The stembarks of Harungana madagascariensis were analyzed for their content of chemical constituents, antinutrients, vitamin levels, and in vitro antioxidant properties in two solvent systems. Phytochemical screening revealed higher levels of alkaloids, saponins, and flavonoids in the methanolic (MHM) extract than in the dichloromethane (DCM) extract. The methanolic extract had higher contents of minerals, vitamins, and antinutrients except K, vitamin B1, and phytic acid, respectively. Antioxidant potentials of the stembark extracts were assessed by the 1, 1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity, metal chelating activity, and ferric reducing power. The methanolic extract showed a better antioxidant activity (IC50=87.66±0.97 μg/mL) in the DPPH system. The metal chelating activity was higher in the methanolic extract (92.4% at 20 mg/mL), but lower than the control ethylenediaminetetraacetic acid (EDTA). The methanolic extract also showed greater ferric reducing power and was richer in phenolics (132.24±0.61 mgGAE/g) and flavonoids (259.05±2.85 mgQE/g). Antinutrient analysis of the extracts indicated low levels of phytic acid, oxalates, and hydrocyanides below the lethal doses. The LD50 (i.p. mice) of the extracts showed relatively low toxicity in the range 1000-1414 mg/kg. These results support the ethnomedicinal uses of this plant in the treatment of diseases related to oxidative stress and suggest that consumption of H. madagascariensis is not harmful nutritively.
Keywords: Harungana madagascariensis; antioxidant activity; bioactive compounds; mineral element; vitamins.