20 species of Thai local vegetables (Table 1) were purchased at retail
in Bangkok and Chonburi, Thailand during October-November,
2005. The plant materials were cut into small pieces, freeze dried
and powdered. Then, 10 g of each were soaked in 150 ml methanol
and shaked at 200 rpm for 24 h at ambient temperature. The mixtures
were filtered. The filtrates were evaporated using vacuum rotary
evaporator and air dried at 40°C. Stock solutions of crude methanolic
extracts were prepared by diluting the dried extracts with
10% dimethyl sulphoxide (DMSO) solution to obtain a final concentration
of 400 mg/ml.