final Flashcards
Diterpenoids
Not as volatile as Sesquiterps.
e.g., They will stay in rosin as terpentine is distilled away
They are difficult to separate and analyze
Mostly cyclics with a few acyclics
1 to 5 ring compounds
From head to tail condensation of IPP + FPP
In some cases it is FPP + DMAPP
Phytol
Diterpenoids
Esterified to porphyrin ring of chlorophyll
Thus, Chlorophyll is one of the most abundant terpenoids
Phytol confers lipid solubility to Chlorophyll
evolutionarily early presence terpenoids and chloropphyll
Also precursor to Vitamins E and K
phorbols
Diterpenoids
Found in croton oils from seeds of Euphorbiacea
anti-leukemic compounds
Important uses in cancer research
Often esterified to C12 fatty acids - esterified compounds are potent carcinogens
4 rings
Gibberellins (GA)
Over 50 C20 and C19 GAs known
Plant growth hormone that causes plants to grow / germinate
ent-Kaurene is an intermediate in GA synthesis
The “ent” seen as the relative stereo chemistry at positions 5 and 10 on the compound But they are enantiomers
onlly ent -kaurene is used to produce GA
GA properties
Promotes flowering Stem Growth Breaking dormancy Enzyme synthesis Fruit development
GA commercial Uses
Commercial uses
Induces malting in barley. In partially germinated barley; Hydrolysis of starch to sugar; Used in brewing to sustain fermentation
Increases sugar cane yield; increases stock growth; 60 g/acre increases yield by 0.5 ton/acre (~10 %)
Triterpenoids are divided into…
Triterpenoids can be conveniently divided into: (a) true triterpenoids, (b) steroids, (c) saponins, and (d) cardiac glycosides.
common triterps
Pentacyclics are very common, e.g. those found in waxy coatings on leaves and fruits, in bark and some resins. Also found in petroleum, especially waste products of oil refining
Four & five-ring compounds are found in (a).
Pentacyclics
β-amyrin (R = Me) oleanic acid (R = COOH) (C30)
Also liminoids - C30 with bitter tastes (in citrus)
Hopanes
Hopanes – C30 compounds from cyanobacteria (photosynthetic bacteria) and plants.
Carries over to petroleum – Marker of petroleum in waste from refining and spills
Tetracyclics
form sterols and steroids. see - pathways sheet for more specifics
Saponins and properties
Diosgenin from wild yams (Dioscorea sp.) and hecogenin from Agave sp. cactus C27 sterol Surface active agents Soap-like Cause foaming – In original Hire’s Root Beer Can hemeolyze blood cells Fish poisons, anti-fungal, anti-biotic Usually in glycoside form
Solanine
Sterol alkaloid and glycoside
In green parts of potato - Potato in sunlight triggers it to make cloroplast = green
Causes Nausea/paralysis
Can be fatal
Cardiac Glycosides
In several plant species
Formed from pregnenelone
+ acetyl-CoA
Usually glycoside – with unusual sugar attached at C3
Genin name given to aglycoside (w/o sugar)
Active when sugar removed – Inhibit Na/K-pumps in cell membranes not strong enough to kill patient
Found in digitalis (foxgolve)
Bufadienolides, C24
cardiac glycosides
Toad poisons
To toxic for treatment of heart disease
In only a few plant species
how is Cardenolides, C23 (digitoxigenin)
Digitoxigenin + 3 digitoxose = digitoxin
other examples of cardio glycosides
Ouabain (strophanthin G) - Potent cardiac glycoside, A Rhamnoside
Convallatoxin (rhamnoside of strophanthidin) - Most toxic of all cardiac glycosides, Found in Lilly of the Valley - Deadly - Oleandrin, Found in oleander, Deadly if ingested
Carotenoids`
C40 Terpenoids
Carotenoids and their precursors
Widely distributed and important compounds
Biosynthesis occurs in chloroplasts of plants, algae, bacteria, and other photosynthetic organisms well as chromoplasts (e.g. tomatos and other fruit)
responsible for Yellow, red, orange colors in leaves, fruits and flowers (absorb at 400 to 500 nm)
Lipid soluble, insluble in water
Important commercial coloring agent
Not synthesized in animals - Accumulated and stored in animals – dietary intake required
n Flamingo, Starfish, Lobster, Sea Urchin; Flamingos in zoos will lose color without a dietary source of carotenoids
Sources of Vit A – Retinol; C20 alcohol
Used as a coloring agent in butter from β-carotene
flavanoids
One of the largest and most important groups of allelochemicals
Some allelopathic – Some mutually beneficial
Most from higher plants make them; animals do not make them (e.g., flavonoids that give butterflies their color come from diet)
Most water soluble - glycosolated
Absorb UV and visible light -conjugate double bonds
difference b/w flavanoids and terpenoids
Difference between flavonoids and terpenoids: there is a basic structure that all flavonoids are built from.
flavanoids characteristics
Characteristic class of compounds in plants In all parts of the plant Flower pigments UV absorbing compounds in leaf epidermi Free radical scavengers -ROS Phytoalexins – Fungicides (allelopathy) Can be used for taxonomy At one point, was used to classify plants; not so much anymore because we use DNA
12 classes of flavanoids
anthrocyanidins flavanone flavanols flavanones catechins flavan chalones dihydrochalcone isoflavones aurones dihydroflavanols flavan 3,4 diols
flavanoids common modifications
Most common modifications
Most are conjugated to sugars at the hydroxy groups on the rings
Glycosides give water solubility
Many of the anthocyanins, flavones, flavonols and flavonones are glycosylated
Many are O-methylated and O-acylated at hydroxyls
Makes the compounds lipophillic
Many chelate metals - Many of the anthocynanins that are giving flower colour have a metal attached to them, which allows for large complexes to form
Affects their spectral properties
Can be dimerized and oligomerized
Biosynthesis of flavonoids
Phenyl propanoid pathway
1 ) Phenyl alanine to 4-coumaroyl-CoA -coumaroyl-CoA is a precursor to a number products – Including flavonoids and lignins
2) 4-coumaroyl-CoA + 3 malonyl-CoA to chalcone (committal step)
3) )Oxidation and reduction of the central pyran ring to the 24 flavonoid skeletons
4) Modification of flavonoids by glycosylation, methylation, acylation, metalation and oligomerization
Flavonoid Occurance and Function
Usually in the vacuole of the cell – especially
for flower coloring and UV protection
However biosynthesis occurs in the cytoplasm
Enzymes may be associated with tonoplast membrane (the membrane around the vacuole)
During the final stage of biosynthesis, flavonoids transported into the vacuole
In vacuole, aggregates of flavonoids may form – anthocyanoplasts for flower coloring
Flavonoids also in cholorplasts (cps) and cytoplasm – important for free radical scavenging
Extracellular flavonoids – in waxey layers and cuticles (methylated flavonoids) – Fungicides & bactericides
flower colouring
Flower coloring
Cyanic color – Stability of color and basis of color variety
Main pigments - anthocyanins
Positive charge in pyran ring can be attacked by OH-
Color lost if attacked
pH of vacuole is acidic (pH ~ 4.5), somewhat protecting the + charge
However, even at pH 4.5, still enough OH- to attack + charge
To preserve color, additional protection of + charge is necessary – done by aggregation of the molecules
how are the colours of flavonoids affected by self- association
Self-association
Solutions of anthocyanins deviate from Beer’s Law as anthocyanin concentration increases
As concentration increases, Abs saturates
Either number of molecules in
solution is not increasing with
concentration or ε is changing
or both
If aggregation (self-association)
is occurring, effective concentration
does not increase in proportion
to number of molecules (dimers, trimers, etc. absorb as single molecules)
That is, aggregates absorb as a single molecule. Abs does not go up with each molecule added into solution
They stack in a planer fashion; promoting π−π interactions and hydrophobic interactions
intermolecular co-pigmentation
Exceptionally stable pigments
Acylated through glycosyl groups
Acyl group is an aromatic ring (e.g. coumaroyl, caffoyal or sinapoyl)
Still protects anthocyanin + charge
Will also change spectral properties of the pigments in the complexes – shifts λmax just like with anthocyanin aggregates
Have very deep blue colors – Heavenly blue
what are cyanoplasts
a flavonoids that is the most common in flower colourings
yellow flower comes from ….
From a combination of anthocyanins and carotenoids
how to flavanoids help protect plants from UV
Flavonoids that absorb UVB (especially flavonols) are synthesized in response to UVB
When plants are exposed to UVB, certain flavonoids are released in specific Parts.
Absorb strongly at 290 to 350 nm, screening mesophyll from UVB
who can we induce flavanoid protection in plants
grow under the conditions for 2 weeks and then extract from the plant
what are allelo-chemicals
Allelo-chemicals allow for mutual relationships between organisms for Mutual benefitand Competition
Made by plants, animals and microbes
Allows chemical signalling
Fighting off enemies
include: Flavonoids Taxol Environmental photochemistry and photobiology Photochemistry of beer
Allelopathic chemicals include…
Natural toxins
Plants are the biggest producers of allelopathic chemicals
Gives selective advantage
Considered generally safe – because they are natural – but can be as or more toxic than pollutants
Generally have evolved to be hazardous to specific competitors
outline a method for the extraction of allelo chemical
Extract from tissue with appropriate solvent – H2O or MeOH or Acetone etc.
Partial purification – Usually chromatography
Test fractions on target organism
Further purify fractions with activity
Test “pure” compounds – identify compound with activity
Mechanisms of action of a few allelopathic chemicals
Many are Phenolics, Benzoic acids, etc.
Cyanogenic glucosides, Monoterpenes, Cinnamic acid, Salacylic Acid, Arbutin, lactones, tannins, etc
Many effects – inhibit nutrient uptake (phosphate), K+ uptake, inhibit plant hormones, inhibit protein synthesis, increase membrane permeability
Especially cause tonoplast leakage (Vacuoles of plants lose water)
Wide range or effects; probably general membrane damage is the main cause
Psoralen
allelochemical
Inhibits cell division and sterilizes blood
Psoralen-DNA adducts are formed via the Diels-Alder reaction:
cross links 2 T form opposite strands
Juglone
Many natural products (natural herbicides) inhibit photosynthesis
Produced by the black walnut tree
Juglone inhibits electron transport
Inhibits photosystem II by binding to the plastoquinone site – competitively inhibits photosynthesis – has similar structure
Also inhibits CoQ reduction in mitochondria
Atrazine (herbicide) acts at same site as juglone
Other allelochemical functions
Attraction of bees to flowers - Flavonoids
Seed dispersal – Flavor, Aroma – Terpenoids; Color – Flavonoids, carotenoids
Repellants
Capsaicins in hot peppers
Production of Allelochemicals
UV radiation in sunlight
Day length – especially end of day effects from far red light – e.g., day length regulates flowering
Stress – e.g., causes synthesis of compounds that protect against oxygen radicals
Elicitors – microbial attack causes synthesis of phytoallexins in plants – e.g., flavonoids
Taxol
Fights cancer, especially breast cancer
Chemotherapeutic drug, now in use
From the bark of the Pacific Yew tree, Taxus brevafolia
Most plentiful in National Forests of Oregon, but not a dominant species
Estimated 300,000 kg of bark for 25 kg of taxol
Must kill tree to get it, need 3 trees per patient
Not practical, so the molecule has been synthesized
Synthesis, was very complex; many chiral centers
Taxol and Taxotère are synthesized from
10-deacetyl-bacctatin
Taxol Mechanism of action
Taxol impacts directly on mictotubules, effects mitosis and the cytoskeleton
Microtubule polymerization and depolymerization important for cell division - interfered with, mitosis and cell division are inhibited
Taxol stabilizes microtubules so that they cannot polymerize and depolymerize - by stabilizing tubulin
By comparison, Colchicine causes microtubule disassembly
Both used to study cancer, only taxol used to treat cancer
what is a potential source for taxols
Taxomyces andreanae, a fungal endophyte, was isolated from the phloem (inner bark) of the Pacific yew, Taxus brevifolia. The fungus when grown in a semi-synthetic liquid medium, produced taxol and related compounds. Taxol was identified by mass spectrometry, chromatography, and reactivity with monoclonal antibodies specific for taxol.
what is environmental photochemistry
drives light processes like photosynthesis and vision
some allelopathic and many xenobiotics compounds are photoactive - they can be activated by UV and radiation but visible is important too
UV (290 to 400 nm) and visible radiation (400 to 700 nm) drive these processes, because they cause electronic transitions in molecules; infrared (> 800 nm) causes vibrational transitions (heat); < 290 nm does not reach the earth
energy is inversely proportion al to wave length
Electronic transitions are required for photochemistry
conjugated double bonds
photons carry quantized energy, electrons absorb quantized energy
what happens to electrons when they absorb low, moderate, and high levels energys
- Low energy = Vibrational/ rotational states:
Photochemistry does not occur
caused by radio waves, microwaves, and infrared radiation - Moderate energy = HOMO to LUMO (transitions)
photochemistry occurs
electron can flip its state (intersystem crossing) and react with triplet O2
caused by UV and visible light - High energy = electron ejected
Caused by x-rays and gamma rays
this is an ionization process
when an e- absorbs energy yet stays in the same state , what hapens to the spin
the spin doesnt change
when would we se a singlet state
with e- that have different spins
s = 2s +1 = 2[ - ½ + ½ ] +1 = 1 (singlet)
when would we see a triplet state
Triplet state: s = 2s + 1 = 2[ + ½ + ½ ] +1 = 3 (triplet)
when intersystem crossing occurs, the electrons now have the same spin, and they’re in triplet state
from the excited state an e- have 4 paths
- get rid of energy by thermal deactivation. This is what the carotenoids do
- intersystem crossing where it switches its spin and state
- reaction from singlet (reaction from singlet). For example, photosynthesis
- gives off energy and
detail the steps of photochemistry
Detailed Steps
- Electron absorbs UV or visible light
Energy is enough to cause a transition going from HOMO to LUMO
the spin remains the same (so it’s still singlet) but is now in the excited state - Intersystem crossing
Goes to the excited triplet state - the spin is changed to opposite
This is a forbidden transition (because you have to flip the spin) and now it is harder to get to ground state
it is rarer and slower…. Not that it doesn’t happen
- From here, the electron has 2 options to get back to ground state
- photosensitization
Electron reacts with triplet O2 and makes it into singlet O2 - this also converts the electron back into the singlet state - now it is back to ground state - deperoxidation:
what options does an electron that has under gone intersystem crossing have to return to its ground state
- Phosphorescence: electron goes back to ground singlet state and loses light in the process
- Photosensitization: react with a photosensitizer (eg triplet state O2) and go back to ground state - this is hard to do
what is a photosensitizer
the molecule that gets excited and undergoes intersystem crossing
it is always regenerated by going back to the ground state
differentiated b/w the different types of photosensitization
Type 1 photosensitization
* Much rarer
* The excited molecule reacts with another molecule to form a radical
once O2 comes in, a peroxide radical is formed then deperoxidation forms the aldehyde
The hydrogen peroxide can undergo a fenton reaction: when it is converted into a highly reactive free radical - this will cause a cross linking chain reaction in the lipid membrane
Type 2 photosensitization
basically the same mechanism as type 1, but you do not get the hydrogen peroxide radical
why is singlet O2 bad
Now that it is in singlet state,
* it can react with other molecules
* From type 1 photosensitization
can make hydrogen peroxide radical this will cross link lipids and it is a chain reaction
Psoralen
Inhibits cell division and sterilizes blood
psoralen - DNA abstracts are formed via diel-alder reaction
Is Psoralen a Photosensitization Reaction?
NO
This is because the psoralen is NOT regenerated
it is a photochemical though because it does absorb light and get excited … but it is not regenerated (it is consumed in the reaction)
Which would we predict to be more effective in damaging DNA at lower concentrations? Photochemicals or photosensitizers?
photosensitizers because it’s catalytic (regenerates itself)
however, we find that they work at the same concentrations.. why? This is because photosensitizers are random in what they effect, but psoralen isn’t… thus, a certain threshold must be reached by the photosensitizer in order to damage DNA, whereas psoralen will always damage DNA and DNA only
A photosensitizer has a threshold to cause damage… psoralen doesn’t
what is photodynamic theory
Used to kill cells… in particular cancer cell, Uses type 2 photosensitization to do this
How do we make sure it gets to the cancer cells? inject it in the blood cancer cells are highly vascularized
then you have to shine light on the cancer tumor that is lower wavelength than red
why must a light with a wl lower than red used in photodynamic treatment
it can’t be red because the heme absorbs red light (Due to being more conjugated due to having HOMO and LUMO closer together and being red shifted)
Why are Conjugated Molecules Better at Transitioning
As we add more double bonds (in a conjugated way) the HOMO and LUMO are brought closer together
this means you the energy needed to transition is lower
this means longer wavelength will excite it
longer wavelength = red shifted
After about 8-10 conjugated double bonds you get a carotid and start absorbing into the visible spectrum
this is the same principle for flavonoids… if we stack, its like we are getting dimers/ trimers. This brings the HOMO and LUMO closer which makes them red shifted
4 types of Malt Volatiles
Lipid oxidation products
Mailard reaction products
Aliphatic sulfur compounds
Phenols
what products are produced from lipid ox from Malting
Short chain aldehydes and shortchain en-ols (low conc)
Mailard products from Malting
create Flavor and color
From sugar oxidation and modification
Pigment (yellow, brown to black) – Meloindens
Carmelization in many foods from heating
Sulfur volatiles products from Malting
Dimethyl sulfide - MeSMe
From degradation of methionine and Cysteine
Must be controlled for flavor quality
Phenols products from Malting
From ferulic and coumaric acid during malting
Consumed by yeast during fermentation
In low content
characteristics of Hops
Source of distinctive bitter taste of beer
Source of skunky flavor in light struck beer
Unseeded flowers used - only female plants used – male plants highly regulated
Originally used in brewing as a preservative
Hop acids allelopathic – kill most fungi, except yeast
Flavor from hop oil
flavour - hop acids
Terenoid alcohols, epoxides ketones and esters
Stabilize the foam
Spicy citrus flavor of hoppy beers
Most important: α-acids, β-acids and iso-α-acids
Also, what will cause light struck beer
