Phytochemical screening and evaluation of the antioxidant activity of the polar extracts Picralima nitida Stapf. (Apocynaceae) family

Picralima nitida Stapf., synonymous Tabernaemontana nitida known under the vernacular name of NgongabA© is a medicinal plant of the family of Apocynaceae, widely used in Central African traditional medicine. This study is a contribution to the phytochemical screening and evaluation of the antioxidant activity of this species. Preliminary phytochemical tests conducted on various crude extracts of P. nitida have revealed the presence of some chemical groups: alkaloids, flavonoids, tannins, saponins, triterpenes and sterols. The estimate of the content of total phenols and flavonoids by calorimetric methods showed that the extracts methanolic, hydro-methanolic and aqueous of bark of trunk and root of Picralima nitida Stapf., showed that the extracts are rich in these compounds. The evaluation of the antiradical capability realized by the DPPH test on TLC plate on the one hand, and by the method of trapping of the free radical DPPH on microplate 96 wells, revealed that the various extracts of P. nitida respectively have a moderated reduction (2, 867 ± 0,002 mg/mL, 3,161 ± 0,016 mg/mL and 2,693 ± 0,004 mg/mL) for the extracts methanolic, hydro-mA©thanolic and aqueous, but relatively low compared to the molecule of reference, the ascorbic acid (0,064 ± 0,000 mg/mL).