Download Plant secondary metabolites

Maximizing phytonutrient content:
Research and perspective
Guido Mase’ 2016
Plant chemistry:
- “Primary” metabolites
- Proteins (structure/enzyme)
- Carbs (energy)
- Fats (energy storage)
Plant chemistry:
- “Secondary” metabolites
- Phenolics
- Terpenoids
- Alkaloids
- …and more!
Insecticide hypothesis:
Dethier 1954
Fraenkel 1959
“Co-evolution” hypothesis:
Erlich & Raven 1964
“Co-evolution” hypothesis:
Erlich & Raven 1964
Is it really an “arms race”?
Carbon / nutrient balance hypothesis:
• Secondary metabolites are often
hydrocarbons, rich in carbon
• When abundant nutrients are available,
growth is preferred (primary met)
• When nutrients are low, carbon
metabolism increases (secondary met)
Bryant 1983
Growth rate hypothesis:
• As growth rate decreases,
secondary metabolites increase
Coley 1985
Growth/Differentiation Balance hypothesis:
• If growth rate decreases, but
photosynthesis stays high, carbon is
diverted to secondary metabolites.
Wilkens 1996, 1997
We’ve known about this “bell curve” of secondary plant metabolite
production for a long time.
Jonathan Gershenzon 1985: Phytochemical Adaptations to Stress
Most likely all secondary plant metabolite production hypotheses
are interrelated and relevant. But I’d like to propose another to add:
Is it really an “arms race”?
No. We’re working together
to support each other and
the ecology
Bioflavonoids (such as morin)
• First produced when plants emerged from
the ocean.
• UV protection, reduces DNA damage
• Had initial browsing deterrent effects
• Later, co-evolution often led to these
molecules becoming useful mediators of
symbiotic connections
• NOW, we depend on them!
Bioflavonoids (such as morin)
• First produced when plants emerged from
the ocean.
• UV protection, reduces DNA damage
• Had initial browsing deterrent effects
• Later, co-evolution often led to these
molecules becoming useful mediators of
symbiotic connections
• NOW, we depend on them!
High bioflavonoid intake = lower rates of chronic disease
Knekt 2002
Bioflavonoids (such as morin)
• First produced when plants emerged from
the ocean.
• UV protection, reduces DNA damage
• Had initial browsing deterrent effects
• Later, co-evolution often led to these
molecules becoming useful mediators of
symbiotic connections
• NOW, we depend on them!
High bioflavonoid intake = lower rates of breast cancer
Shu 2009 (JAMA)
follow-up in 2012 (Am. Journ. Clinical Nutrition)
- Specifically for isoflavones, a secondary metabolite in legumes
Isoflavones:
Necessary signals for
nitrogen-fixing bacteria to
colonize legume roots
Rolfe 1998
Isoflavones:
Carefully choreographed
“dance” between plant and
bacteria, with plant
secondary metabolites as
choreographers.
Subramanian 2007
Isoflavones:
By eliminating an
isoflavone reductase gene,
nodulation is severely
impaired
Ripodas 2013
Secondary plant metabolites are bioremediation agents:
• Clear polycyclic aromatic hydrocarbons (Chen & Aitken 1999)
• Metabolize and clear PCBs (Singer 2000)
… degradation, not bioaccumulation, via coordination of microbial
metabolism and activity!
Secondary plant metabolites are bioremediation agents:
• Even ground-up plant material rich in secondary metabolites cleans
the soil: pine needles, orange peel, ivy leaves (Hernandez 1997)
… degradation, not bioaccumulation, via coordination of microbial
metabolism and activity!
Plant secondary metabolites:
- Not for “war”
- Way more than just defense
- Health benefits not a
“coincidence”!
- Cross-kingdom signals used
to choreograph ecological
function
Plant secondary metabolites:
- They are essential!
- Problem:
Almost universally, these
molecules are bitter-tasting
Over time, we have:
- Bred plants to taste less bitter
- Stimulated growth with extra fertility
Results:
- Lower phytonutrient density
- Primary metabolites / yield have been favored
Jo Robinson, 2013
Results:
- Wild olive trees have consistently greater
polyphenol content (but lower yields!)
Giovanna Massei, 2000
Christina Warinner, 2013 TEDEx talk:
“Debunking the paleo diet”
We need a different approach:
• Perhaps different cultivation ideas
geared less to “high yield”
• Plants as partner, not commodity
Secondary plant metabolites are induced by stress:
Pine, Artemisia annua, basil
Turtola 1995
Secondary plant metabolites are induced by stress:
But excessive stress so minimizes yields as to be
impractical (and less chemistry overall)
Weiss 1997
Increasing CO2 in the environment increases
secondary plant metabolite production
Zobayed 2003
Decreasing water leads to a 70-fold increase in
some metabolites, 2.5x more antioxidant
capacity
Zobayed 2005, Charles 2005
Decreasing water consistently elevates secondary
metabolites in an inverse relationship
Aznar 2011
Decreasing water consistently elevates secondary
metabolites in an inverse relationship
Aznar 2011
Sage grown in more arid conditions has higher
concentrations of secondary metabolites, especially
terpenes
Selmar 2008
Decreasing water available to sage plants elevates
the concentrations of secondary metabolites reliably
and consistently
Selmar 2013
Decreasing water available to sage plants elevates
the concentrations of secondary metabolites reliably
and consistently (old leaves and young leaves)
Selmar 2013
Effects of drought stress and/or nutrient deprivation stress on phytonutrients
Effects of drought stress and/or nutrient deprivation stress on phytonutrients
Effects of drought stress and/or nutrient deprivation stress on phytonutrients
UV Radiation stress:
Gotu Kola produces more bioflavonoids and
saponins in response to moderate UV stress
Muller 2013
Role of fertilizers / nutrients:
Higher levels of nitrogen and phosphorus
reduce secondary metabolite production
(particularly in rhizosphere – less mycorrhizal
cross-signaling molecules)
Yoneyama 2013
Role of fertilizers / nutrients:
But good levels of potassium seem to be
important for medicinal plants to weather
stress effectively, maintain phytonutrient levels
Devi 2011
Implications:
Implications:
• Plants know what they’re doing (most likely
better than we do)
• This implies a measure of trust in our partners
Implications:
• Plants provide benefit to soil, ecology, environment
Implications:
• Plants provide benefit to soil, ecology, environment
• Bacterial symbionts, mycorrhizae
Implications:
• Plants provide benefit to soil, ecology, environment
• Pollinators
Implications:
• Plants provide benefit to soil, ecology, environment
• Humans
Implications:
• Medicinal plants seem to benefit from “benign neglect”
Implications:
• Medicinal plants seem to benefit from “benign neglect”
• Relatively less nitrogen, phosphorus (N,P)
• Normal potassium (K)
• Try:
• topsoil with only a little compost on the surface
• Jersey Greensand (K, minerals, and slow-release P)
Implications:
• Medicinal plants seem to benefit from “benign neglect”
• Lower water if possible
• High drainage (raised areas and/or swales)
• NO irrigation (depending on climate)
• SALT?? (50 mM, approx 3g/L)
Implications:
• Medicinal plants seem to benefit from some browsing
• Allow some insect activity (hard not to!)
• Mowing / cutting naturalized perennials on rotation
• Harvest and make plant medicine!
Plant secondary metabolites:
- Not for “war”
- Way more than just defense
- Health benefits not a
“coincidence”!
- Cross-kingdom signals used
to choreograph ecological
function
Thank you.