Subcritical Ethanol-Water and ionic liquid extraction systems coupled with multi-frequency ultrasound in the extraction and purification of polysaccharides

• Published in: Separation science and technology 2022-06, Vol.57 (9), p.1427-1441
• Main Authors: Naa Yarley, Otu Phyllis, Kojo, Azumah Bright, Felix Adom, Telfer, Zhou, Cunshan, Yu, Xiaojie, Henrietta, Agyapong, Matthew Makafui, Oklu, Reuben Essel, Arhin, Richard, Osae
• Format: Article
• Language: English
• Subjects: Aggregation; Aldehydes; Amylose; Analytical methods; Antiinfectives and antibacterials; Antioxidants; Antiviral agents; Ethanol; Fourier transforms; Functional foods & nutraceuticals; Functional groups; Imidazole; Infrared spectroscopy; Ionic liquids; Ions; molecular weight; particle size distribution; Phytochemicals; Polysaccharides; Saccharides; scanning electron microscopy; Scavenging; Sheaths; Solvent extraction; Sorghum; Sorghum bicolor (L.); Trifluoroacetyl; Ultrasonic imaging; Ultrasound; Uronic acid; viscoelasticity; Water purification
• ISSN: 0149-6395; 1520-5754
• DOI: 10.1080/01496395.2021.1987470

This study obtained crude sorghum leaf sheath polysaccharide (39.99% wet matter (wm)) by subcritical ethanol-water (40% v/v) extraction (180°C, 40 min). The subcritical extraction solution was transformed into an ionic liquid aqueous two-phase extraction system and subsequently coupled with ultrasound extraction to obtain partially purified polysaccharides (PPP). PPP yields of 20.89%, 27.38%, and 36.49% (wm) were obtained using 60 kHz, 20/60 kHz, and 20/40/60 kHz ultrasound frequencies, respectively. Polysaccharide functional groups such as hydroxyl, aldehyde, and amide were detected using Fourier Transform Infrared Spectroscopy (FT-IR). Amylose contents of 15%, 18%, and 25% were obtained for PPP under single, dual, and tri-frequencies, respectively. Amylose contents were associated with aggregation of PPP particles sizes after heat exposure (70°C for 1 h 50 min). Triple-frequency extracted polysaccharides with the highest uronic acid (1.51%) and polyphenolic (27.79%) contents had an IC50 of 1.37 mg/mL in an in-vitro hydroxyl scavenging activity assay. Three interesting co-extracted bioactive phytochemicals; 2-amino-5[(2-carboxy)vinyl]-Imidazole, N-[4-bromo-n butyl]-2-Piperidinone, and 3-Trifluoroacetyl Pentadecane were detected. The PPP extract showed antioxidant activity and contained phytochemicals with potential antimicrobial and antiviral activities, and thus may be useful in food, nutraceutical, and pharmaceutical applications.