Arpit D. Shah, Devanshi J. Raval, Viraj P. Jatakiya, Dr. Dhrubo Jyoti Sen and Dr. R. Badmanaban
Three Schiff bases of Mannich bases of resacetophenone have been synthesized by using three variable electronegative atoms (X=O/S/NH) of urea/thiourea/guanidine and tested for antimicrobial activity and antioxidant screening by DPPH. It has been found that Compound-3a (X=O) showed maximum zone of inhibition in E.coli & S.aureus and minimum zone of inhibition in B.subtilis, Compound-3b (X=S) showed maximum zone of inhibition in E.coli in comparison with standard drug streptomycin. There is no activity found in case of Compound-3c (X=NH). Antimicrobial activity profile of three compounds is as follows: Gm positive bacteria: Compound-3a (S.aureus > B.subtilis) Gm negative bacteria: Compound-3b (E.coli) > Compound-3a (E.coli) LogP values of three compounds were found to be X=O: 4.03, X=S: 4.63 and X=NH: 3.79. So, the partition coefficient is in this order: X=S: 4.63 > X=O: 4.03 > X=NH: 3.79. Partition coefficient of X=S is 4.63 which is greater than X=O (4.03) and X=NH (3.79) electronegativity of S is 2.58 which is in between O=3.44 and NH=3.04. Electronegative atoms O and S both have two lone pair of electrons but electronegativity for O: 3.44 > N: 3.04 > S: 2.58 and the % inhibition of oxidation by DPPH has been observed as NH (45.56) > O (37.76) > S > (36.5). The electronegativity of N is 3.04 so the NH compound (guanidine) showed maximum inhibition 45.46%, electronegativity of O is 3.44 so the O compound (urea) showed 37.76% inhibition and the electronegativity of S is 2.58 so the S compound (thiourea) showed 36.5% inhibition. The log P values of NH compound (guanidine) is 3.79 which is minimum but showed maximum inhibition 45.46%, log P value of O compound (urea) is 4.03 which showed in 37.76 % inhibition and log P value of S compound (thiourea) is 4.63 which showed 36.5% inhibition. Oxygen and Sulfur both have two lone pairs of electrons so the % inhibition values are under very narrow range O (37.76), S (36.5) but this slight variation is due to the difference in electronegativity: O: 3.44 and S: 2.58.
