The first assessment on antioxidant and antidiabetic activities of leaves and stems of Vaccinium secundiflorum Hook. (Ericaceae), an endemic plant of Madagascar

Vaccinium secundiflorum Hook. (Ericaceae family) is an endemic shrub of the Tapia forests of Madagascar widely used by local Malagasy population to treat diabetes mellitus. This study aims to preliminarily determine the antioxidant activity and anti-diabetic properties of this plant. Plant leaf and stem powders were macerated in methanol 95%. The methanol extract (MVS) was used for (i) phytochemical fingerprint by High Performance Liquid Chromatography (HPLC), (ii) total phenolic content (TPC) evaluation by the Folin–Ciocalteu colourimetric method, (iii) 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenger spectrophotometric assay, (iv) antioxidant capacity by Ferric Reducing Antioxidant Power (FRAP) assay, and (v) antidiabetic activity evaluation by oral glucose tolerance test and acute toxicity in mice. Leaves and stems of V. secundiflorum presented a high rate of TPC (4151.02 ± 745.21mgGAE/100 g of dry weight). The HPLC fingerprint analysis showed the presence of several secondary metabolite classes including organic acids (55.31%), phenolic compounds (29.66%), carotenoids (10.90%), vitamin C (3.96%), and monoterpenes (0.10%). The DPPH free radical scavenger spectrometric assay showed a MVS high potential scavenging activity (IC50 = 76.06 ± 1.08 µg/mL). This potential antioxidant capacity was confirmed by the FRAP assay results (69.31 ± 3.31 mmol Fe2+/Kg of dry weight). The oral glucose tolerance test in mice showed a highly significant blood glucose-lowering effect. The acute toxicity in mice revealed that the MVS did not show toxicity at the dose of 2000 mg/kg. Leaves and stems of V. secundiflorum showed significant antioxidant and antidiabetic properties supporting the plant traditional use, even if further studies on bioactive compounds and their action mechanisms should be carried out to confirm these preliminary results.