3'-Fucosyllactose (3'-FL) is a neutral fucosylated trisaccharide and one of the major human milk oligosaccharides (HMOs) in breast milk. It is characterized by an L-fucose residue linked via an α-1,3 glycosidic bond to the galactose unit of a lactose core (Galβ1-4Glc). Although it shares the same molecular formula (C18H32O15) and molecular weight (488.44 g/mol) as its isomer 2'-FL, the difference in fucose linkage position significantly influences its biological interactions.
Chemical Structure and Properties
The structure of 3'-FL is defined as Fuc(α1-3)[Gal(β1-4)]Glc, forming a branched configuration in which fucose attaches to the 3-position of the galactose residue in lactose. It appears as a white to off-white solid with high hygroscopicity, limited solubility in water and DMSO, a decomposition temperature above 165°C, and a predicted boiling point near 916.5°C. Because it resists hydrolysis by human digestive enzymes, 3'-FL reaches the colon intact, functioning as a prebiotic to support beneficial gut microbiota.
Biological Functions and Occurrence
Naturally present in human milk, 3'-FL plays an important role in shaping infant gut microbiota by selectively promoting Bifidobacterium species and preventing pathogen adhesion through competitive inhibition mechanisms. It also exhibits immunomodulatory, anti-inflammatory, and antiviral properties, supporting neonatal immune maturation and intestinal barrier integrity. Its unique fucose orientation, distinct from that of 2'-FL, contributes to specific ligand-binding interactions with host receptors and microbial enzymes.
Production and Applications
Industrial production of 3'-FL relies on microbial fermentation or enzymatic synthesis using fucosyltransferases, enabling its incorporation into infant formula and functional foods. Regulatory authorities such as the Therapeutic Goods Administration recognize its safety for nutritional use. Active research continues to explore its therapeutic potential in gut health, immune modulation, and infection prevention.
