Plant Chemistry Flashcards
Pharmacognosy is:
the study of the physical, chemical, biochemical and biological properties of drugs, drug substances, or potential drugs or drug substances of natural origin as well as the search for new drugs from natural sources
Why should we study pharmacognosy?
to inform our decisions about crafting medicines, how to administer, potential interactions, and physiologic actions.
tea or tincture? how is it absorbed? stability of constituents? constituents present in essential oil? etc
What are secondary metabolites?
compounds not directly involved in the growth, reproduction, or photosynthesis of plants.
generally associated with defense, attraction of pollinators and symbiotes, & protection from environment (like UV)
Aromatic (benzene) ring with an -OH group:
Phenolics
Properties of phenolic constituents:
- resonance stabilization
- antioxidants
- anti-inflammatories
- anti-cancer
- colorful pigments
T/F: Plant chemicals are group according to their chemical action on the body.
False!
they’re organized by their chemical structure
Simple phenolic compounds - properties:
single aromatic ring
smaller molecules are volatile
often form glycosides
Phenolic glycosides - properties:
phenolic with a sugar group
[aglycone + glycone]
Phenolic acids - properties:
at least one phenolic ring with an acidic carboxyl group
Tannins - properties:
astringents
phenolic acids w/ester [-o-] linkages to a sugar molecule
tighten tissues - taste dry in your mouth!
Derivatives of α-pyrone:
Coumarins
Coumarins with an additional O-heterocycle:
Furanocoumarins
these are photosensitizing
Properties of coumarins:
- antioxidant
- anti-inflammatory
- appetite suppressant
Pigmented molecules:
Naphthoquinones
Properties of naphthoquinones:
- fungicidal
- antibacterial
- insecticidal
- phytotoxic
- cytostatic
- anticarcinogenic
- antihelminthic
Polyphenolic compounds based on tri-aromatic ring structure with opposite phenolic groups on the middle ring:
Anthraquinones
Properties of anthroquinones:
- laxative and purgatives
- many are pigments
- many are glycosides
Properties of flavonoids:
- anti-cancer
- anti-inflammatory
- cooling
- colorful
3-ring molecules with one benzene ring connected by only one carbon bond (usu 2 or 3):
flavonoids
Structurally similar to flavonoids, but carrying a charge:
anthocyanidins
called anthocyanins when they have a glycoside
Properties of anthocyanidins:
- sap pigments (color depends on pH)
Properties of anthocyanins:
- odorless
- flavorless
- mildly astringent
Properties of proanthocyanidins:
- related to flavonoid pigments
- no sugar moiety
- oligomers & polymers of flavon-3-ol’s
Dimeric compounds formed by two phenylpropene derivatives:
Lignans
Properties of lignans:
- major class of phytoestrogens
- antioxidant function
- some have toxicity
- some are hepatoprotective
Phenylpropene units linked head-to-head or head-to-tail:
Neolignans
Synthesized from DMAPP and IPP 5-C precursors:
Terpenoids
Characteristics of monoterpenes:
10-C molecules
low molecular wt
structural variations: monocyclic, bicyclic, acyclic
component in essential oils
small change in structure -> big change in action
Cyclic structure with an Oxygen in the ring neighboring a ketone:
Lactone
A cyclopentane ring fused to a 6-membered oxygen heterocycle, often occur as glycosides:
Iridoid - these are bitters
Characteristics of sesquiterpenes:
15-C molecules
volatile
structural variations: monocyclic, bicyclic, acyclic
A mixture of terpenoid molecules & aromatic compounds that combine to form a (semi-)solid substance that is excreted by plants for protection or in response to injury. :
Resin
The (semi-)solid portions are often di- & triterpenes
The aromatic portion is commonly mono- and sesquiterpenes
Resins that have a polysaccharide component as well as volitile oils and heavier terpenes:
Gum resin
Characteristics of triterpenes:
30-C molecule usu pentacyclic precursor to plant steroids usu water-soluble saponins aglycones are oil soluble
Amphipathic:
a chemical compound possessing hydrophilic and lipophilic properties.
e.g. triterpenoid saponins like glycyrrhizin
Characteristics of steroidal saponins:
27-C molecule
multiple sugar units attached (usu 3-5)
many anti-inflammatory & adaptogenics in this class
“-genin” denotes the aglycone
Characteristics of phytosterols:
tetracyclic
plant equivalent to cholesterol in animal cell membranes
plant growth regulators
found in plant oils and lipophilic extracts
Characteristics of cardiac glycosides:
Tetracyclic sterol skeleton w/5-membered lactone ring
cardioactive substances from plants (digitalis, convallaria)
Characteristics of tetraterpenes:
40-C molecules
lipophilic - multiple conjugated double bonds
terminal cyclic structures
lycopene is precursor
carotenoids concentrate in tissues providing antioxidant protection
Oxygenated carotenoids are called:
Xanthophylls
they have ketone, hydroxyl, and epoxide groups on their rings
Characteristics of alkaloids:
nitrogenous molecules (N in the ring)
occur as salts or N-oxides in plants
alkaline nature
soluble in hydroethanolic menstrum
How do amines differ from alkaloids?
In amines, the N is not within the ring.
Toxic alkaloids that build up in tissues over time and have a hepatotoxic & hepatocarcinogenic effect:
Pyrrolizidine alkaloids
Comfrey, butterburr, colt’s foot
Characteristics of inulin:
oligosaccharide prebiotic soluble fiber named for inula helenium sources: chicory, onion, garlic, artichoke, dandelion, burdock
Heteropolysaccharides that can trap water in a 3D structure:
Pectins
- soluble fiber
- helical galacturonic acid backbone, various sugar side groups
Characteristics of a mucilage:
forms gel/slime with water
soothing & emollient
significant crossover btw mucilages & immunomodulating polysaccharides
found in althea off, ulmus fulva
Complex mix of heteropoly- & polysaccharide protein complexes that effect immune system function:
Immunomodulating polysaccharides
- arabinogalactans
- acemannans
- beta-glucans
