Figure 2. The pretreatment with GSPE for 12 h was the optimal time. The cells were incubated with 20.0 mg/l GSPE for different time (12, 24, 48 h), then treated with 100 μmol/l H₂O₂ for 24 h. The cell viability was measured by MTT assay. The results showed that pretreatment with GSPE for 12 h was the optimal time.