and WI-38 cells in 24-well tissue culture plates. The cells
were observed daily for 6 days for any signs of cell cytotoxicity
compared with the controls. In the second method, a
cell viability assay previously reported by Dumsha and
Sydiskis (1) which measures the cell replication was used.
Vero cells (1.2 x 106) and WI-38 cells (30 x 106) were
inoculated into triplicate 75-cm2 flasks (Falcon) with growth
medium or medium containing either senna extract or aloe
emodin to give final concentrations of 0.1 mg/ml. The cells
were incubated at 37°C for 3 days until confluent and were
observed for any signs of cytotoxic effects. The cells were
removed from the flasks, and total numbers of viable cells
were counted and averaged by using the trypan-blue dye
exclusion procedure.