*2.8. Cytotoxicity of Spice Extracts*

Human foreskin fibroblast (HFF) cells were grown in DMEM medium supplemented with 10% fetal bovine serum (FBS), and maintained at 37 ◦C in a humidified 5% CO2 incubator. The toxicity of spice extracts was evaluated by 3-(4,5)-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay as described by Mosmann with slight modification [26]. HFF cells were seeded at a density of <sup>5</sup> <sup>×</sup>104 cells/mL into the 96-well plate and incubated overnight to adhere the cells. The cells were treated with various concentrations (5–100 μg/mL, and the concentration of DMSO was diluted below 0.1%) of different extracts and incubated at 37 ◦C in a humidified 5% CO2 incubator for 24 h. The untreated cells were included as control. After the incubation period, MTT (20 μL of 5 mg/mL) was added into each well and incubated for 4 h. The formazan crystals were dissolved with DMSO (100 μL). The absorbance was measured at 570 nm using a microtitre plate reader (SpectraMax iD3, Molecular Devices, Silicon Valley, NC, USA). The LC50 value was calculated as the concentration of the extract that resulted in 50% reduction of absorbance compared to control cells [27].
