Screening of Hepatoprotective Plant Components using a HepG2 Cell Cytotoxicity Assay

Identification of the active components of plants with hepatoprotective properties requires screening of large numbers of samples during fractionation and purification. A screening assay has been developed based on protection of human liver‐derived HepG2 cells against toxic damage. Various hepatotoxins were incubated with HepG2 cells in 96‐well microtitre plates (30000 cells well−1) for 1 h and viability was determined by metabolism of the tetrazolium dye 3‐(4,5‐dimethylthiazol‐2‐yl)‐5‐(3‐carboxymethoxy phenyl)‐2‐(4‐sulphophenyl)‐2H‐tetrazolium (MTS). Bromobenzene (10 mm) and 2,6‐dimethyl‐N‐acetyl‐p‐quinoneimine (2,6‐diMeNAPQI, 200 mm) had greater toxic effects than tert‐butyl hydroperoxide (1.8 mm) or galactosamine (10 mm), reducing mean viability to 44.6 ± 1.2% (s.e.m.) and 561 ± 21% of control, respectively. Protection against toxic damage by these agents was tested using a crude extract of a known hepatoprotective Sri Lankan plant, Osbeckia aspera, and two pure established hepatoprotective plant compounds, (+)‐catechin and silymarin (1 mg mL−1). Viability was significantly improved by Osbeckia (by 37.7 ± 2.4%, P < 0.05, and 36.5 ± 21%, P < 0.05, for bromobenzene and 2,6‐diMeNAPQI toxicity, respectively). Comparable values for (+)‐catechin were 68.6 ± 2.9% and 63.5 ±11%, and for silymarin 24.9 ± 1.4% and 25.0 ± 1.6%. This rapid and reproducible assay should prove useful for the isolation and identification of active hepatoprotective compounds in crude plant extracts.