T9-05 Screening Antimicrobial Activities of the Herbal Plants against Listeria monocytogenes and Cytotoxicity Assays of the Plants using Caco-2 Cell

Wednesday, July 25, 2012: 9:30 AM
Room 553 (Rhode Island Convention Center)
Yohan Yoon, Sookmyung Women's University, Seoul, South Korea
Hyunjoo Yoon, Sookmyung Women’s University, Seoul, South Korea
Ahreum Park, Sookmyung Women's University, Seoul, South Korea
Kyoung-Hee Choi, Wonkwang University, Iksan, South Korea

Introduction: Although various synthetic antimicrobials have been used to control Listeria monocytogenes in foods, therapeutic herbal plants could be considered as antimicrobial alternatives because of consumers' demand.

Purpose: This study evaluated the antimicrobial activities of therapeutic herbal plants on L. monocytogenes and their cytotoxicity on Caco-2 cell.

 
Methods: The paper disks impregnated with 69 herbal plants were placed on brain heart infusion agar, where L. monocytogenes strains were overlaid. After incubation (37°C, 24 h), clear zone diameters were measured to select the herbal extracts showing antilisterial activity. L. monocytogenes strains were inoculated in 96-well plates containing 100 ¥ìl of two-fold serial diluents of the selected herbal extracts, followed by incubation (37 °C, 24 h) to determine MICs (minimal inhibition concentration). Moreover, aqueous portions of the wells that displayed no growth were spread-plated on BHI agar plates, and the plates were incubated at 37°C for 24 h to determine MBCs (minimal bactericidal concentration). The stability of the selected extracts were also examined to food-related conditions such as heat (60-100°C), NaCl (0-6%), and pH (4-7). In addition, two-serial dilutions of the selected herbal extracts were added to the wells containing Caco-2 cells and incubated at 37°C for 2 days in 5% CO2 atmosphere to evaluate cytotoxicity of the herbal extracts.

Results: Of 69 herbal extracts, Psoraleae semen L. (Bogolji) and Sophorae radix L. (Gosam) extracts showed more than 10 mm of clear zone diameter, and their MICs were 8-16 µg/ml and 128-256 µg/ml depending on strains for Bogolji and Gosam, respectively. The MBCs were also 16 (Bogolji) and 256 µg/ml (Gosam). Heating, NaCl and acidic condition did not affect (> 0.05) the antilisterial activity of Bogolji and Gosam. Cytotoxic activities were observed only at high concentration (128 µg/ml) of Bogolji extract.

Significance: The results indicate that Bogolji and Gosam could be used as potential phytochemicals to control L. monocytogenes.