QSAR or QSPR

#It stands for quantitative structural activity relationship (QSAR) or quantitative structural property relationship.
#It includes a relationship to quantify relationship between chemical structure and biological activity.
#The QSAR approach use parameters which have been assigned to the various chemical groups that can be used to modify the structure of the drug .
#The parameter is a measure of the potential contribution of its group to a particular property of the parent drug.
#In a typical procedure ,a series of related compounds are examined and the relevant parameters of their substituent group compared with the biological activity of the compounds and then by mathematical procedures ,the structure of the most promising derivatives are predicted.

For example, biological activity can be expressed quantitatively as in the concentration of a substance required to give a certain biological response. Additionally, when physicochemical properties or structures are expressed by numbers, one can form a mathematical relationship, or quantitative structure-activity relationship, between the two. The mathematical expression can then be used to predict the biological response of other chemical structures.

APPLICATIONS OF QSAR:
1.
a)As an instrument for prediction
b)Estimation of physicochemical properties using substituent constants.
c)Reduction of the number of compounds to be synthesized.
d)faster detection of the most active compound.
e)Avoidance of synthesis of compound with some activity.

2)
a)As a diagnostic instrument
b)Information on possible types of interaction forces.
c)Information on the nature of the receptor.
d)Information on the mechanism of action.
e)detection of inactive compounds.

reference:
en.wikipedia.org/.../Quantitative_structure-activity_relationship
en.wikipedia.org/.../Quantitative_structure-activity_relationship
www.scienceinthebox.com/en_UK/safety/qsar_en.html