5. Description of components of nutmeg


The nutmeg seed is one of four c components of the fruit obtained from the nutmeg tree, Myristica frangans Houtt (Myristicaceae) About 30-55% of the seed consists of oils and 45-60% consists of solid matter including cellulose materials. There are two types of oils: (1) The "essential oil of nutmeg" also called the "volatile oil" accounts for 5-15% of the nutmeg seed and (2) the "fixed oil of nutmeg" sometimes called "nutmeg butter" or expressed oil of nutmeg accounts for 24-40% of the nutmeg seed.14 The relative percentages of the different components will vary depending on the geographical origin of the nutmeg. From this point on, "essential oil", "volatile oil", and "nutmeg oil" will be used interchangeably.

Essential Oil

Although the essential oil is present in lesser amounts than the fixed oil, the essential oil has received most of the investigative research efforts especially during the last twenty years. This is in accord with the fact that the essential oil contains the greater number of individual compounds or components, most of which are valuable in industries. Furthermore, the psychotropic effects of nutmeg as well as most of its other pharmacological properties have been attributed to the compounds found in the essential oil.

The essential oil is obtained from the nutmeg by steam distillation. It is a colourless or pale yellow liquid with a taste and odour of nutmeg.15 This oil is soluble in alcohol and insoluble in water and has a density, at 25C of 0.859-0.924. Since it is light and air sensitive, it must be kept cool in a tightly closed container and protected from light.16

Components of the Essential Oil

The first major successful analytical works to determine the constituents of nutmeg was performed by Frederick Power and Arthur Henry Salway from 1907 to 1908.17,18 They isolated and identified numerous compounds found in nutmeg. Around the 1960's, more compounds were identified by using modern techniques like gas-liquid chromatography.19

The early articles on the chemistry of nutmeg, including the Merck Index, reported camphene and pinene as the major constituents of the essential oil. More recent articles show sabinene to be the major constituent of the essential oil.20,21 It is still questionable whether sabinene constitutes most of the essential oil because the latest Merck Index still shows camphene and pinene to be the major constituents of the essential oil.

From these analyses, a listing of the major components of the essential oil and their relative percentages is provided below. Note that either sabinene or camphene comprise about 50% of the essential oil:

1. Sabinene

(50%)

or


2. Camphene

(50)%

3. d-Pinene

20%

4. Dipentene

8%

5. d-Linalool

6%

6. d-Borneol

6%

7. i-Terpineol

6%

8. Geraniol

6%

9. Myristcin

4%

10. Safrole

0.6%

11. Eugenol

2%

12. iso Eugenol

2%

In addition, a thorough listing of all the components that have been observed in the essential oil along with their classification based on type is given below:

Aromatic ethers

Methyl Eugenol

Eugenol

Methyl Iso-Eugenol

Myristicin

Methoxy Eugenol

Elemicin

Safrole

Iso-Eugenol

Iso-Elemicin


Terpenes

Alpha-Terpinene

Myrcene

Gamma-Terpinene

Terpinolene

Alpha-Pinene

Camphene

Beta-Pinene

Uinonene (Dipentene)

Alpha-Phellandrene

Sabinene

Beta-Phellandrene

Delta3-Carene

Alpha-Thujene


Monoterpene Alcohol

Geraniol

4-Terpineol

Alpha-Terpineol

Beta-Terpineol

Citronellol

Linalool

Sesquiterpene

Caryophyllene


Terpinic Esters

Geranyl Acetate

Linalyl Acetate

Bornyl acetate


Acids

Formic

Octanoic

Butyric

Acetic

Aromatic hydrocarbons

P-Cymene

Toluene

The following compounds were identified only on the basis of retention times observed from gas chromatography.

Cumene

Cyclamen Aldehyde

Camphor

Menthone

Menthyl Isovalerate


The structures and physical properties of the major compounds in the essential oil is given in Appendix 1.

Uses of the Essential Oil

Because of its aroma, the essential oil has been used as a natural flavouring extract and as a perfume in the cosmetic industries.22 In particular, the oil has been used as a flavouring agent, replacing ground nutmeg in order to avoid leaving particles in foods and beverages. For example, it has been used to flavour baked goods, beverages, candies, meats and syrups.

The essential oil has found widespread use in the cosmetic industry when a spicy odour is required. For example, it has been employed as a flavour in dental creams in combination with peppermint, methyl salicylate and cloves.23

In addition to its use in cosmetic industries, nutmeg oil is prominently used in the pharmaceutical industry. Historically, nutmeg has been used as a form of medicine to treat many illnesses ranging from those affecting the nervous system to the digestive system.24 Presently, the nutmeg oil is used by many pharmaceutical companies in their formulations of products to treat different illnesses. In 1992, Procter and Gamble launched a non-drowsy and alcohol-free Vicks cough syrup and the essential oil of nutmeg is a major ingredient.25 Robinson-Health Care in Britain in 1991 also marketed an impregnated tissue called Easy Breather Tissue which helps to clear congestion, and the essential oil of nutmeg was also an active ingredient.26 In that same year, Ramedica International Corp. marketed in the USA, a pain relieving ointment called Ramedica Herbal Wonder Balm, and nutmeg oil was again one of the active ingredients. This shows that the essential oil of nutmeg continues its historical importance as a major pharmaceutical ingredient.27

Discussion on Some of the Major Components of the Essential Oil

Most of the following information on components of the essential oil including the physical properties in Appendix I was taken from Merck Index, 11th edition and the CRC handbook of Physics and Chemistry.

(i) Sabinene - no information was available on the uses of sabinene

(ii) Camphene and its derivatives are widely used in numerous industrial processes and manufactures. A striking illustration of camphene's industrial importance is shown in the scheme below: Camphene can be easily converted to these other compounds.28

Discussion on Some of the Major Components of the Essential Oil

Thus, camphene is used in the manufacture of camphor and its related compounds. Camphene and its chloro-derivative have strong antibacterial, antifungal, and insecticidal properties.29,30,31 Many of camphene derivatives are known pharmaceutical drugs, and camphene itself has been shown to prevent atheromatosis of the aorta in some animals.32

(iii) d-Pinene accounts for 8-20% of the essential oil of nutmeg. This compound is used widely in industry. It is used in the manufacture of camphor (3/4 of US camphor is made from d-pinene), solvents, plasticizers, perfume bases and synthetic pine oil.

(iv) Dipentene is the dl-form of limonene or the inactive limonene. This terpene is used as a solvent and also a wetting and dispersing agent. It is also used in the manufacture of resins.

(v) d-Linalool is also called coriandrol and is used in perfumery substituting for bergamot oil or french.

(vi) d-Borneol exists mostly as an acetate ester in nutmeg rather than the free alcohol. The acetate ester and other ester derivatives of borneol are used in the manufacturing industries. In addition, some free borneol, ie, the alcohol, is used in perfumery and incense making.

(vii) i- Terpineol is used as an antiseptic. It is also used in the making of perfumes and in soap manufacturing.

(viii) Geraniol is used mainly in perfumery because of its sweet rose aroma. Some of its esters such as butyrate is used for making artificial atter of rose.

(ix) Myristicin is the most studied individual compound found in nutmeg, especially its pharmacological properties. This compound is thought to be responsible for the hallucinogenic effect of nutmeg oil.33 However, the evidence is not very clear as to whether other compounds are involved since natural myristicin is more potent than synthetic myristicin.34

(x) Safrole is used industrially in perfumery, and in the manufacturing of heliotropin and in the denaturing of fats in soap manufacture. Medically, it is used as an antiseptic.

(xi) Eugenol is used in the manufacture of vanillin, and in perfumery, instead of oil of cloves.
Eugenol is also used as a dental analgesic.

(xii) iso-eugenol, like eugenol, is used in the manufacture of vanillin.

Fixed Oil of Nutmeg

Depending upon the method used to obtain the fixed oil of nutmeg from the seed, varying amounts of essential oil will be present in the fixed oil. There are two general ways in which the fixed oil of nutmeg is extracted from nutmeg. In the first process, the ground nutmeg is subjected to intense hydraulic pressure and heat. The other method employs a solvent, for example, diethyl ether. In this process, the ground nutmeg is reflux with diethyl ether, and after filtering off the solid residue, the diethyl ether is distilled off from the filtrate to leave behind the crude fixed oil. These two processes will result in the crude fixed oil containing substantial quantities of essential oil. The quantities of essential oil vary between 10-12%. If the essential oil is removed by steam distillation prior to extracting the crude fixed oil, then the fixed oil of nutmeg will contain only trace amounts of essential oil.

Unlike the liquid essential oil, the fixed oil is a semi-solid, reddish brown material with both the smell and taste of nutmeg. It melts at 45-51C and has a density of 0.990-0.995. Like most oils, it is completely soluble in hot alcohol, however, sparingly soluble in cold alcohol. The fixed oil is freely soluble in ether and chloroform.

The fixed oil of nutmeg has not been subjected to as much investigative research as the essential oil. One possible reason is because of the small number of compounds that are present in the fixed oil.

Components of the Fixed Oil

Power and Salway's of the fixed oil which was obtained from nutmeg without prior removal of the essential oil gave the following components and their relative abundance in the fixed oil.

Trimyristin

73.0%

Essential oil

12.5%

Unsaponifiable constituents

8.5%

Oleic acid (as glyceride)

3.0%

Resinous materials

2.0%

Linolenic acid (as glyceride)

0.5%

Formic, acetate and cerotic acids

(very small amounts)

In this extraction procedure, the essential oil was not removed prior to extracting the fixed oil and thus, the essential oil appears as a component in the fixed oil. If the fixed oil was obtained after initial removal of the essential oil, the relative component ratios would be as shown below:

Trimyristin

84.0%

Unsaponifiable constituents

9.8%

Oleic acid (as glyceride)

3.5%

Resinous material

2.3%

Linolenic acid (as glyceride)

0.6%

Formic, acetic and cerotic acids

(very small amounts)

Uses of the Fixed Oil

The fixed oils that contain a substantial amount of essential oil have the same odour as nutmeg. Therefore, these fixed oils have been used in perfumes.35 In medicine, the fixed oil has been used externally for sprains and rheumatism.36 As a whole, the fixed oil finds very little commercial use; however, components of the fixed oils and derivatives of some of those compounds find extensive commercial uses.

Discussion on the Individual Components of the Fixed Oil

Essential Oil:

Since the essential oil was already dealt with under its own topic heading, no further discussion of essential oil will be covered under this section.

Trimyristin:

Trimyristin accounts for over three quarters of the fixed oil of nutmeg. Because the essential oil was considered as a component of the fixed oil, trimyristin is about 75% of the total oil (fixed and volatile) extracted from nutmeg. This implies that nutmeg is made up of approximately 40% trimyristin.

Other names used for trimyristin are (i) glycerol trimyristate and (ii) glycerol tritetradecanoate. It is a white to yellowish grey solid with a melting point between 56-57 C. The molecular formula of trimyristin is C45H86O6 and it has a molecular weight of 723.14. This fat is soluble in alcohols, benzene, chloroform and diethyl but insoluble in water.

Structure of Trimyristin:

This structure shows that trimyristin is a fat or ester of glycerol and tetradecanoic acid (myristic acid).

The other major naturally occurring sources of trimyristin are coconut oil, palm kernel oil and babassu oil.

A comparison of these sources are shown in the table below and nutmeg has the highest percentage of trimyristin.37

Table 8: Sources of Trimyristin

Source

Percentage of trimyristin

Nutmeg fat

76.7

Babassu oil

19.9

Coconut oil

17.5

Palm kernel oil

14.1

Soybean oil

6.5

Beef tallow

3.0

Palm oil

1.0

The Major Uses of Trimyristin:

Trimyristin is used in situ industrially as a raw material for myristic acid. In most cases, for example from coconut oil, trimyristin is not isolated as an individual component before it is used to produce myristic acid. The oil with all its components is subjected to an ester hydrolysis process, and the different fatty acids are distilled off. In this process, glycerol is also produced and thus trimyristin can. be considered also as a source of glycerol.

As a saturated fat, trimyristin has been studied intensely in research and development.38,39,40 It has been looked at as a possible substitute for cocoa-butter.41 It has been blended with cottonseed oil and palm oil to produce an edible fat compound and has been shown to be used as a tablet lubricant.42

Laboratory Isolation of Trimyristin from Nutmeg

Equipment: Two 500 ml round bottom flask, one reflux condenser, one condenser, still head, heat source (steam bath or electric heater or heating mantle), two erlenmeyer flasks 250 ml, 1 short stem funnel, 1 buchner funnel, 2 filter paper, 1 filter flask.

Procedure: Place 60 g of ground nutmeg into a 500 ml round bottom flask with 225 ml ether. Attach a reflux and allow the mixture to reflex for 1 hour with heating source. After allowing the mixture to cool to room temperature, the ether insoluble material is then removed via gravity filtration. The filtrate is then placed into a 500 ml round bottom and the system is further adopted to perform a simple distillation. The solvent is removed by simple distillation and the crude yellow trimyristin is collected and placed into an erlenmeyer flask.

Note: The ether reclaimed can be used in future extractions. Purification of the impure trimyristin is accomplished by dissolving it in 60 ml acetone with gentle heating. This warm mixture is then poured into a beaker and allowed to cool to room temperature. After initial crystallization has occurred slowly, the mixture can be cooled in an ice bath to produce more crystals.

After all precipitation tends to cease, the white crystals are then collected on a buchner funnel by suction filtration. The trimyristin can be air dried on a filter paper or watch glass.

The purity can be checked either by taking the melting point or performing a gas- chromatography analysis.43 44

Hydrolysis or Splitting of Trimyristin to Obtain Myristic Acid

In general, any fat can be broken down to its two major components - a fatty acid component, and a glycerol as the alcohol component. The process is known as hydrolysis or splitting, and the overall reaction involves the addition of water to the fat in order to produce the fatty acid and glycerol (glycerine). There are two methods by which the hydrolysis process can be accomplished: (1) saponification and (2) direct splitting.

With saponification, the fat is heated in a solution of a hydroxide base, for example, sodium or potassium hydroxide, and this produces the metal salt of the carboxylic acid (soap) and glycerol. Acidification of the metal salt or soap with a mineral acid liberates the carboxylic acid and a mineral salt. The process is shown by the reactions below using trimyristin as the fat:

Saponification is usually the method of choice in the laboratory for preparing a carboxylic acid from fat. Saponification is also sometimes used industrially.45

In the direct hydrolysis process, the fat is treated with water in the presence of a catalyst to yield directly the carboxylic acid and glycerol. Very high temperatures and pressures are necessary to accomplish this splitting procedure. A mineral acid like sulphuric acid is usually the catalyst used, and at times an alkaline catalyst like zinc oxide, calcium hydroxide or magnesium hydroxide can be used.46

Because of the high pressure and. temperature required, this hydrolysis technique is used predominantly in industry.

A Laboratory Preparation of Myristic Acid from Trimyristin

Equipment: One 500 ml round bottom flask; a mechanical stirrer or magnetic stirrer; a steam bath or heating mantel; one 500 ml erlenmeyer flask; steam -jacketed funnel; a graduated cylinder

Procedure: Pure trimyristin (25g, 0.935 mole) is placed into a 500 ml round bottom flask followed by the addition of 50 ml of a 2.5 M solution of sodium hydroxide. This mixture is heated at 100 C with the heat source for 2 hours with constant stirring. At this time, the solution should appear clear indicating that saponification is completed. The solution is then poured into a 500 ml erlenmeyer flask containing 150 ml solution of 20% hydrochloric acid. The crude myristic acid should form a separate phase and appear clear. If this layer is not clear, the mixture is heated until the oily layer is transparent. This mixture is then allowed to cool and the crude myristic acid solidifies. The myristic acid can be collected by filtering through a steam-jacketed funnel.

6. Conclusion from chemical composition analysis of nutmeg


(No in-depth review of the essential oil as a potential marketable commodity will be further discussed since a construction project of a steam distillation plant is in progress in Grenada.)

As seen from the discussion on the chemical composition of nutmeg, the most abundant individual compound in nutmeg is trimyristin. Trimyristin, a triglyceride (fat) is approximately 75% by weight of the total fixed and essential oils of nutmeg and 40% by weight of the nutmeg seed. The relative abundance of trimyristin in nutmeg makes it a potentially desirable target for isolation.

At present, the price of the essential oil on the US market is $14/kg and the market size seems to be good. In 1989, nutmeg oil imports to the US were approximately 115,000 kg, and in 1992 nutmeg oil imports were about 192,000 kg valued at about 2 million US dollars.47,48 Recognizing the favourable market trends and prices of nutmeg oil, it would not be advisable to attempt to isolate any individual compounds from nutmeg oil. Nevertheless, one must keep in mind the possibility of extracting compounds from the nutmeg oil in case nutmeg oil faces any severe marketing problems in the near future.

Trimyristin is a favourable potential compound to isolate from nutmeg. In addition to being the most abundant compound in nutmeg, six times that of the essential oil, derivatives of this compound are highly marketable products, specifically myristic acid, myristyl alcohol and glycerol.

Trimyristin is a vegetable fat and can serve as a feedstock for the production of myristic acid, a saturated C14 fatty acid. An evaluation of the economic viability of producing trimyristin as a raw material for the production of myristic acid and glycerol will warrant examination of the market conditions of the vegetable fat industry and other related industries such as the oleochemical industry.