Sharma, SunitaSahni, Tanvi2022-10-162022-10-162021Sahni, Tanvi (2021) Synthesis and derivatization of substituted 3,5-dimethoxy-4-hydroxy benzaldehydes and their biological activities (Unpublished Ph.D. Dissertation). Punjab Agricultural University, Ludhiana, Punjab, India.https://krishikosh.egranth.ac.in/handle/1/5810188998Naturally occurring phenolic aldehyde 3,5-dimethoxy-4-hydroxybenzaldehyde (syringaldehyde) was derivatized to synthesize compounds like Schiff Bases (I-IX), β-lactams (X-XI), azo derivatives (XII-XV), hydrazones of azo derivatives (XVI-XXVII), hydrazones (XXVIII-XXXI), thiosemicarbazones (XXXII- XXXIII), ,β-unsaturated compounds (XXXIV-XXXVIII) and esters (XXXIX-XLIX). Characterization of synthesized compounds was done using UV-visible, FT-IR, 1H and 13C NMR. All the synthesized compounds were evaluated for antioxidant potential i.e. DPPH, FRAP and Phosphomolybdate assay), microbial potential against Bacillus subtilis, Pseudomonas aeruginosa, Escherichia coli, Klebsiella sp. and Enterobacter sp. and fungicidal potential against four pathogenic fungi of maize against Rhizoctonia solani, Dreschlera maydis, Fusarium verticillioides and Macrophomina phaseolina. In the DPPH assay, syringaldehyde and compounds (VI, VII, XXXVIII and XXXIX) were more effective than standard BHT while none of the compound was more effective than standard ascorbic acid. In FRAP assay, compounds (VII, X, XI, XVIII, XX, XXI, XXII, XXIII, XXIV, XXV, XXVI, XXVII) were effective than ascorbic acid and BHT standards while none of the compound was more effective than ascorbic acid in terms of phosphomolybdate assay. Compounds (VIII, X, XI, XV, XXI, XXIV and XXXIX) were more effective than ampicillin against B. subtilis. Compounds (I, II, III, VI, VIII, IX, X, XI, XII, XIII, XIV, XV, XVIII, XXI, XXII, XXIII, XXIV, XXV, XXVII and XXXIX) showed greater zone of inhibition than ampicillin against P. aeruginosa. Microbial potential at par with ampicillin against E.coli was showed by compounds (VIII, XI, XXI and XXII). Four compounds (XV, XXI, XXII and XXVI) were more effective than ampicillin against Enterobacter sp. while none of compound was found more effective than ampicillin against Klebsiella sp. Antifungal potential of Compound (VI) was found at par with carbendazim 50 WP against R. solani. Mycelial growth of D. maydis was inhibited by fourteen compounds more than carbendazim 50 WP but less than Mancozeb 75 WP. None of the compound was effective than carbendazim 50 WP against F. verticillioides and M. phaseolina.EnglishThesis