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.
Supported by the EU-Marie-Curie Actions (H2020-MSCA-RISE project 691158 “MediHealth”).
[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.