Botanicals: Methods and Techniques for Quality & Authenticity by Kurt A. Reynertson and Khalid Mahmood, eds. Boca Raton, Florida: CRC Press. 2015. Hardcover; 332 pages. ISBN: 978-1-4665-9841-6. $139.95.
The editors of this book — Kurt Reynertson, associate manager of product stewardship at Johnson & Johnson, and Khalid Mahmood, manager of the naturals platform at Johnson & Johnson — set out to provide an overview of methods that can be used to determine the identity and quality of botanical raw materials and finished products. They purposefully have chosen to include a wide variety of methods, including classical methods such as taxonomic identification, organoleptic evaluation, or thin-layer chromatography, as well as more recent analytical tools for ingredients in herbal dietary supplements, including DNA-based methods or nuclear magnetic resonance (NMR).
After a brief chapter on the importance of ingredient authenticity and quality for botanical research and development by the two editors, the book continues with a discussion of one of the most crucial aspects of the analysis, which is the proper selection of botanical ingredient specifications. The authors of this chapter, Paula Brown, PhD, Michael Chan, PhD, and Joseph Betz, PhD, provide a number of examples in which method specifications were inadequate, with focus on instances when methods were not specific enough to distinguish between authentic and adulterated material. Another emphasized point is the relationship between the relative standard deviation and the concentration of the analyte in the sample. The consideration of this relationship is important for the verification of accuracy (for higher analyte concentrations, the permissible deviation from the actual value has to be smaller) and precision (higher analyte concentrations should result in lower relative standard deviation values).
The chapters that follow describe organoleptic analysis, botanical taxonomy, DNA-based methods, high-performance liquid chromatography (HPLC)-fingerprinting methods, multivariate statistics, analysis using stable isotopes, NMR, Fourier transform-near infrared (FT-NIR) spectroscopy, high-performance thin-layer chromatography (HPTLC), and sensory fingerprinting using an electronic nose. Chapter 17 addresses the influence of growing conditions and different processing methods on the constituent profiles of botanical ingredients. The last chapter details some of the particularities of botanical ingredients used in cosmetic formulations.
There are a few chapters in this book that I consider particularly helpful for people involved in quality control of botanical ingredients. The introduction to genetic methods by Danica Harbaugh Reynaud, PhD, provides a good overview of the strengths and limitations of DNA-based authentication of botanical ingredients. Tables 5.2 and 5.3 summarize plant species that the author found adulterated by closely related or very distant species. Examples of unexpected adulteration include the substitution of picrorhiza (Picrorhiza kurrooa, Plantaginaceae) root with banana (Musa acuminata, Musaceae) root, or the substitution of cramp bark (Viburnum opulus, Adoxaceae) with the bark of Tatar maple (Acer tataricum, Sapindaceae). The differences among the various DNA techniques described in this chapter may be rather difficult to understand for readers without any experience in the topic, but overall, this chapter is a helpful introduction to DNA methods, the limitations of which (e.g., the author states that DNA methods are inappropriate to authenticate dried herbal extracts) are of particular relevance in light of the recent actions by the New York Attorney General in testing herbal dietary supplements, many of which were dried herbal extracts.
In Chapter 7, James Harnly, PhD, Joe Jablonski, PhD, and Jeff Moore, PhD, review statistical tools for the identification of botanical ingredients. The chapter is accessible to those who may not have much experience with statistics, and it explains the most commonly used chemometric methods. The difference between supervised models (where samples are identified prior to classification, and the statistical model determines if the unknown sample falls within the acceptable range established using authenticated materials) and unsupervised models (where samples are compared without any knowledge of the identity) is presented, and the most commonly used methods to build a statistical model are explained. The fact that the authors used dairy (milk) rather than a botanical dietary ingredient to illustrate the various statistical approaches does not detract from the usefulness of the chapter. Because the use of statistical models for the identification of botanicals increasingly is regarded as the standard in the industry, this chapter is a great read for anyone interested in becoming more familiar with advanced statistical tools.
A rather unusual analytical approach for botanicals is described in Chapters 9 and 10, where the authors discuss the usefulness of radioactive or stable isotope analysis for dietary supplements. One example is the use of radioactive 14C in assessing if an ingredient is of natural origin. Since equilibrium exists between the 14C production in the atmosphere and its decay, any living plant will incorporate a very small amount of 14CO2 through photosynthesis. This is in contrast with fossil fuel-derived products that are lacking any 14C activity. The difference in 14C activity can be used to determine if a component (e.g., vanillin) originated from a plant source, or if it was manufactured starting with petroleum-based material. The ratio of the stable hydrogen (2H/1H) and oxygen (18O/16O) isotopes can be used to determine the geographical origin of plant material based on the fact that these isotope ratios are affected by the climate and therefore their abundance varies across the globe.
Of the three chapters on NMR for botanical ingredient analysis, the chapter by Kimberly Colson, PhD, Jimmy Yuk, PhD, and Christian Fischer, PhD, is the most effective in providing an overview of the technique’s potential. NMR is shown to be a very powerful method for ingredient identification, but the authors also note the other possibilities that quantitative NMR has to offer. The example given in the book is the quantification of organic acids and saccharides in Aloe vera (Xanthorrhoeaceae). For qualitative analysis, the development of a spectral database is crucial. And while a routine quality control sample may be run by a technician, the database establishment can be performed only by an experienced NMR analyst, since the experiments and the experimental parameters must be carefully selected. The authors have devoted a subchapter to the key points for the development of a spectral database, but a company interested in the technology will most likely depend on the instrument vendor to set this up.
Of much interest to quality control personnel in the dietary supplement industry is Chapter 14, which concerns the practical use of FT-NIR for identification of botanicals. Written by Cynthia Kradjel, the chapter starts with an overview of FT-NIR, emphasizing the importance of the development of a database using authenticated botanical material and the need for adequate statistics. It is one of the few chapters that contains information on the regulatory requirements and specifics on method validation.
Some chapters may have more limited appeal. The application of the complete reduction to amplitude frequency table (CRAFT) for data mining of NMR spectra may be helpful for very specific experiments, but I wonder how much interest readers will have in this particular method. The last chapter on aspects of quality issues with botanicals used in the cosmetics industry is focused heavily on agricultural aspects of botanicals, while some of the important challenges unique to cosmetic ingredients (e.g., the demand for colorless or odorless botanical ingredients, or the solubility and stability issues that result from the large amounts of water in the matrices of cosmetic products) are not discussed.
Overall, the book covers a mixture of methods that are in use and those that show promise to become more widely used for the analysis of botanical ingredients. It is not only an interesting read for analytical geeks like me, or for those who want to learn more about quality control of botanicals, but also a helpful resource for those thinking about expanding their analytical capabilities for botanical ingredient analysis in a contract analytical laboratory or the dietary supplement industry. As the authors state in the preface, “gaps remain, which future editions may rectify.” In this regard, the editors may consider including an overview of HPLC and gas chromatography (GC), two of the most widely used techniques in botanical analysis, in the next edition.
– Stefan Gafner, PhD
Chief Science Officer, American Botanical Council
Technical Director, ABC-AHP-NCNPR Botanical Adulterants Program