Monoterpenoids Flashcards
What’s the source of most common monoterpenoids?
How are monoterpenoids divided
Source - C10 geranyl GPP –> almost every possible arrangements of 2 isoprene units
Monoterpenoids are divided into: acyclic, monocyclic, bicyclic, iridoids, irregular and mixed.
Where can we find monoterpenoids?
They are widely distributed, some in insects and are rare in other organisms.
Major constituents of essential oils (significant in economy- base for flavors, fragrances / perfumes, solvents)
List some functions
-ecological function in plants rather than physiological
-herbicides since they help plants to compete among them
-attract or repel insects
-knsect pehromonse
What are the main characteristics?
Lipid soluble, colorless, fragrant and volatile, steam distillable, readily separated and analyzed by gas chromatography
How are acyclic monoterpenoids formed?
Basically from DMAPP + IPP. Maybe from both GPP into NPP.
Citral - applications?
It has a strong lemon smell (bc it an aldehyde) so it’s used on fragrance and cosmetics, food and baking.
Neral is it’s Z isomer.
Citral is a mixture of geranial and neral.
Why monoterpenoids have a wide variety, >100 compounds?
Due to the carbocation formation–> delocalization / resonance reaction allows for intramolecular rearrangements.
All subsequent cyclic monoterpenoids originate from it.
What bicyclic terpenoids are derived from limonene?
How many classes of bicyclic monoterpenoid
a-pinene and b-pinene.
Camphor, cineole, ascaradiole
7 classes
Cyclic monoterpenoids are mainly derived from…?
NPP - neryl diphosphate–> it is folded such that the cyclization is favored, and the final products come from modifications and addition of functional groups.
P-menthane skeleton?
What’s pepper mint oil mainly composed of?
P-menthane skeleton is the skeleton for most monocyclic monoterpenoids.
Peppermint oil is made 70% out of menthol (monocyclic monoterpenoid)
Monocyclic monoterpenoid examples
Piperitenone, pulegone, menthone, menthol
Same p-menthane skeleton
Limonene characteristics
-lemon flavor in lemon tea
-Very important
-rearrangement of double bond compared to NPP
-Found in turpentine, caraway and dill (same compound in multiple instances)
-Often makes racemic mixture
-attracts male boll weevil to cotton
Thymol (it’s a phenol) characteristics
-major aromatic monoterpenoid-> gives pungent caustic smell of thyme
- good fungicide
-essential oil from thymus vulgaris
Pinene (both are derived from limonene)
- varying: amounts in pine species, from tree to tree, and with age and environmental conditions
-can be alpha-pinene or beta-pinene
-alpha is more stable than beta.
Camphor (derived from limonene)
-good plasticer, used for explosives, antiseptics, and varnishes.
-from camphor tree(naturally)–> manufacture form pinene (commercially)
Cineole (derived from limonene)
-used for respiratory diseases and as antiseptics
-main component of eucalyptus oil
- used in hall’s mentholyptus
Ascaridole (derived from limonene)
-from endoperoxidation of limonene
-used as laxative to expel intestinal worms
-insecticide for plant
- in the plant chenopodium
A-pinene and b-pinene mechanism
Happens through the carbocation intermediate.
-carbocation –> short lived, stabilized by an enzyme - transition state are not proven. Probb enzyme is in low concentration
Iridoids (byciclic)
Ex. Loganin (C11 compound due to Me ester) –> Glucoside
Characterisitcs:
-6 membered lactone ring, connected to a 5 memebered ring.
-Becomes catnip / catmint if Glu, Me and MeOH are gone.
- Water soluble bc of relativeness to glucoside.
-found: in the ants (iridomyrmex) –> iridomyrmecin - derived from NPP (pathway not worked out yet )
in many plants –> not organ specific
uses:
-repellent and irritants - chemical defense for insects –> Natural insecticieds.
-precursor of monoterpenoid alkloids (indoles).
Secoiridoid (bicyclic)
ex. Gentiopicroside from oxidation of loganin
No Cyclopentane ( 5 membered ring) rings of iridoids–> cleaved and replaced with extra lactone ring.
Mixed and irregular monoterpenoids
-C10 - but are biogenic anomalies of the isoprene rule –> unusual pahtways
-Restricted distribution
-Ex. Camphene and crhysanthemyl
Camphene (irregular)
-Looks like bicyclic
-Not made of NPP - rather from Lavandunol which is the fusion between 2 DMAPPs.
Pyrethrins - mixed monoterpenoids
From chrysanthemus flower.
-Chrysanthemyl skeleton.
-Insecticide (kills parasites, lice, tick) - environmentally safe unless they go to the sea / river.
-Toxic to fish and insects
-Mammals and plants are okay wiht it.
-Irregular angled ring (strained ring) readily opens.
- Has an R group with polar contituents.
Why are mammals and plants immune to some insecticides?
Because the cellular / molecular tagets are different. There are also differences in neurophysiology. This is called selective toxicity.
