Starch Hydrolysis Research Articles

Effect of grain structure and cooking method on starch digestibility and antioxidant activity of amaranth (Amaranthus caudatus L.) grains during simulated gastrointestinal digestion

Amaranth has received widespread interest as a high-quality source of nutrition. This study examined changes in starch hydrolysis and antioxidant activity of intact or slurry of amaranth grains, which were cooked with different methods, such as boiled and roasted, during simulated in vitro gastrointestinal digestion. The starch digestibility of amaranth samples was analyzed using starch hydrolysis percentage and digestion kinetics during simulated digestion. Simultaneously, TPC and antioxidant assays, such as ABTS, FRAP, and MIC, assessed the changes in antioxidant potential during digestion. The results showed that the slurry increased starch hydrolysis and antioxidant properties compared with intact grain. Boiling and roasting also showed increased antioxidant activity and starch hydrolysis during digestion. Whether intact grains or slurries, the roasted samples had lower starch hydrolysis and higher antioxidant properties during digestion than the boiled samples. The equilibrium starch hydrolysis percentages of the roasted and boiled intact grains were 15.50 and 67.41 %, and those TPC were 662.78 and 470.21 mg GAE/100 g sample (db.), respectively. In this study, roasting was more beneficial in delaying starch hydrolysis and improving antioxidant activity than boiling. In addition, maintaining the grain state was more conducive to controlling starch hydrolysis. Our findings could be beneficial for the amaranth consumers.

Roseateles agri sp. nov., a New Species Isolated from Fresh Soil in Uiwang, South Korea

Two isolates of Roseateles were discovered in soil samples collected from Uiwang-si, Gyeonggi-do, Republic of Korea. These isolates exhibited rod-shaped morphology and were facultatively anaerobic, non-motile, and tested positive for oxidase and catalase. Designated as strains R3-3T and R3-11, their growth was hindered by NaCl concentrations exceeding 0.5%, while their optimal growth conditions were observed at temperatures ranging from 25 °C to 30 °C and pH levels between 7.0 and 9.0. Both strains exhibited positive results for the hydrolysis of Tween 80 and DNA, but tested negative for starch, casein, chitin, and gelatin hydrolysis. Additionally, they assimilated L-Arabinose, D-mannitol, and D-Maltose, while exhibiting negative results for the fermentation of D-glucose, esculin ferric citrate, D-mannose, N-acetyl-glucosamine, potassium gluconate, capric acid, adipic acid, trisodium citrate, and phenylacetic acid. The DNA G+C content of strain R3-3T was measured at 67.5 mol%. Comparative analysis revealed that the average nucleotide identity (ANI) values between R3-3T and the Roseateles type strains ranged from 75.14% to 78.30% while the digital DNA-DNA hybridization (dDDH) values ranged from 20.70% to 22.70%. Consequently, based on comprehensive genomic, chemotaxonomic, phenotypic, and phylogenomic evaluations, the isolated strains have been designated as a new species within the genus Roseateles, named Roseateles agri sp. nov. (with type strain R3-3T = KACC 23678T = NBRC 116681T).

PSVI-1 Backgrounding and finishing systems for cattle fed corn silages and corn grains differing in amylase expression

Abstract Amylase is a key enzyme involved in the hydrolysis of starch, which typically constitutes the predominant source of energy in feedlot cattle diets. Performance of cattle during the backgrounding phase can influence performance during the subsequent finishing phase. Our objective was to assess growth performance of backgrounding steers fed diets that contained combinations of corn silage (S) and steam-flaked corn (G) from hybrids with high amylase expression (Enogen corn; E; Syngenta Seeds, LLC) or common corn hybrid (C), as well as subsequent finishing performance, carcass characteristics, and liver abscess incidence when fed G produced from the same hybrids. Crossbred steers (n = 911; 306 ± 8 kg initial body weight) were assigned randomly to one of four backgrounding treatments with 12 replicates in a randomized complete block experiment using a factorial treatment arrangement. Factor 1 consisted of two corn silage hybrids (ES or CS), and factor 2 consisted of two SFC hybrids (EG or CG). In the subsequent finishing phase, animals were assigned to one of two treatments consisting of two grain hybrids (EG or CG) with 24 replicates per treatment. Backgrounding diets (dry basis) contained 20.1% flaked corn and 41.6% corn silage, and finishing diets contained 81.5% flaked corn with triticale silage as a common roughage source. There was no three-way interaction for measures of interest, and no differences among treatment combinations with respect to average daily gain (ADG) or incidence of abscessed livers (P > 0.10). Steers fed CG during the backgrounding phase ate more than steers fed EG (P = 0.04), thus leading to improved overall efficiency of steers fed EG in the backgrounding phase compared with their counterparts fed CG (P < 0.01; Table 1). Overall efficiency tended to be greater for cattle fed CG during the finishing phase (P = 0.06) compared with cattle fed EG during the finishing phase. There was a tendency for interaction between G fed in the backgrounding and G fed in the finishing phase for hot carcass weight (P = 0.07), such that steers fed the same hybrid in both phases had greater carcass weight compared with those fed different hybrids in the backgrounding and finishing phases. Type of grain fed in the backgrounding and finishing phases, but not silage, impacted overall system efficiency.

Analysis of the mechanism of resistance to enzymatic hydrolysis of RS-5 resistant starch

RS-5 refers to the resistant starch formed by complexation of starch molecules with other molecules. In this study, the molecular mechanism of RS-5 was analysed. First, it was found, when α-amylase acted on the starch-lipid complexes, the glucose residues involved in complexation cannot be hydrolyzed by α-amylase, while the glucose residues not directly involved in complexation can be hydrolyzed. Second, lipid molecules are not necessary for the formation of RS-5 and can be replaced with small peptides or decanal molecules. Considering the multiple health hazards that may result from excessive lipid intake, small peptides composed of essential amino acids may be more desirable materials for RS-5 preparation. Third, starch-lipid complexes had strong interactions with α-amylase, which provides evidence in support of the sliding continuum hydrolysis hypothesis of α-amylase. These results revealed the mechanism of RS-5 at the molecular level, which provides a reference for the production and research of RS-5.

Chemical and functional properties of starch nanoparticle from purple sweet potato var. ayamurasaki

The native purple sweet potato (PSP) starch of the Ayamurasaki variety has drawbacks that limit its application in food. This study aims to produce starch nanoparticles from PSP by hydrolysis using 3 types of acids, such as citric acid, acetic acid, and lactic acid. The hydrolysis process was carried out by incubating PSP starch suspension using an acid solution with a concentration of 7.5% and the ratio of starch and acid was 1:5 (w/w). The resulting PSP starch nanoparticles were analyzed for their chemical and functional characteristics. The study design used a Completely Randomized Non-Factorial Design with four repetitions. The results showed that the hydrolysis process produced starch with amylose content, total sugar content, reducing sugar content, and swelling power which were significantly different (p<0.05) from the native PSP starch. However, the dextrose equivalent value (DE), degree of polymerization (DP), and solubility of the PSP starch nanoparticles were not significantly different (p>0.05) from the native PSP starch. The type of acid had a significantly different effect on the amylose content, total sugar and reducing sugar content, but had no significant effect on the DE, DP, swelling power and solubility values of the PSP starch nanoparticles. Significantly (p<0.05) hydrolysis of starch with acetic acid resulted in the highest yield of starch nanoparticles. Starch hydrolysis with acetic acid significantly (p<0.05) produced the highest yield of PSP starch nanoparticles.

Alpha-Amylase and Alpha-Glucosidase Inhibitory Potential of Overnight Soaked Aqueous Extract of Abelmoschus esculentus

Phytochemicals are secondary metabolites which act as antioxidants and possess various protective role.Alpha Amylase and Alpha Glucosidase enzymes catalyse hydrolysis of starch to simple sugars. Abelmoschus esculentus is a flowering plant of the Malvaceae family and is valued for its green seed pods. It naturally possesses anti-diabetic property, acts as a starch blocker as it prevents the absorption of starch in the body. Abelmoschus esculentus was cut vertically to open and added to 50ml of water. Soaked overnight and the aqueous extract was decanted and used for the phytochemical screening test followed by the evaluation of antioxidant and antidiabetic potential. The data were analysed statistically by a one-way analysis of variance (ANOVA) followed by Duncan’s multiple range test. Overnight soaked extract of Abelmoschus esculentus exhibited a significant antioxidant potential (IC50=280 µg/ml) and compared with standard vitamin C. Alpha amylase and alpha glucosidase inhibitory potential of Abelmoschus esculentus was analysed (IC50=380µg/ml and 320µg/ml respectively) and compared with standard acarbose. Though Abelmoschus esculentus is a common vegetable, its efficiency increases when soaking overnight.

Isoliquiritigenin retards starch digestion by increasing resistant starch content and inhibiting the activities of α-amylase and α-glucosidase

The inhibition mechanism of starch digestion by a natural plant active ingredient isoliquiritigenin was studied. The results indicated that isoliquiritigenin effectively decreased the starch hydrolysis through increasing the content of resistant starch, and inhibiting the activities of α-amylase and α-glucosidase. The content of resistant starch increased by 18.85% with the addition of isoliquiritigenin at 8% content. Multispectral analyses showed isoliquiritigenin combined with α-amylase or α-glucosidase to form stable complexes by non-covalent bonds, leading to the enzyme's structure to be loose, which was supported by the results of unstable conformations and an increase in the freedom of amino acid residues of the enzymes in molecular dynamics simulation. Molecular docking demonstrated that isoliquiritigenin bound to the amino acid residues 304–310 nearby the active pocket of α-amylase, and inserted the active site of α-glucosidase competing with the substrate to bind the crucial amino acid residues (Asp215, Asp352 and Glu411), thereby inhibiting α-amylase and α-glucosidase activity. These findings highlight the development potential of isoliquiritigenin as a hypoglycaemic dietary supplement.

Classification of industrial tapioca starch hydrolysis products based on their Brix and dextrose equivalent values using near-infrared spectroscopy.

Industrial starch hydrolysis allows the production of syrups with varying functionality depending on their Brix value and dextrose equivalent (DE). As the current methods for evaluating these products are labor-intensive and time-consuming, the objective of this study was to investigate the potential of near-infrared (NIR) spectroscopy for classifying the different tapioca starch hydrolysis products. NIR spectra of samples of seven products (n = 410) were recorded in transflectance mode in the 12 000-4000 cm-1 range. Next, orthogonal partial least squares (OPLS) regression models were built to predict the Brix and DE values of the different samples. To classify the different starch hydrolysis products, support vector machines (SVM) were trained using either the raw spectra or latent variables (LVs) obtained from the OPLS models. The best classification accuracy was obtained by the SVM classifier based on the LVs from the OPLS model for DE prediction, resulting in 95% correct classification over all classes. These results show the potential of NIR spectroscopy for classifying tapioca starch hydrolysis products with respect to their functional properties related to the Brix and DE values. © 2024 Society of Chemical Industry.

Production and Optimization of Extracellular α-amylase From Halophilic Bacteria Cytobacillus oceanisediminis Isolated From Wadi-El-Natrun, Egypt

The current study aimed to maximize α-amylase enzyme production by halophilic bacteria Cytobacillus oceanisediminis isolated from soil of Wadi-El-Natrun, Egypt. The results showed that of 21 halophilic bacterial isolates recovered from saline soil samples, eight isolates were high amylase producers. Interestingly, the bacterial isolate AHB6 exhibited the highest extracellular amylase production and was selected for further studies. This isolate was molecularly identified based on the 16srRNA gene sequencing as Cytobacillus oceanisediminis and has the accession number OM759999. The optimum temperature for α-amylase enzyme was 45 °C and exhibited thermostability at 45 °C for 1 h and retained more than 80% of its original activity. The α-amylase enzyme was active in almost all tested pHs and reached its highest activity at pH 9. Also, the optimum culture conditions for α-amylase enzyme production were wheat bran as carbon source, 2 g/l K2HPO4 as potassium source, 6 g/l MgSO4 as magnesium source and 0.5 g/l KNO3 as nitrogen source. These findings suggest the applicability of bacterial isolate Cytobacillus oceanisediminis as a potent producer of α-amylase for industrial purposes. Keywords: Amylase; Optimization; Cytobacillus oceanisediminis; Starch hydrolysis; Thermo-halophilic bacteria.

Effect of emulsified lipid and saponified lipid on the enzyme desizing of starch and its mechanism

To enhance the flexibility of starch film adhesion on yarns, sizing lipids (saponified lipid or emulsified lipid) must be added during the sizing process. However, different types of sizing lipids may have diverse combinations with starch to impact enzyme desizing. Therefore, this study investigated the effects of saponified lipid and emulsified lipid commonly used in warp sizing on the hydrolysis of starch. Additionally, the desizing efficiency and chain structure of desizing residues were analyzed. Experimental results demonstrated that the existence of saponified lipid or emulsified lipid led to a reduction in the degree of hydrolysis (1.1 % and 2.6 %, respectively) compared to the original corn starch. Notably, saponified lipid exhibited a relatively strong negative impact. Furthermore, the desizing efficiency decreased after adding emulsified lipid (1.2 %) or saponified lipid (2.9 %). Starch-lipid V-type complexes and physical hindrance could inhibit the enzyme desizing, resulting in a larger wavelength of maximum absorbance for desizing residues, along with higher molecular weight, z-average radius of gyration, and an increased proportion of long chains. The presence of saponified lipid significantly negatively influenced desizing, possibly due to the smaller particle size and propensity for complex formation with starch.

Co-ingestion of Cereals and Legumes during Infant Complementary Feeding: Starch and Protein in vitro Digestion.

This study explores the impact of co-ingesting cereals and legumes on starch and protein during simulated infant in vitro digestion. Various legumes (chickpeas, lentils, peas) were added to cereals (durum wheat, brown rice, white maize), and their effects on starch and protein hydrolysis were analyzed. Substituting 50% of cereal with legumes increased proteins, minerals, and dietary fiber. Infant food with legumes exhibited smoother pasting properties. Legumes in cereal purées led to varying starch hydrolysis trends, with the lowest values in durum wheat with chickpea and all cereal blends with peas. Resistant starch levels exceeding 50% were found in infant food samples. Digested protein hydrolysis increased with legumes in durum wheat, except for peas. Brown rice mixtures decreased significantly compared to the control with chickpeas (61%) and peas (42%), while lentil blends increased by 46%. Legumes generally did not significantly affect starch bioavailability, even with α-amylase inhibitors. Lentil-cereal purées could enhance infant food nutritional value.

Isolation and Identification of Soil-Derived Amylase-Producing Bacteria

Soil is a vital ecosystem for various life forms, including bacteria. Bacteria are the main group of soil microbes, mostly because of their ability to produce various extracellular enzymes. Amylases are the enzymes that break down starch, which are essential in biotechnology industries such as food, fermentation, textiles, and paper manufacturing. The demand for amylase is often high since many enterprises do not have access to local supplies of the enzyme. The objective of the current investigation is to isolate and identify bacterial isolates that can produce the enzyme amylase from soil samples. Soil samples were collected from the unexplored Biligiriranga hills (11.9988° N, 77.1398° E) in south-western Karnataka Bacterial isolates were isolated from soil samples and were primarily screened on starch agar medium to determine the amylase production. Three out of fifteen bacterial isolates that produced amylase were selected based on the highest clear zone around the bacterial colony. These three bacterial isolates were identified both microscopically and biochemically. Gram staining demonstrated that the isolates are rod-shaped and gram-positive organisms. Biochemical studies indicated that the isolates were positive for the catalase and starch hydrolysis tests, whereas negative for the potassium hydroxide and methyl red tests. Besides, 16S rRNA gene amplification and sequencing confirmed the isolate as Bacillus subtilis. The 16S rRNA sequence of B. subtilis strain B has been deposited in the NCBI GenBank. The optimal growth conditions observed in B. Subtilis. The optimal growth conditions observed in B. Subtilis were 37° C temperature at pH 7 and incubation period for 37h. Thus, the isolation and identification of soil-derived amylase-producing bacteria are crucial for understanding their potential applications in various industrial processes, such as bioremediation, waste management, and the production of enzymes for food, pharmaceuticals, and biofuel industries.

Comparing mass transfer and reaction rate kinetics in starch hydrolysis during food digestion

AbstractThis study demonstrates evidence that the mass transfer process of an enzyme (a biocatalyst) is the rate‐limiting step in the starch hydrolysis reaction during food digestion. The significance of this work has been to compare the reaction rate of starch hydrolysis by salivary enzymes with the mass transfer rate of rate‐limiting enzymes. This research has applied mass transfer and reaction engineering theory in a quantitative study of starch hydrolysis, and a dimensionless group, the Damköhler number (Da), has been calculated based on glucose measurements from a beaker and stirrer system. The values of the Da number in this study (0.3–19) indicate that both the time constant for mass transfer and the time constant for reaction are significant parameters. Scanning electron microscopy images emphasize that compression (simulated mastication) helps to break the plant cell wall of starch. Mass‐transfer resistance needs to be considered during food digestion studies. The Da numbers are significantly affected by both compression forces (internal mass‐transfer coefficients) and stirrer speeds (external mass‐transfer coefficients) in this beaker and stirrer system.

State diagrams of green peas (Pisum sativum L.) powders with different maltodextrin additions.

The purpose of this study was to examine the effect of maltodextrin addition on the physical stability of powdered green peas. The evaluation of the physical state of the material was based on the equilibrium water content of the monolayer (Xm) and the glass transition temperatures of the powders at room temperature (Tg) and in the frozen state (Tg'). Graphical sorption characteristic at 25°C was determined using static-gravimetric method while capacity of the monolayer values was calculated from the mathematical GAB model. Differential scanning calorimetry was carried out in order to determine glass transition lines and freezing curves which combine together were used to plot state diagrams. Relationship between Tg and solid content were shown by using Gordon-Taylor model. Freezing data were modeled employing the Clausius-Clapeyron equation and its development-Chen model. Sorption isotherms showed sigmoidal shape characteristic for high-molecular weight materials. Monolayer moisture content varied between 0.047 and 0.106 g water/g solids. The glass transition temperature of anhydrous green peas increased in from 89.9 to 175.6°C while Tg' value changed from -43.4 to -26.6°C to as a result of 75% polysaccharide addition. The ultimate maximum-freeze-concentration conditions of the powders were observed in range from 0.783 to 0.814 g solids/g sample. Monolayer capacity, Tg and Tg' values increased with increasing maltodextrin amount in the sample which indicates that the addition of starch hydrolysate has a beneficial effect on the stability of powders stored frozen and at room temperature.

Determination of Optimum Conditions of pH and Temperature on the Saccharification of Cassava Starch by Amyloglucosidase

Saccharification is the process of breaking complex carbohydrate into its monosaccharide components. The present study however was carried out to determine the optimum conditions of pH and temperature on the saccharification of cassava starch by amyloglucosidase. The optimum conditions of cassava starch hydrolysis was determined by using a pure culture of a thermostable amyloglucosidase for saccharification, and the activities of the enzyme determined at varying pH, temperature and time. Results showed that sample dry weight significantly decreased with respect to increased value of pH, temperature and time, while reducing sugar and dextrose equivalent significantly increased with respect to increased time. The optimal reducing sugar and dextrose equivalent were 74.23% and 96.41 DE, respectively at pH 4.5, 55 °C and 72 h. The glucose obtained from this process may serve as a substrate in fructose syrup production.

Effects of stir-frying on the processing characteristics and in vitro digestion of oat flour during storage

This study focused on stir-frying, a traditional Chinese method for treating oats before milling. The effects of stir-frying on the processing properties and in vitro digestion of oat flour during storage have not been explored. The results revealed that stir-frying treatment caused a greater amylopectin content of the oat flour, which made the oat flour easier to improve water absorption and expansion ability. The WAI of stir-fried oat flour was notably greater than that of raw oat flour, while the results of WSI were opposite. The enthalpy of gelatinization of the two oat flours increased significantly (p < 0.05) during storage, and the gelatinization characteristics changed significantly after 9 months of storage. SEM and CLSM studies showed that the dough made from stir-fried oat flour exhibited a well-formed gel network structure, better clumping performance and fat stability during storage. Compared with raw oat flour, stir-fried oat flour had a faster starch hydrolysis rate, a greater rapidly digestible starch (RDS) content, and a lower resistant starch (RS) content. The effect of storage time on the digestibility of stir-fried oat flour was less compared with raw oat flour. Overall, stir-frying improved the processing adaptability, digestibility, and stability of oat flour during storage.

Low-intensity pulsed electric field processing prior to germination improves in vitro digestibility of faba bean (Vicia faba L.) flour and its derived products: A case study on legume-enriched wheat bread

This study investigated the effect of low-intensity pulsed electric field (PEF) (0.3–0.7 kV/cm) and/or germination (0–72 h, 20 °C) on faba beans prior to flour- and breadmaking. PEF (0.5 and 0.7 kV/cm) had no significant effect on the germination performance of faba bean but had a positive effect on in vitro starch and protein hydrolysis of PEF-treated beans germinated for 72 h. The incorporation of flour from soaked, germinated, PEF-treated, and PEF-treated+germinated faba beans into wheat bread, at 30% mass level, improved the nutritional composition (total starch and protein contents) and protein digestibility but it reduced the specific volume and increased the density, brownness, and hardness of the bread. This finding shows for the first time that PEF-treatment (<0.7 kV/cm) of faba beans followed by germination (72 h) improved in vitro starch and protein hydrolysis of its flour and the protein digestibility at gastric phase of its enriched wheat bread.

Property and quality of japonica rice cake prepared with Polygonatum cyrtonema powder

Rice cake is a common traditional food in China. In this study, the effect of Polygonatum cyrtonema (PC) on the qualities and characteristics of rice cake was investigated. The incorporation of PC powder in rice cakes endowed a light-yellow color and increased the water content and water absorption of products. Rheological analysis showed that the rice cake containing PC exhibited weak-gel properties. Additionally, PC (40%) inhibited the rice cake aging and lowered the hardness of rice cakes to 13.86 N after 4 h storage. In vitro starch digestion analysis showed that PC (40%) reduced the digestibility of rice cakes by decreasing the starch hydrolysis rate from 88.70 to 58.95%, displaying a low estimated glycemic index (eGI) of 52.14. The findings mentioned above indicated that the inclusion of PC powder in rice cakes enhanced their characteristics and attributes, which also provided an approach for the development of PC products.

Deacetylated Konjac Glucomannan with a Slower Hydration Rate Delays Rice Digestion and Weakens Appetite Response.

The physical characteristics of chyme during gastrointestinal digestion are considered to significantly affect nutrient digestion and absorption (such as glucose diffusion), which has an impact on postprandial satiety. The present study aims to analyze the hydration rate (HR) and rheological properties of deacetylated konjac glucomannan (DKGM) at different degrees and then explore their effects on rice texture, digestive properties, and the subjects' post-meal appetite. The present results show that, as the deacetylation degree (DD) of KGM increased, the intersection point of the viscoelastic modulus shifted to a high shear rate frequency, and as the swelling time of the DKGM was prolonged, its HR decreased significantly. The results of the in vitro gastrointestinal digestion tests show that the hardness and chewability of the rice in the fast-hydration group (MK1) were remarkably reduced. In contrast, the slow-hydration group (MK5) exhibited an outstanding ability to resist digestion. The kinetics of starch hydrolysis revealed that the HR of the rice in the fast-hydration group was 1.8 times faster than that of the slow-hydration group. Moreover, it was found that the subjects' appetite after the meal was highly related to the HR of the MK. Their hunger (p < 0.001), desire to eat (p < 0.001), and prospective food consumption (p < 0.001) were significantly inhibited in the slow-hydration group (MK5) compared to the control. This study explored the nutritional effects of the hydration properties derived from the DKGM, which may contribute to modifying the high glycemic index food and provide ideas for the fabrication of food with enhanced satiating capacity.

Analysis of the interaction between double-helix starch molecule and α-amylase

Diabetes is a major chronic disease that jeopardises human health. Resistant starch (RS) is important in controlling diabetes. However, the specific relationship between the starch crystalline structure and RS content needs to be further elucidated. In this study, the details of the interactions between different starch molecules (single-amylose and double-helix) and α-amylase were analysed using molecular docking and dynamic simulations. Single-amylose molecules could penetrate deep into the active groove of α-amylase and make full contact with the catalytic triad, and their G3 and G4 glucose residues were firmly bound to the bottom of the active groove throughout the simulation. However, the double-helix molecule in the crystalline region of starch could not fully penetrate to the bottom of the active groove and make full contact with the catalytic triad of α-amylase. This suggests that, without considering other structural factors, the RS content should be positively correlated with relative crystallinity. In addition, starch molecules had strong interactions with α-amylase (approximately 78 kJ/mol) and could form many hydrogen bonds with the amino acid residues of α-amylase such as Thr163, Gln63, and Ile148, which supports the sliding continuum hydrolysis hypothesis of α-amylase. These results explain the intrinsic relationship between the starch hydrolysis efficiency and crystalline structure at the molecular level and provide an important reference for the preparation of RS and elucidation of its mechanism.