Cell-based SOA radical scavenging assay
Monolayer MCF7 cells grown in 96-well plate were exposed to 0.625 U/L xanthine oxidase and 0.5 mM xanthine for 1 h in the presence of L. tigris extract from 2 to 125 µg/mL in series of double dilution. Reaction mixtures were then aspirated and cells were cultured in fresh growth medium for an additional 72 h prior to cell viability assessment by MTT assay. MTT solution (5 mg/mL in phosphate buffered saline, PBS) was added subsequently at 20 µL per well followed by additional incubation at 37 oC for 4 h until purple formazan crystals developed. Total solutions were aspirated and DMSO (200 μL per well) was added to dissolve the formazan. Absorbance at 570 nm was measured. Quercetin and rutin served as positive controls while PBS served as the negative control. The effects of L. tigris sclerotial extracts on the viability of MCF7 in relation to PBS was determined.