. The major use being as an application to the skin.

Oil and water are immiscible liquids, but a temporary emulsion may be formed by a brisk shaking of the liquids. However, upon standing, the oil and water will once again resolve themselves into two separate layers. There are two types of basic emulsions, they are :

(1) Oil in water ( O/W ) (2) Water in oil ( W/O )

The type of emulsion formed is dependent on the relative proportions of oil and water. If water is the predominant proportion, then it will be an O/W emulsion. If oil is predominant, then the emulsion will be W/O.

The predominant liquid is called the Continuous Phase. The lesser proportion is called the Disperse Phase. There are 2 basic requirements to produce an emulsion of immiscible liquids, they are :

(1) The disperse phase must be reduced to fine droplets, which are dispersed through the continuous phase.

(2) A third agent known as the Emulsifier, which should suspend and prevent the immiscible liquids from Cracking or Creaming. Creaming is the concentration of dispersed globules. Milk with a layer of cream on top, is a good example. Cracking is the destruction of the Emulsion system and the ingredients separate. Cracking is the most common problem with emulsions. However, the change may be biological, chemical or physical. The most common causes are ;

(A) Bacterial action, which affects the emulsifier or brings about chemical changes in the phases or the emulsifier.

(B) A change in the pH, which modifies the emulsifier.

(D) The introduction of substances which are not compatible with the emulsifier.

Types of Emulsions.

It is a general rule that the continuous phase will determine what type of emulsion is formed. A further factor in the stability of the emulsion, is the type of emulsifier used. Liquid emulsions and light creams are usually oil in water, whereas, the stiffer preparations such as a Salve or Ointment tend to be water in oil.

The Theory of Emulsification.

Emulsifiers depend for their action on the fact that their molecules have a non polar end and a polar end. A tadpole would be a good analogy. The head is the polar end, whilst the tail is the non polar end. The polar head is charged and is Hydrophilic (water loving). The tail is Hydrophobic (water hating). For convenience, they may be classified into 4 groups as follows:

(1) Anionic Emulsifiers, which form negative ions, e.g., soaps and sulphates.

(2) Cationic Emulsifiers, which form cations or positive ions, e.g., ammonium compounds.

(3) Non Ionising molecules, such as the esters and ethers.

(4) The Natural Colloids, e.g., gums, mucilages, proteins and waxes. It is this class, which is of prime importance for the preparation of natural remedies.

Examples of the natural colloids are as follows :

Gums :
Acacia, which is the dried exudation from the stem and branches of the Acacia spp. Acacia is incompatible with alcohol. Tragacanth, which is a dried exudation of the Astragalus spp., which is also insoluble in alcohol .

Mucilages :
The mucilages are a very useful group of substances, being in most cases both demulcent and nutritive. In general, they may be used as suspending agents. They are obtained from both land and marine plants, for example:

Agar, belongs to the phylum Thallophyta, which comprises the seaweeds and other fresh water forms.
Bladderwrack, Fuscus vesiculosus or Kelpware.
Chondrus, Chondrus crispus commonly known as Carrageen or Irish Moss.
Cydonia, Cydoniae Semen or Quince seeds.
Fenugreek, Trigonella foenum - graecum L. Fenugreek seed.
Psyllium. The seed or husks of Plantago spp. Linseed. Linum usitatissimum L.Althaea ssp. or Malva Officinalis. Common name, Marshmallow root.

Proteins :
As a general rule, these substances need to be avoided in the preparation of natural remedies. Typical examples are : Casein, Egg Yolk (lipids) and Gelatine. These substances are obtained from non plant sources. They are prone to attract virulent bacteria.

Waxes :
The waxes are obtained from diverse sources, e.g., Bees, Mammals and Plants. Chemically they are classed as Esters. Which are large molecules of alcohol and a fatty acid. However, in practice they are very variable. Generally, the true waxes are exudations. There is a very fine chemical line between the Fats, Oils and Waxes.

The Fixed Oils and Fats :
The fixed oils and fats are a mix of the glyceryl esters of high molecular weight, aliphatic acids for example, oleic, palmitic and stearic acids. Chemically they are classed as alcohols, which are representative of a homologous series. The molecular weights and boiling points display the usual gradations observed in other series. They are classed as Primary, which are liquids and are miscible with water. Secondary, which are also liquid but are not totally miscible with water. Tertiary, which are greasy solids.

The Alcohols, Structural Examples :
A molecule of Alcohol contains one or more oxygen atoms in addition to carbon and hydrogen, for example, ethanol, which is a primary alcohol.

A molecule of ethanol is hydrophillic (likes water) and hydrophobic (hates water). It will be seen that the Hydroxyl group (OH) is 1 atom of Hydrogen short of water (H₂O), which explains its affinity for water. The remainder of the molecule is hydrocarbon, which lends to that part of the molecule Lipophilic (fat loving), and hydrophobic properties.

The secondary alcohols are polyhydric, and contain more than one hydroxyl group, and are fats and oils.; some of the constituents of which, may be used as Humectants. The humectants hold moisture in contact with the skin. They are used extensively in the Cosmetics industry as moisturisers., e.g., Glycerol which contains 3 hydroxyl groups.

The tertiary alcohols are greasy solids and almost wax like. The hydrocarbon part of the molecule is predominate. Accordingly, it will not dissolve in water. However, if included in a mixture of oil and water, they will act as an emulsifier. For example, Beeswax or Lanolin.

Manufacturing Emulsions, Light Creams and Ointments

It must be remembered that compounding is more Art than Science. The compounder will have recourse to many different natural substances, which even if of a similar class, will tend to be of great variability in composition. For this reason, melting and solidification points are never precise, but are expressed as a range of temperatures. Theory is subordinate to practice.

The compounder must study the formulation of a preparation and decide whether the preparation is oil in water or water in oil. The fats, oils and waxes should be separated to determine the percentage relative to the water and water soluble substances. If the oil phase is the predominate percentage, then the preparation is W/O. If the water phase is predominate, then the preparation is O/W.

Both types need to be mixed or homogenised in a different manner. If the preparation is O/W, then a whisk or an electric mixer may be used to emulsify the preparation. A W/O preparation must be stirred slowly, to avoid the formation of air bubbles, which tend to destabilise the emulsion or cream. Due to the similarity of substances employed, it will become obvious that the distinction made between emulsions, creams and ointments, is merely based on the density of each preparation, and in all cases where the preparation is intended for topical use, a suitable preservative or inhibitor of micro-organisms must be incorporated.

Manufacturing an Emulsion.
The proportions of gum and water to be added to a fixed oil, in order to produce a satisfactory emulsion, will vary according to the oil used. As a general rule of thumb, when using fixed oils, balsams or oleo-resins as a medicinal emulsion, the following methodology will produce a satisfactory W/O emulsion. To a clean mortar, add 2 parts of oil to 1 part of a gum emulsifier. Triturate until thoroughly mixed. Then immediately add twice as much distilled water as the gum, and triturate rapidly until the oil has emulsified. Then slowly, whilst triturating, add the rest of the vehicle until the emulsion is complete.

If producing an O/W emulsion, the procedure is modified by first producing a mucilage and adding half the amount of oil as mucilage ,and triturate thoroughly until emulsification is achieved. Then add a further proportion of mucilage, and then the oil until the desired quantity of emulsion is produced. The amount of water used to produce the mucilage will vary according to the substance used to produce it.

Manufacturing Creams and Ointments.
Such preparations fall into three broad categories, as follows :

(1) Balm ; A balm is an aromatic healing ointment.

(2) Salve ; A salve is specifically a healing ointment.

(3) Cream; Creams are either cosmetic in nature, or used as an emollient.

There are three main functions of such preparations, which are as follows:

(1) As an emollient to soften the skin.

(2) As a protective surface for the skin.

(3) As a vehicle for medicinal substances which are to be used as an application to the skin, or to be absorbed through the skin.

The ointments are fatty substances of such a consistency that they may be easily applied to the skin. The formulation of the ointment base will vary according to the end use and results required. As a product, they are found in great variety and enjoy universal usage by virtue of their versatility. It should be noted that there are many commercial products which contain glycerine in the formula. Glycerine is contra-indicated for medicinal and cosmetic purposes because of its dehydrating properties. In the case of skin complaints it is injurious and irritating and should be avoided at all costs.

The ointments, if kept for long periods, have a tendency to rancidity or attack by micro-organisms. Two readily available inhibitors are Benzoic Acid, which should be added to the preparation in a ratio of 1:1000. Secondly, Salicylic Acid, at a ratio of 1:1000.

The traditional inhibitors and their ratios of usage are as follows;

Gum Benzoin (Styrax benzoin. Dry.) ................ 1:100

Popular Buds (Balm of Gilead) .................. 1:50

Elm Bark (Ulmus rubra. Muhl.) .................. 1:45

The Gum Benzoin and Popular Buds should first be prepared as a 1:1 liquid extract. The extract is then added to the preparation at the ratio given. An alternative method for the Popular buds, is to place the oil or fat into a bain marie, or double boiler, and heat. Macerate the popular buds in the warm oil or fat for 8 hours. Strain the resulting liquid and discard the buds.

The Elm bark is of a mucilaginous nature and requires different treatment. The dried bark must first be reduced to a fine powder, and macerated in a fixed oil at a temperature of 40C for 24 hours. The ratio of bark to oil is 1:2. The maceration is then filtered and is used in the end preparation at a ratio of 1:45. When using any of the 5 inhibitors mentioned, be sure to check for any Pharmacological incompatibilities.

The Fats, Oils and Waxes employed are of great variety. The choice made, will depend upon the purpose for which the ointment or cream is required. The choice must also include a substance that will remain viable within a given temperature range, which must include bodily, as well as ambient temperature. A selection of such substances and two constants are given in the following table;

AF = Animal fat. .......... Animal fats are absorbed readily by the skin.
AW = Animal wax.......... Are readily absorbed when mixed with vegetable oil.
IW = Insect Wax............ Insect waxes are of minimal absorbency.
VF = Vegetable Fat.........Readily absorbed by the skin.
VO = Vegetable oil......... .Readily absorbed by the skin.
VW = Vegetable wax....... Minimal absorption.

Methodology for Lotions and Creams
By definition, lotions and creams are emulsions. Lotions are oil in water (O/W) The creams are water in oil (W/O). It is necessary to study the formula to decide which type of emulsion it is. Because each type needs to be mixed (homogenised) by a different methods to prevent cracking or creaming. Calculate the oils, fats and waxes as a percentage of the total formula. Then calculate as a percentage, the total of the water, and water soluble constituents. If the oil phase is the greater, then the more viscous the product, and will tend to be a cream. If the water phase is the greater, then the product will tend to be a lotion. O/W preparations may be homogenised by an egg whisk or an electric mixer. W/O preparations will need to be slowly stirred, either by hand or by a paddle mixer set a slow speed. The reason is that, if air bubbles are introduced during the mixing process, then the preparation may crack or cream.

The following formula is an O/W moisturising cream. It is a variation on an ancient formula, originally attributed to Galen.

Bees Wax	120g
Palm Kernel Oil	110g
Oil of Almond	550g
Distilled Water	195g
Gum Benzoin Extract	10ml

Prepare a water bath and add the first three ingredients. Break the bees wax into small pieces. Stir until all of the oil phase is in a homogenised state. Take the temperature of the oil and heat the distilled water to the same temperature. Then stirring steadily, slowly add the water phase to the oil phase. Remove from the heat, and add the Benzoin extract. Then mix vigorously until cool.

The above formula is an Emollient, and may be suitably medicated or lightly perfumed, according to its end use. As a general rule of thumb, add the waxes to the oil. A word of warning, never heat the oil phase over direct heat and then add water. This will cause the hot oil to erupt with possible dire consequences. Always use a water bath or double boiler.
The methodology described may be considered as standard. . If compounding from a Pharmacopeia or Dispensatory, any deviations or special requirements will be clearly stated.

The Ointments (Unguentum) The ointments, as a class of medicament, have a long and venerable history. As a compound, the ointment is ingenious, and may be made to serve many different purposes.

(1) As an emollient to soften or soothe the skin.
(2) As a protective barrier for the skin against noxious substances, insects or ultra violet rays.
(3) As a vehicle for medicinal substances which are to be,

(A) An application to the skin for antiseptic or anaesthetic purposes.
(B) Absorbed through the skin for introduction of the medicament to the circulation.

Ointment bases are also used for suppositories and pessaries. When beeswax is specified in a formula for medicinal purposes, it should be taken to mean yellow unbleached wax. (Cera Flava), and not the bleached wax (Cera Alba). White wax finds use in cosmetics purely because it presents a better appearance. However, experience has demonstrated that preparations made with yellow, unbleached wax has better keeping qualities. This no doubt because it has not been chemically altered.

The ointments are of great variety and serve as a vehicle for hundreds of different substances. The ointments in turn, are made from a wide variety of base materials which may be ;

(A) Animal fats.

(B) Insect exudations.

(C) Vegetable exudations.

(D) Mineral oils and wax

(E) Synthetics.

The point will not be belaboured, but substances which fall under the head of A, D and E, should as a general rule, be avoided, because there is the possibility of the uptake of undesirable substances, and in the case of the animal fats, there are also some problems, not the least of which is the tendency to rancidity.

When compounding an ointment from published formulae, then substitutions for undesirable substances may need to be made. Accordingly, the purpose of the ointment must be considered, i.e., is the ointment, a barrier, an emollient, or is it to introduce medicaments to the circulation?. In addition, consideration must be given to climatic temperatures, Tropical, Temperate or Cold. Therefore, the two factors are Absorbency and Melting Point, of the selected substance. The following table will be of service.

Methodology of Preparation
Prepare a water bath. If the compound calls for a fixed oil, then add the oil first and melt the other ingredients in it. If the formula is comprised of waxes and fats, then add the substance with the highest melting point first, and then melt the other substances in it. Remove from the heat, then stir or use an electric mixer until the ointment has cooled.

Adding the Medicament
The incorporation of ground plant material to an ointment base, is sloppy practice and leads to many uncertainties, e.g, the degree of extraction obtained by the ointment base materials is an unknown, therefore, it presents a problem of posology. Secondly, unless a paint or shear mill is used in the incorporation process, then a grittiness is bound to occur.

The medicament is most easily prepared from a 1 : 1 Extract, by evaporation over a water bath, or by distillation under reduced pressure. It should be reduced to a soft or pasty extract for incorporation into the ointment base. Gently heat the base until it is easily worked, but not in a molten state. The temperature should not exceed 30C. The medicament may then be incorporated into the ointment. At this stage, unless there is a problem of compatibility, a suitable inhibitor should also be added. It must be thoroughly mixed until an even dispersion has been achieved. Allow the finished ointment to congeal. It is then ready for use.

Useful Formulae
The following formulae will be found useful for a variety of purposes. If a preparation is to contain large amounts of liquid or water, then those formula that contain Lanolin will absorb the liquid in a satisfactory manner. When preparing an ointment, the compounder is urged to ensure that the base will meet the criteria required. This is simply achieved by testing the ointment on themselves. If the ointment is too stiff, then it may be rectified by the addition of more oil, or a substance which is of a lower melting point than that of the beeswax. If it is too soft, then the addition of a substance of higher melting point will stiffen the product.