2.6.4 Erythrocentaurin
Biological Sources It is obtained from the plant Centaurium umbellatum Gilib. (Erythraea centaurium Pers.), Gentinaceae or Swertia japonica (Maxim.) Makino Gentianaceae. It is also accomplished by carrying out the hydrolysis of swertiamarin and erytaurin with emulsin.
Chemical Structure
5-Formyl-3, 4-dihydroisocoumarin; (C10H8O3).
Isolation Erythroceantaurin may be isolated from C. umbellatum by the method of Kariyone and Matsushima.**
Characteristic Features
1. It is obtained as long needles having mp 140-141°C.
2. It turns red on being exposed to sunlight.
3. It has uvmax: 223, 290 nm (log ∈ 4.30, 3.13).
Uses It is mostly employed as a bitter tonic.
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* Schenck et. al., Arch. Pharm., 294, 17 (1961).
** Kariyone and Matsushima J., Pharm. Soc., Japan, 47, 25 (1927).
2.6.5 Gentisin
Synonyms Gentianin; Gentiin; Gentianic Acid.
Biological Sources It is obtained from the roots of Gentiana lutea L. (Gentianaceae) (Yellow Gentian).
Chemical Structure
1, 7-Dihydroxy-3-methoxy-9H-xanthen-9-one; (C14H10O5).
Characteristic Features
1. It is obtained as yellow needles from ethanol having mp 266-267°C.
2. It has uvmax (methanol): 260, 275, 315, 410 nm (log ∈ 435, 4.30, 4.10, 3.70).
3. It is observed to be very slightly soluble in water or organic solvents.
Identification Test
Gentisin Diacetate (C18H14O7) It is obtained as crystals from ethanol having mp 196-197°C. Its absorption max (metanol): 240, 270, 300 nm (log ε 4.58, 4.05, 4.10).
Uses It may be used to stimulate gastric secretion, improve appetite and digestion, and alleviate debility.
2.6.6 Cantharidin
Synonym Cantharides Camphor.
Biological Sources It is the active vesicating principle of cantharides (q. v) and other insects, in notorious ‘Spanish Fly’ aphrodisiac, which essentially comprise of the dried insects (Beetles) Lytta (Cantharis) vesicatoria belonging to the order Coleoptera; and family Meloidae. It has been found that the soft parts of the insect are the chief seat of cantharidin. Besides, cantharidis contain 0.5 to 0.95 of cantharidin.
Chemical Structure
Exo-1, 2-cis-Dimethyl-3, 6-epoxy hexahydrophthalic anhydride; (C10H12O4).
Isolation The various steps involved in the isolation of cantharidin are:
1. The dried insects are collected and powdered. It is now treated with an acid whereby the cantharidin gets liberated in the form of its corresponding salts.
2. The resulting product is subjected to extraction, of both cantharidin and fat, by the help of ethyl acetate in a Soxhlet apparatus.
3. The solvent is removed carefully under reduced pressure and the crude cantharidin crystallizes out.
4. The fat may be removed by the help of petroleum ether, in which cantharidin is only negligibly soluble.
5. Ultimately, the crude defatted cantharidin is dissolved in a minimum quantity of hot ethanol and allowed to cool when cantharidin crystallizes out in its purest form.
Charactersitic Features These are as follows:
1. Cantharidin is obtained as orthorhombic plates or as scales having mp 218°C.
2. It sublimes at 110 °C (12 mm Hg, 3-5 mm distances).
3. It is practically insoluble in cold water and somewhat soluble in hot water. 1g dissolves in 40 ml acetone; 65 ml chloroform; 560 ml ether; 150 ml ethyl acetate; and soluble in oils.
Identification Tests
1. Formaldehyde Test: Add to a few crystals of cantharidin 1-2 drop of dilute formaldehyde solution mixed with H2SO4, the development of a brown to black colouration on warming identifies it.
2. A solution of cantharidin in olive oil is vesicant to the skin (i.e., sensitive upto an extent of 0.14 mg).
Uses
1. It is mostly used as a vesicant.
2. It is also employed as a rubefacient and counterirritant in veterinary practice.
