Microscopic Features, Mineral Contents, Anti-sickling, Antioxidant and Antibacterial Activities of Stem Bark of Harungana madagascariensis Lam. Ex Poiret (Hypericaceae)

Abstract

Aims: This study addressed the identification of bioactive compounds, the determination of mineral content and the evaluation of the antibacterial, antioxidant and anti-sickling activities of aqueous extract from stem bark of Harungana madagascariensis. Place and Duration of Study: Centre d’Etudes des Substances Naturelles d’Origine Végétale (CESNOV), Faculty of Pharmaceutical Sciences, University of Kinshasa and Faculty of Sciences, National Pedagogic University in DRC, between October 2018 and January 2021. Methodology: Phytochemical screening was evaluated by chromatographic methods (TLC and HPLC), the mineral composition by ICP-AES and the antioxidant activities using ABTS and DPPH assays, the antibacterial activity against four bacteria strains using the micro-dilution method; and the in vitro anti-sickling activity by the Emmel test. Results: Phytochemical analysis revealed the abundance in this plant of phytochemicals such as alkaloids, flavonoids, tannins, anthraquinones and triterpenoids. The extract contains sodium, iron, selenium and zinc in proportions of 955.40 ppm, 369.65 ppm, 375.70 ppm and 44.79 ppm respectively as well as copper, chromium and other elements. The antioxidant potential of the stem bark infusion extract from H. madagascariensis, evaluated by the ABTS and DPPH tests, showed very high antioxidant activity due to this free radical scavenging capacity linked to IC50 values of 3.08 ± 0.19 µg/mL (ABTS) and 3.53 ± 0.22 µg/mL (DPPH). The antibacterial sensitivity testing with MIC determination performed on a strain isolated from a sickle cell patient and four reference strains showed the MIC values of the extract ranged from 31.25 µg/mL to 250 µg/mL. The lowest MIC value was observed on S. aureus ATCC 25923 while the highest MIC value was obtained on Enterococcus spp Clinical. Conclusion: The stem bark extract of H. madagascariensis showed high anti-sickling activity at 10.42 µg/mL, which may be due to its phytochemical constituents such as saponins, alkaloids and flavonoids Obtained results could justify the efficacy of recipes from stem bark of Harungana madagascariensis in the management of various infections in traditional medicine and anti-sickle cell disease.