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

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 ۶۲.۵ mg kg-۱ prolonged the latency for death with respect to control group (p<۰.۰۱). The effect was dose dependent. At ۲۵۰ mg kg-۱, it prolonged the latency for death with the same activity of propranolol (۲۰ mg kg-۱), that used as positive control (p>۰.۰۵). Extract showed weak activity in haemic model. Only at the highest tested dose, ۲۵۰ mg kg-۱, it significantly prolonged latency for death with respect to control group (p<۰.۰۵). Extract at this dose showed the same activity of propranolol which used as positive control (p>۰.۰۵). In asphytic model, extract at the highest tested dose showed statistically significant activity respect to the control. At ۲۵۰ mg kg-۱, it significantly prolonged the latency for death (۲۶.۸۴ ± ۴.۱۱ vs. ۱۹.۴۵ ± ۱.۱۳ min, p = ۰.۰۰۰۶). At ۱۲۵ mg kg-۱, it also prolonged survival time but this increase was not significantly different. Phenytoin that used as positive control kept mice alive for ۲۹.۶۰ ± ۲.۵۱ min (p<۰.۰۰۰۱). Extract at ۲۵۰ mg kg-۱ showed the same activity of phenytoin (p>۰.۰۵). The total phenolic content was ۳۴۲.۹ ± ۱۱.۵ mg gallic acid equivalent/g of extract powder and flavonoid content was ۹۰.۲ ± ۷.۸ mg quercetin equivalent/g of extract powder. IC۵۰ for DPPH radical-scavenging activity was ۲۱.۹۷ ± ۲.۴ mg/ml. The presence of polyphenols in this plant may be a proposal mechanism for reported antihypoxic activities.