Pyrazole, Isoxazoline and Bypyrimidine Derivatives from Polygonum senegalense and Psiadia punctulata Flavonoids and their Anti-Microbial Activities

Abstract

Currently, researchers have given special attention to the synthesis of heterocyclic compds. with nitrogen and oxygen five in five- or six-membered ring systems. This is mainly due to their wide range of biol. activities. Hence, in this study, isoxazoline, pyrazole and bypyrimidine derivs. were synthesized from flavonoids, previously isolated from Polygonum senegalense and Psiadia panctulata, and assessed for their anti-fungal activity. A flavone was reacted with hydrazine hydrate to afford a pyrazole analog 5-methoxy-2-(5-(2,3,4,5-tetramethoxyphenyl)-1H-pyrazol-3-yl)benzene-1,3-diol (1) Two isoxazoline derivs. namely, 2-(4,5-dihydro-5-phenylisoxazol-3-yl)-5-methoxybenzene-1,3-diol (2) and 2-(4,5-dihydro-5-phenylisoxazol-3-yl)-3,5-dimethoxyphenol (3) were successfully synthesized by the reaction of chalcones with hydroxylamine hydrochloride. An oxime deriv. (4) was also generated from a similar procedure. A reaction between a chalcone and thiourea gave a bypyrimidine deriv., 4,5-dihydro-6-(2,4-dihydroxy-3,6-dimethoxyphenyl)-4-phenylpyrimidine-2-(1H)-thione (5). The products were then assessed for their anti-bacterial and anti-fungal activity. All compds. showed no significant activity except compd. 2 that demonstrated activity against std. anti-bacterial agent, Streptococcus aureus with IC50 value of 7.56 and anti-fungal Candida neoformans, Candida krusei and Candida glabrata strains with IC50 values 8.01, 8.11 and 13.74 μg/mL resp. We, therefore, recommend synthetic optimization of compd. 2 as a potential anti-microbial agent. [on SciFinder(R)]