Safrole (oil of sassafras, comphor oil and oil of star-anise)

B. Safrole

Chemical Structure 5-(2-Propenyl)-1, 3-benzodioxole; 4-allyl-1, 2-methylenedioxybenzene.

Occurrence It is the constituent of a number of volatile oils, notably of sassafras i.e., the dried dark of the roots of Sassafras albidum Nees, belonging to the family Lauraceae, in which it is present to the extent of 75%.

It is extensively found in a variety of other plant sources, namely: Acorus calamus L., Araceae (sweet flag, flagroot, calamus); Angelica polymorpha Max., Apiaceae (dong quai); Cananga odorata (Lam.) Hook. f. & Thoms., Annonaceae (cananga, ylang-ylang); Cinnamomum comphora (L.) J.S. Presl., Lauraceae (camphor, hon-sho); Illicum verum Hook. f. Magnoliaceae (Star-anise, Chinese anise); Myristica fragrans Houtt. Myristicaceae (mace, nutmeg); Ocimum basilicum L. Lamiaceae (sweet basil, garden basil); Piper nigrum L. Piperaceae (black pepper); Theobroma

cacao L. Sterculiaceae (chocolate, cocoa, cacao); Umbellularia california (Hook. and Arn.) Nutt. (California bay, California sassafras, (California laurel).

Isolation Safrole may be isolated from the oil of sassafras, comphor oil and oil of star-anise and also the safrole-rich fraction of the oil to about –10 to –15°C. It may also be isolated by subjecting the above safrole containing oils to fractional distillation under reduced pressure, chilling the fraction and finally crystallization.

Characteristic Features It is colourless or slightly yellow liquid having a specific sassafras odour. Its physical properties are: d²⁰ 1.096, mp ~ 11°C, bp 232-234°C and n²⁰_D 1.5383. It is insoluble in water, very soluble in alcohol and freely miscible with ether and chloroform. It undergoes isomerization on being heated with alkalies to yield isosafrole as shown below:

Identification

1. Bromination: Safrole on bromination yields the corresponding pentabromosafrole (mp

169-170°C).

2. Oxidation: Safrole on oxidation with K₂Cr₂O₇ and dilute H₂SO₄ (6 N) gives rise to the aldehyde derivative piperonol as shown below:

3. Colour test: Both safrole and isosafrole on treatment with concentrated sulphuric acid instantly produces an intense red colouration.

Uses

1. It is widely used as a flavouring agent for a variety of products, such as: beverages,

pharmaceuticals chewing gums, toothpastes, in perfumery and scenting soaps.

2. It is also used in denaturing fats in soap manufacturing process.

3. It is mostly employed for the conversion to isosafrole and the manufacture of heliotropin.

C. Myristicin

Chemical Structure 4-(Methoxy)-6-(2-propenyl)-1, 3-benzodioxole.

Occurrence The aromatic ether is extracted from nutmeg, mace, French parsley, carrots and dill oils.

The botanical sources of myristicin are as follows: Anethum graveolens L. (Apiaciae) (Dil, Dill Seed, Garden Dill); Daucus Carota subsp. Sativus (Hoffm.) Arcang [Apiaceae] (Cultivated carrot,

Queen Anne’s Lace (Wild)); Myristica fragrans Houtt. [Myristaceae] (Mace, Nutmeg); Petroselinum crispum (Mill) Nym. [Apiaceae] (Parsley); Piper nigrum L. [Piperaceae] (Black Pepper); Sassafras albidum (Nutt.) Nees [Lauraceae] (Sassafras).

Isolation The rich source of volatile oil containing myristicin is subjected to fractional distillation under reduced pressure when the latter is collected as a colourless oily liquid.

Characteristic Features It is an oily liquid having a characteristic aromatic odour. It does not congeal at low-temperature.

Myristicin on being treated with either metallic sodium or boiled with alcoholic KOH undergoes isomerism to yield isomyristicin as given below:

i.e., the allyl group in the former gets converted to the propenyl group in the latter.

It has the following physical parameters:

bp₄₀ 173°C; n²⁰_D 1.54032; d²⁰₂₀ 1.1437.

Identification

1. On oxidation with KMnO₄ it gives rise to two products, namely:

(a) Myristicin aldehyde (mp 130°C); and

(b) Myristinic acid (mp 208-210°C).

2. On interaction with bromine it yields the corresponding dibromoderivative having mp 130°C.

Uses It is used as a flavouring agent in food products and confectioneries.

Source:Pharmacognosy And Pharmacobiotechnology By Ashutosh Kar