Xylan

Xylan is a complex, branched polysaccharide and a primary component of hemicellulose found in the cell walls of plants, especially hardwoods and cereal grains [1, 13]. Chemically, it consists of a backbone of beta-1,4-linked xylose units often substituted with arabinose or glucuronic acid side chains [13]. Although it is one of the most abundant biopolymers on Earth, humans lack the xylanolytic enzymes required for its digestion, meaning it reaches the large intestine intact as a dietary fiber [3, 6]. There, it is fermented by commensal gut bacteria into xylo-oligosaccharides and short-chain fatty acids (SCFAs), which provide systemic health benefits by modulating the gut-brain axis and immune signaling [2, 7]. In pharmaceutical science, xylan is not a typical molecular target like an enzyme or receptor; rather, it serves as the parent molecule for semi-synthetic drugs such as pentosan polysulfate sodium, which is indicated for interstitial cystitis and osteoarthritis [1, 3]. Additionally, xylan's resistance to upper gastrointestinal degradation makes it an ideal material for colon-specific drug delivery systems and as a regulatory inducer in synthetic biology to control the production of therapeutic proteins by engineered microbes [4, 10, 15].

Other names

HemicellulosePoly(beta-D-xylopyranose)Pentosan1,4-beta-D-XylanGlucuronoxylanArabinoxylan

Xylan functions primarily as a prebiotic substrate fermented by gut microbiota into short-chain fatty acids (SCFAs), which activate host G-protein-coupled receptors (e.g., GPR41/43) and inhibit pro-inflammatory pathways [1, 5, 9]. Sulfated xylan derivatives, such as pentosan polysulfate, act as heparinoids to inhibit proteases, hyaluronidases, and inflammatory cytokines [1, 6]. In synthetic biology, xylan acts as a chemical inducer for gene promoters in engineered probiotic bacteria, facilitating the temporal and spatial control of therapeutic protein secretion in the gut [1, 10].