BIOSCI 152 1st Edition Lecture 21Secondary Compounds and Medicinal PlantsLearning ObjectivesAfter suitable revision, you should be able to• • Understand the difference between primary and secondary metabolism • recognize a definition of a secondary compound • List the things against which plants need to defend themselves • Explain the key components of plant defense against microbial pathogens • Know the types of compounds which are important secondary compoundsin plants • Recognize the names of some medicinal plants Vocabulary Virus EchinaceaPrimary metabolism Fungi WintergreenSecondary metabolism Bacteria YewAlkaloids Hypersensitive TaxolN-containing response Gingercompounds methyl salicylate DigitalisPhenolics Methyl jasmonate St John’s wortTannins S-containing ValerianPhytoecdysones compounds Ginsengherbivory AlliumsSustainable harvestingMicrobial pathogen Gingko bilobaPrimary and Secondary metabolism – synthesis of metabolites through core processes – photosynthesis, nutrient assimilation, synthesis of amino acids, nucleotides, lipids, carbohydrates etc, respiration, growth – common to all plants!Secondary Metabolism production of compounds required for non-essential functions• May be different between different plant species e.g. flower petal colors (flavanoids)In-class exerciseSecondary compounds function in defense against microbial pathogens (chapter 28)• Some compounds prevent infections • Salicylic acid and methyl salicylate (related to aspirin) …. fight microbialpathogens • Methyl-jasmonate –volatile (airborne) signal – alerts mutualistic wasps,other plants • Methyl-jasmonate –volatile (airborne) signal – alerts mutualistic wasps,other plants e.g. Tomato Hornworm and Braconid Wasps ••Hypersensitive Response Fig. 28.1, 28.3• Proteins on pathogen recognized on plant cell surface • Signaling molecules direct genetic response • Production of compounds which attack pathogen • Pathogen and cells in contact with pathogen killed with oxidative stress • Necrotic cell lesions seal off damage, protecting rest of leafSystemic acquired resistance• Methyl salicylate (volatile) released intothe air • Jasmonic acid – transported to restof plant via phloem Fig. 28.6Signals (e.g. jasmonate) passed from damaged to other plant areas via phloem Fig. 28.6Anti-herbivory compounds• What do they do to herbivores??? • Phytoedysones – found in many plants e.g. Podocarpus macrophyllus (Japanese yew) -Mimic compounds involved in regulating insect molting • Phenolic compounds in plants interrupt mammalian digestion – unpalatablefood source • Cyanide in bracken fern Not all plants produce the same secondary compounds…Medicinal Plants• Contain particular chemical compounds (secondary metabolites) • Leaves, flowers, fruits, roots, bark, extracts… • Ancient and long-term traditional uses (by native peoples…) –healing, recreational ‘drugs’, poisoning, spiritual aids • Basis for many recreational and socially acceptable drugs - Caffeine,Cocaine, Nicotine Drugs from Plants• Basis for many medicinal drugs e.g. opiate narcotics – morphine,oxycodon, codeine (methyl-morphine ) …… heroin• most powerful analgesics (disrupt nerve function) • ‘Numb’ a herbivore? Medicinal PlantsDisclaimer…. DON’T TRY THIS AT HOMEPlants contain powerful chemicals - some are highly poisonous.Just because they are ‘natural’ doesn’t make them safe!Very few in use have undergone clinical trials!!! (FDA certification)World Health Organization (WHO) -No clinical evidence for most herbal medicines – further research needed to determine benefits and safetyUnregulated or inappropriate use of traditional medicines can be dangerous– e.g. the herb “Ma Huang” (Ephedra) is traditionally used in China to treat respiratory congestion. In the US, the herb was marketed as a dietary aid -overdosage led to heart attacks, strokes, >12 deaths. – In Belgium, >70 people required renal transplant or dialysis for kidney damage after taking a herbal preparation made from the wrong plantspecies.Plants with medicinal properties often need careful preparation and dosage controlMedicinal plants often interfere with other drugs e.g. St John’s Wort reduceseffect of contraceptivesOnly use certified preparation from a herbalist, herbal supply company and consult a health-care professional for correct application and dosagehttp://www.who.int/mediacentre/factsheets/fs134/en/Examples of medicinal plants covered in lecture and available in pdf of powerpoint supplementary file (after lecture)Sustainability of global medicinal plant market…?• Commercial benefits of growing medicinal plants market -threatening biodiversity through over-harvesting • May lead to the extinction of endangered species, destruction ofnatural habitats • Traditional knowledge of herbal medicines not protected under currentinternational patent laws – profits only to the exploiters • International treaty: Convention for International Trade in Endangered Species(CITES) • Cultivation rather than wild harvesting…? Referenceshttp://plants.usda.gov/http://www.who.int/mediacentre/factsheets/fs134/en/http://www.chm.bris.ac.uk/motm/digitalis/digtalis.htmBooks –A Field Guide to Medicinal Plants and Herbs: Of Eastern and Central North America (Peterson Field Guides (R)) James A. Duke, Steven Foster, RogerTory PetersonUnderstanding Medicinal Plants: Their Chemistry And Therapeutic Action. BryanHansonThe Constituents of Medicinal Plants: An Introduction to the Chemistry and Therapeutics of Herbal Medicine. Andrew Pengelly and Kerry Bone.Summary• Primary metabolism – primary functions in all plants(photosynthesis, respiration, protein synthesis…) • Secondary metabolism – compounds not essential for life; unique todifferent groups of plants – herbivore protection, pathogen defenses • Drugs and healing compound from plants – alkaloids, N-containing compounds, phenolics, steroids • Plant products can be powerful, many are poisonous – use carefully! • Medicinal plant market expanding rapidly – threats to global plant diversity, traditional knowledge often not rewarded – sustainable harvesting or farming