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Figure 1: D-limonene reduced H2O2-induced cell death in HLECs. (a) HLECs were incubated in 25–800 μM of H2O2 for 12, 24, and 48 h. (b) Morphology of HLECs exposed to H2O2 (0–800 μM) for 24 h. (c) HLECs are shown to be stained with the nuclear dye Hoechst 33342 (blue)/PI (red) and photographed by a confocal-fluorescence microscope. (d) HLECs were incubated in 62.5–2000 μM of D-limonene for 12, 24, and 48 h. (e) HLECs were pretreated with various concentrations of D-limonene (62.5–2000 μM) for 12 h, 24 h, and 48 h and then incubated in the presence of 100 μM H2O2 for 24 h. The results were measured by an MTT assay and expressed as a percentage of the untreated control.