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 μg/ml and significant A2AR antagonist activity with 98% inhibition at 300 μg/mL. A significant adenosine A1 receptor (A1R) antagonist activity with 100% inhibition was observed at 300 μg/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.
Paracetamol (PCM) is a well-known drug widely used for its analgesic and antipyretic properties. PCM is generally considered as safe but overdose of PCM can cause nephrotoxicity. Traditionally, herbs have been used for the treatment of drug or toxin-induced renal disorders and numerous medicinal plants were tested for nephroprotection effect in PCM-induced nephrotoxicity model. The aim of the present study was to evaluate the protective effect of the herbal extract Eurycoma longifolia (EL) against PCM-induced nephrotoxicity rat model. Forty Wistar rats were randomly divided into five groups of eight rats each: control (vehicle 10 ml/kg), PCM alone (200 mg/kg PCM), EL 100 (EL 100 mg/kg+200 mg/kg PCM), EL 200 (EL 200 mg/kg+200 mg/kg PCM), and EL 400 (EL 400 mg/kg+200 mg/kg PCM). All animals from control group received vehicle daily and animals from groups PCM alone, EL 100, EL 200, and EL 400 received repeated dose of PCM and the assigned treatment of EL daily for a period of 14 days. On the 15th day, serum creatinine, blood urea nitrogen, protein, and albumin were measured in blood and creatinine clearance was measured in urine collected over 24 hours. Kidney sections of all experimental groups underwent histopathological analysis. There was a significant (p<0.05) increase in serum creatinine and blood urea levels in the PCM alone group compared to the treatment groups due to nephrotoxicity. In the treatment groups, there was a dose-dependent protection against PCM-induced changes observed in serum total protein, albumin, urea, and creatinine. Significant (p<0.05) drop was seen in serum creatinine and blood urea content in EL 200 and EL 400 groups. Creatinine clearance significantly increased for EL 200 (p<0.01) and EL 400 (p < 0.001) groups. Serum total protein and serum albumin content were significantly increased (p<0.05) in EL 200 and EL 400 groups compared to PCM alone group. Histopathological examination (H&E staining) of the rat kidneys revealed severe degeneration in the PCM alone group, while there was evidence of significant dose-dependent protection in the treatment groups against PCM-induced changes. The serum and urine biochemical results and histopathology analysis of the kidney indicate the nephroprotective potential of EL extract against PCM-induced nephrotoxicity.