Curcuma longa L. (Zingiberaceae family) and its polyphenolic compound curcumin have been subjected to a variety of antimicrobial investigations due to extensive traditional uses and low side effects. Antimicrobial activities for curcumin and rhizome extract of C. longa against different bacteria, viruses, fungi, and parasites have been reported. The promising results for antimicrobial activity of curcumin made it a good candidate to enhance the inhibitory effect of existing antimicrobial agents through synergism. Indeed, different investigations have been done to increase the antimicrobial activity of curcumin, including synthesis of different chemical derivatives to increase its water solubility as well ass cell up take of curcumin. This review aims to summarize previous antimicrobial studies of curcumin towards its application in the future studies as a natural antimicrobial agent.

A series of novel 5-chloro-3-fluorophenoxypyridines with a 1,3,4-oxadiazole ring bearing a thioether moiety was synthesized and their herbicidal activity against some graminaceous plants and crop safety were examined. Target compounds were prepared through S-substitution reaction of 5-mercapto-1,3,4-oxadiazole analogs, which were synthesized by the reaction of 2-propynyl (R)-2-[4-(5-chloro-3-fluoro-pyridin-2-yloxy)-phenoxy]propionate with hydrazine hydrate and the subsequent reaction with carbon disulfide. The newer 3,5-dihalophenoxypyridines and the intermediate, 5-chloro-3-fluoro-2-{4-[(R)-1-(5-mercapto-1,3,4-oxadiazol-2-yl)ethoxy]phenoxy}pyridine, were characterized using 1 H NMR, 13 C NMR, IR spectroscopy and elemental analysis. Almost all 5-chloro-3-fluorophenoxypyridines showed a moderate to high level of activity against all weeds tested at 125 g/ha application. In particular, 5-chloro-3-fluoro-2-(4-{(R)-1-[5-(2-propynylthio)-1,3,4-oxadiazol-2-yl]ethoxy}phenoxy)pyridine exhibited potent activity without crop injury. Fig. 1. Synthetic Route of 5-chloro-3-fluoro-2-(4-[(R)-1-{5-(2-substituted thio)-1,3,4-oxadiazol-2-yl}ethoxy]phenoxy)pyridine.

In this study, structurally functionalized 1,2,4-triazolo[4,3-a]pyrimidines and pyrido[2,3-d]pyrimidines were synthesized by two non-metal DABCO-based ionic liquids which were compared in catalytic activity in both reactions.

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