Comparative study of polyphenols, flavonoids content, antioxidant and antidiabetic activities of Lophira lanceolata Tiegh.ex Keay (Ochnaceae) extracts

Abstract

The objective of this work was to explore the effect of variation in harvesting period and type of ecology on the content of polyphenols, flavonoids, antioxidant activity of Lophira lanceolata extracts and to evaluate the antidiabetic activity of the most promoting extracts. The samples of leaves, barks and roots were collected in Poundou, Dindéresso and Diarabakoko in September and November. Aqueous extracts were obtained from the samples. Polyphenols and flavonoids were quantified by the standard method using the Folin-Ciocalteu reagent and Aluminum trichloride respectively. The evaluation of antioxidant activity involved the DPPH• and ABTS+ scavenging assays and the Fe3+ reduction test (FRAP). The antidiabetic activity was evaluated by the α-amylase inhibition and glucose adsorption assays. The root extract of September of Dindéresso (1236.39±11.59 mgGAE/g DE) and the leaf extract of November of Diarabakoko (65.98±3.51 mgQE/g DE) were presented respectively the highest contents of polyphenols and total flavonoids. With the exception of leaf extracts (p≥0.05), variability in polyphenol and flavonoid contents according to harvesting period and site was observed in extracts of the different organs (p≤0.05). The root extracts was showed the best antioxidant activities respectively with the extract from September of Diarabakoko (IC50-DPPH=18.39±0.00µg/mL), September of Dindéresso (663.08±18.09 µmolAAE/g DE) for ABTS+ decolouration and November of Diarabakoko (2919.897±315.80 µmolAAE/g DE) for iron chelating. An influence of ecology type and harvesting period on antioxidant activity was observed (p≤0.05). The root extract sampled in September in Dindéresso showed the highest inhibition of α-amylase (IC50=0.91mg/mL) and maximum adsorption (119.00±44.89 mM/g DE) at 20mM glucose. Based on the observed antioxidant and antidiabetic activities, these results open new perspectives for the research of new molecules against oxidative stress and diabetes.