Turmeric Supplement Testing — Curcumin Products

Definition

Rhizoma Curcumae Longae is the dried rhizome of Curcuma longa L. (Zingiberaceae) (1).

Dried rhizomes of Curcuma wenyujin Y.H. Lee et C. Ling, C. kwangsiensis S. Lee et C.F. Liang. and C. phaeocaulis Val. are also official sources of Radix Curcumae or Turmeric Root-Tuber in China (2).

Synonyms

Curcuma domestica Valeton., C. rotunda L., C. xanthorrhiza Naves, Amomum curcuma Jacq. (3–5).

Selected vernacular names

Acafrao, arqussofar, asabi-e-safr, avea, cago rerega, chiang-huang, common tumeric, curcum, curcuma, dilau, dilaw, Gelbwurzel, gezo, goeratji, haladi, haldi, haldu, haku halu, hardi, haridra, huang chiang, hsanwen, hurid, Indian saffron, jiânghuang, kaha, kakoenji, kalo haledo, khamin chan, khaminchan, kilunga kuku, kitambwe, kiko eea, koening, koenit, koenjet, kondin, kooneit, kunyit, kurcum, kurkum, Kurkumawurzelstock, luyang dilaw, mandano, manjano, manjal, nghe, nisha, oendre, pasupu, rajani, rame, renga, rhizome de curcuma, saffran vert, safran, safran des indes, skyer-rtsa, tumeric, tumeric root, tumeric rhizome, turmeric, ukon, ul gum, wong keong, wong keung, yellow root, yii-chin, zardchob (1–3, 6–14).

Description

Perennial herb up to 1.0 m in height; stout, fleshy, main rhizome nearly ovoid (about 3 cm in diameter and 4 cm long). Lateral rhizome, slightly bent (1cm × 2–6cm), flesh orange in colour; large leaves lanceolate, uniformly green, up to 50cm long and 7–25cm wide; apex acute and caudate with tapering base, petiole and sheath sparsely to densely pubescent. Spike, apical, cylindrical, 10– 15cm long and 5–7 cm in diameter. Bract white or white with light green upper half, 5–6 cm long, each subtending flowers, bracteoles up to 3.5 cm long. Pale yellow flowers about 5cm long; calyx tubular, unilaterally split, unequally toothed; corolla white, tube funnel shaped, limb 3-lobed. Stamens lateral, petaloid, widely elliptical, longer than the anther; filament united to anther about the middle of the pollen sac, spurred at base. Ovary trilocular; style glabrous. Capsule ellipsoid. Rhizomes orange within (1, 4, 6, 15).

Plant material of interest: dried rhizome

General appearance

The primary rhizome is ovate, oblong or pear-shaped round turmeric, while the secondary rhizome is often short-branched long turmeric; the round form is about half as broad as long; the long form is from 2–5cm long and 1–1.8cm thick; externally yellowish to yellowish brown, with root scars and annulations, the latter from the scars of leaf bases; fracture horny; internally orangeyellow to orange; waxy, showing a cortex separated from a central cylinder by a distinct endodermis (1, 9, 13).

Organoleptic properties

Odour, aromatic; taste, warmly aromatic and bitter (1, 9, 13). Drug when chewed colours the saliva yellow (9).

Microscopic characteristics

The transverse section of the rhizome is characterized by the presence of mostly thin-walled rounded parenchyma cells, scattered vascular bundles, defi- nite endodermis, a few layers of cork developed under the epidermis and scattered oleoresin cells with brownish contents. The cells of the ground tissue are also filled with many starch grains. Epidermis is thin walled, consisting of cubical cells of various dimensions. The cork cambium is developed from the subepidermal layers and even after the development of the cork, the epidermis is retained. Cork is generally composed of 4–6 layers of thin-walled brickshaped parenchymatous cells. The parenchyma of the pith and cortex contains curcumin and is filled with starch grains. Cortical vascular bundles are scattered and are of collateral type. The vascular bundles in the pith region are mostly scattered and they form discontinuous rings just under the endodermis. The vessels have mainly spiral thickening and only a few have reticulate and annular structure (1, 8, 9).

Powdered plant material

Coloured deep yellow. Fragments of parenchymatous cells contain numerous altered, pasty masses of starch grains coloured yellow by curcumin, fragments of vessels; cork fragments of cells in sectional view; scattered unicellular trichomes; abundant starch grains; fragments of epidermal and cork cells in surface view; and scattered oil droplets, rarely seen (1, 13).

Geographical distribution

Cambodia, China, India, Indonesia, Lao People’s Democratic Republic, Madagascar, Malaysia, the Philippines, and Viet Nam (1, 13, 16). It is exten- sively cultivated in China, India, Indonesia, Thailand and throughout the tropics, including tropical regions of Africa (1, 7, 13, 16).

General identity tests

Macroscopic and microscopic examinations; test for the presence of curcuminoids by colorimetric and thin-layer chromatographic methods (1).

Purity tests

Microbiology

The test for Salmonella spp. in Rhizoma Curcumae Longae products should be negative. The maximum acceptable limits of other microorganisms are as follows (17–19). For preparation of decoction: aerobic bacteria-not more than 10⁷/g; fungi-not more than 10⁵/g; Escherichia coli-not more than 10²/g. Preparations for internal use: aerobic bacteria-not more than 10⁵/g or ml; fungi-not more than 10⁴/g or ml; enterobacteria and certain Gram-negative bacteria-not more than 10³/g or ml; Escherichia coli-0/g or ml.

Foreign organic matter

Not more than 2% (1, 9).

Total ash

Not more than 8.0% (1, 15).

Acid-insoluble ash

Not more than 1% (1, 9, 15).

Water-soluble extractive

Not less than 9.0% (1).

Alcohol-soluble extractive

Not less than 10% (1).

Moisture

Not more than 10% (1).

Pesticide residues

To be established in accordance with national requirements. Normally, the maximum residue limit of aldrin and dieldrin in Rhizoma Curcumae Longae is not more than 0.05 mg/kg (19). For other pesticides, see WHO guidelines on quality control methods for medicinal plants (17) and guidelines for predicting dietary intake of pesticide residues (20).

Heavy metals

Recommended lead and cadmium levels are not more than 10 and 0.3mg/kg, respectively, in the final dosage form of the plant material (17).

Radioactive residues

For analysis of strontium-90, iodine-131, caesium-134, caesium-137, and plutonium-239, see WHO guidelines on quality control methods for medicinal plants (17).

Other purity tests

Chemical tests to be established in accordance with national requirements.

Chemical assays

Not less than 4.0% of volatile oil, and not less than 3.0% of curcuminoids (1). Qualitative analysis by thin-layer and high-performance liquid chromatography (1, 21) and quantitative assay for total curcuminoids by spectrophotometric (1, 22) or by high-performance liquid chromatographic methods (23, 24).

Major chemical constituents

Pale yellow to orange-yellow volatile oil (6%) composed of a number of monoterpenes and sesquiterpenes, including zingiberene, curcumene, α- and β- turmerone among others. The colouring principles (5%) are curcuminoids, 50–60% of which are a mixture of curcumin, monodesmethoxycurcumin and bisdesmethoxycurcumin (1, 6, 25). Representative structures of curcuminoids are presented below.