Biostatic activity of Coix lacryma seed extract on Toxoplasma gondii in macrophages

Water extract of Coix lacryma seeds (Co-Ex) was separated into several components; dissolved with Tris-Cl buffer and the supernatant (WC1), ammonium sulfate treatment supernatant (WC2) and the pellet (WC3), QAE column chromatography of WC1 and the peak portions; WC4, WC5 and WC6. Murine peritoneal macrophages in DMEM containing 10% heat-inactivated FCS were infected with tachyzoites of Toxoplasma gondii, RH strain, in vitro. By adding modulators such as Co-Ex, WC1,2,3,4,5,6 and LPS or IFN-gamma for 24 hrs, toxoplasmastatic activity of macrophages was examined in relation to nitrite production. Nitrite production of macrophages was enhanced especially in the series of WC2, WC1 and the combination sample (WC1+WC2+WC3) by order, than other components or fractions (WC4, WC5, WC6) tested. Toxoplasmastatic actions such as percentage of the macrophages infected by T. gondii and fold increase of T. gondii in macrophages showed retroverse relations with the amount of nitrite production; i.e., as nitric oxide (NO) increased the phagocytic index of macrophages and the fold increase of tachyzoites in macrophages decreased. Nitrite (NO2) production was increased by adding IFN-gamma in all cases together with enhancement of biostatic effects. Through the results obtained, it is speculated that some components other than the non-proteinous and defatted components in Coix lacryma seeds may contribute to activate macrophages through induction of NO for the biostatic activity.