Effects of a Proprietary Standardized Orthosiphon stamineus Ethanolic Leaf Extract on Enhancing Memory in Sprague Dawley Rats Possibly via Blockade of Adenosine A 2A Receptors

Abstract EN

The aim of the study was to explore a propriety standardized ethanolic extract from leaves of Orthosiphon stamineus Benth in improving impairments in short-term social memory in vivo, possibly via blockade of adenosine A2A receptors (A2AR).

The ethanolic extract of O.

stamineus leaves showed significant in vitro binding activity of A2AR with 74% inhibition at 150 μ g/ml and significant A2AR antagonist activity with 98% inhibition at 300 μ g/mL.

A significant adenosine A1 receptor (A1R) antagonist activity with 100 % inhibition was observed at 300 μ g/mL.

Its effect on learning and memory was assessed via social recognition task using Sprague Dawley rats whereby the ethanolic extract of O.

stamineus showed significant ( p < 0.001 ) change in recognition index (RI) at 300 mg/kg and 600 mg/kg p.o and 120 mg/kg i.p., respectively, compared to the vehicle control.

In comparison, the ethanolic extract of Polygonum minus aerial parts showed small change in inflexion; however, it remained insignificant in RI at 200 mg/kg p.o.

Our findings suggest that the ethanolic extract of O.

stamineus leaves improves memory by reversing age-related deficits in short-term social memory and the possible involvement of adenosine A1 and adenosine A2A as a target bioactivity site in the restoration of memory.