Characterisation of the arabinose-rich carbohydrate composition of immature and mature marama beans (Tylosema esculentum)

• Published in: Phytochemistry (Oxford) Vol. 72; no. 11-12; pp. 1466 - 1472
• Main Authors: Mosele, Minah M., Hansen, Åse S., Engelsen, Søren B., Diaz, Jerome, Sørensen, Iben, Ulvskov, Peter, Willats, William G.T., Blennow, Andreas, Harholt, Jesper
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Ltd 01.08.2011; Elsevier
• Subjects: acids; arabinans; arabinose; Arabinose - chemistry; beans; Biological and medical sciences; carbohydrate composition; Cell Wall - chemistry; Cell wall composition; cell walls; Chemical constitution; Chemical Fractionation; CoMPP; dietary supplements; drought; Edetic Acid - analogs & derivatives; Edetic Acid - chemistry; Fabaceae - chemistry; Fabaceae - growth & development; Fundamental and applied biological sciences. Psychology; Glycosylation; HPAEC-PAD; Hydrolysis; Legume; Linkage analysis; lipids; mannose; Marama bean; Morama bean; Pectin; pectins; Pectins - chemistry; Plant physiology and development; Plant Proteins - chemistry; seeds; Seeds - chemistry; Seeds - growth & development; Solubility; Soluble sugars; Starch; storage proteins; Tylosema esculentum; Morama bean; Tylosema esculentum; CoMPP; Starch; Cell wall composition; Pectin; HPAEC-PAD; Marama bean; Legume; Soluble sugars; Linkage analysis; Chemical structure; Cell wall; Leguminosae; Dicotyledones; Angiospermae; Plant origin; Spermatophyta; Carbohydrate; Immaturity; Sugar
• ISSN: 0031-9422; 1873-3700
• DOI: 10.1016/j.phytochem.2011.03.027

In alcohol insoluble material of marama beans 40% of the arabinan was recalcitrant to severe alkaline extraction. Mannose from protein glycosylation was also observed. [Display omitted] ► Marama bean has less than 1% starch and soluble sugars. ► Arabinose from arabinan is the main non-cellulosic sugar in the mature marama bean cell wall. ► Two fractions of pectin was identified, a low and a high recalcitrant fraction. Marama bean (Tylosema esculentum) is an important component of the diet around the Kalahari Desert in Southern Africa where this drought resistant plant can grow. The marama bean contains roughly 1/3 proteins, 1/3 lipids and 1/3 carbohydrates, but despite its potential as dietary supplement little is known about the carbohydrate fraction. In this study the carbohydrate fraction of “immature” and “mature” marama seeds are characterised. The study shows that the marama bean contains negligible amounts of starch and soluble sugars, both far less than 1%. The cell wall is characterised by a high arabinose content and a high resistance to extraction as even a 6M NaOH extraction was insufficient to extract considerable amounts of the arabinose. The arabinose fraction was characterised by arabinan-like linkages and recognised by the arabinan antibody LM6 and LM13 indicating that it is pectic arabinan. Two pools of pectin could be detected; a regular CDTA (1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid) or enzymatically extractable pectin fraction and a recalcitrant pectin fraction containing the majority of the arabinans, of which about 40% was unextractable using 6M NaOH. Additionally, a high content of mannose was observed, possibly from mannosylated storage proteins.