Sorbitol

Scheme 1 –GC-MS analysis of sorbitol

500 ng of fructose and sorbitol internal standards (D-[U¹³C₆] fructose and D-[U ¹³C₆] sorbitol) were added to 200 μL aliquots of standards (0.025–25 mg/L), QC samples (in human blood), and clinical study samples. After that, samples were deproteinized using ZnSO4-Ba(OH)2 extraction, dried with nitrogen, oxidized (500 μL 1% o-methylhydroxylamine hydrochloride in pyridine; 2 hours at 70 °C), dried again, derivatized (500 μL BSTFA [N,O-bis[Trimethylsilyl]trifluoroacetamide]; 20 minutes at 70 °C), and then passed through 0.22 μm PVDF filters into autosampler vials. A gas chromatograph with an autosampler and a peltier-cooled sample rack (10 °C) was used to examine these samples using a mass-specific detector (MSD) interface. GC-MS interface and injection ports were maintained at 250° and 280°C, respectively. On a fused silica column (30 M × 250 μm × 1 μm film thickness), separations were carried out. 50:1 split ratio injections of derivatized samples (5 μL) were made using helium as the carrier gas (0.8 ml/min). The temperature of the column was maintained at 220 °C for the whole 15-minute run. With SIM detection (m/z 307 for fructose, m/z 310 for fructose IS, m/z 319 for sorbitol, and m/z 323 for sorbitol IS), the MSD was quantified using EI-mode at 70 eV. When the glucose peaks were eluting, the MSD was switched off.

Gas chromatography chromatogram for quantification of fructose and sorbitol. (Preston G M., et al., 2010)

Scheme 2 – HPLC- refractive index (RI) detection of sorbitol

The frozen samples, enclosed in plastic bags, were maintained at -20 °C until they were extracted. Following a thorough crushing of the samples (known amounts), 10 mL of an extraction solvent (a 70% ethanol solution) was added. After five minutes of ultrasonication, the materials were passed through filter paper. After the extract was filtered, it was injected into the HPLC system by forcing it through PVDF 0.45 μm syringe filters. The chromatograph used for the HPLC studies has an injection valve with a 20 μL sample loop, a ternary gradient unit, an intelligent column thermostat, an intelligent reflex index detector, and an intelligent HPLC pump. Achieved separation on a 300 × 7.8 mm column.

Preliminary studies revealed that the three independent variables: (A) H2SO4 solution concentration (mol/L), (B) flow rate (mL/min), and (C) column temperature (°C) were the primary factors influencing resolution (Rs3,4) between the 3rd (fructose) and 4th (sorbitol) peaks. The variables' values ranged from 0-0.05 mol/L for H2SO4 solution concentration, 0.3-0.7 mL/min for flow rate, and 20-55 °C for column temperature. A total of 17 runs were carried out.

HPLC-RI chromatograms of the sugar standards including sorbitol. (Filip M., et al., 2016)

Case Study 1—Sorbitol regulates glucose uptake in type 2 diabetic rats

Using both ex vivo and in vivo experimental models, the current study examined the effects of sorbitol on intestinal glucose absorption and muscle glucose uptake as potential anti-hyperglycemic or glycemic control potentials. In a concentration-dependent manner, sorbitol (2.5% to 20%) enhanced glucose uptake in isolated rat psoas muscle with (GU50 = 3.5% ± 1.6%) or without insulin (GU50 = 7.0% ± 0.5%) and reduced glucose absorption in isolated rat jejuna (IC50 = 14.6% ± 4.6%).

Additionally, following one hour of coingestion with glucose, sorbitol significantly decreased blood glucose rise, increased digesta transit, prevented intestinal glucose absorption, and delayed stomach emptying in both normoglycemic and type 2 diabetic rats. According to the study's data, sorbitol potentially had anti-hyperglycemic effects by boosting ex vivo muscle glucose uptake and decreasing intestinal glucose absorption in rats with type 2 diabetes and normal blood sugar. Sorbitol might thus be studied more as a potential anti-hyperglycemic sweetener.

Effects of sorbitol on glucose absorption in isolated rat jejunum. (Chukwuma C I., et al., 2017)

Effects of sorbitol on glucose uptake with or without insulin in isolated rat psoas muscle. (Chukwuma C I., et al., 2017)

Case Study 2—Sorbitol accumulation decreases oocyte quality

In vitro-matured oocytes from old mice had considerably greater amounts of sorbitol (14.08 ± 3.78 vs. 0.23 ± 0.04 ng/oocyte) than did oocytes from young mice, according to the current study. In vitro-cultured oocytes from 9-month-old mice had considerably greater expression of aldose reductase (AR) mRNA than the mice's oocytes before culture. Sorbinil, a particular inhibitor of aldose reductase, was added to in vitro maturation (IVM) media to reduce the excess intracellular sorbitol in oocytes from aged mice. This resulted in a considerable drop in sorbitol levels (14.08 ± 3.78 vs. 0.48 ± 0.19 ng/oocyte). The findings showed that the elderly group's sorbitol content had greatly risen, and that the proportion of oocytes with initial polar body extrusion (PBE) was much greater in the sorbinil group (82.4% ± 7.2% vs. 66.1% ± 6.9%). While the GSH fluorescence intensity was noticeably greater, the ROS fluorescence intensity in the sorbinil group was much lower than that in the aged group. Interestingly, the sorbinil group showed an upregulation of SOD1. The current work indicates that in elderly mouse oocytes, excessive sorbitol buildup is generated during IVM, which modifies the intracellular redox balance and adversely affects oocyte quality. One possible strategy to enhance the nuclear maturation of older oocytes is to inhibit the buildup of sorbitol.

Effect of sorbitol accumulation on oocytes of aged mice. (Zhang Y., et al., 2021)

Effects of sorbitol accumulation on the levels of ROS and GSH and the expression of SOD1 in IVM oocytes. (Zhang Y., et al., 2021)

Sorbitol is a polyhydric alcohol derived both naturally from fruits including apples, pears, peaches, and prunes, it can be synthetically from glucose, it is extensively utilized across the food, pharmaceutical, and cosmetic industries due to its multifaceted properties, including its sweetness, hygroscopicity, chemical stability, and biocompatibility.

As a sweetener: Due to its lower calorie content than sucrose, sorbitol serves as a great sweetener for sugar-free and dietetic products. It works especially well in baked goods, confections, and oral care products where it helps maintain sweetness while preventing dental caries, a property linked to its inability to be metabolized by oral bacteria.

As the stabilizer and cryoprotectant: Sorbitol is widely used in pharmaceutical formulations as a binder, filler, and disintegrant in capsules. Its ability to enhance the final product's dissolution profile and structural integrity and it is also useful for stabilizing and sweetening liquid medications, which increases the palatability. In addition to being used as a cryoprotectant to stabilize proteins and enzymes during freeze-drying and storage, sorbitol's osmotic properties are also utilized in the formulation of oral and rectal laxatives, which encourage bowel movements by drawing water into the intestines. This preserves the biological activity of pharmaceuticals.

Develop analytical methods: Sorbitol is used as a standard in analytical chemistry for high-performance liquid chromatography (HPLC) and gas chromatography (GC), owing to its unique retention time, which facilitates precise separation and quantification of related compounds and guarantees the concentration and purity of sorbitol in food and medicine products.

As a building block: Sorbitol is used in the manufacturing of polyurethanes, which are polymers having a wide range of uses including foams, elastomers, coatings, and adhesives. Sorbitol's hydroxyl groups react with isocyanates to generate urethane linkages, which contribute to the flexible and durable properties of the materials. Sorbitol is used as a monomer in the manufacture of polyester. Sorbitol creates ester bonds when it reacts with acids or acid anhydrides, resulting in polyesters used in textiles, films, and plasticizers.

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