**7. Conclusion**

The present work explained the antioxidant properties of coumestrol and its derivatives from a theoretical point of view. Since the measured ionisation potential and proton affinities in gas phase are significantly higher than the phenolic O-H group BDEs, we can infer that from a thermodynamic point of view, homolytic O-H bond splitting-off is the most likely process in the gas phase. All the selected derivatives 16-NH2 Coumestrol, 16-OCH3 Coumestrol, and 16-CH3 Coumestrol showed high antiradical activity than parent molecule. Among the selected derivatives, 16-NH2 Coumestrol showed the best antioxidant activity. The calculated molecular properties (electronegativity, ionisation potential, electron affinity, hardness and electrophilicity index) of coumestrol derivatives substituted by electron withdrawing groups at 16th position indicated that, Ionisation potential, electron affinity, electro negativity, softness and electrophilic index increases with increase electron withdrawing power and hardness and chemical potential decreases with increase in electron withdrawing power. In the case of derivatives substituted with electron donating groups, ionisation potential, electron affinity, hardness and electronegativity decrease with increase in electron donating power while the softness, chemical potential and electrophilic index decreases with increase in electron donating power.

*Theoretical Studies on Anti-Oxidant Activity of the Phytochemical, Coumestrol and Its… DOI: http://dx.doi.org/10.5772/intechopen.96967*
