Abstract

Rhein is an aromatic compound, provides basic framework for number of structural and functional units in plants and animals. Incorporation of amino acids and peptides into the aromatic congeners results in compounds with potent bioactivities. The experimental work involves: synthesis of rhein from barbaloin via formation of aloe-emodin and then diacerein from rhein. The peptide derivatives were synthesized by the coupling of rhein and diacerein with amino acid methyl esters/ dipeptides under continuous stirring for 36 hours. All the synthesized compounds were identified on the basis of Rf values, IR and 1HNMR spectral data. All the synthesized compounds were screened for antimicrobial activity at 40, 80 and 160 μg/ml. The antibacterial activity of synthesized compounds was determined against bacterial strains viz. E. coli and S. aureus using ciprofloxacin as standard. The results revealed that rhein possess potent activity than diacerein and methyl esters of rhein/diacerein exhibited more activity as compared to dipeptides. The antifungal activity was also determined against fungal strains viz. C. albicans and A. niger using fluconazole as standard and results revealed that degree of inhibition increased as rhein/rhein methyl esters/dipeptide and decreased as diacerein/ diacerein methyl ester/dipeptide. Comparison of antibacterial and antifungal screening data suggested that rhein exhibits good antimicrobial activity profile than substituted rhein (diacerein).