Antibacterial properties of Polygonum cuspidatum roots and their major bioactive constituents Bin Shan a , Yi-Zhong Cai a , John D. Brooks b , Harold Corke a, * a School of Biological Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong b Division of Applied Science, Auckland University of Technology, Auckland, New Zealand Received 23 October 2007; received in revised form 11 December 2007; accepted 21 December 2007 Abstract Antibacterial activity, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) of crude extract from Polygonum cuspidatum roots were assayed against five common foodborne bacteria (Bacillus cereus, Listeria monocytogenes, Staph- ylococcus aureus, Escherichia coli, and Salmonella anatum). The crude extract exhibited potent antibacterial properties. Major bioactive compounds in P. cuspidatum roots were identified as stilbenes (e.g., piceid, resveratroloside, and resveratrol) and hydroxyanthraquinones (e.g., emodin, emodin-1-O-glucoside, and physcion) by LC–ESI-MS. Both stilbenes and hydroxyanthraquinoines greatly contributed to the antibacterial properties. Additionally, scanning electron microscopy was used to observe morphological changes of the bacteria trea- ted with the crude extract and its major antibacterial components. Possible mechanisms of the antibacterial action were also discussed. This study suggests that the roots of P. cuspidatum and its antibacterial components may have potential for use as natural preservatives. Ó 2008 Elsevier Ltd. All rights reserved. Keywords: Polygonum cuspidatum; Antibacterial properties; Foodborne pathogenic bacteria; Phenolic compounds; Stilbenes; Hydroxyanthraquinones 1. Introduction Foodborne illnesses are still a major problem and have a dramatic increase throughout the world in recent years (Mead et al., 1999). A variety of microorganisms may lead to food spoilage, so food poisoning is still a threat for both consumers and the food industry. Some synthetic chemicals have been made to control microbial growth and reduce the incidence of food poisoning and spoilage. Although these synthetic preservatives are effective, they might be detrimental to human health. Consumers are concerned about the safety of foods containing artificial preservatives. There has been a growing interest in new and effective anti- microbial substances from natural sources like plants to reduce cases of foodborne illnesses. Crude extracts of spices, herbs and medicinal plants rich in phenolic com- pounds are becoming increasingly important in food pres- ervation because of their antimicrobial activity. Polygonum cuspidatum Sieb. et Zucc. is a perennial of the genus Polygonum in the family Polygonaceae, which is distributed in China, Japan and Korea and also found growing throughout North America (Mexican bamboo) (Gao, Xu, & Li, 2000; Vastano et al., 2000). The dried root of P. cuspidatum is used as a well-known traditional Chinese medicine (called Huzhang) officially listed in the Chinese Pharmacopoeia (China Pharmacopoeia Commit- tee, 1999), and also used for folk medicine in Korea and Japan (called Japanese knotweed or bamboo). It is often used as an analgesic, antipyretic, diuretic, expectorant, and antitussive agent and also used for the treatment of chronic bronchitis, infectious hepatitis, diarrhea, cancer, hypertension, atherosclerosis, hyperlipidemia, leucorrhoea, dysmenorrhea, trauma with blood stasis, burn, snake bites, and allergic inflammatory diseases (Gao et al., 2000; Kim, Kim, Yoo, & Shin, 2004; Yan et al., 1996). 0308-8146/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodchem.2007.12.064 * Corresponding author. Tel.: +852 22990314; fax: +852 28583477. E-mail address: hcorke@yahoo.com (H. Corke). www.elsevier.com/locate/foodchem Available online at www.sciencedirect.com Food Chemistry 109 (2008) 530–537