Enhancing the Yield of Bioactive Compounds from Sclerocarya birrea Bark by Green Extraction Approaches

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.

Obtaining an Extract Rich in Phenolic Compounds from Olive Pomace by Pressurized Liquid Extraction

“…Olive pomace phenolic compounds are a complex mixture of components that include hydroxytyrosol and tyrosol derivatives, iridoid precursors, secoiridoids and derivatives (oleuropein, oleuropein aglycone, ligstroside and its derivatives), phenylpropanoids (verbascoside and its derivatives), flavonoids (luteolin, apigenin, rutin, taxifolin and its derivatives), lignans (pinoresinol and derivatives), and phenolic acids (gallic acid, caffeic acid, cinnamic acid, p -coumaric acid, ferulic acid, vanillic acid, and shikimic acid) [7,8,9,10]. However, the concentration of these phenolic compounds has been reported to be affected by both agronomic and technological process conditions such as type of cultivar, ripening degree, different milling process, and edaphoclimatic factors [8,9].…”

“…Nevertheless, the industrial interest has been addressed to develop new processes based on more selective, environmentally-friendly, and cost-effective extraction techniques. Among these technologies, microwave-assisted extraction (MAE), supercritical fluid extraction (SFE) using CO 2 , and pressurized liquid extraction (PLE) have been applied to olive by-products [7,9].…”

Optimized Extraction of Phenylpropanoids and Flavonoids from Lemon Verbena Leaves by Supercritical Fluid System Using Response Surface Methodology

“…Both scenarios enabled the retrieval of compounds from raw material. Therefore, at constant pressure, an increase of temperature produces a decrease of supercritical fluid density and consequently improves the compounds’ solubility [ 29 ].…”

“…However, this factor did not present any significant values. According to other studies, the decrease of density caused by high temperatures could enable the penetration of solvents into the matrix, improving the solubility of polar compounds into the solvent mix [ 11 , 29 ].…”

“…According to previous reports, high concentrations of ethanol added into the solvent mix may hinder the retrieval of components from matrix. This effect could be related to the reduction of the extraction mixture homogeneity [ 29 ]. Nevertheless, ethanol was needed to improve the solubility of polar compounds [ 28 ].…”