Antibacterial and DPPH Free Radical-scavenging Activities of the Ethanol Extract of Propolis Collected in Taiwan

LI-CHANG LU¹, YUE-WEN CHEN² AND CHENG-CHUN CHOU^1*

^1. Graduate Institute of Food Science and Technology, National Taiwan University, Taipei, Taiwan
^2. Department of Applied Animal Science, National Ilan Institute of Technology, I-Lan, Taiwan

(Received: March 19, 2003; Accepted: May 22, 2003)

ABSTRACT

   In the present study, ethanolic extracts of propolis (EEP) collected from various regions (Taipei, Mingchen and Fangliao) in Taiwan during different time periods (June, August and October-November, 2000) were tested for their antibacterial and antioxidative activities. In addition, the thermal stabilities of these activities exerted by EEP were also investigated.

   It was found that the EEP samples, depending on collecting location and time period, exerted various antioxidative activities in terms of scavenging a,a-diphenyl-2-piorylhydrasyl (DPPH) free radicals and showed various extents of antibacterial activity against Staphylococcus aureus and Listeria monocytogenes, but not against Escherichia coli and Salmonella typhimurium. In general, the Taiwanese propolis extract collected in June showed the most profound antibacterial and free radical-scavenging activities than those collected during other time periods. Among all of the samples tested, EEP collected from the Mingchien area in June exhibited the highest antibacterial activity, while that collected from the Taipei area during the same time period showed the highest free radical-scavenging activity. Further tests of EEP collected from Taipei in June revealed that its DPPH free radical-scavenging effects reduced significantly after heating at 50, 80 or 100℃ for 1 hr, while its antibacterial activity remained unchanged.

Key words: ethanolic extract of propolis, antibacterial and DPPH free radical-scavenging activity, thermal stability