In vitro antioxidant and inhibitory activity of water decoctions of carob tree (Ceratonia siliqua L.) on cholinesterases, α-amylase and α-glucosidase

This work reports the in vitro inhibitory activity of water decoctions of leaves, germ flour, pulp, locust bean gum and stem bark of carob tree on α-amylase, α-glucosidase, acetylcholinesterase and butyrylcholinesterase. The antioxidant activity and the chemical characterisation of the extracts made by spectrophotometric assays and by high-performance liquid chromatography are also reported. Leaves and stem bark decoctions strongly inhibited all the enzymes tested, had significant antioxidant activity and the highest total phenolics content. The major compounds were identified as gallic acid in the leaves and gentisic acid in the stem bark.     

Phytochemical Composition,Antioxidant Activity, α-Glucosidase and Acetylcholinesterase Inhibitory Activity of Quinoa Extract and Its Fractions

This study is aimed to evaluate the chemical compositions and biological activities of quinoa, a novel and excellent food crop. Quinoa extract and its fractions were prepared by ethanol extraction and liquid-liquid extraction, including ethanol crude extract, and petroleum ether, chloroform, ethyl acetate (EAF), and n-butanol and water fractions. The total phenolic and flavonoid contents, antioxidant activities, α-glucosidase and acetylcholinesterase inhibitory abilities of the extract and fractions were further determined. Based on these foundations, the chemical composition of the EAF fraction exhibiting the strongest functional activity was analyzed by ultra-performance liquid chromatography-mass spectrometry. The results showed the EAF fraction had the highest phenolic and flavonoid contents, and the highest antioxidant activities, as well as the strongest α-glucosidase and acetylcholinesterase inhibitory abilities, which is even better than the positive control. The phytochemical composition of the EAF fraction indicated that 661 and 243 metabolites were identified in positive and negative ion modes, which were classified into superclass, class and subclass levels, respectively. Phenolic acids and flavonoids were the major bioactive compounds in the EAF fraction. This study found that quinoa, especially its ethyl acetate fraction, had the potential for the development of natural antioxidants, acetylcholinesterase inhibitors, and hypoglycemic agents.     

Hepatoprotective Constituents of Total Dibenzocyclooctadiene Lignans from Schisandra chinensis Based on the Spectrum-Effect Relationship

To scientifically clarify the hepatoprotective constituents of Fructus Schizandrae chinensis, eleven batches samples of total dibenzocyclooctadiene lignans (TDL) from Schisandra chinensis were prepared by using the optimum extraction technique. Characteristic high-performance liquid chromatography (HPLC) chromatograms were obtained through HPLC analysis technology, and the hepatoprotective effects of the eleven batches of TDL were evaluated by MTT assay. Based on the chemical and biological activity results, the spectrum-effect relationship between the characteristic HPLC fingerprints and the hepatoprotective effect of TDL was established using Minitab 16.0 data analysis software. On the basis of the spectrum-effect relationship, thirteen compounds (1–13) were obtained from the TDL by chemical natural product chemical separation and purification technology, and their structures were identified on the basis of the spectral data and the literature. Based on these compounds, thirteen common peaks among the thirty-three chromatographic peaks in the above HPLC fingerprints were identified. Our findings showed that some components, including, schisandrin B (2), schisandrin A (3), and schisandrol B (7) had significant roles in promoting hepatoprotective activity. Preliminary verification of the spectrum-effect relationship of TDL from S. chinensis was carried out, and the results confirmed that the activity of a composite of these three key components in optimal ratios was better than that of any individual compound, which potentially confirmed the reliability of the spectrum-effect relationship and the synergistic effects of traditional Chinese medicine.     

Characterization of the Phytochemical Profiles and Biological Activities of Ajuga chamaepitys subsp. chia var. chia and Ajuga bombycina by High-Performance Liquid Chromatography–Electrospray Ionization–Tandem Mass Spectrometry (HPLC–ESI–MSn)

This study investigates into the pharmacological potential of three solvent extracts (ethyl acetate, methanol, and water) of two Ajuga species (Ajuga chamaepitys subsp. chia var. chia and Ajuga bombycina) based on their antioxidant activity and enzyme inhibitory effects along with establishing the phytochemical profile. Spectrophotometric and high-performance liquid chromatography–electrospray ionization–tandem mass spectrometry (HPLC–ESI–MSⁿ) were used to determine the total and individual phytocompounds, respectively. Antioxidant potential was assessed using different assays such as DPPH, ABTS, CUPRAC, FRAP, phosphomolybdenum, and metal chelation. Enzyme inhibitory effects were studied against acetylcholinesterase, butyrylcholinesterase, tyrosinase, α-amylase, and α-glucosidase. The aqueous extract of both plants showed better ABTS scavenging, FRAP, and metal chelating activities. The methanol extracts displayed the highest tyrosinase inhibitory and antioxidant activity in the phosphomolybdenum assay while the ethyl acetate extracts of both plants showed better butyrylcholinesterase (BChE), α-amylase, and α-glucosidase inhibition. The total phenolic content was highest in the aqueous extract of A. chamaepitys while the methanolic extract of A. bombycina showed the highest flavonoid content. Identification by HPLC–ESI–MSⁿ revealed the presence of some individual compounds including phenolic acids, flavonoids, iridoid glycosides, phenylethanoid glycosides, and other compounds. To conclude, both A. chamaepitys and A. bombycina can be considered as rich sources of phytocompounds to manage chronic diseases.     

齐墩果酸的结构修饰和α-葡萄糖苷酶抑制活性

以天然五环三萜类化合物齐墩果酸为原料, 通过氧化、酯化、环合和曼尼希等反应, 对A环2, 3位和28位进行结构修饰, 设计合成了16个衍生物; 通过理化性质、质谱和核磁数据确定了化合物结构. 对合成的衍生物进行了体外α-葡萄糖苷酶抑制活性筛选, 结果表明, 受试化合物在200 μg/mL浓度下显示出不同程度的酶抑制活性. 初步构效关系分析表明, 28位游离羧基是活性必需基团, 3位羟基或相应的氢键供体取代基有利于提高活性.     

α-Glucosidase inhibitors screening from Cyclocarya paliurus based on spectrum–effect relationship and UPLC–MS/MS

Cyclocarya paliurus is an edible and medicinal plant exhibiting significant hypoglycemic effect. However, its active components are still unclear and need further elucidation. In this research, the active components of the leaves of C. paliurus responsible for the α-glucosidase inhibitory activity were screened and identified based on a spectrum–effect relationship study in combination with ultra-performance liquid chromatography tandem mass spectrometry (UPLC–MS/MS) analysis. The 70% ethanol eluate fraction of the leaves of C. paliurus with the strongest α-glucosidase inhibitory activity was obtained after extraction and purification with macroporous resin. Their chromatographic fingerprints (15 batches) were established by UPLC analysis and 32 common peaks were specified by similarity analysis. Their IC₅₀ values for α-glucosidase inhibition were measured by an enzymatic reaction. Several multivariate statistical analysis methods including hierarchical cluster analysis, principal component analysis, partial least square analysis and gray relational analysis were applied to explore the spectrum–effect relationship between common peaks and IC₅₀ values, and the chromatographic peaks making a large contribution to efficacy were screened out. To further elucidate the active components of leaves of C. paliurus, the 70% ethanol eluate fraction was characterized by UPLC–MS/MS analysis, and 10 compounds were identified. This study provides a valuable reference for further research and development of hypoglycemic active components of C. paliurus.     

GC-MS analysis of metabolites from soxhlet extraction,ultrasound-assisted extraction and supercritical fluid extraction of Salacca zalacca flesh and its alpha-glucosidase inhibitory activity

Abstract

Different extraction processes were employed to extract bioactive metabolites from Salacca zalacca flesh by a range of aqueous and organic solvents. The highest extraction yield was obtained by 50% ethanol extract of SE (73.18?±?4.35%), whereas SFE_1 showed the lowest yield (0.42?±?0.08%). All extracts were evaluated for in vitro α-glucosidase inhibitory activity, measured by their IC₅₀ values in comparison to that of quercetin, the positive control (IC₅₀ = 2.7?±?0.7?μg/mL). The lowest α-glucosidase inhibitory activity was indicated by water extract of SE (IC₅₀ = 724.3?±?42.9?μg/mL) and the highest activity was demonstrated by 60% ethanol extract by UAE (IC₅₀ = 16.2?±?2.4?μg/mL). All extracts were analysed by GC-MS and identified metabolites like carbohydrates, fatty acids, organic acids, phenolic acids, sterols and alkane-based compounds etcetera that may possess the potential as α-glucosidase inhibitor and may attribute to the α-glucosidase inhibitory activity.     

Spectrum-Effect Relationship-Based Strategy Combined with Molecular Docking to Explore Bioactive Flavonoids from Sceptridium ternatum

Sceptridium ternatum is a herbaceous plant with significant potential for pharmaceutical and cosmetic applications. In this study, we established a spectrum-effect relationship-based strategy to investigate the bioactive basis and tissue distribution in S. ternatum. First, a phytochemical analysis on the ethanol extracts from roots, stems, and leaves of S. ternatum was performed using the colorimetric method, high-performance liquid chromatography–ultraviolet (HPLC–UV), and high-performance liquid chromatography–electrospray ionization quadrupole time-of-flight mass spectrometry (HPLC–ESI-Q-TOF-MS/MS). Then, radical scavenging assays and the lipopolysaccharide-stimulated RAW 264.7 cell model were used to estimate the antioxidant and anti-inflammatory activities, respectively. Spectrum-effect relationship analysis and molecular docking were further employed to evaluate the correlation between the phytochemical profile and anti-inflammatory activity. Our results demonstrate that S. ternatum leaves contained the most abundant flavonoids and exerted the best biological activities. Their IC₅₀ values for scavenging 2,2ʹ-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) and 1,1-diphenyl-2-picrylhydrazyl radicals were 2.43 ± 0.13 and 5.36 ± 0.54 mg/mL, respectively. In lipopolysaccharide-stimulated RAW 264.7 cells, the leaf extract caused the greatest reduction in nitric oxide production (38.15%) and interleukin-6 release (110.86%). Spectrum-effect relationship analysis and molecular docking indicated that quercetin 3-O-rhamnoside-7-O-glucoside possessed high anti-inflammatory activity by binding with interleukin-6. In conclusion, S. ternatum is a rich source of bioactive flavonoids with potential for exploitation in the prevention and treatment of oxidative stress and inflammation-related pathologies.     

Screening out Potential Cardio-Toxic Components of Chinese Herb Radix Aconiti Lateralis in Rat Dosed Plasma by High Performance Liquid Chromatography/Electrospray Ionization Quadrupole Time-Of-Flight Mass Spectrometry

This study established a new, rapid, and accurate method for bioactive compound screening by the combination of serum pharmacochemistry and serum pharmacology based on a spectrum-effect relationship model. HPLC/ESI-Q-TOF-MS was used for the chemical profiling of samples of dosed plasma, control plasma, and Radix Aconiti Lateralis decoction. A comparison was made of the resulting chemical profiles, which totaled 20 compounds including 16 prototype compounds and 4 metabolites derived from SF decoction that were detected as potential bioactive components. Using MS/MS analysis and accurate molecular weight assessments of TOF, 17 components in 20 potential bioactive compounds were structurally identified. Moreover, the pretreated plasma samples were injected into venous sinus of isolated toad hearts to investigate the cardio-toxicity according to heart ratio (HR) situation and electrocardiograph (ECG) parameters, including PR interval, QRS interval, and QT interval. Finally, 4 compounds in these 20 potential bioactive components that had closest correlation with 4 cardio-toxic experimental indexes respectively were investigated by spectrum-effect relationship model for the first time. The 4 compounds were considered as the real cardio-toxic components. This study proposed a series of potential bioactive components in Radix Aconiti Lateralis and provided a general research pattern to identify the potential bioactivity compounds in Chinese herbs or natural pharmacy.     

Multi-targeted potential of Pittosporum senacia Putt.: HPLC-ESI-MSn analysis,in silico docking,DNA protection,antimicrobial, enzyme inhibition,anti-cancer and apoptotic activity

Pittosporum senacia (PS) Putt. (Pittosporaceae), indigenous to the Mascarene Islands, is a common ingredient in traditional medicines. However, there is currently a dearth of studies to validate some of these traditional claims. Given the broad traditional uses of PS against several diseases, we aimed to provide a comprehensive insight into the biological and chemical profile of P. senacia. The antioxidant, enzyme inhibitory activity, anticancer, and phytochemical composition of the methanolic extract of P. senacia leaf extracts were studied. The possible interaction and binding mode of the most abundant phytochemicals were studied via in silico docking experiments on tyrosinase and α-glucosidase. The mechanism behind the cytotoxic property of P. senacia extract for MDA-MB-231 was also examined using different methods including 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cell viability test checking apoptosis-associated genes, and wound healing assays. Twenty-six compounds were identified, of which caffeoylquinic acid derivatives, ferulic acid derivative, cinnamoylquinic acid derivative and two other polyphenols (oleuropeine and isoramnetin glucoside) being abundant, have been tested using in silico studies, against α-glucosidase and tyrosinase. The extract (IC₅₀ = 118.8 μg/ml) exhibited time and dose dependent anti-proliferative effect on human breast cancer cell line, MDA-MB-231. According to the expression profile of apoptosis inhibitors and apoptosis promoters genes, expression of Bax and Bak genes were significantly increased compared to Bcl-2 and Birc5 genes. Based on wound healing analysis, cell migration was inhibited after the application of the plant extract. The present findings suggested that PS might be a good candidate as sources of bioactive compounds for designing functional applications.     

Encapsulation Preserves Antioxidant and Antidiabetic Activities of Cactus Acid Fruit Bioactive Compounds under Simulated Digestion Conditions

Cactus acid fruit (Xoconostle) has been studied due its content of bioactive compounds. Traditional Mexican medicine attributes hypoglycemic, hypocholesterolemic, anti-inflammatory, antiulcerogenic and immunostimulant properties among others. The bioactive compounds contained in xoconostle have shown their ability to inhibit digestive enzymes such as α-amylase and α-glucosidase. Unfortunately, polyphenols and antioxidants in general are molecules susceptible to degradation due to storage conditions, (temperature, oxygen and light) or the gastrointestinal tract, which limits its activity and compromises its potential beneficial effect on health. The objectives of this work were to evaluate the stability, antioxidant and antidiabetic activity of encapsulated extract of xoconostle within double emulsions (water-in-oil-in-water) during storage conditions and simulated digestion. Total phenols, flavonoids, betalains, antioxidant activity, α-amylase and α-glucosidase inhibition were measured before and after the preparation of double emulsions and during the simulation of digestion. The ED40% (treatment with 40% of xoconostle extract) treatment showed the highest percentage of inhibition of α-glucosidase in all phases of digestion. The inhibitory activity of α-amylase and α-glucosidase related to antidiabetic activity was higher in microencapsulated extracts than the non-encapsulated extracts. These results confirm the viability of encapsulation systems based on double emulsions to encapsulate and protect natural antidiabetic compounds.     

超滤亲和结合液相色谱-质谱联用和分子对接技术筛选毛菊苣种子中高亲和性α-葡萄糖苷酶抑制剂

采用超滤亲和结合液相色谱-质谱联用(UF-LC-MS) 和分子对接技术筛选毛菊苣种子中高亲和α-葡萄糖苷酶抑制剂.以4-硝基苯-α-D-吡喃葡萄糖苷(PNPG)为底物,阿卡波糖为阳性对照,评价毛菊苣种子提取物对α-葡萄糖苷酶的抑制活性,其中阿卡波糖IC50为0.003 mg/mL,毛菊苣种子IC50为0.447 mg/mL.利用UF-LC-MS技术对毛菊苣种子提取物进行筛选鉴定,获得4种化合物;通过Autodock软件筛选出2种与α-葡萄糖苷酶有较高亲和力的化合物,分别是绿原酸和异绿原酸A.结合体外酶活实验,验证了绿原酸、异绿原酸A对α-葡萄糖苷酶的抑制活性.结果表明,各化合物对α-葡萄糖苷酶的抑制活性由大到小依次是:阿卡波糖>异绿原酸A>绿原酸,其中异绿原酸A与阿卡波糖抑制率相近.     

Isolation of Anti-Diabetic Active Compounds from Benincasae Exocarpium and Development of Simultaneous Analysis by HPLC-PDA

Diabetes is a chronic metabolic disease that is a constant problem. Previous studies have reported that Benincasa cerifera Savi. extracts are effective in treating diabetes and its complications. Benincasae Exocarpium (BE) is a fruit peel of B. cerifera that has been reported to be used for the prevention and treatment of metabolic diseases such as hyperglycemia, obesity, and hyperlipidemia. However, there are not enough studies on the compounds and bioassays to support the efficacy of BE. The inhibitory activity of the BE extracts and fractions against advanced glycation end-products (AGE) formation and α-glucosidase activity was evaluated. These assays are relevant for the treatment of type 2 diabetes and its complications. Based on these results, compounds 1–11 were isolated through bioassay-guided isolation. In addition, we developed a high-performance liquid chromatography (HPLC) method that can simultaneously analyze these 11 compounds. Activity evaluation of the compounds was also conducted, and eight compounds exhibited significant activity. Among these, flavonoid compounds showed strong activity. A quantitative evaluation of eight bioactive compounds (2, 5–11) was conducted. In conclusion, this study demonstrated the potential of BE for prevention and treatment of type 2 diabetes and its complications.     

Phytochemical analysis,UPLC-ESI-Orbitrap-MS analysis,biological activity,and toxicity of extracts from Tripleurospermum limosum (Maxim.) Pobed

Tripleurospermum limosum (TL) has been used in folk medicine to treat gastritis. Toward the further development and use of TL, we report the phytochemical profiling, determination of active components, and antioxidant and enzyme inhibitory activities of TL. Nineteen compounds were identified by ultra-performance liquid chromatography-electrospray ionization-orbitrap-mass spectrometry for the first time in this plant. Phytochemical studies indicated that TL contained 11 types of phytochemicals. The active components [total carbohydrate content (TCC), total protein content (TP_roC), total triterpenoid content (TTC), total phenolic content (TP_heC), total flavonoid content (TFC), total phenolic acid content (TPAC), condensed tannin content (CTC), and gallotannin content (GC)] of eight different solvent extracts were determined by ultraviolet–visible spectrophotometry. Aqueous extract had highest TP_roC, TP_heC, and GC values. Methanol extract exhibited highest TCC and TFC values. Ethanol extract showed highest TPAC and CTC values and dichloromethane extract exhibited highest TTC value. Methanol extract showed strongest ability to scavenge 2,2-diphenyl-1-picrylhydrazyl radicals, 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt cation radicals, and hydroxyl radicals, and also exhibited highest antioxidant activity in ferric-reducing antioxidant power and cupric ion-reducing antioxidant capacity assays. Best iron and copper chelating activity and H₂O₂ scavenging ability were shown by aqueous extract. Ethanol extract showed strongest ability to scavenge superoxide radicals and effectively prevent β-carotene bleaching. Acetone extract had highest inhibitory activity toward α-glucosidase, α-amylase, and xanthine oxidase. Ethyl ether extract had highest inhibitory activity towards urease and angiotensin converting enzyme. Aqueous and ethanol extracts had strongest inhibitory activity toward acetylcholinesterase. Methanol extract showed highest inhibitory activity toward tyrosinase. Methanol extract showed good stability and antioxidant capacity during heating, at different pH values, and after in vitro digestion and had low toxicity. The efficacy of methanol extract in stabilizing olive and sunflower oils was studied, the results suggested that methanol extract had a protective effect on the primary oxidation of the two oils. TL may be useful as a source of active components for application in human nutrition and/or phytomedicine and methanol extract of TL could be used as a natural oil stabiliser.     

Phenolic Constituents of Lamium album L. subsp. album Flowers: Anatomical,Histochemical, and Phytochemical Study

Flos Lamii albi has a high biological activity and is widely used in herbal medicine. The aim of the study was to characterize the secretory structures present in Lamium album subsp. album corolla and the location of phenolic compounds. Additionally, we carried out qualitative phytochemical analyses of flavonoids and phenolic acids. Light, fluorescence, and scanning electron microscopy were used to analyze the structure of the floral organs. The main classes of phenolic compounds and their localization were determined histochemically. Phytochemical analyses were performed with high-performance thin-layer chromatography (HPTLC) and high-performance liquid chromatography (HPLC). Six types of glandular trichomes were found which contained flavonoids, phenolic acids, and tannins. The phytochemical studies demonstrated the presence of caffeic, chlorogenic, ferulic, gallic, p-coumaric, protocatechuic, syringic, gentisic, and vanillic phenolic acids as well as rutoside, isoquercetin, and quercetin flavonoids. The corolla in L. album subsp. album has antioxidant properties due to the presence of various polyphenols, as shown by the histo- and phytochemical analyses. The distribution and morphology of trichomes and the content of phenolic compounds in the corolla have taxonomic, pharmacognostic, and practical importance, facilitating the identification of the raw material.     

Phytochemical,Antimicrobial, Antidiabetic,Thrombolytic, anticancer Activities,and in silico studies of Ficus palmata Forssk

Ficus palmata Forssk. (Moraceae family) is medicinally valuable plant that is mostly used as folk medicine for the treatment of different diseases. Phytochemical composition was evaluated by preliminary phytochemical investigation, GCMS analysis, and total bioactive contents (TPC and TFC). The antioxidant, enzyme inhibition, antimicrobial, thrombolytic and anticancer activities were performed for biological evaluation. The extract exhibited the maximum total phenolic (49.24 ± 1.21 mg GAE/g) and total flavonoid contents (29.9 ± 1.13 mg QE/g) which may be correlated to higher antioxidant potential of extract. The GCMS investigation identified the presence of 27 phytocompounds of different classes related to aldehydes, esters of fatty acids, triterpenes, steroids, triterpenoid. The extract possessed the strong α-glucosidase (73.4 ± 4.65 %) and moderate α-amylase inhibition activity (47.1 ± 3.29 %). Significant results were observed in case of antiviral, antifungal, and antibacterial activities. F. palmata extract inhibited the growth of HepG2 cancer cells in a dose-dependent manner. The extract also exhibited moderate in vitro thrombolytic activity. In addition, the phytocompounds identified by GCMS were subjected to in silico molecular docking studies to analyze the binding affinity between phytocompounds and enzymes (α-glucosidase and α-amylase). Moreover, the best docked compounds were selected for ADMET studies which provide information about pharmacokinetics, physicochemical properties, drug-likeness, and toxicity of identified phytocompounds. The outcome of our research revealed that ethanolic extract of F. palmata possessed good antidiabetic, antimicrobial, thrombolytic and anticancer potential. This plant should be further explored to isolate the bioactive compounds for new drug development.     

Rapid screening and identification of α-glucosidase inhibitors from mulberry leaves using enzyme-immobilized magnetic beads coupled with HPLC/MS and NMR

α-Glucosidase plays important roles in the digestion and absorption of carbohydrates in the small intestine. The inhibition of α-glucosidase is regarded as a potential way to treat diabetes. We established an approach to screening α-glucosidase inhibitors from medicinal plants using enzyme-coated magnetic bead. Using 1-(3-dimethyl-aminopropyl)-3-ethylcarbodiimide and N-hydroxysuccinimide as reaction reagents, α-glucosidase was immobilized on the magnetic beads by covalent linkage. The conjugation of α-glucosidase to the magnetic beads was characterized using scanning electron microscope and X-ray diffractometer. The proposed approach was applied in fishing potential α-glucosidase inhibitors from extract of Morus alba, a Chinese medicinal plant. The structures of potential active compounds were identified via liquid chromatography-mass spectrometry and nuclear magnetic resonance. The results demonstrated that two flavonoids (isoquercitrin and astragalin) could bind to α-glucosidase, which was confirmed via conventional α-glucosidase inhibitory assay. Our findings suggested that enzyme-coated magnetic beads may be suitable for discovering active compounds from medicinal plants.     

Antioxidant and α-Glucosidase Inhibitory Compounds of Centella Asiatica

Centella asiatica, as known as Pegagan was previously reported to have anti-hyperglycemic effects in animal diabetic model rats. However, its α-glucosidase activity in vitro assay not yet reported. Our goal in this study is to isolate and identify active compounds as α-glucosidase inhibitor and antioxidant from aqueous ethanol 70% (v/v) extract of C. asiatica. The extract was partitioned by n-hexane, EtOAc, and n-butanol sequentially. Among the fractions tested, EtOAc fraction was showed the highest antioxidant and α-glucosidase inhibitory activities with an IC₅₀ values of 45.42 and 73.17 μg/mL, respectively. The antioxidant activity was conducted by determination of DPPH radical scavenging activity, whereas α-glucosidase inhibitory activity was determined against yeast α-glucosidase. Furthermore, isolation of the ethyl acetate extract yielded two active compounds, which were identified as kaempferol (1) and quercetin (2). Both of the compounds showed good yeast α-glucosidase inhibitory activity with IC₅₀ values of 16.50 and 21.61 μg/mL, respectively. In addition those compounds also could scavenge DPPH radical activity with IC₅₀ values of 9.64 and 11.97 μg/mL, respectively. Due to its ability in reducing α-glucosidase activity and scavenging free radical activity, the C. asiatica appears to be a potential as a good resource for future development of antioxidant and antidiabetic drug.     

An online target and rapid screening method for α-glucosidase inhibitors based on capillary electrophoresis

Screening enzymatic active compounds is one of the important fields in drug research. α-Glucosidase can hydrolyze carbohydrates to monosaccharides after meals and lead to the rise of blood glucose levels in human body. Thus, the inhibition of α-glucosidase activity is an effective approach for the diabetes treatment. In this work, we developed a new method to simultaneously screen multiple bioactive compounds within a single CE running. The affect factors on the method performance, including injection, mixing, incubation, separation and detection, were carefully analyzed and discussed. Under the optimum, the mixture consisting of two internal standards (DMSO and 4-nitrophenol) and five compounds (lyoniresinol, hydroxytyrosol, rutin, kaempferol, and quercetin) was simultaneously screened, and kaempferol and quercetin showed stronger activity and this conclusion was also supported by offline assay. Furthermore, molecular docking was employed for investigating its interaction mechanism. Eventually, the established method has been applied to screen potential α-glucosidase inhibitors from an extract of Lycium barbarum and the peak area of rutin, taxifolin, quercetin, and chlorogenic acid in L. barbarum samples changed before and after the enzymatic reaction, confirming that these four compounds had potential inhibitory activities, which was consistent with the literature data. The present work provides a promising method for the target and rapid discovery of bioactive compounds from a plant extract or mixture.     

Synthesis of new α-glucosidase inhibitors based on oleanolic acid incorporating cinnamic amides

A series of α-glucosidase inhibitors with the oleanolic acid core and different cinnamic amide ligands were designed and synthesized. Their preliminary structure-activity relationships were analyzed. In general, the compounds with 3,28-disubstituted oleanolic acid exhibited stronger activity than those 28-monosubstituted analogues, and variation of cinnamic amide substitution significantly affected α-glucosidase inhibition activities. Most of the compounds showed potent inhibitory activity against α-glucosidase with much greater efficacy than a typical α-glucosidase inhibitor, acarbose.