The Plant Cell, January 2013 © 2013 1/12/2013 The … · Water of white lilies: ... The pain-relieving properties of opium have been known for millennia Opium is the dried latex

The Plant Cell, January 2013 © 2013The American Society of Plant Biologists

1/12/2013

www.plantcell.org/cgi/doi/10.1105/tpc.113.tt0113 1

© 2013 American Society of Plant Biologists© 2013 American Society of Plant Biologists

The Past, Present and Future of Medicinal Plants


Herbal medicines have been used for millennia

1000s of plants have medicinal uses

More people in the world depend on herbal medicines

than pharmaceutical medicines

More than half of the 150 most-

prescribed medicines have at

least one compound derived from plants

More than half of the 150 most-

prescribed medicines have at

least one compound derived from plants

Credits: WHO photo by D. Henrioud; Mycelium101


Reprinted by permission from Macmillan Publishers Ltd from Last, R.L., Jones, A.D. and Shachar-Hill, Y. (2007). Towards the plant metabolome and beyond. Nat. Rev. Mol. Cell Biol. 8: 167-174.Image provided by S. O’Connor, reprinted from Glenn, W.S., Runguphan, W. and O’Connor, S.E. (2013) Recent progress in the metabolic engineering of alkaloids in plant systems. Curr. Opin. Plant Biol. (in press).

Traditional knowledge now can be augmented with modern approaches

Metabolomics to identify medicinally active compounds

Metabolic engineering to increase their production

and diversity


Lecture Outline

• Historical uses of plants as medicines• From 1800 to the present

• Quest for active compounds• The best of both

• Plant-based medicines, present and future

• Health care for all


People have used plants as medicines since pre-history

Chemicals preserved in 50,000 year old Neanderthal teeth

suggest medicinal plants such as chamomile were eaten

Reprinted from Wadley, L., Sievers, C., Bamford, M., Goldberg, P., Berna, F. and Miller, C. (2011). Middle stone age bedding construction and settlement patterns at Sibudu, South Africa. Science. 334: 1388-1391 with permission from AAAS. CSIC Comunicación; Köhler’s medicinal plants

77,000 year-old South African Cryptocarya woodiileaves used for bedding – this plant is toxic to mosquitoes


University of Virginia, and Mexiclore; Powell, J. W. Seventh Annual Report of the Bureau of Ethnology. Washington: Government Printing Office, 1891. Page 159; Mycelium101

Historical records are scarce, but evidence suggests that cultures around the world have used plants as medicines for thousands of years

South America: The Badianus Manuscript, or Aztec Herbal

(1552), written and illustrated by two Aztec men, Martín de la Cruz

and Juan Badiano

North America: Ojibwa midewiwin preparing herbal medicine

Persia: Ibn Sina, also known as Avicenna, c. 1000 AD, wrote “The Book of Healing” and “The Canon of Medicine”

Healers who use traditional herbal remedies are the major health providers throughout much of sub-Saharan Africa


Written records of medicinal plants date back 4000 years

NIH – Images from the history of medicine; Beijing Digital Museum of TCM;

Sumerian and Egyptian texts from more than 3500 years ago describe the use of medicinal plants

The use of herbal medicines in China and India date back at least 4000 years

These ancient texts mention hundreds of plants including aloe, peppermint, opium, willow, wormwood and many more


Greek herbals remained in use through the middle ages

Historia Plantarumby Theophrastus

~200 BCThis edition printed 1644

De Materia Medicaby Pedanius Dioscorides

~50 AD This edition copied ~500 AD

Biodiversity heritage library


1500: Liber de arte distillandi simplicia et composita

NIH and BHL

“The same water withdryueth the spottys in the face / whan it is often wasshed and rubbed therwith / and let drye agayne by hym selfe”

Water of white lilies:

A manual for distilling herbs was published in 1500 by Hieronymus Brunschwig(English translation, 1527)

The book contains instructions for how make and use plant extracts


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The “Doctrine of Signatures”: Form reveals purpose

Image credits: Wellcome Library, AndonicO, Wellcome Library, London

"That to which a sign belongs, to it also the effect belongs; and that to which the effect belongs, equally to it the sign belongs; and those which lack the signs also lack the effects” G. della Porta (~1600)

Are pomegranates good for your teeth?

Are walnuts brain food?

Will daisies cure eye problems?


Apothecaries and physic gardens used and cultivated medicinal plants

Botanic Garden Leiden University 1625

National Library of Medicine, NLM, NLM, Orto Botanica di Padova

The oldest existing botanical garden was founded in Padua, 1545


Discovery of cardiac glycosides from foxglove, Digitalis purpura

“We shall sooner obtain the end proposed if we take up the subject as altogether new and, rejecting the fables of the ancient herbalist, build only upon the basis of accurate and well considered experiments’

William Withering (1741 – 1799) English botanist and doctor, he wrote the first book to apply Linnaean taxonomy to British flora. He applied modern, rational methods to the study of folk medicines


1785 “An Account of the Foxglove, and Some of its Medical Uses”

Krikler, D.M. (1985). The foxglove, “the old woman from Shropshire” and William Withering. Journal of the American College of Cardiology. 5: 3A-9A; Lee, M.R. (2001) William Withering (1741–1799): A Birmingham Lunatic. Proc. R. Coll. Physicians Edinb. 31: 77-83. Wilkins, M.R., Kendall, M.J. and Wade, O.L. (1985). William Withering and digitalis, 1785 to 1985. BMJ. 290: 7-8.

“…this medicine was composed of twenty or more different herbs; but ….the active herb could be no other than the Foxglove”

Digoxin, one of several cardiac glycosides

isolated from foxglove.

Withering spent years investigating optimal preparations and doses of foxglove leaves for the treatment of heart conditions


From 1800 to the present: Quest for active compounds

1805 – Morphine purified from opium poppy (Papaver somniferum)

Taxus breviola, Pacific yew

1966 - Taxol purified from Pacific yew (Taxus breviola)

1820 – Quinine purified from

Cinchona tree (Cinchona spp)


Which is “better”, a plant extract or the purified compound?

TraditionalNaturalSafer

ScientificPure

Safer

No “middleman”, often cheaper

Multifactorial effects can

be beneficial

Single defined compound, no

unknowns

Overharvesting and supply shortages

are problems

Synthetic forms can preserve wild

plants, provide consistent supply

Batch-to-batch variation can be a problem

Prohibitively expensive for manyConsistent,

precise dosages


Morphine, a powerful narcotic analgesic alkaloid from poppy

Photo courtesy of Toni Kutchan, Donald Danforth Plant Science Center

The pain-relieving properties of opium have been known for millenniaOpium is the dried latex from the seed capsule of the poppy, and contains many pharmacologically active alkaloids including morphine, codeine, noscapine and thebaine morphine

codeinethebaine

noscapine


Morphine is the best and the worst of drugs - effective but addictive

US National Institute of Drug Abuse; UNODC, World Drug Report 2012 (United Nations publication, Sales No. E.12.XI.1)

Morphine and related opioids are extremely effective pain relievers, but also highly addictive. Prolonged use affects the activity or amount of neurotransmitter receptors, causing a chemical dependency


Making a safer poppy for licit, but not illicit, purposes

Reprinted by permission from Macmillan Publishers Ltd: Millgate, A.G., Pogson, B.J., Wilson, I.W., Kutchan, T.M., Zenk, M.H., Gerlach, W.L., Fist, A.J. and Larkin, P.J. (2004). Analgesia: Morphine-pathway block in top1 poppies. Nature. 431: 413-414. See also Hagel, J.M. and Facchini, P.J. (2010). Dioxygenases catalyze the O-demethylation steps of morphine biosynthesis in opium poppy. Nat. Chem. Biol. 6: 273-275.

The thebaine oripavine poppy 1 (top1) variety accumulates thebaine and oripavine, but not morphine or codeine. These poppies can be used as precursors for synthetic opioid production, but carry “little risk of diversion for illicit purposes”

Wild type extract

top1 extract


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Antimalarials: quinine and artemisinin

Hay, S.I., et al., (2009) PLoS Med 6(3): e1000048. doi:10.1371/ journal.pmed.1000048 Image by Ute Frevert; false color by Margaret Shear. Photo credit: CDC

Malaria kills and debilitates millions of people each year, and accounts for

20% of childhood deaths. It is caused by a mosquito-transmitted protozoan.

Quinine and artemisinin are effective antimalarial drugs


Image credits: Köhler; CDC, H. Zell

Cinchona tree bark contains quinine, which kills Plasmodium

Cinchona bark was brought to Europe from Peru in the 17th century. Quinine was purified from it in 1820. Synthesis is very difficult and too expensive, so cinchona trees remain the source of the drug


Artemisia annua produces artemisinin, an effective antimalarial

Artemisinin

Artemisia has been used by Chinese herbalists for thousands of years. In 1972 the active ingredient, artemisinin, was purified

Artemisia annua

Photo credit: www.anamed.net; Reprinted by permission from Macmillan Publishers Ltd. From Van Noorden, R. (2010) Demand for malaria drug soars. Nature 466: 672 – 673.

Demand for artemisinin exceeds supply


Several approaches are being used to increase artemisinin production

Reprinted from Graham, I.A., et al. and Bowles, D. (2010). The genetic map of Artemisia annua L. identifies loci affecting yield of the antimalarial drug artemisinin. Science. 327: 328-331 with permission from AAAS; Reprinted by permission from Macmillan Publishers Ltd from Ro, D.-Ket al and Keasling, J.D. (2006). Production of the antimalarial drug precursor artemisinic acid in engineered yeast. Nature. 440: 940-943; see also Westfall, P.J. et al . and Paddon, C.J. (2012). Production of amorphadiene in yeast, and its conversion to dihydroartemisinic acid, precursor to the antimalarial agent artemisinin. Proc. Natl. Acad. Sci. 109: E111-E118. Covello, P.S. (2008). Making artemisinin. Phytochemistry. 69: 2881-2885. Lévesque, F. and Seeberger, P.H. (2012). Continuous-Flow Synthesis of the Anti-Malaria Drug Artemisinin. Angewandte Chemie International Edition. 51: 1706-1709.

Genetic approach: Identify genes that increase production for breeding strategy

Semisynthetic approach: Introduce plant genes into metabolically engineered yeast

Both methods have advantages, and its been said that both are needed to ensure adequate supply


Reprinted from Horwitz, S.B. (2003). Personal Recollections on the Early Development of Taxol. Journal of Natural Products. 67: 136-138, copyright American Chemical Society. See also Jennewein, S.J. and Croteau, R.C. (2001). Taxol: biosynthesis, molecular genetics, and biotechnological applications. Applied Microbiology and Biotechnology. 57: 13-19 .

Taxus breviola, Pacific yew

Taxol was discovered through a random screening project

Taxol is an effective anticancer drug because it

stabilizes microtubules, and blocks cell division

Taxol - “It’s the kind ofstructure that only a tree would make’’


Taxol’s success as a therapeutic agent threatened the Pacific yew

Methods for taxol synthesis were worked out in 1994, but they are far too expensive

Photo credit : Dave Powell USDA

In the 1980s thousands of trees were being killed and stripped of their bark for taxol extraction

Currently, taxol is produced semisynthetically, from a precursor harvested from the needles of Taxus baccata(European Yew) that occurs at much higher levels than taxol. Branches can be harvested from trees annually without sacrificing the tree

Another taxol -production method uses cultured plant cells


Camptothecin, an antitumor drug from the happy tree, xi shu

Irinotecan

CamptothecinTopotecan

Natural product – too toxic for therapeutic use

Semisynthetic derivatives – used in the treatment of many cancers

The same project led to camptothecin, from Camptotheca acuminata, the “happy tree” 喜树


Camptothecins block DNA replication via topoisomerase

Reprinted by permission from Macmillan Publishers Ltd from Pommier, Y. (2006). Topoisomerase I inhibitors: camptothecins and beyond. Nat. Rev. Cancer. 6: 789-802.

Camptothecin arrests cancer cell growth by targeting topoisomerase I, and identified a new cellular target for chemotherapy agents


Vinca alkaloids, a fortuitous find

Vinblastine

Vincristine

Noble, R.L. (1990). The discovery of the vinca alkaloids—chemotherapeutic agents against cancer. Biochem. Cell Biol. 68: 1344-1351. Roepke, J., Salim, V., Wu, M., Thamm, A.M.K., Murata, J., Ploss, K., Boland, W. and De Luca, V. (2010). Vinca drug components accumulate exclusively in leaf exudates of Madagascar periwinkle. Proc. Natl. Acad. Sci. USA. 107: 15287-15292. Photo credit titanium22; figure © gtang

Vinca alkaloids bind free tubulin dimers and interfere with microtubule assembly, therefore blocking cell division

Periwinkle initially was used to treat diabetes. Animal studies revealed that the plant extract is toxic to white blood cells, and is an effective treatment for cancer of white blood cells such as lymphoma

Madagascar periwinkle,

Catharanthus roseus


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Summary – medicinal compounds from plants

The medicinal properties of some plants can be traced to a single active compound, which can be purified or synthesized and precisely prescribed

These single purified compounds have specific actions; they are “magic bullets” that affect a very specific target

Not all medicinal plants can be purified to a single active compound

As an example opiates specifically target opiate receptors

National Institute on Drug Abuse


Not all conditions will be treatable by single compounds

Some chronic diseases are pleiotropic in nature and unlikely to be treated by a single compound:

AIDSDiabetesMetabolic syndromeObesityAlzheimer’s

Disease

Many traditional medicines are composed of several plants –perhaps some of their effects arise from multiple factors acting together?


The best of both: Plant-based medicines, present and future

Traditional medicines

Untested plants

New Drug

Identification of clinical efficiency, optimization and standardization

Screening for bioactivity

Identification of active compound(s)

or fractions

Direct to consumer

Via healer

Regulatory approval

Mark de Fraeye, Wellcome Images N0027823; Rkitko


Medicines from traditional Chinese medicine

Yinxingye

Xuanshen

Beijing Digital Museum of Traditional Chinese Medicine

Scrophularia spp.(figwort root)

Bilobalide

Qinghao

Artemisia annua

Artemisinin, for the treatment of malaria

Ginkgo biloba

May help slow memory decline in the elderly. Terpenoids including ginkgolides

and bilobalides are thought to be involved

Used in the treatment of arthritis, several compounds seem to contribute including iridoid glycosides


Medicines from Ayurveda, traditional Indian medicine

Curcumin (haridra) from tumeric (Curcuma longa), thought to have many benefits

See Mukherjee, P.K. and Wahile, A. (2006). Integrated approaches towards drug development from Ayurveda and other Indian system of medicines. J. Ethnopharmacol. 103: 25-35.

Withfarin A, a compound with diverse functions including anti-cancer activity, Withania somnifera (ashwagandha)

Senna glycosides, used as laxatives and dieters’ tea, from Senna alexandrina


Drawing by Gracia Lam and reprinted by permission from Macmillan Publishers Ltd: from Xu, Z. (2011) One step at a time. Nature 480: S90 – S92, and Gilbert, N. (2011). Herbal medicine rule book. Can Western guidelines govern Eastern herbal traditions? Nature 480: S98.

Identification of clinical efficiency, optimization and standardization

Identification of active compound(s)

or fractions

Traditional medicines can be used traditionally, or can benefit from standardization. They also can be sources for new drug discovery

Drugs and therapies from traditional

medicines


Herb Common Name

黃苓 Huang QinBaical skullcap root, Scutellaria, Scute

大棗 Da Zao Jujube, Chinese date

白芍 Bai Shao White peony root, Chinese peony

炙甘草 Zhi Gan Cao Honey prepared licorice, Chinese licorice

Huang Qin Tang – from TCM to clinical trials

Callaway, E. (2010) How an 1,800-year-old herbal mix heals the gut. Nature News.

Huang Qin Tang has been used to treat nausea for nearly 2000 years. It is made from four plants, each of which is needed for its activity


A formulation of Huang Qin Tang called PHY906 is in clinical trials

From Lam, W., Bussom, S., Guan, F., Jiang, Z., Zhang, W., Gullen, E.A., Liu, S.-H. and Cheng, Y.-C. (2010). The four-herb Chinese medicine PHY906 reduces chemotherapy-induced gastrointestinal toxicity. Sci. Transl. Med. 2: 45ra59, with permission from AAAS. Liu, S.-H. and Cheng, Y.-C. (2012). Old formula, new Rx: The journey of PHY906 as cancer adjuvant therapy. J. Ethnopharmacol. 140: 614-623 with permission from Elsevier.

Rats treated with the chemotherapy agent CPT-11 experienced damage to their intestinal epithelium and death

With the addition of PHY906, the toxic effects were greatly reduced


Ginseng (Panax spp.) – is it a panacea?

Ginseng (Panax spp.) is the most widely used and one of the most highly valued herbal medicines, and is believed to have many benefits. There are several species that have different properties and values

100 year old wild ginseng root sold for $250,000

300 year old ginseng root sold for $400,000


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The composition of ginsenosides in ginseng is variable

Briskin, D.P. (2000). Medicinal plants and phytomedicines. Linking plant biochemistry and physiology to human health. Plant Physiol. 124: 507-514; William M. Brown Jr., bugwood..org

Age and growth conditions affect the biochemical properties of the plant and extract


Ephedra (ma huang), use and abuse

Ephedra sinica (ma huang)

麻黃

See Abourashed, E.A., El-Alfy, A.T., Khan, I.A. and Walker, L. (2003). Ephedra in perspective – a current review. Phytother. Res. 17: 703-712; NCCAM; Univ. Maryland Med. Center; Beijing Digital Museum of Traditional Chinese Medicine

ephedrine• Its use and abuse as a performance

enhancer and weight-loss agent is thought to have contributed to many deaths

• Since 2004 its sale in the US has been severely restricted

Ephedra dilates the bronchial passages of the lungs and relieves asthma and respiratory problems

It also stimulates the heart and metabolic rates


21st century science can be applied to ancient medicines

Reprinted from Liu, S.-H. and Cheng, Y.-C. (2012). Old formula, new Rx: The journey of PHY906 as cancer adjuvant therapy. J. Ethnopharmacol. 140: 614-623 with permission from Elsevier.

What are the active compounds? What are optimal dosages? What biochemical pathways do they affect in the patient? What side effects can arise?


Standardizations and quality assurances of herbal medicines

See Betz, J., Fisher, K., Saldanha, L. and Coates, P. (2007). The NIH analytical methods and reference materials program for dietary supplements. Analytical and Bioanalytical Chemistry. 389: 19-25. Cordell, G.A. and Colvard, M.D. (2012). Natural Products and Traditional Medicine: Turning on a Paradigm. Journal of Natural Products. 75: 514-525.

In the United States, it is estimated that there is only a 50:50 chance of selecting an authentic product containing both the correct species and correct plant component at an appropriate strength

How can quality be assured?Quality refers to identity, purity and strength.

DNA barcoding to assess species identity

Biological assays for effectiveness

Mass spectroscopy to assess composition

Analytical tests for common contaminants (e.g. heavy metals, pesticides)


Over-the-counter herbal medicines

Many people are exploring the use of herbs and other alternatives to Western medicine. Many of these are sold over-the-counter as dietary supplements

Percentage of people who have tried

complementary or alternative medicines

Drug Botanical Name

Echinacea Echinacea species

Garlic Allium sativum

Goldenseal Hydratis canadensis

Ginseng Panax species

Gingko Ginkgo biloba

Saw palmeto Serenoa repens

St. John’s wort Hypericum species

Kava kava Piper methysticum

10 best selling OTC herbal medicines


Reprinted by permission from Macmillan Publishers Ltd: from Schmidt, B.M., Ribnicky, D.M., Lipsky, P.E. and Raskin, I. (2007). Revisiting the ancient concept of botanical therapeutics. Nat Chem Biol. 3: 360-366. See also FDA (2004) Guidance for Industry. Botanical Drug Products (FDA, DC, June 2004).

Flow chart and outcomes for the commercialization of medicines from plants. It’s more expensive to be approved as a “drug” than a dietary supplement, but the financial gains can be much higher


Regulator’s main concern – is the product safe as sold?

Consumer has responsibility to ensure that it is used appropriately

Limited oversight of OTC herbal medicines (supplements)

“The Food and Drug Administration suggests that you consult with a health

care professional before using any dietary supplement”


Echinacea, cure for the common cold?

Globally, sales of Echinacea-based products exceed $320 million

Echinacea products (Echinacea spp.) are among the top selling herbal medicines

They are thought to promote the immune system and deter respiratory infections, but do they work?

MAYBE

“Echinacea probably has only a small beneficial effect. Individual choices should be guided by personal health values and preferences…”

-Barrett et al., 2010.

See Barrett, B., Brown, R., Rakel, D., Mundt, M., Bone, K., Barlow, S. and Ewers, T. (2010). Echinacea for treating the common cold: A randomized trial. Ann. Internal Medicine. 153: 769-777.


How can we know which plants are good candidates for drugs?

Ray Carruthers, USDA


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Bioprospecting: Drugs and medicines found by plant screening

Plant samples are collected and extracted

Chemical assays

Biological assays

Heydrienne; Jim Gathany, CDC image 7282;


Collecting and selecting plants to screen

Reprinted by permission from Macmillan Publishers Ltd from Dalton, R. (2000). Political uncertainty halts bioprospecting in Mexico. Nature. 408: 278-278; Manfred Mielke USDA; Poppy photos by Forest and Kim Starr; Bonobo by Kabir Bakie

Random collecting

With indigenous guides

Zoopharmacognosy – many animals have been observed to self-medicate by eating pharmacologically active plants

By family - Certain plant families, such as Papaveraceaeare rich in medicinal compounds


Medicinal compounds are unequally distributed in plant families

Zhu, F., Qin, C., Tao, L., Liu, X., Shi, Z., Ma, X., Jia, J., Tan, Y., Cui, C., Lin, J., Tan, C., Jiang, Y. and Chen, Y. (2011). Clustered patterns of species origins of nature-derived drugs and clues for future bioprospecting. Proc. Natl. Acad. Sci. 108: 12943-12948.

Plant families associated with drug-production are indicated in green, and red indicates families with endangered species

Solanaceae (tobacco, nightshade, peppers) Papavaraceae

(poppy)

Taxaceae(Pacific yew)

Apocynaceae (periwinkle)

Myrtaceae(eucalyptus, clove)


Guilt by association – drug discovery by relatedness

Saslis-Lagoudakis, C.H., Savolainen, V., Williamson, E.M., Forest, F., Wagstaff, S.J., Baral, S.R., Watson, M.F., Pendry, C.A. and Hawkins, J.A. (2012). Phylogenies reveal predictive power of traditional medicine in bioprospecting. Proc. Natl. Acad. Sci. 109: 15835–15840. See also Zhu, F., Qin, C., Tao, L., Liu, X., Shi, Z., Ma, X., Jia, J., Tan, Y., Cui, C., Lin, J., Tan, C., Jiang, Y. and Chen, Y. (2011). Clustered patterns of species origins of nature-derived drugs and clues for future bioprospecting. Proc. Natl. Acad. Sci. 108: 12943-12948.

Some plant families are more likely to have medicinal value. Plant genera used medicinally in three indigenous cultures were mapped, and some overlaps identified; good candidates for further study!


• Plants produce >200.000 compounds

• Many of these chemicals function in defense

Classes of phytochemicals with medicinal properties


Redrawn from Hartmann, T. (1996). Diversity and variability of plant secondary metabolism: a mechanistic view. Entomologia Experimentalis et Applicata 80: 177-188.

Photo-synthesis

Carbohydrate metabolism

Alkaloids

Coumarins

Terpenoids:e.g. Limonoids

SaponinsPinene

Phenolic: e.g. Flavonoids; Salicylic acid; Lignins etc

Alkaloids

Three structural classes of specialized metabolites

Although hugely diverse, specialized metabolites are derived from a few dozen highly versatile central intermediates, which are modified in lots of different ways


Alkaloids are biosynthetically diverse; most derive from amino acids

There are approximately 2500 benzylisoquinoline alkaloids (BIAs), including morphine

Tropane alkaloidsinclude cocaine

The ~2000 monterpenoid indole alkaloids (MIAs) are derived from strictosidine

Caffeine is a purine alkaloid

Senecionine is a pyrrolizidine alkaloid


MIAs are mainly known from two plants “Indian snakeroot” aka Sarpagandha, and Madagascar periwinkle

Monoterpenoid indole alkaloids (MIAs) are derived from strictosidine

Reprinted from Loris, E.A., Panjikar, S., Ruppert, M., Barleben, L., Unger, M., Schübel, H. and Stöckigt, J. (2007). Structure-based engineering of strictosidine synthase: Auxiliary for alkaloid libraries. Chem. Biol. 14: 979-985 with permission from Elsevier; Forest and Kim Starr; Vinayaraj

Rauwolfia serpentina

Catharanthus roseus


Benzylisoquinoline alkaloids (BIAs) share a benzylisoqunoline structure

Reprinted from Liscombe, D.K., MacLeod, B.P., Loukanina, N., Nandi, O.I. and Facchini, P.J. (2005). Evidence for the monophyletic evolution of benzylisoquinoline alkaloid biosynthesis in angiosperms. Phytochemistry. 66: 1374-1393 with permission from Elsevier; Richard Old, XID Services, Inc.

Benzylisoquinoline alkaloids (BIAs) are a family of about 2500 compounds that are all based on the elaboration of a simple skeletal structure

NoscapineCough suppressant from

Papaver somniferum


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Papaver somniferum

Coffee

Nicotiana tabacum

Alkaloids contain nitrogen and include stimulants and narcotics

CocaCaffeine

Nicotine

Cocaine

Morphine

Vincristine

Catharanthus roseus


Terpenoids are diverse compounds derived from isoprene units

Isoprene (C5)

Image sources: Calvero; Wilhelm Thomé; Forest & Kim Starr; Karan A. Rawlins, University of Georgia

Eucalyptol

Linalool

Many low-molecular weight terpenoids are volatile, and

components of essential oils

Limonene, a monoterpene (C10) Farnesol, a

sesquiterpene (C15)

Pinene

Isoprene


Terpenoids are diverse compounds derived from isoprene units

GinkgolidePhoto credit: Dave Powell, USDA Forest Service, Bugwood.org

Tetrahydro-cannabinol (THC)

Cannibus sativa

Ginkgo biloba

Taxol

Taxus breviola

Ginsenoside

Panax ginseng

Artemisia annua

Artemisinin


Phenolics: flavonoids, anthocyanins and related compounds

Curcumin from the spice turmeric

Genistein an isoflavonoid from soy beans

Epigallocatechin gallate (EGCG), a flavonoid from green tea

Syzygium aromaticum

Brian Arthur

Eugenol

Tannins Found in tea, wine, nuts and many plants


Most plant phenolics are products of phenylpropanoid metabolism

From: Buchanan, B.B., Gruissem, W. and Jones, R.L. (2000) Biochemistry and Molecular Biology of Plants. American Society of Plant Physiologists.

Phenylalanine

Zingiber officinale

Gingerol

Cyanidin-glucosideVitis vinifera


-Omics, systems, semi-synthetic methods and metabolic engineering

Reprinted from Schilmiller, A.L., Pichersky, E. and Last, R.L. (2012). Taming the hydra of specialized metabolism: how systems biology and comparative approaches are revolutionizing plant biochemistry. Curr. Opin. Plant Biol. 15: 338-344, with permission from Elsevier.

High-throughput methods are being used to identify genes, proteins and metabolites found in various medicinal plants

Candidate genes, proteins and metabolites can be tested through biochemistry, reverse genetics and analysis of natural variation

Large scale approaches also suggest ecological roles and evolutionary histories


High-throughput methods to identify genes, intermediates and pathways

http://medicinalplantgenomics.msu.edu/index.shtml; http://metnetdb.org/mpmr/, http://www.phytometasyn.ca/, http://uic.edu/pharmacy/MedPlTranscriptome/, http://www.onekp.com/index.html

Goals of these projects include: To identify candidate metabolites, pathway genes and pathwaysTo introduce the synthetic pathways into other organisms (e.g. yeast) To increase production To identify novel derivatives

(See the links below for complete lists of species being investigated)

DNA –Genomics

mRNA ‐Transcriptomics

Protein ‐Proteomics

Metabolites ‐Metabolomics


Genomic sequences are only part of the story…

Reprinted from Schilmiller, A.L., Pichersky, E. and Last, R.L. (2012). Taming the hydra of specialized metabolism: how systems biology and comparative approaches are revolutionizing plant biochemistry. Curr. Opin. Plant Biol. 15: 338-344, with permission from Elsevier.

Specialized metabolites often accumulate in only a few cell types, and their synthesis is regulated by the environment. Furthermore, there can be large variations amongst varieties within the same species.

Therefore, a sequenced genome is only one piece of the puzzle


Many enzymes and metabolites are highly compartmentalized

Bird, D.A., Franceschi, V.R. and Facchini, P.J. (2003). A tale of three cell types: Alkaloid biosynthesis is localized to sieve elements in opium poppy. Plant Cell. 15: 2626-2635. See also Ziegler, J. and Facchini, P.J. (2008). Alkaloid biosynthesis: Metabolism and trafficking. Annu. Rev. Plant Biol. 59: 735-769. Dai, X., Wang, G., Yang, D.S., Tang, Y., Broun, P., Marks, M.D., Sumner, L.W., Dixon, R.A. and Zhao, P.X. (2010). TrichOME: A comparative Omics database for plant trichomes. Plant Physiol. 152: 44-54. Schilmiller, A.L., Miner, D.P., Larson, M., McDowell, E., Gang, D.R., Wilkerson, C. and Last, R.L. (2010). Studies of a biochemical factory: Tomato trichome deep expressed sequence tag sequencing and proteomics. Plant Physiol. 153: 1212-1223.

Companion cell

mRNA

proteinproduct

Sieve element

Lactifer

* For example, in morphine biosynthesis, the genes, proteins and products are found in different cell types; The alkaloid biosynthetic pathway in Catharanthus roseus is also highly compartmentalized

Many specialized metabolites accumulate in trichomes, and trichome –omics databases have been developed to learn more about these “biochemical factories”


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In vitro synthesis is complicated by natural products’ extensive chirality

Reprinted with permission from Feher, M. and Schmidt, J.M. (2002). Property Distributions: Differences between drugs, natural products, and molecules from combinatorial chemistry. J. Chem. Inf. Comput. Sci. 43: 218-227, copyright 2002 American Chemical Society. Facchini, P.J., Bohlmann, J., Covello, P.S., De Luca, V., Mahadevan, R., Page, J.E., Ro, D.-K., Sensen, C.W., Storms, R. and Martin, V.J.J. (2012). Synthetic biosystems for the production of high-value plant metabolites. Trends Biotechnol. 30: 127-131. See also De Luca, V., Salim, V., Atsumi, S.M. and Yu, F. (2012). Mining the biodiversity of plants: A revolution in the making. Science. 336: 1658-1661. Image source NASA.

Natural products have many chiral centers that are hard to reproduce synthetically. Engineered natural systems can produce high yields of compounds with appropriate stereochemistry

Metabolic engineering of natural systems is an important method for the production of plant-derived medicines


Metabolic engineering can increase yields and make novel compounds

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Once a biochemical pathway is identified, it can be altered

Gene functions can be silenced by RNAi, mutations, viral-induced gene silencing or natural variations

Gene functions can be added or augmented by environmental or transgenic manipulations


The metabolic pathway can be introduced into other organisms

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Bacteria and yeast are widely used as chemical factories for the production of high value compounds, but plant cell cultures are used also

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There are pros and cons to plant and microbial cells

Reprinted by permission from Macmillan Publishers Ltd from Leonard, E., Runguphan, W., O'Connor, S. and Prather, K.J. (2009). Opportunities in metabolic engineering to facilitate scalable alkaloid production. Nat. Chem. Biol. 5: 292-300.

Metabolic engineering

Metabolic engineering

Plant cells have pre-existing transcription factors (tfs) and intermediates, but also more types of organelles. Over (green)- or under (red)-expression of genes can have predicted or unintended consequences

To produce a plant specialized metabolite in yeast, often the whole pathway must be introduced (and engineered for efficient expression in yeast), and the necessary precursor (X) provided.


Many medicinal metabolites have been objects of pathway engineering

De Luca, V., Salim, V., Atsumi, S.M. and Yu, F. (2012). Mining the biodiversity of plants: A revolution in the making. Science. 336: 1658-1661.

In bacteria and yeast (black)

In yeast (blue)

In plants (green)

Rare non-opioid pain reliever; higher desirable candidate for engineering


Reprinted by permission from Macmillan Publishers Ltd from Keasling, J. (2008). From yeast to alkaloids. Nat Chem Biol. 4: 524-525; Hawkins, K.M. and Smolke, C.D. (2008). Production of benzylisoquinoline alkaloids in Saccharomyces cerevisiae. Nat. Chem. Biol. 4: 564-573.

Example: Metabolic engineering for

alkaloid production in yeast

Black arrows indicate normal pathway in plant cells. The pathway engineered in yeast used plant enzymes (red and blue arrows) and a human enzyme (purple) to produce several important alkaloids


Metabolic engineering in plants and plant cell cultures

Reprinted by permission from Macmillan Publishers Ltd from Roberts, S.C. (2007). Production and engineering of terpenoids in plant cell culture. Nat. Chem. Biol. 3: 387-395; Muñoz-Bertomeu, J., Arrillaga, I., Ros, R. and Segura, J. (2006). Up-regulation of 1-ceoxy-d-xylulose-5-phosphate synthase enhances production of essential oils in transgenic spike lavender. Plant Physiol. 142: 890-900..

Enzymes affecting the production of terpenoids, phenolics and alkaloids have been enhanced or modified in cell cultures and whole plants

As an example, increasing the production of the terpenoid precursor isopentenyl diphosphate (IPP) can lead to sweeter smelling lavender


Naturally decaffeinated coffee can be made by RNAi-mediated silencing

Reprinted by permission from Macmillan Publishers Ltd. From Ogita, S., Uefuji, H., Yamaguchi, Y., Koizumi, N. and Sano, H. (2003). RNA interference: Producing decaffeinated coffee plants. Nature. 423: 823-823.

Extracts from plants transformed with short (black) and long (grey) RNA interference constructs

7-methylxanthine

theobromine

caffeine

Theobromine synthase

Caffeine synthase

Transgenic silenced plants produced less theobromine and also less caffeine than controls

Theobromine synthase was silenced in coffee plants by RNA-intereference


“Gilding the periwinkle” – enhancing its diversity of alkaloid production

Reprinted by permission from Macmillan Publishers Ltd from Runguphan, W. and O'Connor, S.E. (2009). Metabolic reprogramming of periwinkle plant culture. Nat. Chem. Biol. 5: 151-153.

Example 1. A point mutation (V214M) in strictosidine synthase expands its substrate specificity so it accepts halogenated substrates, leading to the production of novel, halogenated products. The additional substrates and products are shown in blue


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“Gilding the periwinkle” – enhancing its diversity of alkaloid production

Reprinted by permission from Macmillan Publishers Ltd from Runguphan, W., Qu, X. and O'Connor, S.E. (2010). Integrating carbon-halogen bond formation into medicinal plant metabolism. Nature. 468: 461-464.

Example 2. Introducing bacterial tryptophan-modifying enzymes (red) means that new strictosidine synthase substrates are produced in vivo (and new products)


Recognizing the value of and protecting biodiversity

Lew Diehl, Bugwood.org; http://www.cites.org

Goldenseal (Hydrastis canadensis) is being seriously overharvested and is on the CITES (Convention on International Trade in Endangered Species) list of threatened plants

Worldwide, between 50,000 and80,000 flowering plants are usedmedicinally. Of these, at least15,000 may face extinction due tooverharvesting and habitat loss.


"Peru offers a branch of

cinchona to Science”

In past centuries, explorers, scientists and botanists freely collected materials without compensating the people whose lands they were studying

This sense of entitlement is evident in this illustration


See Cordell, G.A. (2000). Biodiversity and drug discovery — a symbiotic relationship. Phytochem. 55: 463-480; Blaustein, R. (2006) Genetic resources and the convention on biological diversity. BioScience. 56: 560-563 (Photo by Phyllis Coley); Kursar, T.A., Cabellero-George, C.C., Capson, T.L., Cubilla-Rios, L., Gerwich, W.H., Gupta, M.P., Ibañez, A., Linington, R.G., McPhail, K.L., Ortega-Barría, E., Romero, L.I., Solis, P.N., and Coley, P.D. (2006) Securing economic benefits and promoting conservation through bioprospecting. BioScience 56: 1005-1012; Convention on Biological Diversity – Nagoya Protocol on Access and Benefit-sharing.

The Convention on Biological Diversity asks for the “fair and equitable sharing of the benefits arising out of the utilization of genetic resources”

Can bioprospecting and equitable sharing promote conservation?

In other words, compensate people who are good stewards of biodiversity for their stewardship


Health care for all

Credit: Theresia Hofer, Mark de Fraeye Wellcome Images

Throughout much of the world, herbal medicines are the foundation of healthcare. Can science improve healthcare as dispensed in its traditional manner?


The World Health Organization provides invaluable information

Photo credits: World Health Organization

Since 1999, WHO has published 116 monographs on selected medicinal plants

Each monograph includes information about the plant’s appearance, synonyms, chemical constituents, medicinal uses, cautions, and references


Medicine’s future draws from Western and traditional medicines

World Health Organization; Adapted from Cheng, Y.-C. (2011) Why and how to globalize traditional Chinese medicine. J. Tradit. Complement. Med. 1: 1 - 4.

The two systems of traditional and Western medicine need not clash…. they can blend together in a beneficial harmony, using the best features of each system, and compensating for certain weaknesses in each

Dr Margaret Chan, Director General of WHO

Traditional Knowledge

Zoopharmacognosy

Phytochemical studies

In vitro assays

GC‐MS

Genomics and metabolomics

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Summary

Plants produce many chemicals that can benefit human health

Traditional and modern methods can each contribute to finding and optimizing the use of these phytochemicals

Drawing by Gracia Lam and reprinted by permission from Macmillan Publishers Ltd: from Xu, Z. (2011) One step at a time. Nature 480: S90 – S92


Future directions

Western medicine

Traditional medicine

Ethnobotany

Phyto-chemistry

Medicinal plants

Finding, optimizing and using plant-based medicines to treat human ailments requires many types of expertise

Finding new drugs to treat emerging diseases and chronic diseases is of particular interest

Documents

The Plant Cell, January 2013 © 2013 1/12/2013 The … · Water of white lilies: ... The pain-relieving properties of opium have been known for millennia Opium is the dried latex