Neotropical Pharmacy

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Neotropical Pharmacy

• Very few leaves have insect damage. Why?
• Blackrivers are black. Why?
• Leaves are constantly exposed to dangers,
  whatever the source

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Neotropical Pharmacy

• In one study, it was estimated that the Amazon
  rainforest produced 900 metric tons per ha.
• The mass of all animals was estimated to be a
  mere 0.2 ha (0.02 of plant biomass)

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Neotropical Pharmacy

• Very few secondary consumers (herbivores - 7)
• Compare this to 19 eating living or dead wood
  (termites)
• 50 ate only dead vegetation
• 24 some sort of carnivore
• Why so few herbivores??

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Neotropical Pharmacyplant defense compounds

• Drugs, drugs, drugs
• Leaves of both tropical and temperate zone plants
  are abundantly full of noxious chemicals
• the world is not colored green to the
  herbivores eyes, but rather is painted morphine,
  L-DOPA, calcium oxalate, cannabinol, caffeine,
  mustard oil, strychnine, rotenone, etc Janzen

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Neotropical Pharmacyplant defense compounds

• Most of these chemicals are termed secondary
  compounds because most seem to lack a direct
  metabolic function, such as those in
  photosynthesis (also called allelochemics for
  defense at large)

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Neotropical Pharmacyplant defense compounds

• Their origin may have been by chance, with each
  combination potentially providing a little better
  defense
• As a result, most plants dont just have a single
  compoundWhy?
• Most have several, primarily to protect against
  herbivores, bacteria and/or fungi

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Neotropical Pharmacyplant defense compounds

• Alkaloids are among the most familiar and
  addictive drugs known
• Such drugs as cocaine (from coca), morphine
  (opium poppy), cannabidiol (hemp), caffeine (teas
  and coffees), and nicotine (tobacco) There are
  over 4,000 known alkaloids from 300 families and
  7,500 sp
• About 20 of temperate sp contain them

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Neotropical Pharmacyplant defense compounds

• Alkaloids have a bitter taste (to mammals) and
  tend to disrupt liver and cell membrane function
• May also cause cessation of lactation, abortion,
  or birth defects
• Clearly many are addictive!!

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Neotropical Pharmacyplant defense compounds

• For example, caffeine has been shown to
  discourage insect feeding
• So is it a stimulant to us, an insecticide!

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Neotropical Pharmacyplant defense compounds

• Phenolic compounds are often abundant in plants
• One group adds the pungency to many of well-known
  spices and tannins provide the basic compounds
  used in tanning leather
• Particularly abundant in oaks and mangroves

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Neotropical Pharmacyplant defense compounds

• Work on Cecropia indicate young trees have high
  levels but older plants have less
• Plants in shade had lessso what?
• In field experiments, plants with low levels
  suffered 2x the herbivory
• More leaves, less toxin per leafso what

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Neotropical Pharmacyplant defense compounds

• Phenolics are small proteins stored in cell
  vacuoles that are broken when an insect or other
  herbivore bites the leaf
• Upon release, the phenols combine with various
  proteins, including those enzymes necessary for
  splitting polypeptides (parts of proteins) in
  digestion, perhaps making it more difficult for a
  herbivore to digest protein

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Neotropical Pharmacy plant defense compounds

• It is thought leaf damage by insects or pathogens
  may stimulate production of phenolics
• However, not all insects are bothered by these
  compounds (e.g. leafcutting ants)
• They may be more valuable against microbes and/or
  pathogens

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Neotropical Pharmacy plant defense compounds

• Saponins are soaplike compounds that are
  relatively common in tropical plants and act to
  destroy the fatty component of the cell membrane.
  Some indigenous people utilize saponins to poison
  and capture fish, interfering with respiration

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Neotropical Pharmacy plant defense compounds

• Cyanogenic Glycosides (cyanide sugar)
• When the sugar is digested, the sugar is released
  leaving the hydrogen cyanide
• Consequently, these plants are avoided by many
  species of herbivore

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Neotropical Pharmacy plant defense compounds

• Passionflowers, fed upon by caterpillars of
  Heliconius butterflies, have a relatively high
  load
• Each species can detoxify one or two cyanogenic
  glycosides, and thus specialize on these species

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Neotropical Pharmacy plant defense compounds

• Some strains of manioc have high concentrations
  of cyanogenic glycoside in the root
• To eat this, root must be washed thoroughly

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Neotropical Pharmacy plant defense compounds

• Cardiac Glycosides interfere with heart function.
  Digitalis, from the temperate zone plant foxglove
  and members of the milkweed family

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Neotropical Pharmacy plant defense compounds

• Terpenoids area a complex group of fat-soluble
  compounds that include monoterpenoids,
  diterpenoids, and sesquiterpenoids. Some are used
  in the synthesis of compounds that may mimic
  insect growth hormones or can be modified into
  cardiac glycosides
• Some discourage both insects and fungi
  (especially those that ants culture)

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Neotropical Pharmacy plant defense compounds

• Toxic Amino Acids are common in the bean and pea
  families and interfere with normal protein
  synthesis
• Some are strong hallucinogens (e.g. L_DOPA)

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Neotropical Pharmacy plant defense compounds

• Among the most familiar tropical plants are
  philodendrons in the arm family
• In the US, we have skunk cabbage, and these
  plants contain crystals of Calcium Oxalate, a
  caustic substance that makes the delicate tissues
  of the mouth burn

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Neotropical Pharmacyother defenses

• Latex is another form of defense
• For those species who have developed chemical
  defense, adhesion to mouth parts is a strong
  defense

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Neotropical Pharmacyother defenses

• Other species may be spiny or thorny or have
  leaves coated with diminutive bed of nails
  called trichomes that sometimes impale
  caterpillars
• Even serrated leaves can be an effective
  deterrent for some predators

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Neotropical Pharmacyother defenses

• Leaf toughness, nutrition value and fiber content
  also affect ability to resist herbivores
• In general, young leaves are eaten more than
  older leaves, even when phenols were present
  suggesting other factors could be quite
  influential

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Neotropical PharmacyLatitudinal Trends

• Levin (1976) made a detailed study of the
  geographic distribution of alkaloid-containing
  plants
• Groups of herb, shrub, and tree species each
  contained a significantly greater percentage of
  tropical species with alkaloids (27-45)

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Neotropical PharmacyEcological Trends

• Although defense compounds occur in species that
  occupy virtually all habitats, there are some
  trends
• Tropical lowland forests, mangrove swamps,
  deserts, and mountain rain and cloud forests are
  all habitats where defense compounds are abundant
• Alpine forests and grasslands, as well as
  disturbed areas have few such plants

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Neotropical PharmacyEcological Trends

• Defense compounds are abundant in lowland forest
  occurring on nutrient poor white, sandy soil
  forests, in the northern Amazon
• Replacing leaves are expensive and consequently,
  are long-lived and have extremely high
  concentrations of defense compounds

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Neotropical PharmacyEcological Trends

• Ultimately, leaves must be leached of compounds
  so they can be broken down
• What else do we find associated with this area?

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Neotropical PharmacyEcological Trends

• Areas undergoing ecological successin tend to
  have species that invest in defense compounds
  differently from those on poor soil
• Most successional species are racing to maximize
  their rates of growth
• They synthesize phenolics, cyanogenics and
  alkaloids, albeit in low concentrations,
  suggesting a low energy cost to do so

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Neotropical PharmacyEcological Trends

• Contrasting strategies may simply reflect the
  resource availability
• E.g. on sites where are poor, expensive, long
  lasting defense compounds are favored and on rich
  sites, cheaper, shorter-lived defense compounds
  are favored because the tree is able both to
  devote sufficient energy to rapid growth and
  replace defense compounds as needed

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Neotropical PharmacyEcological Trends

• As a result, many early-successional species are
  subject to herbivore damage.

• Janzen has estimated insect density may be 5-10x
  higher in successional areas

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Neotropical PharmacyPlants vs. Monkeys

• Most monkeys are vegetarians
• However, they are surrounded by beautiful leaves,
  only of which a small subset are palatable

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Neotropical PharmacyPlants vs. Monkeys

• The serendipitous adventure of Kenneth Glander
• He saw a mantled howler monkey fall 10m from a
  tree
• What would your thoughts be?

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Neotropical PharmacyPlants vs. Monkeys

• She was eating from the madera negra tree, which
  local use to obtain rotenone
• He spent 5,000 hrs watching howlers and maked
  1,699 trees to see what they were eating

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Neotropical PharmacyPlants vs. Monkeys

• Not surprisingly, monkeys are extremely selective
  in their feeding
• Of the 149 madera negra trees in the study area,
  the troop only fed on 3 trees!
• Not surprisingly, these three trees were found to
  have leaves free of alkaloids and cardiac
  glycosides, which are normally very high in this
  species

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Neotropical PharmacyPlants vs. Monkeys

• Glander found that mantled howlers tended to
  favor young leaves that are relatively high in
  nutritional value but have not yet become loaded
  with defense compounds
• But when given little choice, they eat a few
  mature leaves and move to another tree. Why?

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Neotropical PharmacyPlants vs. Monkeys

• Milton, studying on BCI, suggested that it was
  the relative amounts of protein ad fiber content,
  not secondary compounds
• These individuals tended to favor leaves that had
  a higher protein to fiber ratio

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Neotropical PharmacyPlants vs. Insects

• How do those little herbivorous insects cope with
  all the compounds??
• One approach is to become highly specialized on
  just a few kinds of plants
• Being so small, most insects, including temperate
  species, can afford to become dietary specialists

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Neotropical PharmacyPlants vs. Insects

• E.g. heliconius caterpillars feed exclusively on
  the vines of passionflowers
• The author discusses the complete defoliation of
  a single tree while all surrounding plants
  remained untouched

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Neotropical PharmacyPlants vs. Insects

• Imagine if an insect were able to detoxify
  defense compounds (or sequester them), they could
  focus on that particular species and do quite
  well
• Also, if other species cant detoxify the species
  in question, you may have a potential monopoly on
  this species

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Neotropical PharmacyPlants vs. Insects

• Of course, there are generalists as well
• How do these guys get away with being generalists?

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Neotropical PharmacyPlants vs. Insects

• Brachid Beetles provide examples of both feeding
  specialization and adaptation to host defenses
• Bruchids are seed predators, especially on
  legumes
• Females lay eggs on seed pods or directly in
  seeds and larvae enter pods upon hatching and
  feed on seeds before pupating

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Neotropical PharmacyPlants vs. Insects

• In a survey of Bruchidae, Curclionidae, and
  Cerambycidae, about 75 of the species fed on a
  single plant species
• Only about 12 fed on 3 or more sp
• Bruchids are widespread and encounter a variety
  of potential hosts
• However, there are local races adapted to a
  particular species

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Neotropical PharmacyPlants vs. Insects

• Consider the Arms race with Bruchids
• Some hosts evolve toxic seeds, bruchids either
  avoid them or become resistent
• Some seed pods produce sticky gum following
  penetration of bruchid larvae
• Bruchids arrest development until seeds mature
  and it is too late for pods to produce gum

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Neotropical PharmacyPlants vs. Insects

• Some seed pods flake, removing eggs
• Bruchids oviposit beneath the flaking
• Some pods fragment or explode
• Bruchids oviposit directly on the seed
• Some seeds remain very small, then grow quickly
  just prior to dispersal
• Bruchids enter and eat immature seeds or delay
  development, eating the bigger, mature seeds

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Neotropical PharmacyPlants vs. Insects

• Both temperate and tropical butterflies are known
  for their affinities for feeding on specific
  plant families
• Caterpillars are usually much more selective than
  adults, who are feeding on nectar and aiding in
  pollen dispersal
• Furthermore, adults and juveniles have very
  different relationships with plants

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Neotropical PharmacyPlants vs. Insects

• Heliconid Butterflies and Passionflowers
• A relatively exclusive relationship
• Passionflowers contain various cyanogenic
  glycosides and cyanohydrins, probably a response
  to strong herbivory by heliconids
• In addition, many species of passionflower have
  recruited ants

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Neotropical PharmacyPlants vs. Insects

• Additional adaptations

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Neotropical PharmacyPlants vs. Insects

• One species of passionflower is winning as it is
  covered by minute hooked spines called trichomes
• As a result, caterpillars become impaled
• What should they do?
• E.g. Mechantis isthmia and tomatoes

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Neotropical PharmacyEthnobotany Ethnozoology

• Native peoples (locals) in te tropics have much
  experience dealing with some of the toxins of the
  tropics
• Consider manioc it grows well in poor soil, but
  also concentrates defenses like other plants
  growing in poor soils (specifically cyanogenic
  glycosides)
• Must grate it, soak it, and dry it

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Neotropical PharmacyEthnobotany Ethnozoology
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Neotropical PharmacyEthnobotany Ethnozoology

• What toxins are useful?
• Chemicals have been extracted for use in arrow
  (or dart) poisons, hallucinogens, fish poisons,
  drugs for medical and related use, stimulants and
  spices, oils and pigments
• Many plants we just dont know about (e.g. in
  Brazil,

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Neotropical PharmacyEthnobotany Ethnozoology

• Many of our good drugs come from this region
• E.g. quinine, from the alkaloid-laiden Cinchona
  bush, is reasonable against several malarias
• Resin extracts from Virola, a powerful
  hallucinogen, appears to be very effective in
  combating tropical fungal infections

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Neotropical PharmacyEthnobotany Ethnozoology

• Ethnobotany has huge conservation potential
• Consider the formation of the Belize Association
  of Traditional Healers
• Have established a 2,400 reserve where
  cultivation and studying medicinal plants is the
  primary goal

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Neotropical PharmacyEthnobotany Ethnozoology

• The Healing Forest (Schultes and Raffauf) discuss
  approximately 1,500 species and variants of
  plants
• 38 plants for diarrhea, 25 for headache, 18 for
  muscular aches, 38 for toothache, many for insect
  bites, 29 for snakebites, 26 for contraceptives

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Neotropical PharmacyEthnobotany Ethnozoology

• In addition, others are alleged to aid in
  sinusitis, bleeding gums, stomach ulcers,
  cataracts, asthma, swollen breasts, epilepsy,
  testicular swelling, tumors, boils, blisters,
  mange, and baldness

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Neotropical PharmacyEthnobotany Ethnozoology

• Curare, first discovered by Charles Wateron in
  1812, is used in hunting and is a powerful muscle
  relaxent
• There are a number of plants (lianas) in which
  this extract can be derived
• Still commonly used in surgeries

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Neotropical PharmacyEthnobotany Ethnozoology

• Cocaine is a powerful and addictive narcotic
  (alkaloid)
• While a problem here, it is used abundantly in
  the tropics

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Neotropical PharmacyEthnobotany Ethnozoology

• E.g. ingestion of 100g of coca leaves is
  sufficient to supply ones daily needs for
  calcium, iron, phosphorus, and vitamins A, B2,
  and E.
• It also suppresses fatigue and altitude sickness
  and is frequently used by Andean peoples

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Neotropical PharmacyEthnobotany Ethnozoology

• Nutmegs are probably the best-known hallucinogens
  in the Neotropics
• Frequently used in spiritual divination to
  ritualistic diagnosis and treatment of disease

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Neotropical PharmacyPlants vs. Insects