Structural Characterization and Solution Properties of a Galacturonate Polysaccharide Derived from Aloe vera Capable of in Situ Gelation

Abstract

A series of highly purified galacturonate polysaccharides have been extracted from the Aloe vera plant and analyzed in terms of chemical composition and molecular weight. This Aloe vera polysaccharide (AvP) has been found to exist as a high molecular weight species and possess a unique chemical composition, including a high galacturonic acid (GalA) content and low degree of methyl ester substitution. These factors facilitate gel formation upon exposure to low concentrations of calcium ions, leading to potential application in formulations designed for in situ nasal or subcutaneous protein delivery. Thorough examination of classic dilute solution properties, the [eta]-M(w), and R(g)-M(w) relationships, persistence length (L(p)), and inherent chain stiffness (B parameter), indicate an expanded random coil in aqueous salt solutions. The critical concentration for transition from dilute to concentrated solution, C(e), was determined by measuring both the zero shear viscosity (eta(o)) and fluorescence emission of the probe molecule 1,8-anilino-1-naphthalene sulfonic acid (1,8-ANS) as a function of polymer concentration. Examination of zeta potential and C(e) as a function of ionic strength indicates that the shift in C(e) from 0.60 to 0.30 wt % is related to an increased occurrence of intermolecular interactions at high salt concentrations. Additionally, dynamic rheology data are presented highlighting the ability of AvP to form gels at low polymer and calcium ion concentrations, exemplifying the technological potential of this polysaccharide for in situ drug delivery.

Phenolic Hydroxy Groups Incorporated for the Peroxidase‐Catalyzed Gelation of a Carboxymethylcellulose Support: Cellular Adhesion and Proliferation

“…Hydrogels have attracted substantial attention as materials for applications that involve contact with the body and living cells, such as in situ gelation for drug delivery, [2,[12][13][14][15] cell encapsulation for tissue engineering, [7,13,16,17] and cell therapy. [13,14,16] Control of gelation time is essential for these applications.…”

Could We Really Use Aloe Vera Food Supplements to Treat Diabetes?

“…Other high-molecular-weight bioactive components of aloe vera leaf include maloyl glucans (e.g., veracylglucans) and glycoprotein verectin (Davis et al 1994;Esua and Rauwald 2006;Yagi et al 1998;Yagi and Takeo 2003). Some researchers have pointed to pectic substance and galactans as the main components of the polysaccharide fraction in aloe vera leaf (Mandal and Das 1980b;McConaughy et al 2008;Rodríguez-González et al 2011). Pectic substance is the collective term for a group of closely related polysaccharides often found associated with pectin, which include pectin, pectic acid, and arabinogalactan.…”

Pectin: A new perspective from the biorefinery standpoint

“…Two or more chain segments bond together and start to interact. In general, the high content of galacturonic acid and the low degree of methyl esterification promote the availability of COO − groups, involved in the gelling process …”