Microwave-assisted synthesis of 7-hydroxy-4-methyl coumarin and its bioactivity against acne-causing bacteria

Acne is a problem that often occurs in adolescents, especially at puberty phase. One of the acne-causing factors is proliferation of Propionibacterium acnes and Staphylococcus epidermidis bacteria. Acne is usually treated with antibiotics, but the resistance of antibiotics is also found. Therefore, research on new antibacterial compounds continues to be developed. One of the compounds reported to have antibacterial activity is coumarin derivatives. In this research, 7-hydroxy-4-methyl coumarin had been successfully synthesized from resorcinol and ethyl acetoacetate with the presence of p-toluene sulfonic acid (PTSA) as catalyst and solvent free reaction using 800W microwave-assisted method. This compound obtained in 48.36 % in yield with the reaction condition as follow: resorcinol/ethyl acetoacetate molar ratio of 1:1, 10 mol% PTSA, and 150s reaction time. Synthesized compound was further elucidated using FTIR, UV-Vis, and 1H-NMR spectral data. Unfortunately, study on the ability to inhibit the growth of P. acnes and S. epidermidis showed that the compound was inactive towards both acne-causing bacteria. Therefore, it can be concluded that 7-hydroxy-4-methyl coumarin did not have potential antibacterial activity against acne-causing bacteria.