Extraction of Phenolic Compounds from Populus Salicaceae Bark

Abstract

Lignocellulosic residues have the potential for obtaining high value-added products that could be better valorized if biorefinery strategies are adopted. The debarking of short-rotation crops yields important amounts of residues that are currently underexploited as low-grade fuel and could be a renewable source of phenolic compounds and other important phytochemicals. The isolation of these compounds can be carried out by different methods, but for attaining an integral valorization of barks, a preliminary extraction step for phytochemicals should be included. Using optimized extraction methods based on Soxhlet extraction can be effective for the isolation of phenolic compounds with antioxidant properties. In this study, poplar bark (Populus salicaceae) was used to obtain a series of extracts using five different solvents in a sequential extraction of 24 h each in a Soxhlet extractor. Selected solvents were put in contact with the bark sample raffinate following an increasing order of polarity: n-hexane, dichloromethane, ethyl acetate, methanol, and water. The oily residues of the extracts obtained after each extraction were further subjected to flash chromatography, and the fractions obtained were characterized by gas chromatography coupled with mass spectrometry (GC–MS). The total phenolic content (TPC) was determined using the Folin–Ciocalteu method, and the antioxidant activity (AOA) of the samples was evaluated in their reaction with the free radical 2,2-Diphenyl-picrylhydrazyl (DPPH method). Polar solvents allowed for higher individual extraction yields, with overall extraction yields at around 23% (dry, ash-free basis). Different compounds were identified, including hydrolyzable tannins, phenolic monomers such as catechol and vanillin, pentoses and hexoses, and other organic compounds such as long-chain alkanes, alcohols, and carboxylic acids, among others. An excellent correlation was found between TPC and antioxidant activity for the samples analyzed. The fractions obtained using methanol showed the highest phenolic content (608 μg of gallic acid equivalent (GAE)/mg) and the greatest antioxidant activity.

Effect of Extraction Solvents on Total Polyphenolic Content and Antioxidant Capacity of Syzygium Aromaticum L. Flower Bud from Ethiopia

“…Previously, Egigu et al [ 45 ] reported that the extraction potential of solvents depend on their polarity strength. Several studies have proved the significance of high polar organic solvents for the improvement of extraction yield of phenolic compounds [ 46 – 48 ]. Highly hydroxylated aglycone forms of phenolic compounds are soluble in high polar solvents such as water and alcohols (ethanol and methanol) and hydroxy groups of phenolic compounds contribute to antioxidant activity [ 49 ].…”

“…Previously, Egigu et al [45] reported that the extraction potential of solvents depend on their polarity strength. Several studies have proved the significance of high polar organic solvents for the improvement of extraction yield of phenolic compounds [46][47][48]. Highly hydroxylated aglycone…”

Effect of Flowering Stages on the Content of Active Ingredients and Antioxidant Capability of Bletilla striata Flowers

“…The extract was used to determine the content of total phenols and flavonoids. The total phenol content was determined by the Folin‐Ciocalteu method by microplate reader (Spectramax 190, USA) [31] . The total flavonoid content was determined by the aluminum nitrate colorimetric method [32] …”

“…The total phenol content was determined by the Folin-Ciocalteu method by microplate reader (Spectramax 190, USA). [31] The total flavonoid content was determined by the aluminum nitrate colorimetric method. [32] Total Polysaccharide Content Assay…”

Hibiscus sabdariffa L. polyphenolic‐rich extract promotes muscle glucose uptake and inhibits intestinal glucose absorption with concomitant amelioration of Fe 2+ ‐induced hepatic oxidative injury

“…The choice of solvents in the present study was selected based on previous studies on their role in the extraction of polar compounds (Autor et al, 2022; Nawaz et al, 2020).…”