Protective effects of ethanolic extract of Lemon Beebrush (Aloysia citrodora) leaf against hypoxia-induced lethality in mice

Abstract

Lemon Beebrush, known as Lippia citroiodora and Aloysia citrodora is a known medicinal plant in Iran. Many biological activities have been reported from this plant. In spite of many works, nothing is known about protective effect of A. citrodora against hypoxia conditions. In this study, protective effects of A. citrodora leaf extract against hypoxia-induced lethality in mice were evaluated by three experimental models of hypoxia, asphyctic, haemic and circulatory. Its phenol and flavonoid contents and antioxidant activity were also evaluated. Statistically significant protective activities were established in some doses of extract in three models. Antihypoxic activity was especially pronounced in circulatory hypoxia where extract at 62.5 mg kg-1 prolonged the latency for death with respect to control group (p<0.01). The effect was dose dependent. At 250 mg kg-1, it prolonged the latency for death with the same activity of propranolol (20 mg kg-1), that used as positive control (p>0.05). Extract showed weak activity in haemic model. Only at the highest tested dose, 250 mg kg-1, it significantly prolonged latency for death with respect to control group (p<0.05). Extract at this dose showed the same activity of propranolol which used as positive control (p>0.05). In asphytic model, extract at the highest tested dose showed statistically significant activity respect to the control. At 250 mg kg-1, it significantly prolonged the latency for death (26.84 ± 4.11 vs. 19.45 ± 1.13 min, p = 0.0006). At 125 mg kg-1, it also prolonged survival time but this increase was not significantly different. Phenytoin that used as positive control kept mice alive for 29.60 ± 2.51 min (p<0.0001). Extract at 250 mg kg-1 showed the same activity of phenytoin (p>0.05). The total phenolic content was 342.9 ± 11.5 mg gallic acid equivalent/g of extract powder and flavonoid content was 90.2 ± 7.8 mg quercetin equivalent/g of extract powder. IC50 for DPPH radical-scavenging activity was 21.97 ± 2.4 mg/ml. The presence of polyphenols in this plant may be a proposal mechanism for reported antihypoxic activities.