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
