To perform the identification tests of turmeric - Pharmacognosy

Aim: To perform the identification tests of turmeric

Requirements:

Test-tube, Stirrer, Measuring cylinder, Different reagents and solutions.

Theory:

Turmeric

Synonyms: Saffron Indian; Haldi (Hindi); Curcuma; Rhizoma cur-cumae.
Biological Source: Turmeric is the dried rhizome of Curcuma longa Linn. (syn.C.domestica Valeton)., belonging to family Zingiberaceae.

Geographical Source: 

The plant is a native to southern Asia and is cultivated extensively in temperate regions. It is grown on a larger scale in India, China, East Indies, Pakistan, and Malaya.

Cultivation:

• Turmeric plant is a perennial herb, 60–90 cm high with a short stem and tufted leaves; the rhizomes, which are short and thick, constitute the turmeric of commerce.
• The crop requires a hot and moist climate, a liberal water supply and a well-drained soil. It thrives on any soil-loamy or alluvial, but the soil should be loose and friable.
• The field should be well prepared by ploughing and turning over to a depth of about 30 cm and liberally manured with farmyard and green manures. Sets or fingers of the previous crop with one or two buds are planted 7 cm deep at distance of 30–37 cm from April to August.
• The crop is ready for harvesting in about 9–10 months when the lower leaves turn yellow. The rhizomes are carefully dug up with hard picks, washed, and dried.

Macroscopy:

Colour: Outer surface is deep yellow to brown

Odour: Distinct

Taste: Aromatic, Pungent and Bitter

Fracture: Horny; Cut surface is waxy, resinous

Size & Size: Primary rhizomes are ovate, pear-shaped, oblong or pyriform or cylindrical called 'bulb'. Secondary, more cylindrical, lateral branched, tapering on both ends, rhizomes are 4–7 cm long and 1–1.5 cm wide and called as ‘fingers’.

Microscopy:

• The transverse section of the rhizome is characterized by the presence of mostly thin-walled rounded parenchyma cells, scattered vascular bundles, definite endodermis, few layers of cork developed under the epidermis, and scattered oleoresin cells with brownish contents.
• The epidermis is consisted of thick-walled cells, cubical in shape, of various dimensions. The cork cambium is developed from the sub-epidermal layers and even after the development of the cork, the epidermis is retained. Cork is generally composed of four to six layers of thin-walled brick-shaped parenchymatous cells.
• The parenchyma of the pith and cortex contains grains altered to a paste, in which sometimes long lens shaped unaltered starch grains of 4–15 μm diameter are found. Oil cells have suberised walls and contain either orange-yellow globules of a volatile oil or amorphous resinous masses.
• Cortical vascular bundles are scattered and are of a collateral type. The vascular bundles in the pith region are mostly scattered and they form discontinuous ring just under the endodermis.
• The vessels have mainly spiral thickenings and only a few have reticulate and annular structure.

Chemical Constituents: 

• Turmeric contains yellow colouring matter called as curcuminoids (5%) and essential oil (6%).
• The chief constituent of the colouring matter is curcumin I (60%) in addition with small quantities of curcumin III, curcumin II and dihydrocurcumin.
• The volatile oil contains mono- and sesquiterpenes like zingiberene (25%), α-phellandrene, sabinene, turmerone, arturmerone, borneol, and cineole. Choleretic action of the essential oil is attributed to β-tolylmethyl carbinol.
• The volatile oil also contains α- andβ-pinene, camphene, limonene, terpinene, terpinolene, caryophyllene, linalool, isoborneol, camphor, eugenol, curdione, curzerenone, curlone, AR-curcumenes, β-curcumene, γ-curcumene. α- and β-turmerones, and curzerenone.

Chemical Tests :-

1. Turmeric powder on treatment with concentrated sulphuric acid forms red colour.
2. On addition of alkali solution to Turmeric powder red to violet colour is produced.
3.  With acetic anhydride and concentrated sulphuric acid Turmeric gives violet colour. Under UV light this colour is seen as an intense red fluorescence.
4. A paper containing Turmeric extract produces a green colour with borax solution.
5. On addition of boric acid a reddish-brown colour is formed which, on addition of alkalies, changes to greenish-blue.

Uses:

• Turmeric is used as aromatic, anti-inflammatory, stomachic, uretic, anodyne for billiary calculus, stimulant, tonic, carminative, blood purifier, antiperiodic, alterative, spice, colouring agent for ointments and a common household remedy for cold and cough. Externally, it is used in the form of a cream to improve complexion.
• Dye-stuff acts as a cholagogue causing the contraction of the gall bladder.
• It is also used in menstrual pains.
• Curcumin has choleretic and cholagogue action and is used in liver diseases.
• Curcumin is a nontoxic authorized colour, heat resistant and sensitive to changes in pH.
• Curcuminoids have antiphlogistic activity which is due to inhibition of leukotriene biosynthesis. ar-Turmerone has antisnake venom activity and blocks the haemorrhagic effect of venom.

Reference: https://gpatindia.com/turmeric-classification-formation-sources-chemical-constituents-identification-test-adulterants-and-uses-mcq-10/