Plants that … CURE

Plants that cure: A natural history of the world’s most important medicinal plants* by Elizabeth A Dauncey and Melanie–Jayne R Howes, 2020. Kew Publishing.

A few years ago Kew published a book about the deadly side of plants, Plants that kill by Elizabeth Dauncey and Sonny Larsson. I’m pleased to report that the antidote is now available. Accordingly, Plants that cure by Elizabeth Dauncey and Melanie-Jayne Howes is here appraised.

Starting at the beginning, the 2-page Introduction explains the book’s scope, the arrangement of plant information, and has a useful “How this book works” section explaining the formulaic lay-out employed throughout Plants that cure for the numerous 2-page plant accounts that occupy the bulk of the book.

Chapter 1 “The great botanical medical chest” is a stand-alone introduction to medicinal plant biology, and well worth reading in its entirety in one sitting. Thereafter, the main part of the book is organised into 9 categories by ‘body systems’, e.g. “Strong at heart”, “Calming the nerves”, “Fighting cancer”. Each category is a Chapter which highlights several plants that have medicinal value in treating the conditions concerned. Although that approach may sound a little dry, the writing style makes each entry readable and entertaining. And each of Chapters 2 – 9 has plenty of ‘boxes’ that give additional information, as well as providing an introduction to a traditional system of medicine, e.g. Indian, Middle Eastern, African, and Central and South American. It’s not only refreshing to see show-casing of systems of medical knowledge and practice other than the more-often mentioned Western, and Traditional Chinese Medicine [although they do also feature here], their inclusion is a much-needed reminder of the debt owed by modern medicinal practice to more ancient herbal-based regimes. Which further underlines the important – and continued – role of ethnobotany (e.g. Gina Porras et al., Chem. Rev. 2020; https://doi.org/10.1021/acs.chemrev.0c00922) in highlighting previously unknown potential sources of drugs from plants.

The text includes some lovely headings and titles – one guesses that the authors must have had a lot of fun choosing them. Plants that cure is full of fascinating accounts that are well-written and abundantly illustrated (and with an amazing set of images!). Almost inevitably, the subject matter of the book means that it includes a lot of technical terms, e.g. chemical names, and medical phrasing. For the latter, the Glossary helps**. For the former, and there’s no real way of avoiding them, all those chemical names should cause us to reflect upon – and admire – the wonderful biosynthetic prowess of plants. Because of the wealth of technical detail it contains, and notwithstanding the readability and therefore accessibility of the writing, this is probably a book that’s best to ‘dip into’, rather than read ‘in one go’ – apart from Chapter 1. But, however you choose to access it, the book is full of fascinating stuff!

The focus of Plants that cure is angiosperms (the flowering plants), but, by way of giving some indication of the breadth of plant medicinal utility, some gymnosperms are included – e.g. Ephedra (MR Lee, J R Coll Physicians Edinb 41: 78–84, 2011; doi: 10.4997/JRCPE.2011.116), Ginkgo, and Taxus spp. (yew – MR Lee, Proc. R. Coll. Physicians Edinb. 28: 569-575, 1998). There is also a mention for ferns – Dryopteris, lycopods – Huperzia (e.g. Dang Kim Thu et al., Journal of Basic and Clinical Physiology and Pharmacology, Volume 31, Issue 3, 20190159; doi: https://doi.org/10.1515/jbcpp-2019-0159), and even fungi – e.g. Claviceps (source of ergot – MR Lee, J R Coll Physicians Edinb 40: 77–80, 2010; doi:10.4997/JRCPE.2010.115). The layout of Plants That Cure will be familiar to those who have seen Plants that kill – it’s practically identical, even down to having the same number of pages(!). And I’m really pleased to share that, after careful scrutiny of the text, I only noticed a single – presumed – ‘typo’, oestorgenic (on p. 185), which presumably should be oestrogenic.

All of the above is to the book’s credit and represent ‘positives’ for this publication. However, there is one feature of Plants that cure that, in my view, is a major ‘negative’: There are no in-text references (except on p. 28 – and somewhat bizarrely, in connection with the approximate number of species in the Asparagus family; maybe it would have been more relevant regarding the number of medicinal plants in that family..?). Although we are told on p. 9 that the “latest research has been used throughout and is presented in a readily accessible way” [and which is good to know], that important assertion cannot be readily checked by the reader eager to find out more. It is possible that omission of references or citations in-text is deliberate and designed to provide information in an ‘accessible way’. Maybe, but if so, it’s a great shame since this dearth of evidence rather undermines any claim to pedagogy the book would otherwise legitimately have. Although Further reading is listed on p. 219, that only consists of books; no scientific articles are included, so there’s little opportunity there to access that latest research.

Several plants featured in Plants that Cure were also extensively covered in Plants that Kill; e.g. deadly nightshade (Atropa belladonna – MR Lee, J R Coll Physicians Edinb 37: 77–84, 2007); henbane (Hyoscyamus niger – MR Lee, J R Coll Physicians Edinb 36: 366–373, 2006); foxglove (Digitalis spp.); Chondrodendron tomentosum (from which tubocurarine is obtained – MR Lee, J R Coll Physicians Edinb 35: 83–92, 2005); opium poppy (Papaver somniferum); and tobacco (Nicotiana tabacum – Anne Charlton, J R Soc Med. 97(6): 292–296, 2004; doi: 10.1258/jrsm.97.6.292), which dramatically demonstrates the dual nature of many plants, which both cure and kill. And that is also a reminder that we need to study the plant resource carefully to understand its true potential – whether for good or ill. And, by way of underlining this double-edged nature of plants, Plants that cure contains the obligate disclaimer that readers shouldn’t try any of the treatments, etc. mentioned without consulting appropriate medical experts is included – twice, in full at the front of the book, and in much-abbreviated form at the bottom of p. 9. You have been duly ‘warned’.

Plants that cure is not a dry and dusty, collection of encyclopaedic accounts of plants and treatments, or lists of plant chemicals and medical terminology (which, where used, is usually explained in a Glossary** or in-text). Rather, Plants that cure is alive with fascinating facts that keep the reader entertained – and informed, and educated. Such as: The use of Silybum (e.g. Gholamreza Karimi et al., Iran J Basic Med Sci. 14(4): 308–317, 2011) to counter mushroom poisoning by reducing the liver damage resulting therefrom; the suggestion that the rodent-ridding power of the Pied Piper of Hamelin may be as much due to the rat-attracting capacity of valerian in his pocket, as any musical prowess he may have possessed; snowdrops (Galanthus nivalis – MR Lee, Proc R Coll Physicians Edinb 29: 349-352, 1999) are also known as death’s flower; a novel source of insulin is pro-insulin made by genetically-modified safflower, and is termed ‘prairie insulin’; the word ‘cotton’ was first applied to low-grade sheep’s wool; endophytic bacteria may actually produce the anti-tumour compound maytansine extracted from Roth’s spike-thorn (Gymnosporia rothiana – AS Jain & SJ Surana, Phcog Mag 2009;5, Suppl S2:100-4); and Camptotheca acuminata, which provides compounds used in cancer chemotherapy, is also known as the happy tree. Plants that cure also contains the best account I’ve seen that explains the reason why ‘flu virus strains are designated by H and N numbers. It is notable that the malaria section is largely devoted to artemisinin (MR Lee, J R Coll Physicians Edinb. 32: 300–305, 2002), rather than quinine (sourced from Cinchona – MR Lee, J R Coll Physicians Edinb 32: 189–196, 2002). But, this is surely a sign of the times as treatment with quinine is nowadays much less effective than it was (e.g. Jane Achan et al., Malar J 10, 144 (2011); https://doi.org/10.1186/1475-2875-10-144). Curiously, there’s no specific mention of ACT (Artemisinin-based Combination Therapy), although this treatment was hinted at on p. 135. However, Plants that cure does appear to downplay the seriousness of concerns over tobacco in saying that, “The leaves are used in cigarettes, which have been linked to adverse effects on health” (p. 69).

Although the number of plants covered in Plants that cure is very impressive, two of my particular favourite ‘phytomedicinals’ – Sutherlandia frutescens, known as ‘cancer bush’ or ‘balloon-pea’ (Oluwaseyi M. Aboyade et al., J Altern Complement Med. 20(2): 71–76, 2014; doi: 10.1089/acm.2012.0343), and Hoodia gordonii (e.g. Chrystian Araújo Pereira et al., Journal of Medicinal Plants Research 4(22): 2305-2312, 2010; doi: 10.5897/JMPR10.572; Shuyong Zhang et al., Proc Natl Acad Sci USA 111(40): 14571–14576, 2014; doi: 10.1073/pnas.1324130111} – weren’t included. Neither was one of my favourite medicinal compounds, cyclic peptides (e.g. Xiaoshu Jing & Kang Jin, Med Res Rev. 2019;1‐58; https://doi.org/10.1002/med.21639), except very briefly, and almost in passing, when cyclopeptides was mentioned in connection with toadstools of the genus Amanita (e.g. fly agaric – MR Lee, J R Coll Physicians Edinb 48: 85–91, 2018; doi: 10.4997/JRCPE.2018.119). That we still have a very full book, even with these omissions, is testament to the truly awesome potential of the plant kingdom to produce plenty of potent compounds with therapeutic potential.

We often read statements to the effect that anything from 11% (Ciddi Veeresham, J Adv Pharm Technol Res. 3(4): 200–201, 2012; doi: 10.4103/2231-4040.104709) to 25% (Ameenah Gurib-Fakim, Molecular Aspects of Medicine 27: 1–93, 2006; doi: 10.1016/j.mam.2005.07.008) or even 40% of modern pharmaceuticals are either plant-derived, or inspired by plant compounds. And the catalogue of such pharmaceuticals is impressive (e.g. here, here, and here). But those sort of ‘statistics’ tends not to mean that much as bare statements or lists. It’s only when you read some of the stories behind the seemingly endless number of compounds that have been identified in plants and the wide range of human conditions they’ve been used to treat, that you truly appreciate how wonderful this aspect of plant biology truly is. And not only what has been achieved to date, but the potential that exists for more discoveries to be made in future from the thousands – probably tens of thousands – of plant species that haven’t really been investigated yet. Which realisation makes it all the more important that we truly value plants, and strive to preserve, protect and conserve them for the benefit of all, an important message that is underlined by reports of how many plants – and fungi – are under threat in the wild [e.g. Stuart Pimm, Plants, People, Planet. 2020;00:1–9; https://doi.org/10.1002/ppp3.10160; Oscar A. Pérez-Escobar et al., Science 369: 781-782, 2020; doi: 10.1126/science.abc8085; and here, here, here, and here]. And that’s why books such as Plants that cure have an important role to play in educating us all to the powerful pharmaceutical potential of plants.

Summary

Plants that cure by Elizabeth Dauncey and Melanie-Jane Howes is a super book that is as much a photographic feast for the eyes as a satisfying smörgåsbord of facts for the brain. It’s well-written and magnificently-illustrated, and can only increase your appreciation of the power of plants.

* I’m curious: The book cover on the Kew book site clearly shows its sub-title as “A natural history of the world’s most important medicinal plants”. Which would be in keeping with the style of its predecessor tome Plants that kill: A natural history of the world’s most poisonous plants. However, the copy of the book I appraised for this blog item has the sub-title: “Plants as a source of medicines – from pharmaceuticals to herbal remedies” – as seen in the image above. Curious…

** The term rubefacient, introduced on p. 144, is not in the Glossary. Fortunately, its meaning is explained in-text, on p. 145 – although then rather curiously it is spelt rubifacient…