Imperatorin (Synonyms Ammidin; Pentosalen; Marmelosin)

2.3.3.4 Imperatorin

Synonyms Ammidin; Pentosalen; Marmelosin;

Biological Sources It is obtained from the roots and fruits of Angelica archangelica L. (Apiaceae)

(Angelica, Garden Angelica, European Angelica); from the roots of Imperatoria osthruthium L. (Umbelliferae); from fruit of Pastinaea sativa L. (Umbelliferae); and also in the fruits of Ammimajus (Umbelliferae). However, the seed oil of A. archangelica is said to contain upto 0.5% imperatorin.

Chemical Structure

9-[(3-Methyl-2-butenyl)oxy]-7H-furo [3, 2-g] [1] benzopyran-7-one; (C₁₆H₁₄O₄).

Isolation The various steps involved are as follows:

1. The petroleum ether mother liquor left after the separation of methoxsalen (Xanthotoxin), is concentrated under vacuo and allowed to cool in a refrigerator overnight when the crude imperatorin separates out.

2. The crude product is collected, dissolved in ether, filtered and concentrated under reduced pressure. It is kept in a refrigerator, and the crystals separating out are purified subsequently by recrystallization from ethanol.

Characteristic Features These are as given below:

1. It is obtained in two forms: First—as prisms from ether, and secondly—as long fine needles from hot water, having mp 102°C.

2. It has uvmax: 302, 265, 250 nm (log ε 3.95, 4.00, 4.24).

3. Solubility Profile: It is practically insoluble in cold water; very sparingly soluble in boiling water; freely soluble in chloroform; and soluble in benzene, ethanol, ether, petroleum, ether alkali hydroxides.

Identification Tests These are as stated below:

1. Sulphuric Acid Test: Imperatorin gives an intense deep orange colouration with a few drops of sulphuric acid which ultimately changes to brown colour.

2. Marqui’s Reagent: It gives an orange colouration with Marqui’s Reagent that rapidly changes to brown.

3. Tollen’s Reagent (Ammoniacal AgNO₃): It reduces Tollen’s Reagent to produce a silver mirror.

4. Fehlings Test: It reduces Fehling’s solution to give a brick-red precipitate of cupric oxide.

5. Nitric Acid Test: It gives a distinct yellow colour on boiling with dilute HNO₃, and this colour changes to purple on being treated with strong alkali e.g. NaOH or KOH.

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* Pomeranz, Monatsh, 12, 379 (1891), 14, 28 (1893).

** H. Thoms., E. Baeteke, Ber., 44, 3326 (1911).

Source:Pharmacognosy And Pharmacobiotechnology By Ashutosh Kar