Analgesic effects of Arum maculatum plant extract in rats compared to other routine analgesics

Due to low side effects and costs as well as proper adaptation to body’s physiology, there is a global trend in using herbal medications. To investigate the analgesic effects of Arum maculatum plant extract in rats via an experimental study, 60 healthy male Wistar rats were divided into 6 equal groups including 3 plant extract groups, a negative control with normal saline and 2 positive control groups with morphine and diclofenac Na injections. Morphine, diclofenac or different dosages of extract were injected subcutaneously into the left sole of rats via insulin syringes. Two hundred microliters of 1% formalin were then subcutaneously injected into the left paw of each rat for pain induction. The duration of the left paw licking was measured just after formalin injection (phase I) and 20 min after the injection (phase II). Finally, the mean duration of paw licks was compared between treatment and control groups. The shortest duration of licks was found in the morphine injected group (30.6 ±1.9 and 37.2±1.1 seconds at phase I and II, respectively). Compared to diclofenac injection, plant extract of 500 and 750 mg/kg reduced the licks duration significantly during both phases (p<0.0001). The lick durations, after the injection of 500 and 750 mg/kg extracts, were almost the same as that in the morphine injected group during phase I, but took longer during phase II. Rats in the 750 mg/kg extract injected group, compared to those in the 500 mg/kg extract injected group, showed a significantly shorter lick duration during phase II (p<0.0001), but not phase I (p=0.708). Following further investigations in human, A. maculatum plant extract can be introduced as a natural and better analgesic substitution for diclofenac Na which has the same effect as morphine during phase I.     Key words:  Arum maculatum, morphine, diclofenac Na, formalin, Iran.