You would have to have a specific, high-resolution target structure (typically a protein) with which the compound interacts at a known location, then use computational methods to investigate that interaction.

Thank you, Adam B Shapiro, for your valuable suggestions.

Actually, I need to study the antibacterial activity for a particular compound like natural antioxidants such as flavonoids. 

Theoretically, we can study the antioxidant property from HOMO and LUMO values, Bond dissociation enthalpy and Ionization potential and so on. Like that is there any quantum chemical descriptors for studying the antibacterial and antimicrobial property of that compound only.  

The interactions of compounds with living organisms such as bacteria are usually complex. The molecule must be able to pass through the cellular membrane (or membranes in some cases) and bind to its target(s). It may also interact with efflux pump proteins that expel it from the cell. It may be degraded or modified by enzymes in the cell.

There are some relatively simple cases that you might be able to explore, such as the interaction of vancomycin with the peptidoglycan of Gram positive bacteria, which is accessible from outside the cell.

Thank you Adam B Shapiro

Dear Pitchumani

According to me  antimicrobial activities are commonly be refitting to the specifity of biactives molécules. Study of different interactions  requires strong knowledge and large time of investigation. Quantum chemical methods will recommen hard regard.

Best regards

Marius