Fig. 1. Dose–response curves of C. elegans lethality upon 6-hour MeHg (0–150 μM) exposure and a 24-hour recovery period ± pre-treatment with guarana ethanolic extract (GEE). The L4-larval stage worms untreated and pretreated with GEE from L1 were exposed to methylmercury chloride (CH₃HgCl, MeHgCl) for 6 hours. Following washing, worms were transferred to NGM plates seeded with E. coli OP50, allowed to recover for 24 hours and then scored as dead or alive using a stereomicroscope. GEE had no effect against MeHg-induced lethality on wild type (WT) worms (LD50 ≈ 66 μM) (A) but significantly increased survival in skn-1(ok2315) worms (LD50 = 38, 45, 51 and 59 μM to untreated and GEE pretreated worms at 100, 500 and 1000 μg ml^–1, respectively) (B). Data were compared with the extra sum-of-squares F test method, p < 0.05, and are expressed as means ± SEM, n = 4, approximately 100 worms analyzed per group in each assay.