Cells. Tylosema esculentum extracts were dissolved in DMEM (Sigma-Aldrich, Grand Island, USA), supplemented with 10% foetal calf serum (Cambrex, Verviers, Belgium), L-glutamine (2 mmol/L, Sigma), penicillin (100 units/mL, Sigma), and streptomycin (1 mg/mL, Fluka, Buchs, Switzerland) using a rotary magnetic stirrer (Yellowline, BigSquid, Kika-Werke GMBH & Co, Germany). As control, DMEM (Sigma-Aldrich, Grand Island, USA), supplemented with 10% foetal calf serum (Cambrex, Verviers, Belgium), L-glutamine (2 mmol/L, Sigma), penicillin (100 units/mL, Sigma), and streptomycin (1 mg/mL, Fluka, Buchs, Switzerland), was used. The extracts were added diluted 10-fold to monolayers of cells in 96 well plates, then maintained at 37 • C in a humidified atmosphere of 4 Evidence-Based Complementary and Alternative Medicine 5% CO 2 and 95% air for 24 h. Following incubation, cells were carefully rinsed with PBS to remove T. esculentum extracts and other debris. Upon washing, plates were stained with 0.01% crystal violet for 5 minutes and then rinsed with water. Plates were then dried, and then crystal violet incorporated in viable cells was resuspended with 10% acetic acid (100 μL per well). Photometric quantification of crystal violet previously retained in living cells was done at 595 nm with a microplate reader (Multiscan, Finland) as described by Agelis et al. [32] . After this test for cytotoxicity, certain concentrations of T. esculentum extracts were selected for antiviral tests as shown in Table 2 .