Description
The carbon nutritional status in plants and the quality characteristics of agricultural products are often evaluated using sugar content as an important indicator. Monosaccharides and some oligosaccharides (such as maltose) contain free aldehyde or ketone groups, possess reducibility, and are classified as reducing sugars. Polysaccharides and sucrose are non-reducing sugars. The total sugar content can be determined by measuring the monosaccharide content after hydrolysis, utilizing the property that non-reducing sugars can be hydrolyzed to monosaccharides by acid.Detection Principle: Reducing sugars are oxidized to sugar acids under alkaline heating conditions, while 3,5-dinitrosalicylic acid (DNS) is reduced to a brownish-red amino compound. Within a certain range, the amount of reducing sugar is proportional to the color intensity of the brownish-red product. The absorbance of this brownish-red substance is measured at 540 nm using a microplate reader. This absorbance value has a linear relationship with the reducing sugar content. The reducing sugar and total sugar content in the sample are calculated using a standard curve.This kit is for scientific research use only and is not intended for clinical diagnosis or other purposes.P1501777Component100T300TStorageP1501777AGlu Standard (1 mg/mL)1 mL1 mL2-8℃P1501777BDNS Detection Solution10 mL30 mLRT. Store in the dark.P1501777CColor Solution (for Total Sugar)5 mL10 mLRT. Store in the dark.User-Prepared Instruments and Reagents1. Distilled water, Hydrochloric acid solution, Sodium hydroxide solution2. 50 mL centrifuge tubes, 1 mL centrifuge tubes, Centrifuge, Water bath or incubator, Microplate reader, 96-well plate, Water bathExperimental Procedure1. Extraction of Reducing Sugars1.1 Weigh 0.5-3 g of plant sample, cut into pieces, add about 3 mL of distilled water and homogenize. Transfer to a beaker or conical flask. Rinse the grinder 2-3 times with 12 mL of distilled water and transfer the rinsate to the same container.1.2 Incubate in a 50°C water bath for 30 min, stirring occasionally to ensure thorough extraction of reducing sugars.1.3 Transfer the precipitate and extract to a 50 mL centrifuge tube. Centrifuge at 4000 g for 5 min.1.4 Collect the supernatant. Add 20 mL of distilled water to the precipitate, mix well, and centrifuge again at 4000 g for 5 min.1.5 Collect the supernatant. Combine the supernatants from the two steps. Dilute to 100 mL with distilled water (this is the extract). Mix well. This serves as the test solution for reducing sugars.2. Hydrolysis and Extraction of Total Sugars2.1 Weigh 0.5-3 g of plant sample, cut into pieces, add about 3 mL of distilled water and homogenize. Transfer to a beaker or conical flask. Rinse the grinder 2-3 times with 12 mL of distilled water and transfer the rinsate to the same container.2.2 Add 10 mL of 6 M hydrochloric acid solution to the container, mix well, then heat in a boiling water bath for 30 min for hydrolysis, stirring occasionally.2.3 Take 2 drops and place on a glass slide, add 1 drop of Color Solution (about 50 µL) to check if hydrolysis is complete. If hydrolysis is complete, no blue color should develop.2.4 After hydrolysis, cool to room temperature. Add 6 M sodium hydroxide solution to adjust the pH to 7.4. Dilute to 100 mL with distilled water, mix well. Centrifuge at 4000 g for 5 min or filter.2.5 Take 10 mL of the supernatant or filtrate and dilute to 100 mL with distilled water, creating a 10-fold diluted total sugar hydrolysate (extract). Take 50 µL of this total sugar hydrolysate to measure its reducing sugar content.3. Glucose Standard PreparationTake clean centrifuge tubes or test tubes and prepare a series of Glu standards according to the table below.Standard Working SolutionGlu Standard (1 mg/mL) (mL)Distilled Water (mL)Concentration (mg/mL)10.010.040.220.020.030.430.030.020.640.040.010.850.0501.04. Assay SetupTake 1 mL centrifuge tubes. Set up Blank, Standard, and Test wells according to the table below. Add solutions sequentially, avoiding bubbles. Mix carefully. If the sugar concentration in the sample is too high, reduce the sample volume or dilute appropriately before assay. It is best to set up 2-3 replicate wells for samples and take the average.Reagent (µL)Blank WellStandard WellTest WellDistilled Water50//Glu Standard (1-5)/50/Extract//50DNS Detection Solution100100100Heat accurately in a boiling water bath for 5 min. Remove, cool to room temperature with tap water. Add 250 µL distilled water.5. Reducing Sugar MeasurementMix well. Transfer 300 µL sequentially to the corresponding wells of a 96-well plate. Measure the absorbance of Standard and Test wells at 540 nm, using the Blank well to zero the instrument.6. Result Calculation6.1 Standard Curve PlottingUsing the Glu standards (1-5), i.e., the standard glucose concentrations (mg/mL) as the x-axis and the corresponding absorbance values as the y-axis, plot the standard curve. Find the corresponding glucose concentration on the standard curve based on the absorbance of the extract.6.2 Content CalculationPercentage Content of Reducing Sugars:Reducing sugar content per 100 g sample (g) = (c × V T ) / (m × 1000) × 100 = (c × V T ) / (m × 10)Percentage Content of Total Sugars:Total sugar content per 100 g sample (g) = (c × N × V T ) / (m × 1000) × 100 × 0.9 = (c × N × V T ) / (m × 10) × 0.9Parameter Descriptionc: Sugar amount found from the standard curve (mg/mL)V T : Total volume of the extract, 100 mLm: Mass of the plant sample, gN: Dilution factor of the total sugar hydrolysate, 10Precautions1. Avoid repeated freeze-thaw cycles for the aforementioned low-temperature reagents to prevent inactivation or decreased efficiency.2. If test samples cannot be assayed immediately, store at 2-8°C; stable for 3 days.3. If the sample reducing sugar concentration is too high, dilute with distilled water and re-assay, multiplying the result by the dilution factor.4. The total sugar calculation formula is used when there are few interfering impurities and the reducing sugar content is relatively small compared to the total sugar content. Multiplying by 0.9 accounts for the water consumed during the hydrolysis of total sugars to monosaccharides.5. 6 M Hydrochloric Acid Preparation: Generally, commercially available concentrated hydrochloric acid is 11.6-12 M. Mix concentrated hydrochloric acid with distilled or deionized water 1:1 (v/v) to prepare 6 M HCl. Caution: Hydrochloric acid dissolution in water releases heat; handle carefully to avoid injury.6. 6 M Sodium Hydroxide Preparation: Dissolve 24 g of sodium hydroxide in distilled or deionized water, make up to 100 mL. Caution: Sodium hydroxide dissolution in water releases heat; handle carefully to avoid injury.7. Use reagents promptly after opening to avoid affecting subsequent experimental results