Sclerocarya birrea (A. Rich) Hochst (Marula), commonly known as the tree of life, belongs to the Anarcadiaceae family and is widely distributed in southern African regions including South Africa, Zimbabwe, Botswana, Mozambique, Zambia, and Namibia. Generally, stem bark and leaves are used for medicinal purposes and fruits in the food and beverages industries. Known constituents of S. birrea include gallotannins, flavonoids, alkaloids, steroids (β-sitosterol), coumarins, triterpenoids, sesquiterpenes, ascorbic acid, oleic, myristic and stearic acids, amino acids, gallic acid, myricetin, (-)-epigallacatechin-3-O-galloylester and (-)-epicatechin.1 Known biological activities of S. birrea include antidiabetic, anti-inflammatory, antiplasmodial, antimalarial, antiproliferative, antimicrobial, and apoptopic effects.2 In the current study, analysis of an ethanolic extract of S. birrea bark revealed a strong NOX4 inhibitory effect (66%). TLC and HPLC-MS were used to chemically characterise the extract. Furthermore, the extract was subjected to liquid-liquid partitioning using solvents of different polarity. Biological testing on NOX4 showed that the butanol and the ethylacetat fraction had the most superior inhibitory activity, 84% and 79%, respectively. Thus, all isolation work was performed on these two fractions. Major compounds were isolated and purified using various chromatographic techniques including column chromatography, flash chromatography, and semi-preparative HPLC. Isolated compounds were identified and characterised using MS and NMR. The following compounds were isolated from the ethylacetate fraction, (+)-catechin (290.27 m/z), (-)-epicatechin (290.27 m/z), (-)-epigallocatechin-3-O-gallate (EGCG) (458.37 m/z), (-)4’-O-methylepigallocatechin-3-O-gallate (4’-O-methyl-EGCG) (472.40 m/z), and (-)-epicatechin-3-O-gallate (ECG) (442.37 m/z). To our knowledge, (-)4’-O-methylepigallocatechin-3-O-gallate (4’-O-methyl-EGCG) (472.40 m/z) was identified and isolated for the first time in this study from S. birrea bark.
Acknowledgements: Supported by the EU-Marie-Curie Actions (H2020-MSCA-RISE project 691158 “MediHealth”).
References:
[1] Jiménez-Sánchez C., Lozano-Sánchez J., Gabaldón-Hernández J.A., Segura-Carretero A., Fernández-Gutiérrez A. Ind Crops Prod 2015; 7:214-234.
[2] Mariod A.A., Abdelwahab S.I. Food Rev Int 2012; 28:375-388.