Methanol stem extract of Parquetina nigrescens (Asclepiadaceae) possesses memory-enhancing potential in acute mice models of cognition

Parquetina nigrescens is an important plant in the Southwestern part of Nigeria used as memory enhancer. This study aimed to investigate the memory enhancing effect of the methanol stem extract of P. nigrescens (MSEPN).  Experimental: Phytochemical screening was carried out on the extract and the oral median lethal dose (LD50) determined using the OECD 425 limit test. The effects of MPN (250, 500 and 1000 mg/kg) on learning and memory was evaluated in elevated plus maze (EPM), Barnes maze (BM) and novel object recognition test (NORT). The locomotive activity was studied using the open field test (OFT). The antiamnesic effect of the extract was assessed in EPM. 

The phytochemical constituents in MSEPN were tannins, saponins, phenolics, carbohydrates and unsaturated sterols. The LD50 was ≥ 5000mg/kg. Piracetam and the extract significantly (p≤0.05) decreased transfer latencies (TL) on day 1 and 2 in EPM. In the BM, the escape latencies and escape errors were decreased significantly (p≤ 0.05, p≤ 0.01) at 250 and 1000 mg/kg, respectively. The time spent in target quadrant (TSQ) was significantly (p≤ 0.01) increased at 250 and 500 mg/kg of extract. Piracetam significantly decreased escape latency (p≤ 0.05), escape errors (p ≤ 0.01) and increased TSQ. Discrimination index in the NORT was significantly (p ≤ 0.01) increased. The extract did not significantly alter the number of square cross (NSC) and rearing (NR) but significantly (p ≤ 0.05) decreased TL increased by diazepam on day 1. Piracetam increased NSC and NR and significantly (p≤ 0.01, p≤ 0.05) decreased TL on day 1 and 2 in EPM.  Recommended applications/industries: The memory enhancing potential of MSEPN can be applied in the treatment of amnesia.