Trisaccharides are oligosaccharides composed of three monosaccharides with two glycosidic bonds connecting them. Similar to the disaccharides, each glycosidic bond can be formed between any hydroxyl group on the component monosaccharides. Even if all three component sugars are the same (e.g., glucose), different bond combinations (regiochemistry) and stereochemistry (alpha- or beta-) result in trisaccharides that are diastereoisomers with different chemical and physical properties.
Examples Trisaccharide Unit 1 Bond Unit 2 Bond Unit 3 Nigerotriose glucose α(1→3) glucose α(1→3) glucose Maltotriose glucose α(1→4) glucose α(1→4) glucose Melezitose glucose α(1→2) fructose α(1→3) glucose Maltotriulose glucose α(1→4) glucose α(1→4) fructose Raffinose galactose α(1→6) glucose β(1→2) fructose Kestose glucose α(1↔2) fructose β(1←2) fructose
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