Prediction of the sweetening effect of Siraitia grosvenorii (luo han guo) fruits by two-dimensional quantitative NMR

Quality control of traditional Chinese medicine Chelidonii herba based on 2D-Q-NMR

Chelidonii herba is a traditional Chinese medicinal herb with effects including antispasmodic, analgesic, antitussive, and bronchodilator properties. Alkaloids are the main bioactive ingredients in Chelidonii herba. In this study, a two-dimensional nuclear magnetic resonance (Heteronuclear Singular Quantum Correlation, HSQC-2D-NMR) technique was employed to quantitatively analyze the total alkaloid content and three major active alkaloid monomers in Chelidonii herba from eleven different sources. The quantification results of the three monomeric alkaloids were also verified using conventional quantitative control methods such as HPLC. Experimental findings indicate that the total alkaloid content is not directly correlated with the content of the three monomeric alkaloids. Furthermore, the content of any individual monomeric alkaloid does not accurately reflect the overall quality of Chelidonii herba. It was demonstrated that the 2D-Q-NMR NMR can be applied as an alternative method. While maintaining the same levels of accuracy and precision, the 2D-Q-NMR method is simpler to operate and provides more comprehensive results with higher reproducibility in some cases.

Determination of Total Sennosides and Sennosides A, B, and A1 in Senna Leaflets, Pods, and Tablets by Two-Dimensional qNMR

In the present work, a two-dimensional qNMR method for the determination of sennosides was established. Using band-selective HSQC and the cross correlations of the characteristic 10-10' bonds, we quantified the total amount of the value-determining dianthranoids in five minutes, thus, rendering the method not only fast, but also specific and stability indicating. The validation of the method revealed excellent accuracy (recovery rates of 98.5 to 103%), precision (RSD values of 3.1%), and repeatability (2.2%) and demonstrated the potential of 2D qNMR in the quality control of medicinal plants. In a second method, the use of 2D qNMR for the single analysis of sennosides A, B, and A1 was evaluated with acceptable measurement times (31 min), accuracy (93.8%), and repeatability (5.4% and 5.6%) for the two major purgatives sennoside A and B. However, the precision for sennoside B and A1 was not satisfactory, mainly due to the low resolution of the HSQC signals of the two compounds.

Direct Quantitation of Phytocannabinoids by One-Dimensional 1H qNMR and Two-Dimensional 1H-1H COSY qNMR in Complex Natural Mixtures

The widespread use of phytocannabinoids or cannabis extracts as ingredients in numerous types of products, in combination with the legal restrictions on THC content, has created a need for the development of new, rapid, and universal analytical methods for their quantitation that ideally could be applied without separation and standards. Based on previously described qNMR studies, we developed an expanded ¹H qNMR method and a novel 2D-COSY qNMR method for the rapid quantitation of ten major phytocannabinoids in cannabis plant extracts and cannabis-based products. The ¹H qNMR method was successfully developed for the quantitation of cannabidiol (CBD), cannabidiolic acid (CBDA), cannabinol (CBN), cannabichromene (CBC), cannabichromenic acid (CBCA), cannabigerol (CBG), cannabigerolic acid (CBGA), Δ9-tetrahydrocannabinol (Δ9-THC), Δ9-tetrahydrocannabinolic acid (Δ9-THCA), Δ8-tetrahydrocannabinol (Δ8-THC), cannabielsoin (CBE), and cannabidivarin (CBDV). Moreover, cannabidivarinic acid (CBDVA) and Δ9-tetrahydrocannabivarinic acid (Δ9-THCVA) can be distinguished from CBDA and Δ9-THCA respectively, while cannabigerovarin (CBGV) and Δ8-tetrahydrocannabivarin (Δ8-THCV) present the same ¹H-spectra as CBG and Δ8-THC, respectively. The COSY qNMR method was applied for the quantitation of CBD, CBDA, CBN, CBG/CBGA, and THC/THCA. The two methods were applied for the analysis of hemp plants; cannabis extracts; edible cannabis medium-chain triglycerides (MCT); and hemp seed oils and cosmetic products with cannabinoids. The ¹H-NMR method does not require the use of reference compounds, and it requires only a short time for analysis. However, complex extracts in ¹H-NMR may have a lot of signals, and quantitation with this method is often hampered by peak overlap, with 2D NMR providing a solution to this obstacle. The most important advantage of the COSY NMR quantitation method was the determination of the legality of cannabis plants, extracts, and edible oils based on their THC/THCA content, particularly in the cases of some samples for which the determination of THC/THCA content by ¹H qNMR was not feasible.

Chemical Comparison of Monk Fruit Products Processed by Different Drying Methods Using High-Performance Thin-Layer Chromatography Combined With Chemometric Analysis

Monk fruit, also named Luo Han Guo, is the fruit of Siraitia grosvenorii (Swingle) C. Jeffrey ex A. M. Lu et Z. Y. Zhang and has been used as both food and traditional Chinese medicine. Due to preservation concerns, monk fruit is usually processed by hot-air drying or using low-temperature techniques after harvest. In this study, high-performance thin-layer chromatography (HPTLC) method was developed for the analysis of 13 mogrosides, 1 flavonoid, and 3 sugars in monk fruit products. Then chemometric analysis was applied to investigate the chemical characteristics in the samples dried by different methods. The results showed that the contents of mogroside V, 11-oxo-mogroside V, isomogroside V, and sucrose in monk fruits dried at low temperature were much higher than those in traditional hot-air drying samples, which was also confirmed by HPTLC-scanning. These findings indicate that HPTLC combined with chemometric analysis provides a reliable tool to understand the chemical differences between the monk fruit products processed by different drying methods, which will be helpful for their quality evaluation.

Engineering of a UDP-Glycosyltransferase for the Efficient Whole-Cell Biosynthesis of Siamenoside I in Escherichia coli

The combination of the insufficient availability and the complex structure of siamenoside I (SI), the sweetest glucoside isolated from Siraitia grosvenorii to date, limited its use as a natural sweetener. To solve this problem, an improved biocatalyst, UGT-M2, was semi-rationally created by engineering the uridine diphosphate glycosyltransferase UGT94-289-2 from S. grosvenorii for the monoglucosylation of mogroside IIIE (MG IIIE) to SI. Subsequently, an engineered Escherichia coli cell was constructed, which combined UGT-M2 with a UDP-glucose regeneration system to circumvent the need for expensive UDP-glucose to produce SI. After optimization, high-purity SI (>96.4%) was efficiently prepared from MG IIIE at a 1 L scale with a productivity of 29.78 g/(L day) and a molar yield of 76.5% and without using exogenous UDP-glucose. This study not only developed a whole-cell approach for the preparation of SI but also provided an alternative glycosyltransferase variant for SI biosynthesis with synthetic biology in the future.

Nuclear Magnetic Resonance Spectroscopy for Quantitative Analysis: A Review for Its Application in the Chemical, Pharmaceutical and Medicinal Domains

Nuclear magnetic resonance (NMR) is a rapid and accurate analytical tool for qualification and quantification. The capacity of NMR of being quantitative can also justify the calibration of other analytical methods. In pharmaceutical domain, quantitative NMR (qNMR) can be applied in the identification and quantification of drug simultaneously. The early drug development stage requires a minimum sample for analysis. Thus, priority should be given to utilize this technique to attain results with least investment, rapid analysis time and minimum sample consumption. This technique is a significant phenomenon to identify impurities, drug substance, residual solvents of in-process control (IPC) samples and characterizing the formulations. From an analyst's perspective, qNMR proved to be a routine practice in pharmaceutical industry to qualify any drug product. The absolute and relative methods offer great help in quantifying the component of interest in the process control samples and finished products. This review highlights the evolution of NMR application in the pharmaceutical industry, where determining the purity of drug substance, drug product and establishing the identity of impurities and its level are the challenging aspects. NMR in medicinal field emerging as a numero uno for Covid-19 severity detection and its dire consequences, accelerated vaccine development and the mapping of SAR-COV-2 RNA and proteins via chemical shift assignments.

Research Progress of NMR in Natural Product Quantification

In the fields of medicine and health, traditional high-performance liquid chromatography or UV-visible spectrophotometry is generally used for substance quantification. However, over time, nuclear magnetic resonance spectroscopy (NMR) has gradually become more mature. Nuclear magnetic resonance spectroscopy has certain advantages in the quantitative analysis of substances, such as being nondestructive, having a high flux and short analysis time. Nuclear magnetic resonance spectroscopy has been included in the pharmacopoeiae of various countries. In this paper, the principle of nuclear magnetic resonance spectroscopy and the recent progress in the quantitative study of natural products by NMR are reviewed, and its application in the quantitative study of natural products is proposed. At the same time, the problems of using NMR alone to quantify natural products are summarized and corresponding suggestions are put forward.

Artificial Sweeteners: History and New Concepts on Inflammation

Since the introduction of artificial sweeteners (AS) to the North American market in the 1950s, a growing number of epidemiological and animal studies have suggested that AS may induce changes in gut bacteria and gut wall immune reactivity, which could negatively affect individuals with or susceptible to chronic inflammatory conditions such as inflammatory bowel disease (IBD), a disorder that has been growing exponentially in westernized countries. This review summarizes the history of current FDA-approved AS and their chemical composition, metabolism, and bacterial utilization, and provides a scoping overview of the disease mechanisms associated with the induction or prevention of inflammation in IBD. We provide a general outlook on areas that have been both largely and scarcely studied, emerging concepts using silica, and describe the effects of AS on acute and chronic forms of intestinal inflammation.

Selective enzymatic α-1,6- monoglucosylation of mogroside IIIE for the bio-creation of α-siamenoside I, a potential high-intensity sweetener

A new compound, α-siamenoside I (α-SI), with a glucose unit selectively bound to the 6-hydroxyl group of the 24-O-β-glucosyl moiety of mogroside IIIE by α-1,6-glucosidic bond, was bio-created by two screened cyclodextrin glycosyltransferases with a maximum yield of 59.3%. Compared to mogroside IIIE, α-SI showed a significantly increased sweetness intensity (508 times sweeter than 5% sucrose), which is superior to siamenoside I (SI), the sweetest triterpenoid saponin isolated from Siraitia grosvenorii to date. Sensory evaluation showed that the taste quality of α-SI also was obviously better than mogroside IIIE. In addition to α-SI possessing a good stability similar to that of SI, it also did not cause a significant decrease in cell viability at a concentration of 200 μg/mL and had a negative influence on islets function at 1 μM. All of these preliminarily results pave the way for promoting α-SI as a potential low-calorie sweetener.