O -Alkyl derivatives of naringenin ( 1a - 10a ) were prepared from naringenin using the corresponding alkyl iodides and anhydrous potassium carbonate. The resulting products were used to obtain oximes ( 1b - 10b ). All compounds were tested for antimicrobial activity against Escherichia coli ATCC10536, Staphylococcus aureus DSM799, Candida albicans DSM1386, Alternaria alternata CBS1526, Fusarium linii KB-F1, and Aspergillus niger DSM1957. The resulting biological activity was expressed as the increase in optical density (ΔOD). The highest inhibitory effect against E. coli ATCC10536 was observed for 7,4'-di- O -pentylnaringenin ( 8a ), 7- O -dodecylnaringenin ( 9a ), naringenin oxime ( NG-OX ), 7,4'-di- O -pentylnaringenin oxime ( 8b ), and 7- O -dodecylnaringenin oxime ( 9b ) (ΔOD = 0). 7- O -dodecylnaringenin oxime ( 9b ) also inhibited the growth of S. aureus DSM799 (ΔOD = 0.35) and C. albicans DSM1386 (ΔOD = 0.22). The growth of A. alternata CBS1526 was inhibited as a result of the action of 7,4'-di- O -methylnaringenin ( 2a ), 7- O -ethylnaringenin ( 4a ), 7,4'-di- O -ethylnaringenin ( 5a ), 5,7,4'-tri- O -ethylnaringenin ( 6a ), 7,4'-di- O -pentylnaringenin ( 8a ), and 7- O -dodecylnaringenin ( 9a ) (ΔOD in the range of 0.49-0.42) in comparison to that of the control culture (ΔOD = 1.87). In the case of F. linii KB-F1, naringenin ( NG ), 7,4'-di- O -dodecylnaringenin ( 10a ), 7- O -dodecylnaringenin oxime ( 9b ), and 7,4'-di- O -dodecylnaringenin oxime ( 10b ) showed the strongest effect (ΔOD = 0). 7,4'-Di- O -pentylnaringenin ( 8a ) and naringenin oxime ( NG-OX ) hindered the growth of A. niger DSM1957 (ΔOD = 0).
Keywords: O-alkyl derivatives; antimicrobial activity; naringenin; oximes.