3. Turmeric
Synonyms Curcuma; Indian Saffron; Tumeric.
Biological Source Turmeric is obtained from the rhizome of Curcuma longa Linn. (Curcuma domestica Valeton) belonging to the natural order Zingiberaceae.
Preparation The plant is normally harvested after 9-10 months when the lower leaves start becoming yellow. The rhizome is carefully dug out from the soil with a blunt knife without damaging it. The fibrous roots are discarded. The raw green turmeric is cured and processed by boiling the rhizomes with water for a duration ranging between 12-14 hours. Subsequently, the cooked rhizomes are dried in the sun for 5-7 days. Cooking process helps in achieving two objects, namely:
(a) Gelatinization of starch, and
(b) Yellow colouration, due to curcumin, spreads over the entire rhizome.
Characteristic Features Turmeric has an aromatic pepper-like but somewhat bitter taste. It gives curry dishes their characteristic yellowish colouration.
Chemical Constituents It contains volatile oil (5-6%), resin and substantial quantity of zingiberaceous starch grains. The marked and pronounced yellow colour in turmeric is due to the presence of curcuminoids which essentially contains curcumin as given below:
The curcuma oil* obtained from turmeric contains (±)-ar-turmerone as given below:
The volatile oil contains a host of chemical substances, such as: d-α-phellandene, d-sabinene, cineol, borneol, zingiberene, and sesquiterpenes.
Turmeric also contains some other chemical constituents, namely: p,p-dihydroxy dicinnamoylmethane; p-α-dimethy benzyl alcohol; p-hydroxy-cinnamoylferuloylmethane; 1-methyl-4-acetyl-1-cyclohexene; and caprylic acid.
Chemical Tests
1. Turmeric powder when triturated with alcohol it imparts a deep yellow colour to the resulting solution.
2. The powdered drug when treated with sulphuric acid it imparts a crimson colour.
3. The aqueous solution of turmeric with boric acid gives rise to a reddish-brown colouration which on subsequent addition of dilute alkali changes instantly to greenish-blue.
4. Turmeric powder when reacted with acetic anhydride and a few drops of concentrated sulphuric acid (36 N), it readily gives a violet colouration. Interestingly, the resulting solution when observed under the ultraviolet light (preferably in a uv-chamber), it exhibits an intense red fluorescence, which is due to the presence of Curcumin.
Uses
1. It is extensively used across the globe as a condiment as curry powder.
2. It is employed as a colouring agent for ointments.
3. It is used medicinally as a tonic, as a blood purifier, as an anthelmintic and finally as an aid to digestion.
4. It is used extennally in the form of a facial cream to improve complexion and get rid of pimples.
5. A small quantity of turmeric when boiled with milk and sugar; it helps to cure common cold and cough symptoms.
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* H. Rupe et. al. Helv. Chim. Acta, 17, 372 (1934).
