August 26, 2008
Turmeric: The Salt of the Orients is the Spice of Life
By Dhawan, B N
Turmeric: The salt of the orients is the spice of life, Kamala Krishnaswamy (Allied Publishers Private Limited, New Delhi) 2007. 248 pages. Price: Rs.350/-ISBN 81-8424-126-7 Spices have been used since times immemorial for culinary purposes but the discovery of their physiological properties and therapeutic potential is much more recent. Several spices had been used in traditional systems of medicine, mainly for preventive purposes. The most important among them undoubtedly is turmeric (rhizome of Curcuma longa Linn). About 30 species of Curcuma have been described and several of these are used for food colouring and flavouring but C. longa is most extensively used. Turmeric occupies an unique place among the spices since besides being used for culinary and medicinal use it is also employed extensively as a cosmetic, colouring agent and preservative.
The medicinal use of turmeric is mentioned even among the Vedas and elaborated in classical Ayurvedic texts like the Charaka Samhita. A systematic experimental and clinical evaluation of its medicinal properties, however, has been done largely from the middle of the last century. Major attention has centered round curcumin and related curcuminoids which constitute 2-5 per cent of the biomass of the rhizome and are responsible for its characteristic yellow colour. Curcumin free extracts also exhibit biological activity.
There have been several reviews on pharmacology and chemistry of C. longa including a monograph in WHO Monographs on Selected Medicinal Plants, Volume I (1999). The present book is perhaps the first book to comprehensively cover all aspects of the plant, including the historical development, botany, chemistry, pharmacology and uses in medical and other fields.
The opening chapter has reviewed the traditional uses vis-a-vis modern concepts of functional foods and nutraceuticals. It has highlighted the need to provide evidence information to support its traditional uses. It provides justification for turmeric being considered the world's 'most important herb' today and lists about 20 medicinal uses in countries from all parts of the world even though the plant is a native of tropical and subtropical regions. The chapter also illustrates the wide variation in chemical composition of various varieties of turmeric. Thus, the curcumin content varies from 2.8 (Krishna) to 9.3 per cent (Roma, Suroma), oleoresins from 3.8 (Krishna) to 16.2 per cent (IISR Pratibha) and essential oil from 2 (Krishna) to 7 per cent (Suvarna, Sudarsana). These may be responsible partly for the varying results obtained with the crude extracts by different investigators.
The next chapter describes the chemical and nutritional composition of turmeric. The chemical description mainly covers curcumin and some other curcuminoids. An important omission is any mention of the pharmacologically active peptide turmerin. The yield of this 5-KDa water soluble cyclic peptide is 0.1 per cent and it contains 40 amino acid residues.
The remaining chapters of the book review the major pharmacological activities, mainly of curcuminoids, and related clinical and pharmacokinetic studies. The activities reviewed include antiinflammatory, anti-carcinogenic anti-mutagenic, antioxidant, anti-atherosclerotic and some other minor effects. The experimental data have been reviewed in chapters 3-11. The basic mechanisms underlying the pathological processes like inflammation, carcinogenesis, atherosclerosis, etc., have been reviewed in adequate detail thereby helping to locate the possible sites of action of curcumin, its analogues and metabolites.
Curcuminoids act on multiple sites in each of these conditions and some of these sites are common. These include kinins like PKC and tyrosine kinase, TNF, NFkappa B, cyclic D, protein API, STAT family agents, etc. They play important role in mutagenesis, tumour initiation, transformation, progression and metastasis. Pathogenic changes in vasculature are involved in different ways in growth and differentiation of tumours, wound healing, immune responses and thrombotic episodes. Curcumin suppresses proliferation of normal, transformed and malignant cells by modulating growth factors and induces apoptosis in a variety of tumour and other cells. The mechanisms include mitochondrial dependent and independent pathways. An important observation evident from the review is the potentiation of effects of anti-cancer drugs like cis-platinum by curcumin.
The prostaglandins are growth factors for inflammation and angiogenesis and perform a house keeping function. Curcumin modulates their activity by acting on the arachidonic acid metabolism. Other mechanisms involved in its anti-inflammatory activity include effect on lysosomal enzymes and membranes, inhibition of adhesion molecules and cytokine production by inhibition of NF-Kappa B target genes. The mechanism of other effects like hypolipidaemic, wound healing, anti-infective activity, etc., has also been similarly reviewed.
The author has reviewed the extensive data exhaustively but has not commented on the procedures used or the results obtained. Some of the studies have employed very high amounts of the test substances like 5 per cent in the diet and up to 5 mg/ml in some in vitro studies. Results of such studies must be interpreted with caution.
The clinical studies have been reviewed in a separate chapter and their inadequacies, and in many cases poor design of the trial, have been clearly brought out. It may have been better if the clinical studies had been given along with experimental studies on the condition and permitted better correlation. Still the clinical data provide enough evidence for chemopreventive and therapeutic potential of curcuminoids in malignancy and several chronic conditions.
Chronic disorders including degenerative (atherosclerosis, Alzheimer's disease), proliferative (cancer) or inflammatory (rheumatoid arthritis, chronic infections) conditions share cellular/ subcellular biochemical, molecular regulatory and pathological events including abnormal redox sites, cytokines, apoptotic mechanisms, etc. The book elegantly brings out how the effect of curcuminoids on basic modulators of these processes is responsible for their beneficial effects in such diverse conditions. It helps to identify potential targets on which future work may help in developing novel chemical entities for the management of these chronic conditions. It also highlights the therapeutic potential of the polypeptide tumerin which has not received adequate attention. Similarly data on bioavailability studies suggest the possibility of improving it by combining with piperine.
The studies reviewed in the book also clearly demonstrate that the safety and excellent tolerance of even large doses of curcuminoids and turmeric extracts enhance their utility in preventive health programmes and as nutraceuticals. The author aptly points out (p 237) the paucity of in vivo bioefficacy data in terms of their concentration and synergistic or additive effects with other bioactive compounds. She has also emphasized (p 298) the impact food-based approach for enhancing the intake of such phytochemicals may have on the onset and progression of several chronic diseases. The approach may also provide means of improving and prolonging the success of standard therapies.
The book is extensively documented and covers references of papers published up to 2004. There are many patents on the curcuminoids and analogues, etc., but they have not been so well covered. The book has been profusely illustrated with black and white photographs, bar diagrams, etc. It would have been better to provide coloured photograph, for example, of the plant (Fig. 1) or the tissues (Fig. 6.1) The legends of some of the figures (e.g. Fig. 7.3, 14.4) could have been more explicit. Similarly the splitting of some of the figures (e.g., 4.3) and tables (e.g., 5.3) should have been avoided.
These minor aberrations, however, detract very little from the merits of a timely and authoritative document on biomedical aspects of turmeric. This well produced monograph will be a useful reference book not only for research workers and clinicians but also those involved in economic utilization of turmeric and its value added products in pharmaceuticals, cosmetics, etc.
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Copyright Indian Council of Medical Research Apr 2008
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