Assessment of constituents in Allium by multivariate data analysis, high-resolution α-glucosidase inhibition assay and HPLC-SPE-NMR

Wild-Edible Allium Species from Highlands of Eastern Anatolia: Phytochemical Composition and In Vitro Biological Activities

This study presents the phytochemical composition, antioxidant (hydrogen atom and single-atom transfer mechanisms), and digestive enzyme inhibitory (alpha-amylase, alpha-glucosidase, and pancreatic lipase) activities of ethanol-based extractions and traditional preparations (infusion) of the leaves of wild-edible Allium species (A. kharputense, A. affine, A. shirnakiense, and A. akaka) from the highlands of Eastern Anatolia. Among the eight extracts analyzed, ethanol extractions of the A. kharputense and A. akaka leaves exhibited better biotherapeutic activities and had the highest bioactive content. The dominant bioactive profile was composed of mainly allicin and phenolic compounds (chlorogenic acid, hesperidin, rutin, isoquercitrin, and quercetin) with small amounts of fatty acids. These data were similar to the biological activities and chemical composition of common Allium species and suggest the utilization of the extracts of wild-edible Allium species in the development of Allium-based biotherapeutics or nutraceuticals.

N-p-coumaroyloctopamine ameliorates hepatic glucose metabolism and oxidative stress involved in a PI3K/AKT/GSK3β pathway

Type 2 diabetes mellitus is regarded as a chronic metabolic disease characterized by hyperglycemia. Long-term hyperglycemia may result in oxidative stress, damage pancreatic β-cell function and induce insulin resistance. Herein we explored the anti-hypoglycemic effects and mechanisms of action of N-p-coumaroyloctopamine (N-p-CO) in vitro and in vivo. N-p-CO exhibited high antioxidant activity, as indicated by the increased activity of SOD, GSH and GSH-Px in HL-7702 cells induced by both high glucose (HG) and palmitic acid (PA). N-p-CO treatment significantly augmented glucose uptake and glycogen synthesis in HG/PA-treated HL-7702 cells. Moreover, administration of N-p-CO in diabetic mice induced by both high-fat diet (HFD) and streptozotocin (STZ) not only significantly increased the antioxidant levels of GSH-PX, SOD and GSH, but also dramatically alleviated hyperglycemia and hepatic glucose metabolism in a dose-dependent manner. More importantly, N-p-CO upregulated the expressions of PI3K, AKT and GSK3β proteins in both HG/PA-induced HL-7702 cells and HFD/STZ-induced mice. These findings clearly suggest that N-p-CO exerts anti-hypoglycemic and anti-oxidant effects, most probably via the regulation of a PI3K/AKT/GSK3β signaling pathway. Thus, N-p-CO may have high potentials as a new candidate for the prevention and treatment of diabetes.

Biochemical and computational inhibition of α-glucosidase by novel metronidazole-linked 1H-1,2,3-triazole and carboxylate moieties: kinetics and dynamic investigations

In the current study, metronidazole derivatives containing 1H-1,2,3-triazole and carboxylate moieties were evaluated in vitro and by computational methods for their anti-diabetic potential to insight into their medicinal use for the management of type II diabetes mellitus. Interestingly all 14 compounds displayed high to significant inhibitory capability against the key carbohydrate's digestive enzyme α-glucosidase with IC50 values in range of 9.73-56.39 μM, as compared to marketed drug acarbose (IC50 = 873.34 ± 1.67 μM). Compounds 5i and 7c exhibited the highest inhibition, therefore, these two compounds were further evaluated for their mechanistic studies to explore its type of inhibition. Compounds 5i and 7c both displayed a concentration-dependent (competitive type of inhibition) with Ki values 7.14 ± 0.01, 6.15 ± 0.02 μM, respectively, which conclude their favourable interactions with the active site residues of the α-glucosidase. Interestingly all compounds are non-cytotoxic against BJ cell line. To further validate our findings, in-silico approaches like molecular docking, and molecular dynamic simulations were applied to investigate the mode of bindings of compounds with the enzyme and identifies their inhibition mechanism, which strongly complements our experimental findings.Communicated by Ramaswamy H. Sarma.

Metabolites of Geum aleppicum and Sibbaldianthe bifurca: Diversity and α-Glucosidase Inhibitory Potential

α-Glucosidase inhibitors are essential in the treatment of diabetes mellitus. Plant-derived drugs are promising sources of new compounds with glucosidase-inhibiting ability. The Geum aleppicum Jacq. and Sibbaldianthe bifurca (L.) Kurtto & T.Erikss. herbs are used in many traditional medical systems to treat diabetes. In this study, metabolites of the G. aleppicum and S. bifurca herbs in active growth, flowering, and fruiting stages were investigated using high-performance liquid chromatography with photodiode array and electrospray ionization triple quadrupole mass spectrometric detection (HPLC-PDA-ESI-tQ-MS/MS). In total, 29 compounds in G. aleppicum and 41 components in S. bifurca were identified including carbohydrates, organic acids, benzoic and ellagic acid derivatives, ellagitannins, flavonoids, and triterpenoids. Gemin A, miquelianin, niga-ichigoside F1, and 3,4-dihydroxybenzoic acid 4-O-glucoside were the dominant compounds in the G. aleppicum herb, while guaiaverin, miquelianin, tellimagrandin II₂, casuarictin, and glucose were prevailing compounds in the S. bifurca herb. On the basis of HPLC activity-based profiling of the G. aleppicum herb extract, the most pronounced inhibition of α-glucosidase was observed for gemin A and quercetin-3-O-glucuronide. The latter compound and quercetin-3-O-arabinoside demonstrated maximal inhibition of α-glucosidase in the S. bifurca herb extract. The obtained results confirm the prospects of using these plant compounds as possible sources of hypoglycemic nutraceuticals.

Development and characterization of active packaging based on chitosan/chitin nanofibers incorporated with scallion flower extract and its preservation in fresh-cut bananas

The aim of this study was to develop a novel active packaging using chitosan (CS) and esterified chitin nanofibers (CF) combined with different contents (1, 2 and 4 wt% on CS basis) of scallion flower extract (SFE) to protect banana samples. The addition of CF significantly improved the barrier and mechanical properties of the CS films (p < 0.05) due to hydrogen bonds and electrostatic interactions. Moreover, the addition of SFE not only improved the physical properties of the CS film but also improved the CS film biological activity. The oxygen barrier property and antibacterial ability of CF-4%SFE were approximately 5.3 and 1.9 times higher than those of the CS film, respectively. In addition, CF-4%SFE had strong DPPH radical scavenging activity (74.8 ± 2.3 %) and ABTS radical scavenging activity (84.06 ± 2.08 %). Fresh-cut bananas stored in CF-4%SFE showed less weight loss, starch loss, color and appearance change than those stored in traditional polyethylene film, which indicated that CF-4%SFE was much better at storing fresh-cut bananas than conventional plastic packaging. For these reasons, CF-SFE films have great potential as a candidate to replace traditional plastic packaging and extend the shelf life of packaged foods.

A Strategy for Pinpointing Natural Bioactive Components Using Two-Dimensional Bioassay Profilings Combined with Comprehensive Two-Dimensional Countercurrent Chromatography × High-Performance Liquid Chromatography

Inspired by the interpretation of two-dimensional (2D) nuclear magnetic resonance spectra, an efficient strategy was proposed for pinpointing bioactive components from complex natural products. An off-line comprehensive countercurrent chromatography (CCC) × high-performance liquid chromatography (HPLC) was employed to achieve a 2D chemical chromatogram, and 2D bioassay profilings were obtained from bioassays of the eluent of the first dimension (¹D) CCC and the eluent of the second dimension (²D) HPLC. Then 2D chemical chromatograms and 2D bioassay profilings were matched for pinpointing bioactive natural components from complex matrices. Thus, bioactive components in a complex matrix could be efficiently analyzed, separated, and bioactivity-determined. This experimental scheme was successfully demonstrated with a traditional medicinal herb Polygonum cuspidatum Sieb. et Zucc. The feasibility of this 2D strategy was verified with tyrosinase inhibition assay, α-glucosidase inhibition assay, DPPH radical scavenging assay, and ABTS^•+ decolorization assay. Eight natural inhibitors were successfully pinpointed and identified from P. cuspidatum. Both pieceid-2″-O-gallate (10) and vanicoside B (20) were screened and identified as natural tyrosinase inhibitors for the first time. Meanwhile, vanicoside B (20) was also found as the strongest α-glucosidase inhibitor among all the isolated components. Most of the compounds exhibited much higher radical scavenging activities. Compared with traditional methodology based on one-dimensional chromatographic separation, the present 2D strategy would be more precise, efficient, and convenient to screen and separate bioactive compounds from complex matrices.

Two new antidiabetic xanthones from the twigs of Garcinia oblongifolia

Two new xanthones, oblongixanthones I (1) and J (2), and seven known compounds (3-9), were isolated from an EtOAc extract of the twigs of Garcinia oblongifolia. Their structures were elucidated using spectroscopic methods, mainly 1 D and 2 D NMR. The antidiabetic effects of the two new compounds were evaluated using α-glucosidase and PTP1B inhibition assays. Both compounds displayed strong inhibition towards α-glucosidase with IC₅₀ values of 258.7 ± 49.3 and 187.1 ± 27.5 μM, respectively (compared with acarbose, IC₅₀ = 900.0 ± 3.0 μM) and moderate effects against PTP1B with IC₅₀ values of 93.9 ± 12.3 and 64.1 ± 5.8 μM, respectively (compared with RK682, IC₅₀ = 4.4 ± 0.3 l μM).

Authentication of organically grown vegetables by the application of ambient mass spectrometry and inductively coupled plasma (ICP) mass spectrometry; The leek case study

Health conscious and environmentally aware consumers are purchasing more organically produced foods. They prefer organic fruits and leafy vegetables as these are much less likely to have been exposed to contaminants such as pesticides. The detection of fraudulent activity in this area is difficult to undertake, because many chemical plant protection treatments degrade very quickly or can be washed off to remove evidence of their existence. It was found that when combining DART-MS with a compact, inexpensive and robust single quadrupole mass spectrometer, it was possible to differentiate organic from conventional leeks with 93.8% to 100% accuracy. ICP-MS results showed similar performance, with an ability to differentiate conventional from organic leeks with 92.5% to 98.1% accuracy. This study has paved the way for the certification of vegetables as being organically produced. The next step is to create data libraries to support the roll out of the methodologies described.

Barbeya oleoides Leaves Extracts: In Vitro Carbohydrate Digestive Enzymes Inhibition and Phytochemical Characterization

This study investigated the in vitro inhibitory potential of different solvent extracts of leaves of Barbeya oleoides on key enzymes related to type 2 diabetes mellitus (α-glucosidase and α-amylase) in combination with an aggregation assay (using 0.01% Triton X-100 detergent) to assess the specificity of action. The methanol extract was the most active in inhibiting α-glucosidase and α-amylase, with IC₅₀ values of 6.67 ± 0.30 and 25.62 ± 4.12 µg/mL, respectively. However, these activities were significantly attenuated in the presence of 0.01% Triton X-100. The chemical analysis of the methanol extract was conducted utilizing a dereplication approach combing LC-ESI-MS/MS and database searching. The chemical analysis detected 27 major peaks in the negative ion mode, and 24 phenolic compounds, predominantly tannins and flavonol glycosides derivatives, were tentatively identified. Our data indicate that the enzyme inhibitory activity was probably due to aggregation-based inhibition, perhaps linked to polyphenols.

Natural Antioxidants, Health Effects and Bioactive Properties of Wild Allium Species

BACKGROUND

There is an increasing interest from the pharmaceutical and food industry in natural antioxidant and bioactive compounds derived from plants as substitutes for synthetic compounds. The genus Allium is one of the largest genera, with more than 900 species, including important cultivated and wild species, having beneficial health effects.

OBJECTIVE

The present review aims to unravel the chemical composition of wild Allium species and their healthrelated effects, focusing on the main antioxidant compounds. For this purpose, a thorough study of the literature was carried out to compile reports related to health effects and the principal bioactive compounds. Considering the vast number of species, this review is divided into subsections where the most studied species are presented, namely Allium ampeloprasum, A. flavum, A. hookeri, A. jesdianum, A. neapolitanum, A. roseum, A. stipitatum, A. tricoccum, and A. ursinum, with an additional composite section for less studied species.

METHODS

The information presented in this review was obtained from worldwide accepted databases such as Scopus, ScienceDirect, PubMed, Google Scholar and Researchgate, using as keywords the respective names of the studied species (both common and Latin names) and the additional terms of"antioxidants" "health effects" and "bioactive properties".

CONCLUSION

The genus Allium includes several wild species, many of which are commonly used in traditional and folklore medicine while others are lesser known or are of regional interest. These species can be used as sources of natural bioactive compounds with remarkable health benefits. Several studies have reported these effects and confirmed the mechanisms of action in several cases, although more research is needed in this field. Moreover, considering that most of the studies refer to the results obtained from species collected in the wild under uncontrolled conditions, further research is needed to elucidate the effects of growing conditions on bioactive compounds and to promote the exploitation of this invaluable genetic material.

Development of a method to screen and isolate lipoxidase inhibitors from Radix Saposhnikoviae via ultrafiltration liquid chromatography combined with metablism in vitro

INTRODUCTION

Radix Saposhnikoviae is an excellent source of chromones, the consumption of which has been shown to positively affect human health, such as anti-inflammatory and antioxidant activities in vivo, and it also has been used to treat headache, inflammation, and cancer as a herbal medicine or functional soup.

OBJECTIVE

Isolation and screening of lipoxidase (LOX) inhibitors from Radix Saposhnikoviae. As a result, the metabolism of the active ingredients in cytochrome P450 (CYP450) in vitro was identified.

METHODS

Screen and identify the LOX inhibitors from Radix Saposhnikoviae by ultrafiltration-liquid chromatography-mass spectrometry (UF-LC-MS). Then take the isolation and purification of the inhibitors by high-speed counter-current chromatography (HSCCC) and semi-preparative high-performance liquid chromatography (HPLC). Furthermore, the active ingredients were used to study the metabolism in vitro in CYP450.

RESULTS

Subsequently, the specific binding ligands, prim-O-glucosylcimifugin, cimifugin, and 5-O-methylvisamminol (with purities of 95.28, 92.33%, and 97.89, respectively) were separated by HSCCC. Semi-preparative HPLC was applied to separate the four major compounds in Radix Saposhnikoviae and identify them as prim-O-glucosylcimifugin, 5-O-methylvisamminol, sec-O-glucosylhamaudol, and hamaudol, which were obtained with relatively high purity. Furthermore, the three chromone possible metabolism pathways were obtained.

CONCLUSION

The results demonstrated that UF-LC-MS combined with HSCCC and semi-preparative HPLC is not only a powerful tool for screening and isolating LOX inhibitors in complex samples, but also a useful platform for discovering bioactive compounds for anti-inflammatory activity. This study provides information regarding the active ingredients of chromones in Radix Saposhnikoviae and a framework for anti-inflammatory activity treatment.

Omics approaches in Allium research: Progress and way ahead

BACKGROUND

The genus Allium (Family: Amaryllidaceae) is an economically important group of crops cultivated worldwide for their use as a vegetable and spices. Alliums are also well known for their nutraceutical properties. Among alliums, onion, garlic, leek, and chives cultivated worldwide. Despite their substantial economic and medicinal importance, the genome sequence of any of the Allium is not available, probably due to their large genome sizes. Recently evolved omics technologies are highly efficient and robust in elucidating molecular mechanisms of several complex life processes in plants. Omics technologies, such as genomics, transcriptomics, proteomics, metabolomics, metagenomics, etc. have the potential to open new avenues in research and improvement of allium crops where genome sequence information is limited. A significant amount of data has been generated using these technologies for various Allium species; it will help in understanding the key traits in Allium crops such as flowering, bulb development, flavonoid biosynthesis, male sterility and stress tolerance at molecular and metabolite level. This information will ultimately assist us in speeding up the breeding in Allium crops.

METHOD

In the present review, major omics approaches, and their progress, as well as potential applications in Allium crops, could be discussed in detail.

RESULTS

Here, we have discussed the recent progress made in Allium research using omics technologies such as genomics, transcriptomics, micro RNAs, proteomics, metabolomics, and metagenomics. These omics interventions have been used in alliums for marker discovery, the study of the biotic and abiotic stress response, male sterility, organ development, flavonoid and bulb color, micro RNA discovery, and microbiome associated with Allium crops. Further, we also emphasized the integrated use of these omics platforms for a better understanding of the complex molecular mechanisms to speed up the breeding programs for better cultivars.

CONCLUSION

All the information and literature provided in the present review throws light on the progress and potential of omics platforms in the research of Allium crops. We also mentioned a few research areas in Allium crops that need to be explored using omics technologies to get more insight. Overall, alliums are an under-studied group of plants, and thus, there is tremendous scope and need for research in Allium species.

Bioactivity, Compounds Isolated, Chemical Qualitative, and Quantitative Analysis of Cymbaria daurica Extracts

Cymbaria daurica L. is widely used in traditional Mongolian medicine for the treatment of impetigo, psoriasis, pruritus, fetotoxicity, and diabetes. Therefore, the anti-inflammatory and α-glucosidase-inhibitory activities of four polar C. daurica extracts (water, n-butanol, ethyl acetate, and petroleum ether extract) were preliminarily evaluated to identify the active extracts. We also investigated the chemical composition of the active extracts by phytochemical analysis. The n-butanol and ethyl acetate extracts exhibited significant (p < 0.05) anti-inflammatory activities by inhibiting lipopolysaccharide-induced nitric oxide (NO) production in RAW 264.7 cells. None of the tested extracts exhibited cytotoxic effects at the effective concentrations. The ethyl acetate extract significantly inhibited α-glucosidase activity, and the inhibition potency was equivalent to that of acarbose (p > 0.05). The n-Butanol extract presented the second highest inhibitory activity. As the n-butanol and ethyl acetate extracts were found to have potent anti-inflammatory and α-glucosidase-inhibitory activities, we separated and identified 10 compounds from the extracts. Among them, vanillic acid, cistanoside F, echinacoside, arenarioside, verbascoside, isoacteoside, and tricin were isolated from C. daurica for the first time. Further, 30 compounds from the n-butanol and ethyl acetate extracts of C. daurica were identified using UHPLC-Q-Exactive. The present study demonstrates for the first time that C. daurica contains phenylethanoid glycosides. In addition, this novel HPLC method was subsequently used for simultaneous identification of five compounds in the n-butanol and ethyl acetate extracts of C. daurica. This study provides a chemical basis for further characterization and utilization of C. daurica, which could be a potential source of novel anti-diabetic and anti-inflammatory agents.

Chemical and Antifungal Variability of Several Accessions of Azadirachta indica A. Juss. from Six Locations Across the Colombian Caribbean Coast: Identification of Antifungal Azadirone Limonoids

Plant materials (i.e., leaves, fruits, and seeds) from 40 trees of Azadirachta indica A. Juss. were collected from six different locations across the Colombian Caribbean coast. Eighty-four ethanolic extracts were prepared and the total limonoid contents (TLiC) and the antifungal activity against Fusarium oxysporum conidia were measured. Their chemical profiles were also recorded via liquid chromatography-electrospray ionization interface-mass spectrometry (LC-ESI-MS) analysis and the top-ranked features were then annotated after supervised multivariate statistics. Inter-location chemical variability within sample set was assessed by sparse partial least squares discriminant analysis (sPLS-DA) and the chemical profiles and biological activity datasets were integrated through single-Y orthogonal partial least squares (OPLS) to identify antifungal bioactives in test extracts. The TLiC and antifungal activity (IC₅₀ values) of the A. indica-derived extracts were found to be ranging from 4.5 to 48.5 mg limonin equivalent per g dry extract and 0.08-44.8 μg/mL, respectively. The presence/abundance of particular limonoids between collected samples influenced the variability among locations. In addition, the integration of chemical and antifungal activity datasets showed five features as markers probably contributing to the bioactivity, annotated as compounds with an azadirone-like moiety. To validate the information provided by the single-Y OPLS model, a high performance liquid chromatography (HPLC)-based microfractionation was then carried out on an active extract. The combined plot of chromatographic profile and microfraction bioactivity also evidenced five signals possessing the highest antifungal activity. The most active limonoid was identified as nimonol 1. Hence, this untargeted metabolite profiling was considered as a convenient tool for identifying metabolites as inter-location markers as well as antifungals against Fusarium oxysporum.

Synthesis, α-Glucosidase inhibition and molecular docking studies of tyrosol derivatives

To find a potent α-glucosidase inhibitor, 24 tyrosol derivatives with different substituents located at the meta, ortho, or para position of the phenyl group have been synthesised via the Mitsunobu reaction, characterised by ¹H NMR, ¹³C NMR, ESI-MS and IR and evaluated for inhibition. The derivatives possessed varying degrees of in vitro inhibitory activity against α-glucosidase and a relationship between the structure and activity was subsequently established for all compounds. Two of these compounds with substituents at the para position showed significant inhibitory effects surpassing that of the control standard acarbose. Molecular docking studies performed to better understand the binding interactions between the enzyme and the two most active compounds showed substantial binding within the active site of α-glucosidase. Taken together, these results indicate that the position of the substituent plays a crucial role in this inhibition and may facilitate the development of new α-glucosidase inhibitors.

Inhibitory kinetics and mechanism of rifampicin on α-glucosidase: Insights from spectroscopic and molecular docking analyses

α-Glucosidase is a critical enzyme associated with diabetes mellitus, and the inhibitors of the enzyme play important roles in the treatment of the disease. In this study, the inhibitory effect and mechanism of rifampicin on α-glucosidase were investigated by multispectroscopic methods along with molecular docking technique. The results showed that rifampicin inhibited α-glucosidase activity prominently (IC₅₀ = 135 ± 1.2 μM) in a reversible and competitive-type manner. The fluorescence intensity of α-glucosidase was quenched by rifampicin through forming rifampicin-α-glucosidase complex in a static procedure. And the formation of the rifampicin-α-glucosidase complex was driven spontaneously by hydrophobic forces and hydrogen bonds. The results obtained from molecular docking further indicated that hydrophobic forces were formed between rifampicin and amino acid residues Phe 173, Pro151, and hydrogen bonds were generated by the interactions of rifampicin with residues Ser 180, Asn 414, Gly160, and Gly161 of α-glucosidase. Moreover, it was found that the binding of rifampicin to α-glucosidase could alter the conformation of the enzyme to make it steady, and the binding distance was estimated to be 1.02 nm. Therefore, this study confirmed a novel α-glucosidase inhibitor and possibly contributed to the improvement of newfangled anti-diabetic agent.

Proanthocyanidin B2 attenuates postprandial blood glucose and its inhibitory effect on alpha-glucosidase: analysis by kinetics, fluorescence spectroscopy, atomic force microscopy and molecular docking

As a dimer of proanthocyanidin, proanthocyanidin B₂ (PB₂) was found to effectively attenuate postprandial blood glucose in mice after sucrose loading.

Characterization of Antileishmanial Compounds from Lawsonia inermis L. Leaves Using Semi-High Resolution Antileishmanial Profiling Combined with HPLC-HRMS-SPE-NMR

This work describes an analytical platform based on semi-high-resolution antileishmanial profiling combined with hyphenation of high-performance liquid chromatography – high-resolution mass spectrometry – solid-phase extraction – nuclear magnetic resonance spectroscopy, i.e., semiHR-antileishmanial assay/HPLC-HRMS-SPE-NMR. The platform enables fast pinpointing of HPLC peaks representing Leishmania tropica inhibitors in complex matrices, with subsequent structural identification of targeted inhibitors. Active analytes were cumulatively trapped on SPE cartridges and the structures elucidated by analysis of NMR spectra obtained in the HPLC-HRMS-SPE-NMR mode. This led to the identification of six known compounds 2,4,6-trihydroxyacetophenone-2-O-β-D-glucopyranoside (1), lalioside (2), luteolin-4′-O-β-D-glucopyranoside (3), apigenin-4′-O-β-D-glucopyranoside (4), luteolin (5), and apigenin (6). IC₅₀ of the active compounds were determined with luteolin being the most potent inhibitor with an IC₅₀ value of 4.15 μg/ml. The platform proved to be an efficient method for the identification of L. tropica inhibitors.

Phytochemical Profiles and Antimicrobial Activities of Allium cepa Red cv. and A. sativum Subjected to Different Drying Methods: A Comparative MS-Based Metabolomics

Plants of the Allium genus produce sulphur compounds that give them a characteristic (alliaceous) flavour and mediate for their medicinal use. In this study, the chemical composition and antimicrobial properties of Allium cepa red cv. and A. sativum in the context of three different drying processes were assessed using metabolomics. Bulbs were dried using either microwave, air drying, or freeze drying and further subjected to chemical analysis of their composition of volatile and non-volatile metabolites. Volatiles were collected using solid phase micro-extraction (SPME) coupled to gas chromatography–mass spectrometry (GC/MS) with 42 identified volatiles including 30 sulphur compounds, four nitriles, three aromatics, and three esters. Profiling of the polar non-volatile metabolites via ultra-performance liquid chromatography coupled to high resolution MS (UPLC/MS) annotated 51 metabolites including dipeptides, flavonoids, phenolic acids, and fatty acids. Major peaks in GC/MS or UPLC/MS contributing to the discrimination between A. sativum and A. cepa red cv. were assigned to sulphur compounds and flavonoids. Whereas sulphur conjugates amounted to the major forms in A. sativum, flavonoids predominated in the chemical composition of A. cepa red cv. With regard to drying impact on Allium metabolites, notable and clear separations among specimens were revealed using principal component analysis (PCA). The PCA scores plot of the UPLC/MS dataset showed closer metabolite composition of microwave dried specimens to freeze dried ones, and distant from air dried bulbs, observed in both A. cepa and A. sativum. Compared to GC/MS, the UPLC/MS derived PCA model was more consistent and better in assessing the impact of drying on Allium metabolism. A phthalate derivative was found exclusively in a commercial garlic preparation via GC/MS, of yet unknown origin. The freeze dried samples of both Allium species exhibited stronger antimicrobial activities compared to dried specimens with A. sativum being in general more active than A. cepa red cv.

Facilitated Visual Interpretation of Scores in Principal Component Analysis by Bioactivity-Labeling of 1H-NMR Spectra-Metabolomics Investigation and Identification of a New α-Glucosidase Inhibitor in Radix Astragali

Radix Astragali is a component of several traditional medicines used for the treatment of type 2 diabetes in China. Radix Astragali is known to contain isoflavones, which inhibit α-glucosidase in the small intestines, and thus lowers the blood glucose levels. In this study, 21 samples obtained from different regions of China were extracted with ethyl acetate, then the IC50-values were determined, and the crude extracts were analyzed by 1H-NMR spectroscopy. A principal component analysis of the 1H-NMR spectra labeled with their IC50-values, that is, bioactivity-labeled 1H-NMR spectra, showed a clear correlation between spectral profiles and the α-glucosidase inhibitory activity. The loading plot and LC-HRMS/NMR of microfractions indicated that previously unknown long chain ferulates could be partly responsible for the observed antidiabetic activity of Radix Astragali. Subsequent preparative scale isolation revealed a compound not previously reported, linoleyl ferulate (1), showing α-glucosidase inhibitory activity (IC50 0.5 mM) at a level comparable to the previously studied isoflavones. A closely related analogue, hexadecyl ferulate (2), did not show significant inhibitory activity, and the double bonds in the alcohol part of 1 seem to be important structural features for the α-glucosidase inhibitory activity. This proof of concept study demonstrates that bioactivity-labeling of the 1H-NMR spectral data of crude extracts allows global and nonselective identification of individual constituents contributing to the crude extract's bioactivity.

Screening for potential α-glucosidase and α-amylase inhibitory constituents from selected Vietnamese plants used to treat type 2 diabetes

ETHNOPHARMACOLOGICAL RELEVANCE

The 18 plant species investigated in this study have been used as herbal antidiabetic remedies in Vietnamese traditional medicines. This study aimed to evaluate their ability to inhibit α-glucosidase and α-amylase, two key enzymes involved in serum glucose regulation.

MATERIALS AND METHODS

Chloroform, ethanol and water extracts of 18 plants were screened for α-glucosidase and α-amylase inhibitory activity. Analytical-scale HPLC was subsequently used to investigate the most active extracts, where samples with low level of tannins were identified and fractionated into 96-well microplates, followed by α-glucosidase and α-amylase assessment of each well. High-resolution α-glucosidase and α-amylase inhibition profiles constructed from these assays allowed identification of HPLC peaks correlated with α-glucosidase and α-amylase inhibitory activity. The active constituents were subsequently isolated using preparative-scale HPLC and their structure was elucidated by HR-ESIMS and NMR.

RESULTS

Ethanol extracts of Nepenthes mirabilis, Phyllanthus urinaria, and Kandelia candel significantly inhibited α-glucosidase with IC50 values of 32.7±6.3, 39.7±9.7, and 35.4±13.9μg/mL, respectively. Water extracts of N. mirabilis, Phyllanthus amarus, P. urinaria, Lagerstroemia speciosa, Syzygium cumini, Rhizophora mucronata, and K. candel showed IC50 values of 3.3±0.8, 34.9±1.5, 14.6±4.6, 5.4±0.5, 20.9±1.8, 3.3±0.6, and 4.0±0.8μg/mL, respectively. In the α-amylase inhibition assay, ethanol extracts of K. candel and Ficus racemosa showed IC50 of 7.6±0.9 and 46.7±23.6μg/mL, respectively. Showing low tannin constituents as seen from HPLC profiles, P. amarus and P. urinaria water extracts and F. racemosa ethanol extract were subjected to microfractionation. Only high-resolution α-glucosidase inhibition profiles of P. amarus and P. urinaria water extracts showed several active compounds, which were isolated and identified as corilagin (1), repandusinic acid A (2), and mallotinin (3). IC50 of these compounds were 1.70±0.03, 6.10±0.10, and 3.76±0.15μM, respectively. Kinetics analysis revealed that 1 displayed a mixed type mode of inhibition with Ki and Ki' values of 2.37±0.90 and 2.61±0.61μM, respectively, whereas 2 and 3 competitively inhibited α-glucosidase with Ki values of 4.01±0.47 and 0.65±0.11μM, respectively.

CONCLUSION

Corilagin (1), repandusinic acid A (2), and mallotinin (3) were potent α-glucosidase inhibitors contributing significantly to the inhibitory effect observed for the water extracts of P. amarus and P. urinaria.

High-Resolution α-Glucosidase Inhibition Profiling Combined with HPLC-HRMS-SPE-NMR for Identification of Antidiabetic Compounds in Eremanthus crotonoides (Asteraceae)

α-Glucosidase inhibitors decrease the cleavage- and absorption rate of monosaccharides from complex dietary carbohydrates, and represent therefore an important class of drugs for management of type 2 diabetes. In this study, a defatted ethyl acetate extract of Eremanthus crotonoides leaves with an inhibitory concentration (IC₅₀) of 34.5 μg/mL towards α-glucosidase was investigated by high-resolution α-glucosidase inhibition profiling combined with HPLC-HRMS-SPE-NMR. This led to identification of six α-glucosidase inhibitors, namely quercetin (16), trans-tiliroside (17), luteolin (19), quercetin-3-methyl ether (20), 3,5-di-O-caffeoylquinic acid n-butyl ester (26) and 4,5-di-O-caffeoylquinic acid n-butyl ester (29). In addition, nineteen other metabolites were identified. The most active compounds were the two regioisomeric di-O-caffeoylquinic acid derivatives 26 and 29, with IC₅₀ values of 5.93 and 5.20 μM, respectively. This is the first report of the α-glucosidase inhibitory activity of compounds 20, 26, and 29, and the findings support the important role of Eremanthus species as novel sources of new drugs and/or herbal remedies for treatment of type 2 diabetes.

High-resolution PTP1B inhibition profiling combined with high-performance liquid chromatography-high-resolution mass spectrometry-solid-phase extraction-nuclear magnetic resonance spectroscopy: Proof-of-concept and antidiabetic constituents in crude extract of Eremophila lucida

Type 2 diabetes (T2D) constituted 90% of the global 387 million diabetes cases in 2014. The enzyme protein-tyrosine phosphatase 1B (PTP1B) has been recognized as a therapeutic target for treatment of T2D and its adverse complications. With the aim of accelerating the investigation of complex natural sources, such as crude plant extracts, for potential PTP1B inhibitors, we have developed a bio-analytical platform combining high-resolution PTP1B inhibition profiling and high-performance liquid chromatography-high-resolution mass spectrometry-solid-phase extraction-nuclear magnetic resonance spectroscopy, i.e., HR-bioassay/HPLC-HRMS-SPE-NMR. Human recombinant PTP1B enzyme was used for the microplate-based PTP1B inhibition assay, which was optimized for pH and substrate concentration to be compatible with rate measurements within the 10 min incubation time. Subsequently, analytical-scale HPLC-based microfractionation followed by colorimetric microplate-based PTP1B bioassaying enabled construction of a high-resolution inhibition profile corresponding to the HPLC profile. The high-resolution PTP1B inhibition profiling was validated using an artificial mixture of known PTP1B inhibitors and non-inhibiting compounds as negative controls. Finally, a proof-of-concept study with a real sample was performed using crude ethyl acetate extract of the phytochemically hitherto unexplored plant Eremophila lucida. This led to the identification of the first viscidane type diterpene, i.e., 5-hydroxyviscida-3,14-dien-20-oic acid (9) as PTP1B inhibitor with an IC50 value of 42.0 ± 5.9 μM. In addition, a series of flavonoids, i.e., luteolin (1), dinatin (3a), tricin (3b), 3,6-dimethoxyapigenin (4), jaceidin (5), and cirsimaritin (6) as well as a cembrene diterpene, (3Z, 7E, 11Z)-15-hydroxycembra-3,7,11-trien-19-oic acid (8), were also identified for the first time from E. lucida.

Edible seaweed as future functional food: Identification of α-glucosidase inhibitors by combined use of high-resolution α-glucosidase inhibition profiling and HPLC-HRMS-SPE-NMR

Crude chloroform, ethanol and acetone extracts of nineteen seaweed species were screened for their antioxidant and α-glucosidase inhibitory activity. Samples showing more than 60% α-glucosidase inhibitory activity, at a concentration of 1 mg/ml, were furthermore investigated using high-resolution α-glucosidase inhibition profiling combined with high-performance liquid chromatography-high-resolution mass spectrometry-solid-phase extraction-nuclear magnetic resonance spectroscopy (HR-bioassay/HPLC-HRMS-SPE-NMR). The results showed Ascophyllum nodosum and Fucus vesicolosus to be rich in antioxidants, equaling a Trolox equivalent antioxidant capacity of 135 and 108 mM Troloxmg(-1) extract, respectively. HR-bioassay/HPLC-HRMS-SPE-NMR showed the α-glucosidase inhibitory activity of A. nodosum, F. vesoculosus, Laminaria digitata, Laminaria japonica and Undaria pinnatifida to be caused by phlorotannins as well as fatty acids - with oleic acid, linoleic acid and eicosapentaenoic acid being the most potent with IC50 values of 0.069, 0.075 and 0.10 mM, respectively, and showing a mixed-type inhibition mode.

Magnetic Ligand Fishing as a Targeting Tool for HPLC-HRMS-SPE-NMR: α-Glucosidase Inhibitory Ligands and Alkylresorcinol Glycosides from Eugenia catharinae

A bioanalytical platform combining magnetic ligand fishing for α-glucosidase inhibition profiling and HPLC-HRMS-SPE-NMR for structural identification of α-glucosidase inhibitory ligands, both directly from crude plant extracts, is presented. Magnetic beads with N-terminus-coupled α-glucosidase were synthesized and characterized for their inherent catalytic activity. Ligand fishing with the immobilized enzyme was optimized using an artificial test mixture consisting of caffeine, ferulic acid, and luteolin before proof-of-concept with the crude extract of Eugenia catharinae. The combination of ligand fishing and HPLC-HRMS-SPE-NMR identified myricetin 3-O-α-L-rhamnopyranoside, myricetin, quercetin, and kaempferol as α-glucosidase inhibitory ligands in E. catharinae. Furthermore, HPLC-HRMS-SPE-NMR analysis led to identification of six new alkylresorcinol glycosides, i.e., 5-(2-oxopentyl)resorcinol 4-O-β-D-glucopyranoside, 5-propylresorcinol 4-O-β-D-glucopyranoside, 5-pentylresorcinol 4-O-[α-D-apiofuranosyl-(1→6)]-β-D-glucopyranoside, 5-pentylresorcinol 4-O-β-D-glucopyranoside, 4-hydroxy-3-O-methyl-5-pentylresorcinol 1-O-β-D-glucopyranoside, and 3-O-methyl-5-pentylresorcinol 1-O-[β-D-glucopyranosyl-(1→6)]-β-D-glucopyranoside.

High-resolution hyaluronidase inhibition profiling combined with HPLC-HRMS-SPE-NMR for identification of anti-necrosis constituents in Chinese plants used to treat snakebite

Inhibition of the necrotizing hyaluronidase, phospholipase A2 and protease enzymes in four snake venoms by crude water and ethanol extracts of 88 plant species used against snakebites in traditional Chinese medicine was measured. High-resolution hyaluronidase inhibition profiles were constructed for the 22 plants showing highest hyaluronidase inhibition, and the results were used to guide subsequent structural analysis towards specific hyaluronidase inhibitors. Structural analysis was performed by high-performance liquid chromatography, high-resolution mass spectrometry, solid-phase extraction and nuclear magnetic resonance spectroscopy, i.e., HPLC-HRMS-SPE-NMR. This allowed identification of four non-tannin inhibitors, i.e., lansiumamide B (6) from Clausena excavata Burm.f., myricetin 3-O-β-D-glucopyranoside (7) from Androsace umbellata (Lour.) Merr., and vitexin (8) and 4',7-dihydroxy-5-methoxyflavone-8-C-β-D-glucopyranoside (9) from Oxalis corniculata L. Absolute configuration of 2,3-dihydroxy-N-methyl-3-phenyl-N-[(Z)-styryl]propanamide (1) was determined using the Mosher method, which revealed two enantiomers, i.e., (2S,3R)-2,3-dihydroxy-N-methyl-3-phenyl-N-[(Z)-styryl]propanamide and (2R,3S)-2,3-dihydroxy-N-methyl-3-phenyl-N-[(Z)-styryl]propanamide with a ratio of 7:3.

High-resolution bioactivity profiling combined with HPLC-HRMS-SPE-NMR: α-Glucosidase inhibitors and acetylated ellagic acid rhamnosides from Myrcia palustris DC. (Myrtaceae)

Type 2 diabetes (T2D) is an endocrine metabolic disease with a worldwide prevalence of more than 8%, and an expected increase close to 50% in the next 15-20years. T2D is associated with severe and life-threatening complications like retinopathy, neuropathy, nephropathy, and cardiovascular diseases, and therefore improved drug leads or functional foods containing α-glucosidase inhibitors are needed for management of blood glucose. In this study, leaves of Myrcia palustris were investigated by high-resolution α-glucosidase inhibition profiling combined with HPLC-HRMS-SPE-NMR. This led to identification of casuarinin, myricetin 3-O-β-d-(6″-galloyl)galactopyranoside, kaempferol 3-O-β-d-galactopyranoside, myricetin, and quercetin as α-glucosidase inhibitors. In addition, four acetylated ellagic acid rhamnosides, i.e., 4-O-(2″,4″-O-diacetyl-α-l-rhamnopyranosyl)ellagic acid, 4-O-(2″,3″-O-diacetyl-α-l-rhamnopyranosyl)ellagic acid, 4-O-(3″,4″-O-diacetyl-α-l-rhamnopyranosyl)ellagic acid, and 4-O-(2″,3″,4″-O-triacetyl-α-l-rhamnopyranosyl)ellagic acid were identified.

Triple aldose reductase/α-glucosidase/radical scavenging high-resolution profiling combined with high-performance liquid chromatography-high-resolution mass spectrometry-solid-phase extraction-nuclear magnetic resonance spectroscopy for identification of antidiabetic constituents in crude extract of Radix Scutellariae

In this work, development of a new microplate-based high-resolution profiling assay using recombinant human aldose reductase is presented. Used together with high-resolution radical scavenging and high-resolution α-glucosidase assays, it provided the first report of a triple aldose reductase/α-glucosidase/radical scavenging high-resolution inhibition profile - allowing proof of concept with Radix Scutellariae crude extract as a polypharmacological herbal drug. The triple bioactivity high-resolution profiles were used to pinpoint bioactive compounds, and subsequent structure elucidation was performed with hyphenated high-performance liquid chromatography-high-resolution mass spectrometry-solid-phase extraction-nuclear magnetic resonance spectroscopy. The only α-glucosidase inhibitor was baicalein, whereas main aldose reductase inhibitors in the crude extract were baicalein and skullcapflavone II, and main radical scavengers were ganhuangemin, viscidulin III, baicalin, oroxylin A 7-O-glucuronide, wogonoside, baicalein, wogonin, and skullcapflavone II.

Fungal plasma membrane H⁺-ATPase inhibitory activity of o-hydroxybenzylated flavanones and chalcones from Uvaria chamae P. Beauv

In our ongoing efforts of finding natural fungicides to fight food and feed spoilage during production and storage, the antifungal potential of Ghanaian Uvaria chamae P. Beauv. was investigated, with emphasis on plant metabolites targeting the fungal plasma membrane (PM) H(+)-ATPase. Ethyl acetate extract of U. chamae was subjected to high-resolution fungal PM H(+)-ATPase inhibition screening followed by structural elucidation by high-performance liquid chromatography-high-resolution mass spectrometry-solid-phase extraction-nuclear magnetic resonance spectroscopy (HPLC-HRMS-SPE-NMR). This led to identification of a series of uncommon o-hydroxybenzylated flavanones and chalcones, i.e., chamanetin (8), isochamanetin (9), isouvaretin (10), uvaretin (11), dichamanetin (12), and diuvaretin (15). Preparative-scale isolation of the active metabolites allowed determination of IC50 values for inhibition of the PM H(+)-ATPase, and growth inhibition of Saccharomyces cerevisiae and Candida albicans. These revealed a strong correlation between o-hydroxybenzyl substituents and PM H(+)-ATPase activity, with dichamanetin being the most potent compound, but showing moderate activity in the fungal growth inhibition assays.

Combined use of high-resolution α-glucosidase inhibition profiling and high-performance liquid chromatography-high-resolution mass spectrometry-solid-phase extraction-nuclear magnetic resonance spectroscopy for investigation of antidiabetic principles in crude plant extracts

Type 2 diabetes is a metabolic disorder affecting millions of people worldwide, and new drug leads or functional foods containing selective α-glucosidase inhibitors are needed. Crude extract of 24 plants were assessed for α-glucosidase inhibitory activity. Methanol extracts of Cinnamomum zeylanicum bark, Rheum rhabarbarum peel, and Rheum palmatum root and ethyl acetate extracts of C. zeylanicum bark, Allium ascalonicum peel, and R. palmatum root showed IC50 values below 20 μg/mL. Subsequently, high-resolution α-glucosidase profiling was used in combination with high-performance liquid chromatography-high-resolution mass spectrometry-solid-phase extraction-nuclear magnetic resonance spectroscopy for identification of metabolites responsible for the α-glucosidase inhibitory activity. Quercetin (1) and its dimer (2), trimer (3), and tetramer (4) were identified as main α-glucosidase inhibitors in A. ascalonicum peel, whereas (E)-piceatannol 3'-O-β-D-glucopyranoside (5), (E)-rhapontigenin 3'-O-β-D-glucopyranoside (6), (E)-piceatannol (8), and emodin (12) were identified as main α-glucosidase inhibitors in R. palmatum root.

High-resolution bacterial growth inhibition profiling combined with HPLC-HRMS-SPE-NMR for identification of antibacterial constituents in Chinese plants used to treat snakebites

ETHNOPHARMACOGICAL RELEVANCE

Bacterial infection is one of the main secondary infections caused by snakebite. The 88 plant species investigated in this study have been used as folk remedies for treatment of snakebite, and it is therefore the aim of this study to investigate whether the plants contain compounds with bacterial growth inhibition.

MATERIALS AND METHODS

The water and ethanol extracts of 88 plant species were screened at 200 μg/mL against Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa for their antibacterial activity by micro-broth dilution assay. The most active extracts were fractionated into microplates using analytical-scale RP-HPLC, and subsequently growth inhibition was assessed for each well. The biochromatograms constructed from these assays were used to identify compounds responsible for antibacterial activity. The structures of five compounds were elucidated by HPLC-HRMS-SPE-NMR.

RESULTS

Crude extracts of Boehmeria nivea, Colocasia esculenta, Fagopyrum cymosum, Glochidion puberum, Melastoma dodecandrum, Polygonum bistorta, Polygonum cuspidatum and Sanguisorba officinalis showed MIC values below 200 μg/mL against either Bacillus subtilis, Staphylococcus aureus, Escherichia coli or Pseudomonas aeruginosa. The biochromatograms demonstrated that tannins play a main role for the bacterial growth inhibition observed for all above-mentioned plants except for Polygonum cuspidatum. Furthermore, the high-resolution bacterial growth inhibition profiling combined with HPLC-HRMS-SPE-NMR allowed fast identification of three non-tannin active compounds, i.e., piceid, resveratrol and emodin from ethanol extract of Polygonum cuspidatum.

CONCLUSION

The high-resolution bacterial growth inhibition profiling allowed fast pinpointing of constituents responsible for the bioactivity, e.g., either showing tannins being the main bacterial growth inhibitors as observed for the majority of the active plants, or combined with HPLC-HRMS-SPE-NMR for fast structural identification of non-tannin constituents correlated with antibacterial activity.