Stachyose is a tetrasaccharide belonging to the raffinose family of oligosaccharides (RFOs), composed of two α-D-galactose units, one α-D-glucose unit, and one β-D-fructose unit, with the molecular formula C₂₄H₄₂O₂₁ and a molecular weight of 666.58 g/mol. It features sequential linkages as Gal(α1→6)Gal(α1→6)Glc(α1↔2β)Fru, appearing as a white to off-white powder soluble in water. It occurs naturally in legumes such as soybeans, green beans, and plants like Stachys tubifera.

Chemical Structure

Stachyose consists of a sucrose core (glucose–fructose) with two α-D-galactosyl units attached via α-(1→6) bonds to the glucose at position 6. Its IUPAC name reflects its complex pyranose and furanose composition: O-α-D-galactopyranosyl-(1→6)-O-α-D-galactopyranosyl-(1→6)-O-α-D-glucopyranosyl-(1→2)-β-D-fructofuranoside. Computed structural properties, including InChI and SMILES notations, confirm its non-reducing nature and hydrophilic biochemical profile.

Biological Occurrence and Role

Stachyose accumulates in seeds of legumes and tubers, where it functions as a storage carbohydrate and osmoprotectant during seed development and abiotic stress. In humans, it resists hydrolysis by digestive enzymes, reaching the colon intact, where it is fermented by gut microbiota. This fermentation supports potential prebiotic effects but may also contribute to flatulence due to microbial gas production.

Preparation and Applications

Stachyose is typically isolated from soybean meal or synthesized enzymatically using galactosyltransferases acting on raffinose. Commercial preparations are used in research on prebiotic activity, plant metabolism, and food processing strategies aimed at reducing RFO content in legumes. Its chemical stability also makes it valuable for studies involving α-galactosidase enzymes and evaluating nutritional impacts in animal feed formulations.