Galactomannan is a neutral hemicellulose biopolymer, mainly extracted from the endosperm of plant seeds and located in the cell wall of the seed endosperm. For example, during the development of Sophora japonica seeds, galactomannan is first formed in the vesicle cavity of the rough endoplasmic reticulum of the endosperm cells adjacent to the embryo, and is secreted around the cell wall through the cytoplasmic membrane. After that, the accumulation of galactomannan gradually extends to the seed coat, and when the seeds mature, all endosperm cells are almost completely filled with polysaccharides except for the endosperm layer. Galactomannan is widely used in cosmetics, pharmaceuticals, biomedicine, food, paper and other industries due to its functions (binder, emulsifier, stabilizer, thickener, fat substitute) and biological activities (lowering blood sugar, preventing constipation, regulating insulin levels, improving intestinal bacteria, lowering cholesterol, and preventing cancer). Locust bean gum (LBG) is a galactomannan. Locust bean gum is a vegetable gum processed from the seeds of the black locust tree, which grows in the Mediterranean region. It is a colourless and odourless refined polysaccharide of the plant endosperm, mainly containing mannose and galactocarboxylate, and is a white or slightly yellow powder, odourless or slightly smelly. Locust bean gum comes from the endosperm of the bean kernel in the pod of the legume carob tree. It is white to yellowish-white in colour, powdery in consistency, odourless and tasteless. In the highest quality products, there are no obvious brown skin spots and the mesh size ranges from 140 to 200 mesh. The main component of locust bean gum is high molecular weight galactomannan with a relative molecular weight of approximately 50,000 to 3 million. It is used as a thickener, water retention agent, stabiliser, etc. in the food, pharmaceutical, cosmetic and other industrial sectors. Locust bean gum is characterised by its high viscosity, low impurities and almost transparent colour.
Figure 1. Carob fruit and locust bean gum. (Petitjean M, et al.; 2022)
Galactomannan is a neutral heteropolysaccharide. Its main chain is connected by d-mannose through β-1,4 glycosidic bonds, and the side chain is connected by d-galactose through α-1,6 glycosidic bonds. Galactomannan is generally considered to be a random coil polymer, and a small amount of helical structure can be formed under alkaline conditions. Galactomannan is mainly extracted from plants such as carob, guar, tara and fenugreek. Its properties are affected by factors such as molecular weight, mannose/galactose ratio (M/G) and the distribution of galactosyl groups along the main chain. The molecular weight range of galactomannan is very wide, and the plant source, origin, preparation process and biodegradation during storage will affect its molecular weight. Galactomannan has good water solubility and cross-linking properties, and can form a translucent viscous liquid when dissolved in water. Galactomannan has good water solubility and cross-linking properties, and can form a translucent viscous liquid when dissolved in water.
Galactomannan is a natural, stable, safe, non-toxic, hydrophilic, and degradable biopolymer with ideal physical and biological properties. For example, researchers can improve the stability of carotenoids by encapsulating them in galactomannan polymers through spray drying. Galactomannan is also widely designed as a carrier for various drug transport, such as matrix tablets, particles, nano/nanocomposites, polymer micelles, hydrogels, and medicinal materials for oral vaccines, oral insulin delivery, controlled drug delivery, targeting cancer cells and macrophages, wound dressings, etc. For example, scientists use Cassia galactomannan and sodium trimethyl phosphate to prepare hydrogels for drug delivery systems as sustained drug delivery agents for the treatment of colon cancer and other colon diseases. Other researchers have found that the prepared curcumin-galactomannan complex can enhance the effect of curcumin in reducing the toxicity of the pesticide furan. In addition, researchers have prepared gelatin films containing different concentrations of galactomannan. Rat mesenchymal stem cells can adhere to the film without showing cytotoxicity, indicating that gelatin films containing galactomannan are expected to be used in wound healing dressings. Other researchers added glutamine-grafted galactomannan and thickened sodium alginate to water, heated it to 60-70°C and stirred it, then added auxiliary materials, continued to stir it at 60-70°C, and cooled it naturally to prepare a hydrogel material with excellent moisturizing properties, moisturizing effects and long moisturizing time, which is suitable for use as a skin antipruritic and antibacterial patch. Hyaluronic acid and galactomannan can also be prepared into films or hydrogels, and their viscosity and viscoelasticity are improved. Galactomannan is a neutral polysaccharide with excellent thickening and gelling ability. Its properties are affected by factors such as molecular weight and mannose/galactose ratio. In addition, it has a variety of physiological functions, such as anti-cancer, lowering blood pressure, lowering blood sugar, and promoting the proliferation of small intestinal bifidobacteria. The relationship between the structure and physiological activity of galactomannan is still worth exploring to guide the modification direction. Galactomannan is widely used in food, biomedicine, papermaking, textiles, petroleum, cosmetics and other fields. The combination of chemical, physical and enzymatic modification or dual physical modification is still worth exploring to broaden the application of galactomannan.
Alternate Names:
Carob bean gum
LBG
Carob gum
Ceratonia siliqua gum
References:
1. Petitjean M, Isasi JR. Locust Bean Gum, a Vegetable Hydrocolloid with Industrial and Biopharmaceutical Applications. Molecules. 2022, 27(23):8265.
Locust bean gum: a versatile biopolymer
Carbohydr Polym.
Authors: Prajapati VD, Jani GK, Moradiya NG, Randeria NP, Nagar BJ.
Abstract
Biopolymers or natural polymers are an attractive class of biodegradable polymers since they are derived from natural sources, easily available, relatively cheap and can be modified by suitable reagent. Locust bean gum is one of them that have a wide potentiality in drug formulations due to its extensive application as food additive and its recognized lack of toxicity. It can be tailored to suit its demands of applicants in both the pharmaceutical and biomedical areas. Locust bean gum has a wide application either in the field of novel drug delivery system as rate controlling excipients or in tissue engineering as scaffold formation. Through keen references of reported literature on locust bean gum, in this review, we have described critical aspects of locust bean gum, its manufacturing process, physicochemical properties and applications in various drug delivery systems.
Locust bean gum provides excellent mechanical and release attributes to soy protein-based natural hydrogels
Int J Biol Macromol
Authors: Ba?yi?it B, Altun G, Yücetepe M, Karaaslan A, Karaaslan M.
Abstract
The current study concentrated on designing soy protein (SP)-based natural hydrogels in the presence of locust bean gum (LBG). For this, the gums were recovered from the kernel of the relevant plant and incorporated into SP gel models. Three more hydrogels were fabricated using commercial carbohydrates (gum Arabic (GA), maltodextrin (MD), and pectin (PC)) to decipher exactly the ability of LBG in these models. The chemical and morphological structures of the samples were elaborated by FTIR and SEM analyses. The coexistence of protein and carbohydrates led to an enhancement in functional (water holding capacity (WHC), swelling ratio, protein leachability, volumetric gel index (VGI)) and mechanical (textural and rheological behavior) features of natural gels compared to SP alone (control) but the quality of hydrogels was impressed by the carbohydrate type. Hydrogels designed with LBG came to the fore in terms of these attributes. Additionally, these gel models created awareness for phenolic delivery.
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