Isolation and identification of an arabinogalactan extracted from pistachio external hull: Assessment of immunostimulatory activity

• Published in: Food chemistry 2022-03, Vol.373 (Pt A), p.131416-131416, Article 131416
• Main Authors: Hamed, Mariem, Coelho, Elisabete, Bastos, Rita, Evtuguin, Dmitry V., Ferreira, Sónia S., Lima, Tânia, Vilanova, Manuel, Sila, Assaad, Coimbra, Manuel A., Bougatef, Ali
• Format: Article
• Language: English
• Subjects: Arabinogalactan-protein; Galactans; Immunostimulatory activity; Methylation analysis; Molecular Weight; NMR spectroscopy; Pistacia; Polysaccharides; Structural characterization
• ISSN: 0308-8146; 1873-7072
• DOI: 10.1016/j.foodchem.2021.131416

•A branched arabinogalactan (AG) was isolated from Pistachio hull.•The purified fractions contained a type II arabinogalactan carbohydrate moiety.•AG structural elucidation was attained by methylation analysis, 1D/2D NMR, and SEC.•Arabinogalactans displayedimmuno-enhancing effects.•Pistachio AG could be explored as a potent food additive or nutritional supplement. This work studies the extraction and purification of a novel arabinogalactan from pistachio external hull. It was extracted with a simple method from pistachio hull which is considered as unexploited waste. Based on the results of sugar analysis by GC-FID, glycosidic linkage by GC–MS, NMR spectroscopy, and molecular weight by Size Exclusion Chromatography, pistachio hull water soluble polysaccharides (PHWSP) were identified as a type II arabinogalactan (AG), with characteristic terminally linked α-Araf, (α1 → 5)-Araf, (α1 → 3,5)-Araf, terminally linked β-Galp, (β1 → 6)-Galp, and (β1 → 3,6)-Galp. DEPT-135, HSQC, HMBC and COSY NMR data suggested the presence of (β1 → 3)-Galp mainly branched at O-6 with (β1 → 6)-Galp chains, α-Araf chains, and terminally linked α-Araf. These AG from pistachio external hulls showed in vitro stimulatory activity for B cells, suggesting their possible use as an immunological stimulant in nutraceutical and biomedical applications.