Total antioxidant and Anti-tyrosinase Activities of Methanol Extract of Ripe Nauclea latifolia Fruits and its Chromatographic Fractions

Abstract

Nauclea latifolia smith (family: Rubiaceae) is a valued medicinal plant widely distributed in the West and Central Africa with notable therapeutic values supporting its usage in the treatment of various ailments. This research focused on the investigation of the methanol extract of the plants’ fruits for phytochemical content, antioxidant and anti-tyrosinase inhibition activities in an in vitro system. The phytochemical content of the plant and its chromatographic fractions were investigated using total phenolics, flavanol and flavonol, while the total antioxidant capacities were determined using a series of assays such as: ferric reducing antioxidant power (FRAP), trolox equivalent antioxidant capacity (TEAC), oxygen radical absorbance capacity (ORAC) and inhibition of iron-II induced lipid peroxidation (LPO). The plant demonstrated skin pigmentation inhibitory activity with an IC50 value of 127.3µg/mL. Some notable activities displayed by the chromatographic fractions from the plant extract include: NL-VII had the highest total phenolics (53340.5µmol GAE/g) and flavonol (84275.9µmol CE/g) contents. This same fraction also showed the best antioxidant activity using TEAC (12054µmol TE/g), and ORAC (19348.8µmol TE/g) assays. Similarly, NL-VIII had the best lipid peroxidation activity with IC50 value of 49.8µg/mL and tyrosinase enzyme inhibition (TYR): IC50 124.4µg/mL. The methanol extract of the plant and some of its chromatographic fractions demonstrated varying degree of chemical composition, total antioxidant capacities and skin depigmentation activity. This is an indication that the plant may be useful in the management of oxidative stress related diseases.