Antioxidants and hypoglycemic effect of some medicinal plants

There is an increasing trend to replace synthetic drugs, which are of safety concern, with the natural remedies available from plant extracts. This study investigated the phytoconstituents as well as antioxidants and hypoglycemic effect of Anarcadium occidentales, Huntaria umbellata, Parkia biglobosa, Psidium guajava and Vitellaria paradoxa. Phytochemicals compositions were assayed using standard procedures. Antioxidant assays employed were ferric reducing antioxidant power and scavenging effect on the 1, 1-diphenyl-2-picrylhydrazyl radicals. Oral glucose tolerance test (OGTT) and amylase inhibitory assays were employed for hypoglycemic study. The concentration of phenols ranges from 184.368±0.23 mg/g (Anacardium occidentales) to 120.241±0.01 mg/g (Hunteria umbellata). However, Hunteria umbellata extract had the highest alkaloids (76.76±0.01 mg/g), Parkia biglobosa extract had the highest tanins (137.55±0.05 mg/g) while Vitellaria paradoxa extract had higher saponins (188.50±0.01 mg/g). Flavonoids was higher in Parkia biglobosa (458.06±0.06 mg/g) while Psidium guajava had the least. In DPPH assay A. occidentales extract had the lowest IC50 (217.78±3.45 µg/ml) comparable with the standards while H. umbellata had the highest (IC50=311.72±3.45 µg/ml) and thus lowest activity. Anarcadium occidentales had higher α-amylase inhibitory activity (IC50 =171.13±0.14 μg/ml) while Psidium guajava (IC50 =304.64 ±0.14 μg/ml) had the least activity. Oral glucose tolerance revealed the activities of the extracts in order of Anacardium occidentales>Hunteria umbellata>Vitellaria paradoxa>Parkia biglobosa>Psidium guajava. In conclusion, five medicinal plants investigated in this study possesses some antioxidants and hypoglycemic properties with Anacardium occidentales extract being the most potent, which may be attributed to their polyphenolic constituents.