Eugenol

(Ph Eur monograph 1100)

C10H12O2 164.2 97-53-0

 

Ph Eur


 

 

Definition

 

Eugenol is 2-methoxy-4-(prop-2-enyl)phenol.

 

Characters

 

A colourless or pale yellow, clear  liquid, darkening on exposure to air, with a strong odour of clove, practically insoluble in water, freely soluble in alcohol (70 per cent V/V), practically insoluble in glycerol, miscible with glacial acetic acid, with alcohol, with ether, with fatty oils and with methylene chloride.

 

Identification

 

First identification

 

B.

 

Second identification

 

A, C, D.

 

A.    It complies with the test for refractive index (see Tests).

 

B.    Examine by infrared absorption spectrophotometry (2.2.24), comparing with the spectrum obtained with eugenol  CRS.

 

C.    Examine by thin-layer chromatography (2.2.27), using a TLC silica gel F254 plate R.

 

Test solution

 

Dissolve 50 ml of the substance to be examined in alcohol  R and dilute to 25 ml with the same solvent.

 

Reference solution

 

Dissolve 50 ml of eugenol  CRS in alcohol  R and dilute to 25 ml with the same solvent.

 

Apply to the plate 5 ml of each solution. Develop over a path of 15 cm using a mixture of 10 volumes of ethyl acetate R and 90 volumes of toluene R. Dry the plate in a current of cold air and examine in ultraviolet light at 254 nm. The principal spot in the chromatogram obtained with the test solution is similar in position and size to the principal spot in the chromatogram obtained with the reference solution. Spray with anisaldehyde solution R. Heat at 100-105C for 10 min. The principal spot in the chromatogram obtained with the test solution is similar in position, colour and size to the principal spot in the chromatogram obtained with the reference solution.

 

D.    Dissolve 0.05 ml in 2 ml of alcohol  R and add 0.1 ml of ferric chloride solution R1. A dark green colour is produced which changes to yellowish-green within 10 min.

 

Tests

 

Relative density (2.2.5)

 

1.066 to 1.070.

 

Refractive index (2.2.6)

 

1.540 to 1.542.

 

Dimeric and oligomeric compounds

 

Dissolve 0.150 g of the substance to be examined in ethanol  R and dilute to 100.0 ml with the same solvent. The absorbance of the solution (2.2.25) at 330 nm is not greater than 0.25.

 

Related substances

 

Examine by gas chromatography (2.2.28).

 

Test solution

 

Dissolve 1.00 g of the substance to be examined in ethanol  R and dilute to 5.0 ml with the same solvent.

 

Reference solution (a)

 

Dilute 1.0 ml of the test solution to 100.0 ml with ethanol  R.

 

Reference solution (b)

 

Dissolve 50 mg of vanillin R in 1 ml of the test solution and dilute to 5 ml with ethanol  R.

 

The chromatographic procedure may be carried out using:

 

a fused-silica capillary column 30 m long and 0.25 mm in internal diameter coated with a film of polymethylphenylsiloxane R (film thickness 0.25 mm),

 

helium for chromatography R as the carrier gas at a flow rate of 1 ml/min,

 

a flame-ionisation detector,

 

a split ratio of 1:40,

 

Inject 1 ml of the test solution and 1 ml each of reference solutions (a) and (b). The test is not valid unless in the chromatogram obtained with reference solution (b), the relative retention time of the peak due to vanillin is at least 1.1 with respect to the peak due to eugenol. Calculate the percentage content of related substances from the areas of the peaks in the chromatogram obtained with the test solution by the normalisation procedure; disregard the solvent peak and any peak with an area less than 0.05 times that of the principal peak in the chromatogram obtained with reference solution (a). The content of related substances with a relative retention time greater than 2.0 in respect to the main peak is not greater than 1.0 per cent; the content of any related substances is not greater than 0.5 per cent; the total content of related substances is not greater than 3.0 per cent.

 

Hydrocarbons

 

Dissolve 1 ml in 5 ml of dilute sodium hydroxide solution R and add 30 ml of water  R in a stoppered test-tube. Examined immediately, the solution is yellow and clear  (2.2.1).

 

Sulphated ash (2.4.14)

 

Not more than 0.1 per cent, determined on 1.0 g.

 

Storage

 

Store in a well-filled container, protected from light.

 

Impurities

 

A.    (1R,4E,9S)-4,11,11-trimethyl-8-methylenebicyclo[7.2.0]undec-4-ene (b-caryophyllene),

 

B.    (1E,4E,8E)-2,6,6,9-tetramethylcycloundeca-1,4,8-triene (a-humulene, a-caryophyllene),

 

C.    (1R,4R,6R,10S)-4,12,12-trimethyl-9-methylene-5-oxatricyclo[8.2.0.04,6]dodecane (b-caryophyllene oxide),

 

D.    R1 = H, R2 = H, R3 = CH2-CH=CH2: 4-(prop-2-enyl)phenol,

 

E.    R1 = CH3, R2 = OCH3, R3 = CH2-CH=CH2: 1,2-dimethoxy-4-(prop-2-enyl)benzene (eugenol methyl ether),

 

F.    R1 = H, R2 = OCH3, R3 = CH=CH-CH3 (cis): 2-methoxy-4-[(Z)-prop-1-enyl]phenol (cis-isoeugenol),

 

G.    R1 = H, R2 = OCH3, R3 = CH=CH-CH3 (trans): 2-methoxy-4-[(E)-prop-1-enyl]phenol (trans-isoeugenol),

 

H.    R1 = H, R2 = OCH3, R3 = CHO: 4-hydroxy-3-methoxybenzaldehyde (vanillin),

 

I.     R1 = CO-CH3, R2 = OCH3, R3 = CH2-CH=CH2: 2-methoxy-4-(prop-2-enyl)phenyl acetate (acetyleugenol),

 

J.    R1 = H, R2 = OCH3, R3 = CO-CH=CH2: 1-(4-hydroxy-3-methoxyphenyl)prop-2-enone,

 

K.    R1 = H, R2 = OCH3, R3 = CH=CH-CHO: (E)-3-(4-hydroxy-3-methoxyphenyl)prop-2-enal (trans-coniferyl aldehyde),

 

L.    2-methoxy-4-[3-methyl-5-(prop-2-enyl)-2,3-dihydrobenzofuran-2-yl]phenol (dehydrodi-isoeugenol),

 

M.   3,3¢-dimethoxy-5,5¢-bis(prop-2-enyl)biphenyl-2,2¢-diol (dehydrodieugenol),

 

N.    O.        two further unknown dimeric compounds,

 

P.    toluene.

 

 


 Ph Eur

 

Action and use

 

Local anaesthetic used in dentistry.