In vitro Effects of Saponins on Lysozyme Activity of Human Cells 339 Results and Discussion Human monocytic cells THP-1 Secretion of lysozyme activity in cell cultures after short-term treatment with saponins Most examined saponins, which have been reportedly known for their influence on the immune response, stimulated the release of lysozyme activity after one hour incubation with monocytes (Fig. 1). Fig. 1. Percent change in the secreted lysozyme activity of 1×10+6 cells/ml THP-1 cell cultures treated with various saponins for 1 hour using sensitive fluorescence- based lysozyme activity assay. Control cultures without saponin addition were considered to have 100% lysozyme activity. All points were measured in triplicate, and each column is representative of average value of six separate experiments. Values with asterisk are significantly different (P<0.05, Mann- Whitney U test) from values of control cultures. Dose-dependent effect on lysozyme activity secreted in THP-1 cultures was observed with saponins extracted from Hydrocotyle vulgaris. 3.125µg/ml final concentration of this saponin had no significant effect, while 6.25µg/ml led to significant increase of 43% in the secreted lysozyme activity and 12.5µg/ml caused further significant increase of 95% after one hour incubation with cells. However, 12.5µg/ml of Hydrocotyle saponins started to show slight toxic effects to THP-1 cells that were statistically non-significant after one hour treatment, whereas lower concentrations were non-toxic to cells. Aescin and saponins from Quillaja saponaria bark at 100µg/ml caused statistically significant increases of about 50% and 40%, respectively, in the secreted lysozyme activity of monocytes after one hour treatment compared to control cultures, whereas no significant effects were observed with lower concentrations. None of these two saponins showed significant toxic effects to the cells after one hour exposure at concentrations equal to or lower than 100µg/ml. Sci Pharm. 2011; 79: 337–349