Screening of monoamine oxidase B inhibitors in Tibetan strawberry by ligand fishing based on enzyme functionalized cellulose filter paper.

Tibetan strawberry (Fragaria nubicola) is a wild medicinal and edible plant in Tibet possessing various health benefits such as neuroprotection and anti-oxidation. However, there has been little study reported on its chemical constituents. To investigate the inhibitors of monoamine oxidase B (MAO-B) in Tibetan strawberry, we immobilized the enzyme onto cellulose filter paper for the first time to develop a new screening method. Two known glycosides (compounds 1 and 2) and one new iridoid glucoside (Compound 3) were fished out by this method, which was found to effectively inhibit MAO-B with IC50 values of 16.95 ± 0.93, 24.69 ± 0.20, and 46.77 ± 0.78 µM, respectively. Molecular docking and kinetic analysis were performed to reveal the inhibition mechanism of these compounds. Furthermore, compound 1 exhibited neuroprotective effects against 6-OHDA-induced injury on PC12 cells. The developed method exhibits the advantages of rapidness and effectiveness in screening of MAO-B inhibitors from complex herbal extracts.

Ligand fishing of monoamine oxidase B inhibitors from Platycodon grandiflorus (Jacq.) A.DC. roots by the enzyme functionalised magnetic nanoparticles.

INTRODUCTION: As a famous traditional Chinese medicine, roots of Platycodon grandiflorus (Jacq.) A.DC. have shown multiple effects against neurodegenerative diseases. To investigate the components against Parkinson's disease (PD), the roots of P. grandiflora were selected as the research subject. OBJECTIVE: Screening and identifying of monoamine oxidase B (MAO-B) inhibitors from the roots of P. grandiflorum via enzyme functionalised magnetic nanoparticles (MNPs)-based ligand fishing combined with high-performance liquid chromatography-mass spectrometry (HPLC-MS) analysis. METHOD: MAO-B functionalised MNPs have been synthesised for screening MAO-B inhibitors from the roots of P. grandiflorum. The ligands were identified by HPLC-MS and nuclear magnetic resonance (NMR) analysis, and their anti-PD activity was evaluated via MAO-B inhibition assay and cell viability assay in vitro. RESULTS: Two MAO-B inhibitors were fished out and identified by HPLC-MS as protocatechuic aldehyde (1) and coumarin (2), with the half maximal inhibitory concentrations of 28.54 ± 0.39 and 25.39 ± 0.29 µM, respectively. Among them, 1 could also significantly increase the viability of 6-hydroxydopamine-damaged PC12 cells. CONCLUSION: The results are helpful to elucidate the anti-PD activity of the plant, and the ligand fishing method has shown good potential in discovery of MAO-B inhibitors.

Phloroglucinol derivatives with α-glucosidase inhibitory activities from Syzygium fluviatile.

Four new phloroglucinol derivatives (1 - 4) were isolated from the leaves of Syzygium fluviatile. Their structures were elucidated by means of extensive spectroscopic data. Among them, compounds 1 and 3 showed significant inhibitory activity against α-glucosidase with IC50 values of 10.60 and 5.07 µM, respectively. The structure-activity relationship was also discussed briefly.

Ligand fishing based on tubular microchannel modified with monoamine oxidase B for screening of the enzyme's inhibitors from Crocus sativus and Edgeworthia gardneri.

A novel strategy of performing ligand fishing with enzyme-modified open tubular microchannel was proposed for screening bioactive components present in medicinal plants. Monoamine oxidase B was immobilized onto the surface of the microchannel for the first time to specifically extract its ligands when the plant's extracts solution flows through the channel. The thermal and the storage stability of immobilized monoamine oxidase B were significantly enhanced after immobilization. Crocin I and Ⅱ were extracted from Crocus sativus, and tiliroside was extracted from Edgeworthia gardneri. All the three compounds were inhibitors of the enzyme with the half-maximal inhibitory concentration values of 26.70 ±â€¯0.91, 19.88 ±â€¯2.78, and 15.65 ± 0.85 µM, respectively. The enzyme inhibition kinetics and molecular docking were investigated. This is the first report on the inhibitory effects of tiliroside and crocin Ⅱ. The novel ligand fishing method proposed in this work possesses advantages of rapidness, high efficiency, and tiny sample consumption compared to routine ligand fishing, with promising potential for screening active natural products in complex mixtures.

Fishing of α-Glucosidase's Ligands from Aloe vera by α-Glucosidase Functionalized Magnetic Nanoparticles.

α-Glucosidase was immobilized on magnetic nanoparticles (MNPs) for selective solid-phase extraction of the enzyme's ligands present in Aloe vera, which is a medicinal plant used for the treatment of various diseases and possesses anti-diabetic activity. One new compound, aloeacone (2), together with two known compounds, aloenin aglycone (1) and aloin A (3), were fished out as the enzyme's ligands. The structure of 2 was determined by HR-MS and comprehensive NMR techniques. Compound 3 exhibited a weak inhibitory effect on α-glucosidase, while compounds 1 and 2 were found to possess activation effects on the enzyme for the first time. It is interesting that both an inhibitor and agonists of α-glucosidase were fished out in one experiment.

Screening of Monoamine Oxidase B Inhibitors from Fragaria nubicola by Ligand Fishing and Their Neuroprotective Effects.

Fragaria nubicola, known as Tibetan strawberry, is an edible plant possessing various health-promoting effects. However, its functional compositions were rarely studied. In this work, monoamine oxidase B (MAO-B) inhibitors in this plant were rapidly screened using the enzyme-functionalized magnetic nanoparticles coupled with UPLC-QTOF-MS. Two inhibitors, quercetin-3-O-ß-d-glucuronide-6″-methyl ester (1) and kaempferol-3-O-ß-d-glucuronide-6″-methyl ester (2), were identified from this plant with the IC50 values of 19.44 ± 1.17 and 22.63 ± 1.78 µM, respectively. Enzyme kinetic analysis and molecular docking were carried out to investigate the mechanism of inhibition. Contents of both compounds as well as those of total phenolics and flavonoids were quantified to be 24.76 ± 1.26, 35.59 ± 1.17, 837.67 ± 10.62, and 593.46 ± 10.37 µg/g, respectively. In addition, both compounds exhibited significant neuroprotective effects on 6-hydroxydopamine-induced PC12 cells. This is the first report on the neuroprotective components of F. nubicola, suggesting its potential for developing neuroprotective functional food.

Polyphenolic glycosides with unusual four-membered ring possessing anti-Parkinson's disease potential from black wolfberry.

This work reports the isolation of seven undescribed polyphenolic glycosides (1-7) together with fourteen known compounds (8-21) from the fruit of Lycium ruthenicum Murray. The structures of the undescribed compounds were identified based on comprehensive spectroscopic methods including IR, HRESIMS, NMR and ECD, and chemical hydrolysis. Compounds 1-3 possess an unusual four-membered ring, while 11-15 were firstly isolated from this fruit. Interestingly, compounds 1-3 inhibited monoamine oxidase B with IC50 of 25.36 ± 0.44, 35.36 ± 0.54, and 25.12 ± 1.59 µM, respectively, and showed significant neuroprotective effect on PC12 cells injured by 6-OHDA. Moreover, compound 1 improved the lifespan, dopamine level, climbing behavior, and olfactory ability of the PINK1B9 flies, a Drosophila model of Parkinson's disease. This work presents the first in vivo neuroprotective evidence of the small molecular compounds in L. ruthenicum Murray fruit, indicating its good potential as neuroprotectant.

Polyphenolic Glycosides from the Fruits Extract of Lycium ruthenicum Murr and Their Monoamine Oxidase B Inhibitory and Neuroprotective Activities.

The fruits ofLycium ruthenicum Murr have long been consumed as health food and used in folk medicine in China. Apart from the well-known polysaccharides, the active small molecular constituents in this fruit have not been fully studied. In this work, a systematic phytochemical study was carried out to investigate the small molecules and their potential health benefits. Nine new polyphenolic glycosides, lyciumserin A-I (1-9), together with 16 known compounds (10-25), were isolated and elucidated by high-resolution electrospray ionization mass spectrometry and comprehensive NMR analyses in combination with chemical hydrolysis. Compounds 1, 2, and 16 exhibited moderate inhibitory activity of monoamine oxidase B (MAO-B), while compounds 1 (50 µM) and 2 (100 µM) displayed significant neuroprotective effects (69.22 and 72.38% of cell viability, respectively) in the 6-hydroxydopamine-induced injury of the PC12 cell model (54.41%), comparable to the positive drug rasagiline (70.45%). The neuroprotective effect of 1 and 2 was further evidenced by the observation of the morphological change and fluorescein diacetate/propidium iodide staining. In addition, the levels of the major active compounds (1, 3, 5/6, and 16-18) vary from 21.5 to 892.3 µg/g. This is the first report on phenolic glycosides from the fruits ofL. ruthenicum Murr that possess both significant MAO-B inhibitory and neuroprotective effects, indicating the promising potential of the fruits for the development of health care products and even therapeutic agents for the treatment of Parkinson's disease and other neurodegenerative diseases.

Turn-on fluorescent probe for dopamine detection in solutions and live cells based on in situ formation of aminosilane-functionalized carbon dots.

Dopamine (DA) is a critical biomarker for a variety of neurological diseases. Methods for simple and rapid DA detection are crucial for clinical diagnosis and treatments for those diseases. In this work, we developed a novel pretreatment-free method for dopamine detection using carbon dots as a turn-on fluorescent probe synthesized in situ. The aminosilane-functionalized carbon dots (SiCDs) were produced in a mild condensation reaction between N-[3-(Trimethoxysilyl)propyl]ethylenediamine (AEATMS) and dopamine, which were directly used for probing of dopamine. The prepared SiCDs exhibited green fluorescence with excitation/emission maximum at 380/495 nm, the intensity of which can be measured to quantify the DA present in the reaction mixture. The linear range of the assay was between 0.1 and 100 µM with a limit of detection (LOD) of 56.2 nM. The probe is of good selectivity and the recoveries of the developed method were in the range of 101.77-119.91% with RSDs within 3.67% in human serum sample tests. The SiCDs were also synthesized within MN9D cells under 37 °C and generated bright fluorescence, which can probe the DA's distribution in the cells. The described method exhibit potential in DA detection and live-cell imaging for its feature of facility, inexpensiveness, and sensitivity.

Resorcinol derivatives with α-glucosidase inhibitory activities from Syzygium samarangense.

Nine resorcinol derivatives including two new ones, 5-[(8Z,11Z,14Z)-nonadeca-8,11,14-trienyl] resorcinol (1) and 5-[(8Z,11Z,14E)-heptadeca-8,11,14-trienyl] resorcinol (2), were isolated from the leaves of Syzygium samarangense. The new structures were elucidated by means of extensive spectroscopic techniques including interpretation of 1D and 2D NMR spectra. Among them, compounds 3, 4, 6 and 7 exhibited significant α-glucosidase inhibitory activities with IC50 of 3.16, 3.16, 2.34 and 0.99 µM, respectively. This finding provides evidence that resorcinol derivatives with long aliphatic chain function as new promising antidiabetic alternatives.

New phloroglucinol derivatives with protein tyrosine phosphatase 1B (PTP1B) inhibitory activities from Syzygium austroyunnanense.

Five new phloroglucinol derivatives (1-5) together with one known analogue (6) were isolated from the leaves of Syzygium austroyunnanense which is an edible folk medicine used for the treatment of diabetes. The new structures were elucidated as austroyunones A - E (1-5) by means of the extensive spectroscopic analyses including high-resolution electrospray ionization mass spectrometry (HRESIMS) and 1D and 2D nuclear magnetic resonance (NMR). Compounds 4-6 showed obvious protein tyrosine phosphatase 1B (PTP1B) inhibitory activity. This discovery of new phloroglucinols and their bioactivities provided a scientific basis for the application of S. austroyunnanense as an edible and medicinal plant.