Abstract

EVALUATION OF THE ANTIOXIDANT PROPERTIES AND DETERMINATION OF PHENOLIC CONTENT OF N-HEXANE AND DICHLOROMETHANE EXTRACTS OF DIFFERENT PARTS OF PICRALIMA NITIDA (STAPF) T. DURAND AND H. DURAND (APOCYNACEAE).

Arnold C. Igboasoiyi*, Paul S. Thomas, Idongesit P. Sunday and
Amarachi P. Egeolu

ABSTRACT

Picralima nitida (Staphf) T. Durand and H. Durand (Apocynaceae) is a rainforest tree rich in alkaloids, and occurring in Africa forest region. It has varied applications in West Africa folk medicine. Various parts of the plant like the leaves, seeds, stem bark and roots are used for the treatment of fever, hypertension, jaundice, gastrointestinal disorders and malaria. The n-hexane and dichloromethane (DCM) oily extract of the leaves, fruit mesocarp, fruit pericarp, seed, seed rind and stem bark of Picralima nitida were evaluated for antioxidant properties as well as determination of phenolic content. The leaves, fruit mesocarp, fruit pericarp, seed, seed rind and stem bark of P. nitida were collected, dried, pulverized and extracted successively with n-hexane and DCM for 72 h at room temperature using maceration method. The liquid extracts obtained after filtration were concentrated in vacuo at 30oC to obtain the oily extracts. The concentrated oily extracts of the various parts of the plant were analysed for antioxidant properties using 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay and Ferric ion Reducing Antioxidant Power (FRAP) assay as well as determination of total phenolic content. The results were compared with that of a standard antioxidant. Both the n-hexane and DCM extracts of the P. nitida parts exhibited good antioxidant activity, although the activity was not comparable with that of the standard - ascorbic acid. At the concentration of 100 μg/mL, the highest antioxidant scavenging activity was expressed by DCM seed extract (75%) followed by seed rind extract (74%) in the DPPH assay. In the FRAP assay the highest antioxidant reducing power was exhibited by DCM seed extract (0.646 nm) followed by mesocarp extract (0.639 nm) at 100 μg/mL, and this was not comparable to that of ascorbic acid (1.735 nm) used as a standard. Phenolic content was more in the DCM seed extract (20.0 mg/g) and seed rind (17.8 mg/g). However other extracts also exhibited antioxidant properties in varying proportions.

Keywords: Ferric Reducing Antioxidant Power, 2, 2-diphenyl-1-picrylhydrazyl, Picralima nitida, Apocynaceae, Alkaloids.