Phytochemical screening, antioxidant, analgesic and acetylcholinesterase inhibitory effects of Pittosporum tobira leaves

Abstract

The objective of this study was to determine in the first time the phytoconstituents and the in vitro antioxidant and enzyme inhibitory properties of the ethanol extract of P. tobira leaves (PTL) and to assess its in vivo pharmacological action on pain.Phytochemical screening was done using standard protocols. The antioxidant potential was investigated using two methods including hydrogen peroxide and DPPH radical-scavenging assays. An assessment of the anti-acetylcholinesterase activity of PTL was performed. The analgesic activity was also evaluated using a hot plate and acetic acid assays.Alkaloid, saponins, cardiac glycoside, terpenoids, flavonoids and reducing sugars were found to be present in the leaf of P. tobira. PTL showed a significant antioxidant capacity by inhibition of DPPH radical (EC50 = 143.4 µg/mL) and H2O2 (EC50 = 46.29± 2.1 µg/mL) scavenging activities. Moreover, acetylcholinesterase enzyme was strongly inhibited by PTL with the IC50 value of 100.79 µg/mL. The analgesic effect of PTL was evaluated in mice after intraperitoneal injection of acetic acid (1%, 10 mL/kg, ip). The results showed that PTL reduced significantly the abdominal writhing in mice with an inhibition percentage of 14.78%, comparable with standard paracetamol (10.31%). Furthermore, PTL (350 mg / kg) increased remarkably the reaction time of mice with relatively extended duration of stimulation in the hot-plate test when compared to the control groups.We conclude that the leaf extract of P. tobira possesses potential antioxidant, anti-nociceptive, and anti-acetylcholinesterase properties which could be assigned to the presence of bioactive compounds in its composition.