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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 ± 0.00 µg/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=0.91 mg/mL) and maximum adsorption (119.00 ± 44.89 mM/g DE) at 20 mM 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.

Objective: The aim of this study was to evaluate the antiradical and inhibitory activity of whole plant extracts of Phyllanthus amarus and Striga hermonthica on a-amylase. Methods: The crude 70% (v/v) hydroethanolic extracts obtained were used for the assay of polyphenols, the antiradical test with DPPH, the test for the inhibition of a-amylase with DNS (3,5-dinitrosalicylic). The enzyme extracts were obtained from sorghum malt (Sorghum bicolor). Results: It appears from this study that the extract of P. amarus was richer in polyphenols than the extract of S. hermonthica. Regarding the antiradical activity, the extract of S. hermonthica showed an IC50 of 339.06 ± 1.43 µg/mL against 77.74 ±2.73 µg/mL for the extract of P. amarus. Regarding the anti a-amylase activity, the extract of P. amarus inhibited IMS127 and KMTC 274 respectively 43.64 ±0.59% and 66.28 ±1.97%. On the other hand, the extract of S. hermonthica presented an inhibition of 3.93 ±0.91% on IMS127 and 14.85 ±1.62% on KMTC 274. The extract of P. amarus presents a good antiradical activity and anti a-amylase compared to S. hermonthica extract. In conclusion, these results partly explain the use of these plants in traditional medicine to treat or relieve people suffering from diabetes. [ABSTRACT FROM AUTHOR]