Plant-derived glucomannans: Sources, preparation methods, structural features, and biological properties

Background: Glucomannans (GMs) are a group of hydrophilic polysaccharides, which have been produced from different parts of natural plants. Studies on plant-derived GMs contribute to wide applications of GMs or GMs-added products that have desirable quality and health characteristics. Among those popular GMs, konjac glucomannan (KGM) and acemannan are the most famous ones that have been widely reviewed from various points in recent years. However, there is a lack of a comprehensive review to introduce the sources, extraction and purification methods, structural features, and other aspects of GMs from common natural plants such as Aloe, Dendrobium, Bletilla, and so on. Scope and approach: This review firstly presents the extraction and purification technologies of GMs from different plant sources, aiming at optimizing more effective production methods with specific treatments for special plant origins. After that, structural features, biological properties, as well as structure-function relationship are summarized. Key findings and conclusions: GMs have been widely isolated from different sectors (leaf, stem, and roots) of many plant resources. A general extraction and purification procedure together with several suggestions is put forward to prepare GMs. Although the beta-(1 -> 4)-linked main chain has been confirmed, detailed structural characteristics of GMs such as side chain and functional group related properties need further studies. Molecular weights, monosaccharide composition, and acetyl group of GMs are key factors that have been identified to affect plentiful biological properties such as immunomodulatory, anti-tumor, anti-diabetic activities. However, the inherent action mechanisms remain unclear. Several research interests in the future are recommended.