The document discusses key physicochemical properties of drugs that influence their biological action, including ionization, solubility, partition coefficient, and various forms of isomerism. It emphasizes how these physical and chemical characteristics affect drug absorption, distribution, metabolism, and excretion. Additionally, it covers concepts like protein binding, chelation, and bioisosterism, which further impact a drug's efficacy and pharmacological properties.

1. MEDICINAL CHEMISTRY
PHYSICOCHEMICAL PROPERTIES IN RELATION TO BIOLOGICAL ACTION
SCHOOL OF PHARMACY(PARUL UNIVERSITY)
B.PHARM 2ND YEAR(4TH SEMESTER)
PRESENTED BY:
SWAGAT RATH
SARTHAK JHA
PRATHAM ROHIT
ANITA KUNWAR

2. CONTENTS
• PHYSICOCHEMICAL PROPERTIES OF DRUGS
• IONIZATION
• SOLUBILITY
• PARTITION COEFFICIENT
• HYDROGEN BONDING
• PROTEIN BINDING
• CHELATION
• BIOISOSTERISM
• OPTICAL AND GEOMETRICAL ISOMERISM

3. PHYSICOCHEMICAL PROPERTIES OF DRUGS
• PHYSICOCHEMICAL PROPERTIES OF DRUGS REFER TO THE PHYSICAL AND CHEMICAL
CHARACTERISTICS OF A DRUG MOLECULE THAT CAN INFLUENCE ITS BEHAVIOR IN THE BODY.
THESE PROPERTIES CAN IMPACT THE ABSORPTION, DISTRIBUTION, METABOLISM, AND
EXCRETION OF A DRUG, AS WELL AS ITS PHARMACOLOGICAL ACTIVITY.
• THIS INCLUDE PROPERTIES LIKE IONIZATION, SOLUBILITY, PARTITION COEFFICIENT, ETC

4. IONIZATION
• IONIZATION REFERS TO THE PROCESS OF A DRUG MOLECULE BECOMING CHARGED, EITHER
POSITIVELY OR NEGATIVELY, BY GAINING OR LOSING ELECTRONS. THIS PROCESS CAN
INFLUENCE THE BIOLOGICAL ACTION OF A DRUG IN SEVERAL WAYS.
• ABSORPTION: THE IONIZATION STATE OF A DRUG CAN AFFECT ITS SOLUBILITY AND
PERMEABILITY, WHICH IN TURN CAN INFLUENCE ITS ABSORPTION INTO THE BLOODSTREAM.
• DISTRIBUTION: IONIZED DRUGS TEND TO BE MORE HYDROPHILIC AND LESS LIPID-SOLUBLE,
WHICH CAN LIMIT THEIR DISTRIBUTION INTO LIPID-RICH TISSUES.
• METABOLISM: SOME DRUGS ARE METABOLIZED BY ENZYMES IN THE LIVER, WHICH CAN BE
INFLUENCED BY THEIR IONIZATION STATE. FOR EXAMPLE, IONIZED DRUGS MAY BE MORE
EASILY EXCRETED BY THE KIDNEYS, REDUCING THEIR AVAILABILITY FOR METABOLISM BY LIVER
ENZYMES.

5. SOLUBILITY
• SOLUBILITY REFERS TO THE MAXIMUM AMOUNT OF A DRUG THAT CAN DISSOLVE IN A SOLVENT
(USUALLY WATER) AT A GIVEN TEMPERATURE AND PRESSURE, FORMING A CLEAR AND
HOMOGENEOUS SOLUTION.
• FACTORS INFLUENCING THE SOLUBILITY OF DRUG :
• PH: THE PH OF THE SURROUNDING ENVIRONMENT CAN IMPACT THE IONIZATION STATE OF THE
DRUG, WHICH CAN IN TURN IMPACT ITS SOLUBILITY. FOR EXAMPLE, ACIDIC DRUGS WILL TEND TO BE
MORE SOLUBLE IN ACIDIC ENVIRONMENTS, WHILE BASIC DRUGS WILL TEND TO BE MORE SOLUBLE IN
BASIC ENVIRONMENTS.
• TEMPERATURE: INCREASED TEMPERATURE CAN GENERALLY INCREASE THE SOLUBILITY OF DRUGS IN A
SOLVENT, AS IT INCREASES THE ENERGY OF THE SOLUTE PARTICLES AND MAKES IT EASIER FOR THEM
TO DISSOLVE.

6. PARTITION COEFFICIENT
• THE PARTITION COEFFICIENT IS A MEASURE OF THE RELATIVE DISTRIBUTION OF A DRUG
BETWEEN TWO IMMISCIBLE PHASES, SUCH AS BETWEEN A LIPID PHASE AND AN AQUEOUS PHASE.
THIS PROPERTY CAN IMPACT THE DISTRIBUTION OF A DRUG WITHIN THE BODY, WITH
LIPOPHILIC DRUGS TENDING TO DISTRIBUTE MORE READILY INTO LIPID-RICH TISSUES SUCH AS
THE BRAIN OR ADIPOSE TISSUE.
• LIPOPHILICITY IS OFTEN QUANTIFIED AS THE LOGARITHM OF THE PARTITION COEFFICIENT,
WHICH IS KNOWN AS THE LOGP VALUE. DRUGS WITH HIGH LOGP VALUES ARE MORE LIPOPHILIC
AND WILL TEND TO PARTITION INTO LIPID-RICH ENVIRONMENTS, WHILE DRUGS WITH LOW
LOGP VALUES ARE MORE HYDROPHILIC AND WILL TEND TO REMAIN IN AQUEOUS
ENVIRONMENTS.

7. HYDROGEN BONDING
• HYDROGEN BONDING IS AN ATTRACTIVE INTERACTION BETWEEN A HYDROGEN
ATOM COVALENTLY BONDED TO ONE ELECTRONEGATIVE ATOM (SUCH AS
NITROGEN, OXYGEN, OR FLUORINE) AND ANOTHER ELECTRONEGATIVE ATOM.
THIS INTERACTION RESULTS IN A HIGHLY POLAR BOND THAT CAN HAVE
SIGNIFICANT EFFECTS ON THE PHYSICAL AND CHEMICAL PROPERTIES OF
MOLECULES.
• IMPACT ON BIOLOGICAL ACTION: CAN IMPACT THE SOLUBILITY AND STABILITY
OF A DRUG
• FACTORS INFLUENCING HYDROGEN BONDING: PH, TEMPERATURE, AND THE
PRESENCE OF OTHER SUBSTANCES

8. PROTEIN BINDING
• PROTEIN BINDING REFERS TO THE PROCESS BY WHICH A DRUG MOLECULE BINDS TO A PROTEIN
IN THE BLOOD OR TISSUES. THIS CAN IMPACT THE DISTRIBUTION, METABOLISM, AND
EXCRETION OF A DRUG, AS WELL AS ITS BIOAVAILABILITY AND EFFICACY.
• FACTORS THAT CAN INFLUENCE PROTEIN BINDING INCLUDE THE PH OF THE SURROUNDING
ENVIRONMENT, THE TEMPERATURE, AND THE PRESENCE OF OTHER DRUGS OR SUBSTANCES
THAT CAN COMPETE FOR BINDING SITES ON THE PROTEIN. FOR EXAMPLE, DRUGS THAT ARE
HIGHLY PROTEIN-BOUND WILL TEND TO HAVE A LONGER HALF-LIFE, AS THEY WILL BE LESS
LIKELY TO BE METABOLIZED OR EXCRETED FROM THE BODY.

9. CHELATION
• CHELATION REFERS TO THE PROCESS BY WHICH A MOLECULE (OFTEN A METAL ION) IS
SURROUNDED AND HELD BY A COMPLEX OF LIGANDS (MOLECULES OR IONS) TO FORM A
STABLE COORDINATION COMPOUND. IN THE CONTEXT OF DRUG BIOLOGICAL ACTION,
CHELATION REFERS TO THE BINDING OF A DRUG TO A METAL ION, TYPICALLY WITH THE GOAL
OF MODIFYING ITS PHARMACOLOGICAL PROPERTIES OR THERAPEUTIC EFFECT.
• IMPACT ON BIOLOGICAL ACTION: CAN IMPACT THE ABSORPTION, DISTRIBUTION, METABOLISM,
AND EXCRETION OF A DRUG, AS WELL AS ITS BIOAVAILABILITY AND EFFICACY

10. BIOISOSTERISM
• BIOISOSTERISM REFERS TO THE PHENOMENON IN WHICH TWO OR MORE CHEMICALLY
DIFFERENT COMPOUNDS EXHIBIT SIMILAR BIOLOGICAL ACTIVITY. THIS CAN IMPACT THE
PHARMACOLOGICAL PROPERTIES OF A DRUG, SUCH AS ITS EFFICACY, TOXICITY, AND
PHARMACOKINETICS.
• BIOISOSTERIC COMPOUNDS CAN BE DESIGNED TO HAVE SIMILAR STRUCTURES OR FUNCTIONAL
GROUPS, OR TO EXHIBIT SIMILAR PHYSICAL OR CHEMICAL PROPERTIES, WITH THE GOAL OF
PRESERVING OR ENHANCING THE DESIRED BIOLOGICAL ACTIVITY WHILE REDUCING OR
MITIGATING UNWANTED SIDE EFFECTS. FOR EXAMPLE, BIOISOSTERIC COMPOUNDS MAY HAVE
SIMILAR BINDING AFFINITIES FOR A TARGET RECEPTOR, OR SIMILAR PHARMACOKINETIC
PROPERTIES.

11. OPTICAL & GEOMETRICAL ISOMERISM
• OPTICAL ISOMERISM- THE PHENOMENON IN WHICH TWO OR MORE COMPOUNDS HAVE THE
SAME MOLECULAR FORMULA BUT DIFFER IN THE ARRANGEMENT OF THEIR ATOMS IN SPACE
• GEOMETRICAL ISOMERISM- THE PHENOMENON IN WHICH TWO OR MORE COMPOUNDS HAVE
THE SAME MOLECULAR FORMULA BUT DIFFER IN THE ARRANGEMENT OF THEIR ATOMS IN
SPACE
• IMPACT ON BIOLOGICAL ACTION: CAN IMPACT THE PHARMACOLOGICAL PROPERTIES OF A
DRUG, SUCH AS ITS EFFICACY, TOXICITY, AND PHARMACOKINETICS

12. THANK YOU