Isolation and characterization of α-glucosidase inhibitory constituents from Rhodiola crenulata

Phytoactives for Obesity Management: Integrating Nanomedicine for Its Effective Delivery

Obesity is a global health concern that requires urgent investigation and management. While synthetic anti-obesity medications are available, they come with a high risk of side-effects and variability in their efficacy. Therefore, natural compounds are increasingly being used to treat obesity worldwide. The proposition that naturally occurring compounds, mainly polyphenols, can be effective and safer for obesity management through food and nutrient fortification is strongly supported by extensive experimental research. This review focuses on the pathogenesis of obesity while reviewing the efficacy of an array of phytoactives used for obesity treatment. It details mechanisms such as enzyme inhibition, energy expenditure, appetite suppression, adipocyte differentiation, lipid metabolism, and modulation of gut microbiota. Comprehensive in vitro, in vivo, and preclinical studies underscore the promise of phytoactives in combating obesity, which have been thoroughly reviewed. However, challenges, such as poor bioavailability and metabolism, limit their potential. Advances in nanomedicines may overcome these constraints, offering a new avenue for enhancing the efficacy of phytoactives. Nonetheless, rigorous and targeted clinical trials are essential before applying phytoactives as a primary treatment for obesity.

Protective Effect of Hawthorn Fruit Extract against High Fructose-Induced Oxidative Stress and Endoplasmic Reticulum Stress in Pancreatic β-Cells

Hyperglycemia has deleterious effects on pancreatic β-cells, causing dysfunction and insulin resistance that lead to diabetes mellitus (DM). The possible causes of injury can be caused by glucose- or fructose-induced oxidative and endoplasmic reticulum (ER) stress. Hawthorn (Crataegus pinnatifida) fruit has been widely used as a hypolipidemic agent in traditional herbal medicine. The study aimed to investigate whether high fructose-induced pancreatic β-cell dysfunction could be reversed through amelioration of ER stress by the treatment of polyphenol-enriched extract (PEHE) from hawthorn fruit. The extract was partitioned using ethyl acetate as a solvent from crude water extract (WE) of hawthorn fruits, followed by column fractionation. The results showed that the contents of total polyphenols, flavonoids and triterpenoids in PEHE could be enhanced by 2.2-, 7.7- and 1.1-fold, respectively, in comparison to the original obtained WE from hawthorn fruit. In ER stress studies, a sharp increase in the inhibitory activity on the gene expression levels of GRP79, ATF6, IRE1α and CHOP involved in ER stress was evident when dosages of PEHE at 50–100 μg/mL were used against high-fructose (150 mM)-treated cells. HPLC–MS/MS analysis showed that polyphenols and flavonoids collectively accounted for 87.03% of the total content of PEHE.

Novel Signposts on the Road from Natural Sources to Pharmaceutical Applications: A Combinative Approach between LC-DAD-MS and Offline LC-NMR for the Biochemical Characterization of Two Hypericum Species (H. montbretii and H. origanifolium)

The members of the genus Hypericum have great potential to develop functional uses in nutraceutical and pharmaceutical applications. With this in mind, we aimed to determine the chemical profiling and biological properties of different extracts (ethyl acetate, methanol and water) from two Hypericum species (H. montbretii and H. origanifolium). We combined two approaches (LC-DAD-MS and LC-NMR) to identify and quantify chemical compounds of the extracts. Antioxidant properties (free radical quenching, reducing power and metal chelating) and enzyme inhibitory effects (cholinesterase, tyrosinase, amylase and glucosidase) were determined as biological properties. The tested extracts were rich in caffeic acid derivatives and flavonoids, and among them, 3-caffeoyl quinic acid and myricetin-3-O-rhamnoside were found to be the main compounds. The total phenolic and flavonoid levels were determined to be 50.97-134.99 mg GAE/g and 9.87-82.63 mg RE/g, respectively. With the exception of metal chelating, the methanol and water extracts showed stronger antioxidant properties than the ethyl acetate extracts. However, different results were obtained for each enzyme inhibition assay, and in general, the ethyl acetate extracts present more enzyme-inhibiting properties than the water or methanol extracts. Results from chemical and biological analyses were combined using multivariate analysis, which allowed establishing relationships between composition and observed effects of the Hypericum extracts based on the extraction solvents. To gain more insights between chemical compounds and enzyme-inhibiting effects, we performed molecular docking analysis. We observed favorable interactions between certain compounds and the tested enzymes during our analysis, confirming the data obtained from the multivariate approach. In conclusion, the obtained results may shed light on the road from natural sources to functional applications, and the tested Hypericum species may be considered potential raw materials, with promising chemical constituents and biological activities.

Mechanistic insights into the inhibitory activities of chemical constituents from the fruits of Terminalia boivinii on α-glucosidase

Regulation of key digestive enzymes is currently considered an effective remedy for diabetes mellitus. In this study, bioactive constituents were purified from Terminalia boivinii fruits and identified by 1 H NMR, 13 C NMR and EI-MS. In vitro and in silico methods were used to evaluate α-glucosidase, α-amylase, and lipase inhibition activities. Compounds 1 , 2 , and 4-7 with IC50 values between 89 and 445 µM showed stronger α-glucosidase inhibitory activities than the antihyperglycemic drug acarbose (IC 50 =1463.0 ± 29.5 µM). However, the compounds showed lower inhibitory effects against α-amylase and lipase with IC 50 values above 500 µM than acarbose (IC 50 = 16.7 ± 3.5 µM) and ursolic acid (IC 50 = 89.5 ± 5.6 µM), respectively. Lineweaver-Burk plots showed that compounds 1 , 2 , and 7 were non-competitive inhibitors, compounds 4 and 5 were competitive inhibitors and compound 6 was a mixed-type inhibitor. Fluorescence spectroscopic data showed that the compounds altered the microenvironment and conformation of α-glucosidase. Computer simulations indicated that the compounds and enzyme interacted primarily through hydrogen bonding. The findings indicated that the compounds were inhibitors of α-glucosidase and provided significant structural basis for understanding the binding activity of the compounds with α-glucosidase.

Hypoglycemic effects of Rhodiola crenulata (HK. f. et. Thoms) H. Ohba in vitro and in vivo and its ingredient identification by UPLC-triple-TOF/MS

Rhodiola crenulata (HK. f. et. Thoms) H. Ohba (RC), mainly distributed in the highly cold region of China, has long been used as a medicine/healthy food for eliminating fatigue and increasing blood circulation. This study aimed to evaluate the inhibitory effects of the RCRS extract on α-amylase and α-glucosidase (sucrase and maltase) in vitro and in vivo, and tentatively analyze and identify its chemical ingredients using UPLC-Triple-TOF/MS. The Rhodiola crenulata RCRS extract had strong inhibitory activities against α-amylase, sucrase and maltase with an IC₅₀ of 0.031 mg mL^-1, 0.142 mg mL^-1 and 0.214 mg mL^-1, respectively. Furthermore, the RCRS extract could significantly decrease the postprandial blood glucose (PBG) level of normal mice in a starch tolerance test, and reduce the PBG levels of diabetic mice in a starch/maltose/sucrose tolerance test. UHPLC-Triple-TOF-MS/MS analysis indicated that hydroxybenzoic acids, hydroxycinnamic acids, alcohol glycosides, flavonols and their derivatives were the main active ingredients in the RCRS extract. The results demonstrate that the RCRS extract of Rhodiola crenulata could be employed as a healthy food or medicine for controlling postprandial blood glucose levels.

Inhibitory Effect of Fisetin on α-Glucosidase Activity: Kinetic and Molecular Docking Studies

The inhibition of α-glucosidase is a clinical strategy for the treatment of type 2 diabetes mellitus (T2DM), and many natural plant ingredients have been reported to be effective in alleviating hyperglycemia by inhibiting α-glucosidase. In this study, the α-glucosidase inhibitory activity of fisetin extracted from Cotinus coggygria Scop. was evaluated in vitro. The results showed that fisetin exhibited strong inhibitory activity with an IC₅₀ value of 4.099 × 10⁻⁴ mM. Enzyme kinetic analysis revealed that fisetin is a non-competitive inhibitor of α-glucosidase, with an inhibition constant value of 0.01065 ± 0.003255 mM. Moreover, fluorescence spectrometric measurements indicated the presence of only one binding site between fisetin and α-glucosidase, with a binding constant (lgKa) of 5.896 L·mol⁻¹. Further molecular docking studies were performed to evaluate the interaction of fisetin with several residues close to the inactive site of α-glucosidase. These studies showed that the structure of the complex was maintained by Pi-Sigma and Pi-Pi stacked interactions. These findings illustrate that fisetin extracted from Cotinus coggygria Scop. is a promising therapeutic agent for the treatment of T2DM.

Rapid identification of chemical constituents of Rhodiola crenulata using liquid chromatography-mass spectrometry pseudotargeted analysis

Rhodiola crenulata (R. crenulata), is a famous traditional Chinese medicine, with observable effects such as anti-high-altitude illness and fatigue resistance. Nevertheless, comprehensive and systematic structural identification of its components remains a challenge. In this study, a pseudotargeted analytical method, involving key fragment filtering by ultra-high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry and ultra-high performance liquid chromatography-linear ion trap-Orbitrap mass spectrometry, was developed for rapid detection and identification of the chemical constituents of R. crenulata. The process consists of three steps: (i) acquiring sufficient mass spectral data, (ii) constructing a key fragments schedule and discovering the substructures rapidly by pseudotargeted key fragment filtering, and (iii) further identification of the compound structures based on accurate masses, fragment ions, related literatures, and authentic standards. As a result, 104 compounds were identified and divided into five categories, among which three potentially new and 59 ones were reported for the first time in R. crenulata. These results indicated that the major types of components are flavanols and gallic acid derivatives, organic acids, alcohols and their glycosides, flavonoids and their glycosides. This study enhances the understanding of R. crenulata and provides a reference for rapid and comprehensive identification of constituents in other herbal medicines.

Simultaneous Determination of 78 Compounds of Rhodiola rosea Extract by Supercritical CO2-Extraction and HPLC-ESI-MS/MS Spectrometry

The plant Rhodiola rosea L. of family Crassulaceae was extracted using the supercritical CO₂-extraction method. Several experimental conditions were investigated in the pressure range of 200–500 bar, with the used volume of cosolvent ethanol in the amount of 1% in the liquid phase at a temperature in the range of 31–70°C. The most effective extraction conditions are pressure 350 bar and temperature 60°C. The extracts were analyzed by HPLC with MS/MS identification. 78 target analytes were isolated from Rhodiola rosea (Russia) using a series of column chromatography and mass spectrometry experiments. The results of the analysis showed a spectrum of the main active ingredients Rh. rosea: salidroside, rhodiolosides (B and C), rhodiosin, luteolin, catechin, quercetin, quercitrin, herbacetin, sacranoside A, vimalin, and others. In addition to the reported metabolites, 29 metabolites were newly annotated in Rh. rosea. There were flavonols: dihydroquercetin, acacetin, mearnsetin, and taxifolin-O-pentoside; flavones: apigenin-O-hexoside derivative, tricetin trimethyl ether 7-O-hexosyl-hexoside, tricin 7-O-glucoronyl-O-hexoside, tricin O-pentoside, and tricin-O-dihexoside; flavanones: eriodictyol-7-O-glucoside; flavan-3-ols: gallocatechin, hydroxycinnamic acid caffeoylmalic acid, and di-O-caffeoylquinic acid; coumarins: esculetin; esculin: fraxin; and lignans: hinokinin, pinoresinol, L-ascorbic acid, glucaric acid, palmitic acid, and linolenic acid. The results of supercritical CO₂-extraction from roots and rhizomes of Rh. rosea, in particular, indicate that the extract contained all biologically active components of the plant, as well as inert mixtures of extracted compositions.

Synthesis of 2-(4-hydroxyphenyl)ethyl 3,4,5-Trihydroxybenzoate and Its Inhibitory Effect on Sucrase and Maltase

We report on the synthesis of an active component, 2-(4-hydroxyphenyl)ethyl 3,4,5-trihydroxybenzoate (HETB), from Rhodiola crenulata. Subsequent analysis revealed that HETB exhibits α-glucosidase inhibitory activities on maltase and sucrase, with potency exceeding that of the known α-glucosidase inhibitors (voglibose and acarbose). An inhibition kinetics study revealed that HETB, acarbose, and voglibose bind to maltase and sucrase, and HETB was shown to be a strong competitive inhibitor of maltase and sucrase. In a molecular docking study based on the crystal structure of α-glucosidase from Saccharomyces cerevisiae, we revealed the HETB binding in the active site of maltase via hydrogen-bond interactions with five amino acid residues: Ser 240, Asp 242, Glu 277, Arg 315, and Asn 350. For HETB docked to the sucrase active site, seven hydrogen bonds (with Asn 114, Glu 148, Gln 201, Asn 228, Gln 381, Ile 383, and Ser 412) were shown.

Alpha Glucosidase Inhibitory Activities of Plants with Focus on Common Vegetables

Type-2 diabetes mellitus is one of the most prevalent metabolic diseases in the world, and is characterized by hyperglycemia (i.e., high levels of glucose in the blood). Alpha-glucosidases are enzymes in the digestive tract that hydrolyze carbohydrates into glucose. One strategy that has been developed to treat type-2 diabetes is inhibition of the activity of alpha-glucosidases using synthetic drugs. However, these inhibitors are usually associated with gastrointestinal side effects. Therefore, the development of inhibitors from natural products offers an alternative option for the control of hyperglycemia. In recent years, various studies have been conducted to identify alpha-glucosidases inhibitors from natural sources such as plants, and many candidates have transpired to be secondary metabolites including alkaloids, flavonoids, phenols, and terpenoids. In this review, we focus on the alpha-glucosidases inhibitors found in common vegetable crops and the major classes of phytochemicals responsible for the inhibitory activity, and also as potential/natural drug candidates for the treatment of type-2 diabetes mellitus. In addition, possible breeding strategies for production of improved vegetable crops with higher content of the inhibitors are also described.

Characterization of Maltase and Sucrase Inhibitory Constituents from Rhodiola crenulata

The inhibitory properties of epicatechin-(4β,8)-epicatechingallate (B2-3'-O-gallate), epicatechin gallate (ECG), and epicatechin (EC) isolated from Rhodiola crenulata toward maltase and sucrase were investigated. The half-maximal inhibitory concentration (IC50) values for maltase were as follows: B2-3'-O-gallate (1.73 ± 1.37 μM), ECG (3.64 ± 2.99 μM), and EC (6.25 ± 1.84 μM). Inhibition kinetic assays revealed the inhibition constants (Ki) of the mixed-competitive inhibitors of maltase, as follows: B2-3'-O-gallate (1.99 ± 0.02 μM), ECG (3.14 ± 0.04 μM), and EC (7.02 ± 0.26 μM). These compounds also showed a strong inhibitory activity toward sucrase, and the IC50 values of B2-3'-O-gallate, ECG, and EC were 6.91 ± 3.41, 18.27 ± 3.99, and 18.91 ± 3.66 μM, respectively. Inhibition kinetic assays revealed the inhibition constants (Ki) of the mixed-competitive inhibitors of sucrase as follows: B2-3'-O-gallate (6.05 ± 0.04 μM), ECG (8.58 ± 0.08 μM), and EC (13.72 ± 0.15 μM). Overall, these results suggest that B2-3'-O-gallate, ECG, and EC are potent maltase and sucrase inhibitors.

Novel Catechin-Tiopronin Conjugates Derived from Grape Seed Proanthocyanidin Degradation: Process Optimization, High-Speed Counter-Current Chromatography Preparation, as Well as Antibacterial Activity

Tiopronin, as a novel thiol-containing nucleophile, was introduced for depolymerizing polymeric proanthocyanidins from grape seed into catechins and three new proanthocyanidin-tiopronin degradation products: (+)-catechin-4β-S-tiopronin methyl ester (CT), (-)-epicatechin-4β-S-tiopronin methyl ester (ECT), and (-)-epicatechin gallate-4β-S-tiopronin methyl ester (ECGT). A Box-Behnken design was employed to optimize degradation conditions based on single-factor experiments to obtain target products. Each of the new degradation compounds was isolated by the high-speed counter-current chromatography combined with semipreparative high performance liquid chromatography in large amounts, and then, their structures were identified by ¹H NMR, ¹³C NMR, 2D-NMR, as well as mass spectrometry analysis. The absolute configurations were further confirmed by comparison between the calculated electronic circular dichroism and experimental spectra. Further evaluation of antibacterial activities of these compounds showed that CT and ECT possessed more inhibiting capacity against Staphylococcus aureus and Escherichia coli than parent compound catechin and epicatechin. However, ECGT has no bacteriostatic capacity against these two bacteria.

Rhodiola species: A comprehensive review of traditional use, phytochemistry, pharmacology, toxicity, and clinical study

Rhodiola species, belonging to the family Crassulaceae, have long been used as an adaptogen, tonic, antidepressant, and antistress medicine or functional food in Asia and Europe. Due to the valuable application, the growing demand of Rhodiola species has led to a rapid decrease in resource content. This review aims to summarize the integrated research progress of seven mainstream Rhodiola species. We first outline both traditional and current use of Rhodiola for the treatment of various diseases. A detailed summary and comparison of chemical, pharmacological, toxicological, and clinical studies of various Rhodiola species highlight recent scientific advances and gaps, which gives insights into the understanding of Rhodiola application and would be helpful to improve the situation of biological resources and diversities of Rhodiola plants.

Molecular Insight and Mode of Inhibition of α-Glucosidase and α-Amylase by Pahangensin A from Alpinia pahangensis Ridl

The inhibition of carbohydrate-hydrolyzing enzymes in human digestive organs is crucial in controlling blood sugar levels, which is important in treating type 2 diabetes. In the current study, pahangensin A (1), a bis-labdanic diterpene characterized previously in the rhizomes of Alpinia pahangensis Ridl., was identified as an active dual inhibitor for α-amylase (IC₅₀ =114.80 μm) and α-glucosidase (IC₅₀ =153.87 μm). This is the first report on the dual α-amylase and α-glucosidase inhibitory activities of a bis-labdanic diterpene. The Lineweaver-Burk plots of compound 1 indicate that it is a mixed-type inhibitor with regard to both enzymes. Based on molecular docking studies, compound 1 docked in a non-active site of both enzymes. The dual inhibitory activity of compound 1 makes it a suitable natural alternative in the treatment of type 2 diabetes.

Evaluation of the Enzyme Inhibitory and Antioxidant Activities of Entada spiralis Stem Bark and Isolation of the Active Constituents

Digestive enzymes and free radical inhibitors are used to prevent complications resulting from diabetes. Entadaspiralis (family Leguminosae), which is a well-known medicinal plant in herbal medicine due to its various traditional and medicinal applications, was studied. Crude extracts were successively obtained from the stem bark using petroleum ether, chloroform and methanol as extracting solvents. The antioxidant activity of all the extracts, fractions and isolated compounds were estimated using 2,2-diphenyl-1-picrylhydrazyl (DPPH), β-carotene and 2,2′-azinobis(-3-ethylbenzothiazine-6-sulfonic acid) (ABTS) assays, while digestive enzymes inhibitory activity was assessed using α-amylase and α-glucosidase inhibitory methods. Structure elucidation of pure compounds was achieved through different spectroscopic analysis methods. Fractionation and purification of the most active methanol extract resulted in the isolation of a ferulic ester namely; (e)-hexyl 3-(4-hydroxy-3-methoxyphenyl) acrylate (FEQ-2) together with five known phenolic constituents, identified as kaempferol (FEQ-3), 5,4′-dihydroxy-3,7,3′-trimethoxyflavone (FEQ-2), gallic acid (FEQ-5), (+)-catechin (FEQ-7) and (−)-epicatechin (FEQ-8). FEQ-5 exhibited the strongest antioxidant and enzyme inhibitory activities followed by FEQ-3 and FEQ-4. FEQ-2 also displayed potent free radical scavenging activity with IC₅₀ values of 13.79 ± 2.13 (DPPH) and 4.69 ± 1.25 (ABTS) µg/mL, respectively. All other compounds were found active either against free radicals or digestive enzymes.

Novel Antihypertensive Prodrug from Grape Seed Proanthocyanidin Extract via Acid-Mediated Depolymerization in the Presence of Captopril: Synthesis, Process Optimization, and Metabolism in Rats

Grape seed extract contains a high content of proanthocyanidins that can be depolymerized into C-4-substituted (epi)catechin derivatives in the presence of nucleophiles. However, the biological and medicinal values of depolymerization products have been rarely investigated. Recently, we developed a novel depolymerization product (-)-epicatechin-4β- S-captopril methyl ester (ECC) derived from the reaction of grape seed proanthocyanidin extract with captopril in the presence of acidified methanol. A central composite design was employed to select the most appropriate depolymerization temperature and time to obtain the target product ECC with a high yield. A total of 16 metabolites of ECC in rat urine, feces, and plasma were identified using liquid chromatography quadrupole time-of-flight tandem mass spectrometry. The in vivo results suggested that ECC could release captopril methyl ester and epicatechin, followed by the generation of further metabolites captopril and epicatechin sulfate conjugates. Therefore, ECC may be used as a potential prodrug with synergistic or additive hypotensive effects.

Rhobupcyanoside B, A new cyanoside from Rhodiola bupleuroides

One new cyanoside, rhobupcyanoside B (1), together with 7 known ones, was isolated from the 70% ethanol extract of the roots and rhizomes of Rhodiola bupleuroides. Their structures were determined by spectroscopic methods, including 2D NMR techniques. Compound 1 was evaluated for its inhibitory activity against α-glucosidase with IC50 value of 278.28 ± 0.55 μM by comparing with the positive control (acarbose) at 210.40 ± 0.32 μM.

A potent alpha-glucosidase inhibitor from Myristica cinnamomea King

A dimeric acylphenol and a potent α-glucosidase inhibitor, giganteone D (IC50 5.05μM), was isolated and characterized from the bark of Myristica cinnamomea King. The bark also yielded an acylphenol with an unprecedented skeleton for which the name cinnamomeone A (IC50 358.80μM) was proposed. Their structures were established by means of NMR and MS spectrometric analyses. The Lineweaver-Burk plot of giganteone D indicated that it was a mixed-type inhibitor. This is the first report on the α-glucosidase inhibiting potential of acylphenols.

Phenolic Compounds from the Roots of Rhodiola crenulata and Their Antioxidant and Inducing IFN-γ Production Activities

In the present study, two new phenolic compounds 1 and 11, a pair of lignan isomers 12 and 13 with their absolute configurations established for the first time, were isolated from the ethanol extract of the roots of Rhodiola crenulata, together with 13 known phenolic compounds, and their structures were elucidated via NMR, HRESIMS, UV, IR and CD analyses. All the isolated compounds were evaluated for their in vitro antioxidant activities using the 2,2-diphenyl-1-picryhydrazyl (DPPH) and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging assays. Ten of them exhibited significant antioxidant activities compared to ascorbic acid. Furthermore, the inducibilities of the isolated compounds to IFN-γ production were also assessed. Compounds 1, 8, 9, 12, 13, 14 and 15 could moderately stimulate IFN-γ expression.

Effects of Rhodiola on production, health and gut development of broilers reared at high altitude in Tibet

Rhodiola has long been used as a traditional medicine to increase resistance to physical stress in humans in Tibet. The current study was designed to investigate whether Rhodiola crenulata (R. crenulata) could alleviate the negative effects of hypoxia on broiler chickens reared in Tibet Plateau. The effect of supplementing crushed roots of R. crenulata on production performance, health and intestinal morphology in commercial male broilers was investigated. Dietary treatments included CTL (basal diet), Low-R (basal diet + 0.5% R. crenulata) and High-R (basal diet + 1.5% R. crenulata). In comparison with broilers fed the control diet, Low-R had no effect on production performance while High-R significantly decreased average daily feed intake at d 14, 28 and 42, body weight at d 28 and 42 and gut development. Ascites induced mortality did not differ among treatments. Nevertheless Low-R significantly reduced non-ascites induced mortality and total mortality compared with broilers fed CTL and High-R diets. Broilers fed the High-R diet had significantly increased blood red blood cell counts and hemoglobin levels at 28 d compared with other treatments. Our results suggest that supplementation with Rhodiola might reduce the effects of hypoxia on broilers and consequently decrease mortality rate.