Molecular characteristics and rheological properties of water-extractable polysaccharides derived from okra (Abelmoschus esculentus L.)

Effects of okra (Abelmoschus esculentus (L.) Moench) on glycemic markers in animal models of diabetes: A systematic review

ETHNOPHARMACOLOGICAL RELEVANCE

Okra (Abelmoschus esculentus (L.) Moench) is traditionally used by different populations of Africa, América, Asia, and Europa to control diabetes. Although its action has been evaluated in several preclinical rodent trials, they have not been systematically analyzed.

OBJECTIVE

To evaluate the effectiveness of using okra in the treatment of diabetes in experimental rodent models.

MATERIAL AND METHODS

Controlled and randomized rodent animal trials with induced diabetes published between January 2000 and January 2021 were searched in the PubMed, Scopus, Scielo, and Web of Science databases. The search strategy included studies comprising the descriptors: animal species, diabetes induction method, intervention time, part of okra fruit used (whole, seeds, or peels), and dose as well as observed effects on biochemical and metabolic parameters. The systematic review was carried out according to the PRISMA statement, Cochrane bias risk tool (SYRCLE's RoB tool), and registered for systematic review protocols (PROSPERO).

RESULTS

A total of 326 articles were identified and after the exclusion of studies with gestational animal models, non-rodent animals, and non-diabetic animals, 11 studies involving 388 rodents were selected for the synthesis of results. The diabetes induction methods included streptozotocin, streptozotocin-nicotinamide, alloxan monohydrate, insulin resistance by high-fat diets or formulation described in AIN - 76, and feeding with high-fat food. Both Wistar albino rats, Sprague-Dawley males, and rats of both sexes of the Long-Evans lineage as well as male albino mice and C57BL females were included in the experiments. Studies showed that extracts of the fruit, the fresh fruit, or its various fractions had positive effects on the following markers: glycated hemoglobin, cholesterol, HOMA-IR, oral glucose tolerance test, and blood glucose, in acute (2 and 24 h), and chronic (up to 4 months) treatment.

CONCLUSION

An important hypoglycemic effect of okra in its various fractions on induced diabetes was observed by different authors. Moreover, okra promoted improvement in metabolic markers such as insulin sensitivity, lipid profile, and bodyweight loss.

Experimental Study on the Application of Cellulosic Biopolymer for Enhanced Oil Recovery in Carbonate Cores under Harsh Conditions

Polymer flooding is used to improve the viscosity of an injectant, thereby decreasing the mobility ratio and improving oil displacement efficiency in the reservoir. Thanks to their environmentally benign nature, natural polymers are receiving prodigious attention for enhanced oil recovery. Herein, the rheology and oil displacement properties of okra mucilage were investigated for its enhanced oil recovery potential at a high temperature and high pressure (HTHP) in carbonate cores. The cellulosic polysaccharide used in the study is composed of okra mucilage extracted from okra (Abelmoschus esculentus) via a hot water extraction process. The morphological property of okra mucilage was characterized with Fourier transform infrared (FTIR), while the thermal stability was investigated using a thermogravimetric analyzer (TGA). The rheological property of the okra mucilage was investigated for seawater salinity and high-temperature conditions using a TA rheometer. Finally, an oil displacement experiment of the okra mucilage was conducted in a high-temperature, high-pressure core flooding equipment. The TGA analysis of the biopolymer reveals that the polymeric solution was stable over a wide range of temperatures. The FTIR results depict that the mucilage is composed of galactose and rhamnose constituents, which are essentially found in polysaccharides. The polymer exhibited pseudoplastic behavior at varying shear rates. The viscosity of okra mucilage was slightly reduced when aged in seawater salinity and at a high temperature. Nonetheless, the cellulosic polysaccharide exemplified sufficiently good viscosity under high-temperature and high-salinity (HTHS) conditions. Finally, the oil recovery results from the carbonate core plug reveal that the okra mucilage recorded a 12.7% incremental oil recovery over waterflooding. The mechanism of its better displacement efficiency is elucidated

Evaluation of OKRA (Abelmoschus esculentus) Macromolecular Solution for Enhanced Oil Recovery in Kazakhstan Carbonate Reservoir

Natural polymers have been investigated as part of the endeavors of green chemistry practice in the oil field. However, natural polymer studies are still preliminary. The current study examines okra’s (natural polymer) efficiency for polymer flooding, particularly in Kazakhstan. The evaluation targets the heavy oil trapped in carbonate reservoirs. SEM and FTIR were used to characterize morphology and chemical composition. A rheology study was conducted under different shear rates for three plausible concentrations: 1 wt.%, 2 wt.% and 5 wt.%. The core flooding was challenged by the low porosity and permeability of the core. The results showed that okra’s size is between 150–900 μm. The morphology can be described by rod-like structures with pores and staking as sheet structures. The FTIR confirmed that the solution contains a substantial amount of polysaccharides. During the rheology test, okra showed a proportional relationship between the concentration and viscosity increase, and an inversely proportional relationship with the shear rate. At reservoir temperature, the viscosity reduction was insignificant, which indicated good polymer stability. Okra showed shear-thinning behavior. It was fitted to the Ostwald–de Waele power-law model by a (90–99)% regression coefficient. The findings confirm okra’s pseudo-plasticity, and that it is proportional to the solution concentration. The incremental oil recovery was 7%. The flow was found to be restricted due to the mechanical entrapment resulting from the large molecule size and the low porosity–permeability of the system. This study proves that the dominating feature of natural polysaccharide derivatives is their applicability to moderate reservoir conditions. The current study is a positive attempt at natural polymer application in Kazakhstan and similar field conditions.

Hybrid techniques of pre and assisted processing modify structural, physicochemical and functional characteristics of okra pectin: Controlled-temperature ultrasonic-assisted extraction from preparative dry powders and its field monitoring

Diversiform okra dry powders were prepared and controlled-temperature ultrasonic-assisted extraction (CTUAE) was then utilized to obtain okra pectin (OP) from the preparative powders. During processing of hybrid techniques, 6 types of dry powders were prepared through different drying technologies (hot air drying, HD; freeze-drying, FD) and meshes (60, 80, 120 meshes) at first. Next, the extraction yield, physicochemical and function characteristics, and molecular structure of OP were analyzed with or without CTUAE technique. Meanwhile, the time-frequency domains of acoustic fields during extraction process of OP were monitored to analyze the effects of ultrasonic fields. Results showed that OP main chains with less cracking by FD than that by HD; the yield, GalA, esterification degree (DE), M_w and viscosity of OP increased, but its particle size decreased. Water holding capacity (WHC) and oil holding capacity (OHC) of OP by HD were more prominent. Secondly, HD OP had dendritic rigid chains, while FD OP had flexible chains with multiple branches. For HD OP, as meshes of okra dry powders decreased, GalA, viscosity and emulsification ability decreased; while gel strength and thermal stability increased. For FD OP, the reduction of meshes improved thermal stability. Above all, CTUAE technique increased the yield and GalA, and decreased DE, M_w and particle size of OP. In terms of functional characteristics, the technique also improved gel strength, resilience and viscoelasticity, enhanced emulsifying stability, WHC and thermal stability, and reduced viscosity. Finally, the correlation between functional and structural characteristics of OP was quantified, and some suggestions were made for its application in food areas.

Characterization, Antioxidant Activities, and Functional Properties of Mucilage Extracted from Corchorus olitorius L

This study extracted the mucilage from Corchorus olitorius L. to observe its chemical and functional properties and suggest its possible applications in various fields. Corchorus olitorius L. mucilage was isolated by hot water extraction. FT-IR and HPAEC-PAD were used to describe the chemical composition, and the functional properties and antioxidant activities of the mucilage were also examined. The mucilage was mainly composed of uronic acid (34.24%, w/w). The solubility was 79.48 ± 1.08% at 65 °C, the swelling index was 29.01 ± 2.54% at 25 °C, and the water-holding capacity and oil-binding capacity were 28.66 ± 1.48 and 8.423 ± 0.23 g/g, respectively. The mucilage viscosity increased from 4.38 to 154.97 cP in a concentration-dependent manner. Increasing the concentration decreased the emulsion activity and increased the emulsion stability, most likely because of the corresponding increase in surface tension and viscosity. Results from antioxidant assays confirmed that the in-vitro radical scavenging activity of the mucilage increased with concentration. This study shows that C. olitorius L. can be utilized as a new hydrocolloid source, with potential applications in fields ranging from foods to cosmetics and pharmaceuticals.

Biological activity and development of functional foods fortified with okra (Abelmoschus esculentus)

The Abelmoschus esculentus plant, better known as okra, is an interesting crop from a nutritional standpoint. The okra plant is native to the African region but can now be found throughout tropical and subtropical areas of the world. This plant, known for its healing abilities, has been used as a traditional medicine to treat several diseases and external ailments, such as wounds or boils. This article reviews the potential health benefits from okra consumption, as well as the bioactive compounds that are suggested to be responsible. Furthermore, the okra plant and its derivatives have been evaluated in the formulation and manufacture of new functional food products. The latest advances in this direction, which includes characterizing the technical properties of functional foods fortified with okra are also presented in this review. A series of bioactive compounds such as flavonoids and catechins have been found in the okra plant, which were associated with numerous biological properties observed in research studies that reported potential anti-diabetic, anti-cancer, anti-hypertensive, and antimicrobial effects, among others, as a result of their consumption. These potential health benefits contribute to the development of new and useful functional foods, with okra (or its derivatives) being used as the highlighted ingredient.

Development and Characterization of Novel Biopolymer Derived from Abelmoschus esculentus L. Extract and Its Antidiabetic Potential

Abelmoschus esculentus (Okra) is an important vegetable crop, widely cultivated around the world due to its high nutritional significance along with several health benefits. Different parts of okra including its mucilage have been currently studied for its role in various therapeutic applications. Therefore, we aimed to develop and characterize the okra mucilage biopolymer (OMB) for its physicochemical properties as well as to evaluate its in vitro antidiabetic activity. The characterization of OMB using Fourier-transform infrared spectroscopy (FT-IR) revealed that okra mucilage containing polysaccharides lies in the bandwidth of 3279 and 1030 cm^-1, which constitutes the fingerprint region of the spectrum. In addition, physicochemical parameters such as percentage yield, percentage solubility, and swelling index were found to be 2.66%, 96.9%, and 5, respectively. A mineral analysis of newly developed biopolymers showed a substantial amount of calcium (412 mg/100 g), potassium (418 mg/100 g), phosphorus (60 mg/100 g), iron (47 mg/100 g), zinc (16 mg/100 g), and sodium (9 mg/100 g). The significant antidiabetic potential of OMB was demonstrated using α-amylase and α-glucosidase enzyme inhibitory assay. Further investigations are required to explore the newly developed biopolymer for its toxicity, efficacy, and its possible utilization in food, nutraceutical, as well as pharmaceutical industries.

Preparation, characterization, antioxidant and anti-inflammatory activities of acid-soluble pectin from okra (Abelmoschus esculentus L.)

Currently, there are few studies on acid-soluble pectin from okra, especially in biological activity for antioxidant and anti-inflammatory. In this study, the antioxidant properties of acid-soluble okra pectin components and their anti-inflammatory were explored. Firstly, two acid-soluble okra pectic fractions, namely crude acid-soluble okra pectin (CAOP) and acid-soluble okra pectin (AOP), were obtained and exhibited structural and compositional variation. The two pectic fractions contained a low degree of esterification (42.0-46.5%) and a relatively high uronic acid content (31.6-37.3%). AOP was composed of galacturonic acid (79.1 mol/%), galactose (4.3 mol/%), rhamnose (14.5 mol/%) and xylose (2.1 mol/%), and the molecular weight was 92.8 kDa. Morphological and thermal properties of acid-soluble okra pectin components were also investigated. Compared to CAOP, AOP expressed better antioxidant activity, and suppressed the NO production in LPS-induced RAW 264.7 macrophages. All the above results indicated that AOP had the potential to act as a natural antioxidant or a functional anti-inflammatory food, which would broaden the development and utilization of okra resources.

Structural Properties, Bioactivities, and Applications of Polysaccharides from Okra [Abelmoschus esculentus (L.) Moench]: A Review

Okra [Abelmoschus esculentus (L.) Moench], as a kind of nutritive vegetable, is rich in flavonoids, polyphenols, polysaccharides, amino acids, and other bioactive substances and has various biological activities. As one of main bioactive components, okra polysaccharides (OPs), mainly comprising pectic polysaccharides, have various biological activities. OPs have been extensively investigated in recent years. Many studies characterized structures of OPs obtained by different extraction methods, which were confirmed to be rhamnogalacturonan-I-type polysaccharides in most cases. OPs have a thick and slimy texture, suggesting that they can be a promising source of texture modifiers for complex food matrices. They have various biological activities, such as antioxidant activity, immunomodulatory activity, hypoglycaemic activity, and improving intestinal function. Therefore, OPs may potentially serve as novel immunomodulators or an adjuvant for diabetic nephropathy. Up to now, there is no specific summary on the research progress of OPs. In this paper, the latest research progress on the extraction, purification, characterization, rheological properties, biological activities, and applications of OPs is reviewed, to provide the reference for the processing and comprehensive utilization of OPs in the future.