Exam 1 - Lecture 5 - 9, Organic functional groups and drug metabolism Flashcards
Lipinski’s Rule of Five
orally active drug has no more than 1 violation of the following criteria
Not more than 5 HBD
Not more than 10 HBA
Molecular weight under 500 g/mol
Partition coefficient log P less than 5, 3-4 is optimal
rank Intramolecular forces between drug and binding site
Covalent (strongest, 200 - 400kJ) irreversible
Electrostatic or Ionic ( 20 - 40 kJ)
Hydrogen bonds ( 16 - 30 kJ)
Van Der Waals (2 - 4 kJ)
Characteristics of Electrostatic or ionic bond
Takes place between 2 opposite charge groups
Strong interactions in Hydrophilic environment
Strength inversely proportional to distance, drops off less rapidly than other forms
Most important initial interaction as drug enters binding site
Characteristics of Hydrogen Bonds
Between deficient hydrogen and electron rich heteroatom (N or O)
optimum orientation where angle between X,H and Y is 180
H-Bond donor
Group with electron deficient hydrogen
H-Bond acceptor
Group with electron rich heteroatom
Strong hydrogen bond acceptors
carboxylate ion, phosphate ion, tertiary amine
Moderate hydrogen bond acceptors
Carboxylic acid, amide oxygen, ketone, ester, ether, alcohol
Poor hydrogen bond acceptors
Sulfur, fluorine, chlorine, aromatic ring, amide nitrogen,, aromatic amine
Good Hydrogen bond donor
Quaternary ammonium ion
Characteristics of Van Der Waals interaction
occur between hydrophobic region of drug and target
interactions drop off rapidly with distance, crucial contribution to binding
Functional groups that exhibit Van Der Waals
Alkanes
Aromatic Hydrocarbons
Halogenated Hydrocarbons
Characteristics of Dipole-dipole interaction
occur if drug and binding site have dipole moments
orientation is beneficial if other binding groups are position correctly
orientation is detrimental if other binding groups are not positioned correctly
strength decreases more quickly than electrostatic but less quickly than VdW with distance
Io-dipole vs Dipole-dipole
Ion-dipole stronger
Functional groups that form dipole-dipole
Ether and amines
Functional groups that form ion-dipole
Alcohols, sulfuric acids, quaternary ammonium, phenol
Bronsted-Lowery Acid
substance capable of giving a proton, acid turned into conjugate base
Bronsted-Lowery Base
substance capable of accepting proton, base turned into conjugate acid
Bronsted-Lowery neutral
functional groups that cannot give up or accept a proton
Hydrophobic and lipophilic
Water hating and lipid loving
Hydrophilic and lipophobic
Water loving and lipid hating
Lipophilic functional groups
Aromatic hydrocarbons, Halogenated Hydrocarbons, Thioethers, Alkanes, Alkenes
Hydrophilic functional groups
Alcohols, carboxylic acids, amines
Characteristics of alkane functional groups
They are lipophilic
Can only do Van Der Waals
Immisicble in water, but will dissolve in lipid solvent or oil layer
Inert to conditions “on the shelf”, bc hard to oxidize C-H bond under atmospheric conditions
Metabolism of Alkane
Relatively nonreactive, excreted from body unchanged
Exception is oxidation of w-1 carbon by CYP450 (adding of OH)
Characteristics of alkene functional groups
Lipophilic and hydrophobic, dissolve well in non polar solvents
Geometric isomers possible, cis = same side…trans = opposite side
No hydrogen bonding
Alkene stability to “on the shelf” conditons
Lower members gaseous at room them, higher members liquids (more carbons = stronger bonds from VdW interactions)
Prone to oxidation in presence of oxygen, forming peroxide which is explosive
Metabolism of Alkene
Hydration, epoxidation, peroxidation and reduction
Characteristics of cycloalkane group
Chemically inert like alkanes, lipid soluble and quite flammable
No free rotation around C-C bonds, isomers possible
Hint: 1,2 diaxial is trans; 1,2 diequatorial is also trans; 1,2 axial-equatoral/equatorial-axial is cis.
Aromatic Hydrocarbons characteristics
lipophilic, flammable….formation of peroxides not a problem
Aromatic Hydrocarbons possible interactions
Ion induce dipole
Aromatic Hydrocarbons shelf stability
stable, won’t undergo aromatic hydroxylation
Aromatic Hydrocarbons in vivo metabolism
aromatic hydroxylation
Aromatic Hydrocarbons (Aromatic Hydroxylation)
- involves initial epoxidation
- Intermediate epoxides toxic, responsible for carcinogenic effect
- Mediated by several CYP450 isoforms
- Phase I reaction, significantly improves solubility
Para position preferred, least hindered and easiest to attack
Aromatic Hydrocarbons ( what conjugate reaction aromatic-OH undergo)
Sulfation or glucuronidation
becomes more water soluble
Enzyme involved in glucuronidation
UDP - glucuronyltransferase
Cofactor involved in glucuronidation
UDPGA, Uridine - 5’-diphospho-a-d–glucuronic acid
Enzyme involved in sulfation
sulfotransferases
Cofactor involved in sulfation
PAPS (3’-phosphoadenosine-5’phosphosulfate)
Aromatic Hydrocarbons (how to make aromatic-OH more non-polar)
It can undergo methylation
Enzyme: Family of O,N,S- methyltransferases
Cofactor:S-adenosyl-L-methionine (SAM)
Halogenated hydrocarbons characteristics
long half lives/ biosphere of hydrogen
increase hydrophobicity and lipophilicity of the molecule
can only do VdW
shelf stable
Not metabolized in vivo, this significant increases potential for human toxicity
not readily excreted by the kidneys
Binding possible between alcohol groups and target binding site
Strong H-bonding, utilization of intermolecular and intramolecular forces
Characteristics of Alcohol groups
cause hydrophilicity
readily metabolized in body
Primary alcohol oxidized into
aldehydes and then acids
Secondary alcohol oxidized into
Ketones
Enzymes involved in alcohol oxidation
Cytochrome P450 and alcohol dehydrogenase
Can alcohol form Phase II metabolites?
yes, glucuronide or sulfate conjugates