Institutional Repository UIN Sunan Kalijaga YogyakartaSINTESIS 5,7-DIHIDROKSI-4-METILKUMARIN MELALUI METODE MICROWAVE-ASSISTED PECHMANNN CONDENSATION SERTA UJI AKTIVITASNYA SEBAGAI ANTIBAKTERI TERHADAP STAPHYLOCOCCUS AUREUS DAN ESCHERICHIA COLINIM.: 22106030001Sukesi Diyah Tri AndiniauthorAntibiotic resistance is a global health threat that drives the need for new antibacterial compounds. Coumarins and their derivatives, particularly 5,7-dihydroxy-4-methylcoumarin, have potential as antibacterial agents because they contain hydroxy (-OH) and methyl (-CH₃) groups that are believed to enhance interactions with bacterial cell targets. This study aims to synthesize 5,7-dihydroxy-4-methylcoumarin via a microwave-assisted Pechmann condensation under solvent-free conditions using FeCl₃ as a catalyst, characterize the structure of the synthesized compound, and test its antibacterial activity against Staphylococcus aureus and Escherichia coli. The synthesis was carried out by reacting phloroglucinol and ethyl acetoacetate using microwave irradiation at a power of 300–450 W for 3 minutes. The product obtained was brownish-cream-colored needle-like crystals with a yield of 42.83% and a melting point of 282,8-283,3°C. Characterization using FTIR spectroscopy revealed characteristic absorptions of the phenolic O–H group (3433.20 cm⁻¹), the conjugated lactone C=O group (1667.96 cm⁻¹), and the aromatic C=C group (1553.77 cm⁻¹), while the ¹H-NMR spectrum showed hydroxyl proton signals at δ 10.242 and 10.468 ppm, aromatic proton signals at δ 6.210 and 6.122 ppm, an H-3 proton signal at δ 5.787 ppm, and a methyl proton signal at δ 2.432 ppm; the overall characterization results were consistent with the target structure. The antibacterial activity test was conducted using the disk diffusion method with compound concentrations of 5%, 10%, 15%, and 20%, which showed weak activity against Staphylococcus aureus with an inhibition zone of 4.5 mm and moderate to weak activity against Escherichia coli with an inhibition zone of 6.5 mm. Based on the results of this study, the compound 5,7-dihydroxy-4-methylcoumarin has a 5% MIC value for each bacterium.543 Kimia Analitikal, Kimia Analisis2026-08-26UIN SUNAN KALIJAGA YOGYAKARTA;FAKULTAS SAINS DAN TEKNOLOGIThesis

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