Hydro-ethanolic leaf extract of Ziziphus abyssinica Hochst Ex A. Rich (Rhamnaceae) exhibits anti-nociceptive effects in murine models

Background: Despite substantial advances in pain research and treatment, millions of people continue to suffer from pain and this has been attributed mainly to the unavailability of effective and safer analgesics. The use of plants as medicines is still widespread and plants constitute a large source of novel phytocompounds that might become leads for the discovery of newer, effective and safer alternatives. Various parts of Ziziphus abyssinica have been used in folk medicine in several African countries as painkillers. However, there is no report on the possible anti-nociceptive effects of this plant especially the leaves, hence the need for this current study. Methods: The possible anti-nociceptive activity of hydro-ethanolic leaf extract of Ziziphus abyssinica (EthE) was assessed in rodents using chemical (acetic acid, formalin and glutamate), thermal (tail-immersion test) and mechanical/inflammatory (carrageenan) models of nociception. Results: EthE (30-300 mg/ kg, p.o.) dose-dependently and significantly inhibited chemical-induced nociception with a maximum inhibition of 86.29 +/- 2.27%, 76.34 +/- 5.67%, 84.97 +/- 5.35%, and 82.81 +/- 5.97% respectively for acetic acid, formalin (phase 1), formalin (phase 2) and glutamate tests at its highest dose. EthE also dose-dependently and significantly increased reaction times in both tail-immersion and carrageenan-induced hypernociceptive tests. The activities of the extract in the various models were comparable with the effect of morphine hydrochloride and diclofenac sodium used as standard analgesic drugs. Conclusion: Oral administration of hydro-ethanolic leaf extract of Ziziphus abyssinica ameliorates nocifensive behaviours associated with chemical-,thermal-and mechanical/inflammatory -induced nociceptive pain.