Abstract
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).
Highlights
Flavonoids are polyphenolic compounds, which are widespread in plants and food
O-Alkyl derivatives were obtained by a one-step synthesis from naringenin using the appropriate appropriate alkyl iodide in the presence of potassium carbonate (1a–10a)
In the second step, which involved the reaction with hydrochloride hydroxylamine which involved the reaction with hydrochloride hydroxylamine and anhydrous sodium acetate in and anhydrous sodium acetate in ethanol, naringenin analogues were transformed into oximes ethanol, naringenin analogues were transformed into oximes (1b–10b) (Scheme 1)
Summary
Flavonoids are polyphenolic compounds, which are widespread in plants and food. This group comprises flavones, flavanones, flavonols, isoflavones, anthocyanidins and flavanols [1]. Flavonoids usually occur in glycoside form [2,3]. Naringin is the 7-rhamno-glucoside of naringenin, which is one of the most popular flavonoids present in citrus fruits. The presence of such glycoside derivatives of flavonoids is responsible for the bitter taste of grapefruit juice [4]. There are known O-alkyl derivatives of naringenin containing methyl and ethyl groups attached to ring A and B. 5-O-methylnaringenin, 7,40 -di-O-methylnaringenin and sakuranetin (7-O-methylnaringenin) (Figure 1) were isolated from
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