Abstract:

Aqueous, 50% ethanol and absolute ethanol extracts from burdock roots or peel were investigated for in vitro antimicrobial activity. Meanwhile, the thermal stability, pH stability and ultraviolet (UV) illumination stability of the extracts were also discussed. Results showed that all these extracts revealed the potential antimicrobial activities against Escherichia coil, Bacillus subtil, Staphylococcus aureus, Aspergillus niger and Saccharomyces cerevisiae. A higher antimicrobial activity was observed in 50% ethanol extracts in comparison with aqueous and absolute ethanol extracts. In addition, the extracts from burdock peel exhibited higher antimicrobial activity than those from burdock roots. Microorganisms tested were inhibited in the following order of S. aureus > B. subtilis > E. coil > Asp. niger > S. cerevisiae. The 50% ethanol extracts exhibited excellent antimicrobial activities under acidic conditions (pH 3－5), whereas both high-temperature (higher than 100 ℃) treatment and long-time (longer than or equal to 5 min) UV illumination could attenuate the antimicrobial activities.

Key words: Arctium lappa root and peel, microorganism, antimicrobial activity