Enhancement of the gelling properties of Aristichthys nobilis: Insights into intermolecular interactions between okra polysaccharide and myofibrillar protein.

The effects of various contents of okra polysaccharide (OP) (0%-1%) on myofibrillar protein (MP) gelation and the interaction mechanism between OP and MP were investigated. OP improved the gelling properties of MP with an additive limitation of 0.75%. Rheological analysis demonstrated that the addition of OP enhanced the interactions between MPs, resulting in a denser intermolecular gel network structure. The addition of OP shifted the I850/I830 of Fourier transform infrared spectroscopy, indicating that hydrogen bonds were formed between OP and MP. Adding OP promoted the transition from α-helix to ß-sheet in the MP. OP exposed the hydrophobic groups of MPs and increased the number of hydrophobic interactions between them, favoring the formation of a dense gel network. Molecular docking predicted that hydrogen bonds were the main force involved in the binding of OP and MP. Moderate OP promoted the aggregation of MPs and improved their functional properties, facilitating heat-induced gelation.

A stretchable, self-healing, okra polysaccharide-based hydrogel for fast-response and ultra-sensitive strain sensors.

Self-healing conductive hydrogels have attracted widespread attention as a new generation of smart wearable devices and human motion monitoring sensors. To improve the biocompatibility and degradability of such strain sensors, we report a sensor with a sandwich structure based on a biomucopolysaccharide hydrogel. The sensor was constructed with a stretchable self-healing hydrogel composed of polyvinyl alcohol (PVA), okra polysaccharide (OP), borax, and a conductive layer of silver nanowires. The obtained OP/PVA/borax hydrogel exhibited excellent stretchability (~1073.7%) and self-healing ability (93.6% within 5 min), and the resultant hydrogel-based strain sensor demonstrated high sensitivity (gauge factor = 6.34), short response time (~20 ms), and good working stability. This study provides innovative ideas for the development of biopolysaccharide hydrogels for applications in the field of sensors.

Okra polysaccharide-2 plays a vital role on the activation of RAW264.7 cells by TLR2/4-mediated signal transduction pathways.

Polysaccharide is the main active component of okra (Abelmoschus esculentus L.) and it can effectively stimulate the activation of macrophages. However, the immune regulatory mechanism is still not clear. Therefore, the present study aimed to reveal the possible mechanism by investigating the effect of okra polysaccharide-2 (RPS-2) on Toll-like receptor (TLR) 2/4-mediated signal transduction pathways in RAW264.7 murine macrophage cells. In order to confirm whether RPS-2 stimulated macrophages activation via TLR2 or TLR4, RAW264.7 murine macrophage cells were pretreated with TLR2/4 inhibitors for 1 h before RPS-2 treatment, and then the NO, IL-10, TNF-α levels were tested. The results indicated that both TLR2 and TLR4 were the keys of immune regulatory effect of RPS-2. Afterwards, the effect of RPS-2 on NF-κB and MAPKs signaling pathways were studied by western blot analysis. It showed RPS-2 induced the phosphorylation of p65, IκBα, p38, ERK1/2 and JNK. At the same time, the specific inhibitors reduced these phosphorylation levels as well as NO, IL-10 and TNF-α amounts. In a word, RPS-2 activated macrophages by NF-κB and MAPKs signal transduction pathways.

Influences of different drying methods on the structural characteristics and multiple bioactivities of polysaccharides from okra (Abelmoschus esculentus).

In this study, in order to evaluate the influences of drying methods on the chemical structures and bioactivities of polysaccharides from okra (OPPs), four drying methods, including microwave drying at 400 W, 600 W, and 800 W, freezing drying, hot air drying, and vacuum drying, were applied to dry okra fruits. Six different OPPs were extracted from okra dried by different drying methods. Results showed that physicochemical characteristics and bioactivities of OPPs varied by different drying methods. Noticeable variations in extraction yields, molecular weights, rheological properties, molar ratios of constituent monosaccharides, contents of uronic acids, degrees of esterification, and contents of total phenolics were observed in OPPs obtained by different drying methods. In addition, results showed that OPPs, especially OPP-H and OPP-V obtained by hot air drying and vacuum drying, respectively, exhibited remarkable antioxidant activities (ABTS, DPPH, and nitric oxide radical scavenging activities, and ferric reducing antioxidant powers), strong in vitro binding capacities (fat, cholesterol, and bile acids binding capacities), and obvious inhibitory activities on α-amylase and α-glucosidase. Results suggested that the hot air and vacuum drying techniques could be appropriate drying methods before extraction of OPPs with high bioactivities for applications in the functional food and medicine industries.

Okra polysaccharide: Effect on the texture and microstructure of set yoghurt as a new natural stabilizer.

Four plant-derived polysaccharides including okra polysaccharide (OP), apple pectin (AP), sodium alginate (SA) and konjac glucomannan (KGM) were studied in yoghurt formulation to investigate their effect on gelling characteristics. The results indicated that OP, KGM and AP enhanced the water-holding capacity, firmness and elasticity of yoghurt while SA demonstrated the opposite effects. Gel structure was better improved with OP, the firmness of yoghurt increased from 9.01 g to 14.86 g when 0.08% OP was added. The yoghurt with OP achieved the closest transverse relaxation time (T2) to the control. The free water area (A23) decreased from 1592 for control to 1414 for yoghurt with 0.08% OP addition. All samples exhibited shear-thinning behavior, both apparent viscosity and elastic modulus (G', G″) increased with increasing concentrations of OP and KGM, with peak values at 0.06% OP and 0.015% KGM. Both G' and G'' reduced significantly as pectin concentration rose to 0.1%, while modules went up with the increasing concentration of SA. Microscopy results showed that addition of OP and AP reduced the porous structure of gel and promoted formation of larger protein clusters, which eventually led to more compact protein network. This study provided new insights for food application with plant-derived polysaccharides.