Efficacy of methanol extracts of Mentha haplocalyx Briq. and Paeonia suffruticosa Andr. for potential antibacterial activity

Indoor air quality has been a worldwide concern due to the exposure to bioaerosols and its adverse health effects. These issues become important when researchers found that indoor pollutant levels in many cases exceed those of outdoor levels. Filtration of air, economical and efficient, is the most widely used method for capturing aerosols in indoor air environments. However, bioaerosols that are captured by filters remain viable and potentially harmful. Recently, the natural products are applied to antimicrobial treatments for being less toxic and human friendly. In this study, two medicinal plants namely Mentha haplocalyx Briq. and Paeonia suffruticosa Andr. were studied for their antibacterial activity as applied to polypropylene filter. Powdered plant parts were extracted using methanol and the extracts of M. haplocalyx Briq (PM) and P. suffruticosa Andr. (MB) were concentrated. The antibacterial activity of the PM and the MB was tested first with Escherichia coli using agar diffusion method. Then, the PM and the MB were applied to polypropylene filter as coating material by means of dipping and air drying processes. The PM and the MB showed significant antibacterial activity on E. coli. Their effect on inhibiting the growth of airborne bacteria on the filter is outstanding with inactivation efficiency of 99.12% for the MB and 99.05% for the PM in a 15-min retention time. Inactivation efficiency of 100% for the MB and almost 100% for the PM were achieved at retention times of 3 and 24 h, respectively. These findings suggest that these Chinese medicinal plant extracts can be used as natural antibacterial agents on inhibiting airborne bacteria. © 2013, (Chinese Institute of Environmental Engineering). All rights reserved.