Laboratory testing of turmeric supplements and curcumin products is important for quality, safety, dosage and bioavailability. NaturPro Scientific offers testing and analysis consulting for turmeric, and works with expert research and quality control testing laboratories.
A number of analytical methods and monographs have been developed for turmeric to ensure bioavailability, consistency, potency and purity of curcumin products.
Turmeric Supplement Testing — Curcumin Products
We recommend all turmeric products have routine and/or periodic independent testing for the following parameters:
- Curcuminoids (curcumin) by HPLC
- Biological activity
- Heavy metals
- Microbiology and pathogens
- Residual solvents
- Natural source by carbon radioisotope (if labeled as ‘turmeric’)
- Food allergens
- Sudan dyes
Traditional dosage forms listed by the EU Community Herbal Monograph include the following herbal preparations:
- Powdered herbal substance
- Comminuted herbal substance
- Tincture (Ratio of herbal substance to extraction solvent 1:10), extraction solvent ethanol 70% (v/v)
- Dry extract (DER 13-25:1), extraction solvent ethanol 96% (v/v)
- Dry extract (DER 5.5-6.5:1), extraction solvent ethanol 50% (v/v)
- Tincture (Ratio of herbal substance to extraction solvent 1:5), extraction solvent ethanol 70% (v/v)
Other solvents are commonly used to extract curcuminoids.
The JECFA has developed a monograph on turmeric oleoresin:
“Obtained by solvent extraction of turmeric (Curcuma longa L.). Only the following solvents may be used in the extraction: acetone, dichloromethane, 1,2-dichloroethane, methanol, ethanol, isopropanol and light petroleum (hexanes).
The selection of a turmeric oleoresin of a particular composition is based on the intended use in food. In general, all turmeric oleoresins contain colouring matter and most contain flavouring matter but some oleoresins are processed to remove aromatic compounds. Commercial products include oleoresins (per se) and formulations in which oleoresin is diluted in carrier solvents and which may contain emulsifiers and antioxidants. Purified extracts of turmeric containing more than 90% total colouring matter are subject to specifications for “Curcumin”.
Turmeric Oleoresins are sold on the basis of “colour value” or “curcumin content”, which generally means the total content of the curcuminoid substances: (I) curcumin, (II) demethoxycurcumin and (III) bis- demethoxycurcumin.
The principle colouring components are:
I. 1,7-Bis(4-hydroxy-3-methoxyphenyl)hepta-1,6-diene- 3,5-dione
II. 1-(4-Hydroxyphenyl)-7-(4-hydroxy-3-methoxyphenyl)-hepta-1,6-diene- 3,5-dione
Turmeric Oleoresins, per se, are deep brownish-orange viscous oily fluids, pasty semisolids or hard amorphous solids containing 37-55% curcuminoids and up to 25% volatile oil. Diluted turmeric oleoresin formulations are, generally yellow solutions containing 6-15% curcuminoids and nil to 10% volatile oil.
Residual solvents limits:
Acetone : Not more than 30 mg/kg
Methanol: Not more than 50 mg/kg
Ethanol: Not more than 50 mg/kg
Isopropanol: Not more than 50 mg/kg
Dichloromethane and 1,2-dichloroethane: Not more than 30 mg/kg, singly or in combination
Light petroleum (hexanes): Not more than 25 mg/kg
The WHO monograph for medicinal plants for turmeric is excerpted below:
Rhizome (root) of Curcuma Longa L. (turmeric)
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).
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).
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
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).
Odour, aromatic; taste, warmly aromatic and bitter (1, 9, 13). Drug when chewed colours the saliva yellow (9).
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).
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).
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).
Not more than 8.0% (1, 15).
Not more than 1% (1, 9, 15).
Not less than 9.0% (1).
Not less than 10% (1).
Not more than 10% (1).
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).
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).
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.
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.
Powdered crude plant material, rhizomes (1, 2), and corresponding preparations (25). Store in a dry environment protected from light. Air dry the crude drug every 2–3 months (1).
Uses supported by clinical data
The principal use of Rhizoma Curcumae Longae is for the treatment of acid, flatulent, or atonic dyspepsia (26–28).
Uses described in pharmacopoeias and in traditional systems of medicine
Treatment of peptic ulcers, and pain and inflammation due to rheumatoid arthritis (2, 11, 14, 29, 30) and of amenorrhoea, dysmenorrhoea, diarrhoea, epilepsy, pain, and skin diseases (2, 3, 16).
Uses described in folk medicine, not supported by experimental or clinical data
The treatment of asthma, boils, bruises, coughs, dizziness, epilepsy, haemorrhages, insect bites, jaundice, ringworm, urinary calculi, and slow lactation (3, 7, 8–10, 14).