What is Structure–Activity Relationship (SAR)?

Structure–Activity Relationship (SAR) describes the connection between the chemical structure of a molecule and its biological activity. It helps scientists understand how chemical modifications affect potency, selectivity, and therapeutic use.

Why is SAR important in medicinal chemistry?

SAR is important because it guides drug discovery. By studying structural changes and their effects on biological activity, scientists can design more effective and safer medicines.

What is the difference between SAR and QSAR?

SAR examines the relationship between chemical structure and biological activity qualitatively. QSAR (Quantitative Structure–Activity Relationship) uses mathematical models to predict biological activity based on chemical structure.

How is SAR applied in drug design?

SAR is applied in drug design to identify which parts of a molecule are critical for activity. By modifying these groups, researchers can enhance potency, improve selectivity, or reduce side effects.

Structure–Activity Relationship (SAR) in Medicinal Chemistry: Definition, Importance, and Applications

Ahmed Gad December 11, 2021 Study corner

The Structure Activity Relationship is the relationship between the chemical or 3D structure of a molecule and its biological activity. The analysis of SAR enables the determination of the chemical groups responsible for evoking a target biological effect in the organism. This allows modification of the effect or the potency of a bioactive compound by changing its chemical structure.

A Structure-Activity Relationship is the relationship of the molecular structure of a chemical with a physicochemical property, environmental fate attribute, and/or specific effect on human health or an environmental species.

Part 1

Sympathomimetic agents

directly bind to the adrenergic receptors in the postsynaptic membrane.

Structure Activity Relationship of catecholamines:

Catechol ring is important.
β-hydroxyl group is important.
Stereochemistry at β position should be R.
Bulkiness of groups attached to the amino has a significant effect on selectivity (alpha or Beta receptor activity).
alpha substitution increases stability and selectivity but reduces activity.