Natural products identified in the MTS assay reduce rotavirus infectivity in a dose-dependent manner. Representative data are shown for four compounds: 18-β-glycyrrhetinic acid, abietic acid, mangostin, and all-trans retinoic acid. A) Data from initial screen. The y-axis is relative light units (n = 3). B) Secondary screen that includes a dose-response (red) and cell viability (blue) data. The left y-axis is relative light units and the right y-axis is viability (n = 3). Error bars are standard errors of the means. The highest concentration of mangostin was toxic under the conditions of this assay.