Alleviation of lead poisoning in the brain with aqueous leaf extract of the Thunbergia laurifolia (Linn.).

We used seven groups of 8-week-old male ICR mice, with 6 mice in each group, to test if aqueous leaf extract of the Thai medicinal plant Thunbergia laurifolia Linn. (TL) protects against lead poisoning. We found that co-treatment with aqueous TL leaf extract did not affect levels of lead in blood and brain of mice given lead in drinking water at 1 g/L for 8 weeks. However, co-treatment with aqueous TL leaf extract at 100mg/kg or 200mg/kg body weight was found to alleviate adverse effects of lead on learning deficit and memory loss, evaluated with water maze swimming test. Further, increased activity of the cell-death marker enzyme caspase-3 was observed in the brain of mice treated with lead, thereby suggesting that the memory loss could be caused by lead-induced loss of neurons in the brain. Co-treatment with aqueous TL leaf extract at 100 mg/kg or 200 mg/kg body weight was found to restore the levels of caspase-3 activity and maintain total anti-oxidant capacity and anti-oxidant enzymes in the brain. TL leaf extract thus reduced neuronal cell death and memory loss caused by lead uptake in mice, and the anti-oxidant activities of the TL leaf extract might account for these effects.