Abstract
Sclerocarya birrea is a tree indigenous to Southern Africa with significant importance in rural livelihoods for food, medicine, and carving. The bark, which contains 10–20% tannin, provides several pharmacological benefits as an antidiabetic, anti-inflammatory, antimicrobial, anti-atherogenic, and antioxidant medication, among others. This study compared different extraction techniques used to recover bioactive compounds from marula bark. For this purpose, solid–liquid extraction, supercritical fluid extraction (SFE), and pressurized liquid extraction (PLE) were performed under selected conditions, using only “food-grade” solvents. The potential use of the proposed extraction methodologies was evaluated in term of yield, and the individual phenolic composition determined by HPLC–ESI–TOF–MS. PLE provided a high extraction yield in all experimental conditions. With regard to bioactive compounds composition, a total of 71 compounds, a significant percentage of which in a galloyl form, were distributed in five major categories. The largest number of compounds, mostly flavonoid aglycones, were extracted by PLE, generally when the extraction was developed at low temperatures. SFE did prove effective as a way of extracting antidiabetic proanthocyanidins. Advanced extraction techniques represent a powerful tool to obtain bioactive compounds from S. birrea bark, which can be used as supplements or food ingredients, promoting the valorization of this crop.
Highlights
Sclerocarya birrea, known as marula, is a medium-sized to large deciduous Savannah tree indigenous to Southern Africa belonging to the family Anacardiaceae
This table includes the complete information obtained by HPLC–electrospray ionization (ESI)–TOF–mass spectrometry (MS) analysis and a list of extracts in which the proposed compounds have been detected
Different extraction processes lead to the obtainment of different phenolic compounds in relation to their chemical structures
Summary
Sclerocarya birrea, known as marula, is a medium-sized to large deciduous Savannah tree indigenous to Southern Africa belonging to the family Anacardiaceae. It is favored by wildlife in conservation areas and is of significant importance in rural livelihoods [1]. The amounts produced in recent years are surprising (at least considering that this is a “lost” crop and as yet, is moderately grown in organized production). The bark, which contains 10–20% tannin as well as traces of alkaloids, provides fiber and gum to produce ink or red dye [3]. Several studies about S. birrea steam bark extracts
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