Screening and mechanism study of components targeting DNA from the Chinese herbLonicera japonicaby liquid chromatography/mass spectrometry and fluorescence spectroscopy

Benzopyrone-mediated quinolones as potential multitargeting antibacterial agents

A new type of benzopyrone-mediated quinolones (BMQs) was rationally designed and efficiently synthesized as novel potential antibacterial molecules to overcome the global increasingly serious drug resistance. Some synthesized BMQs effectively suppressed the growth of the tested strains, outperforming clinical drugs. Notably, ethylidene-derived BMQ 17a exhibited superior antibacterial potential with low MICs of 0.5-2 μg/mL to clinical drugs norfloxacin, it not only displayed rapid bactericidal performance and inhibited bacterial biofilm formation, but also showed low toxicity toward human red blood cells and normal MDA-kb2 cells. Mechanistic investigation demonstrated that BMQ 17a could effectually induce bacterial metabolic disorders and promote the enhancement of reactive oxygen species to disrupt the bacterial antioxidant defense system. It was found that the active molecule BMQ 17a could not only form supramolecular complex with lactate dehydrogenase, which disturbed the biological functions, but also effectively embed into calf thymus DNA, thus affecting the normal function of DNA and achieving cell death. This work would provide an insight into developing new molecules to reduce drug resistance and expand antibacterial spectrum.

A Novel Method for Identifying Parkin Binding Agents in Complex Preparations of Herbal Medicines

Parkin is a crucial E3 ubiquitin ligase for initiating mitophagy through the PINK1/Parkin pathway. Regulating the expression and activity of parkin can remedy mitophagy and human disease. We developed an efficient method to isolate natural parkin ligands from herbal medicines by combining centrifugal ultrafiltration and liquid chromatography/mass spectrometry. The heterologous expression technology identified functionally active and pure parkin proteins. After evaluating the reliability of the method using DL-selenomethionine and DL-dithiothreitol as positive controls, this method was successfully applied to capture parkin ligands from Polygoni Cuspidati Rhizoma et Radix and Sophorae Flavescentis Radix. LC/MS identified seven novel parkin-targeting compounds, namely, 7,4′-dihydroxy-5-methoxy-8-(γ, γ-dimethylallyl)-flavanone, kushenol I, kurarinone, sophoraflavanone G, torachrysone-8-O-glucoside, apigenin, and emodin, supported by the molecular docking analysis. Five of the seven novel compounds (kushenol I, kurarinone, sophoraflavanone G, apigenin, and emodin) can activate parkin in in vitro autoubiquitination assays. Meanwhile, kushenol I and kurarinone had antisteatosis activity in fat emulsion-damaged human hepatocytes. These results confirmed the effectiveness of the method for identifying parkin ligands from complex preparations, useful to advance drug discovery from medicinal herbs.

The effect of dimerization on the interaction of ibuprofen drug with calf thymus DNA: Molecularmodeling and spectroscopic investigation

The interaction between the dimer structure of ibuprofen drug (D-IB) and calf thymus DNA under simulative physiological conditions was investigated with the use of Hoechst 33258 and methylene blue dye as spectral probes by the methods of UV-visible absorption, fluorescence spectroscopy, circular dichroism spectroscopy and molecular modeling study.Using the Job's plot, a single class of binding sites for theD-IB on DNA was put in evidence. The Stern-Volmer analysis of fluorescence quenching data shows the presence of both the static and dynamic quenching mechanisms. The binding constants, K_b were calculated at different temperatures, and the thermodynamic parameters ∆G^∘, ∆H^∘ and ∆S^∘ were given. The experimental results showed that D-IB molecules could bind with DNA via groove binding mode as evidenced by: I. DNA binding constant from spectrophotometric studies of the interaction of D-IB with DNA is comparable to groove binding drugs. II. Competitive fluorimetric studies with Hoechst 33258 have shown that D-IB exhibits the ability of this complex to displace with DNA-bounded Hoechst, indicating that it binds to DNA in strong competition with Hoechst for the groove binding. III. There is no significantly change in the absorption of the MB-DNA system upon adding the D-IB, indicates that MB molecules are not released from the DNA helix after addition of the D-IB and are indicative of a non-intercalative mode of binding. IV. Small changes in DNA viscosity in the presence of D-IB, indicating weak link to DNA, which is consistent with DNA groove binding. As well as, induced CD spectral changes, and the docking results revealed that groove mechanism is followed by D-IB to bind with DNA.

Screening for the bioactive constituents of traditional Chinese medicines—progress and challenges

The search for lead compounds from traditional Chinese medicines (TCMs) may be promising for new drug development.

High-throughput screening of triplex DNA binders from complicated samples by 96-well pate format in conjunction with peak area-fading UHPLC-Orbitrap MS

Screening triplex DNA binders from complicated samples in a high-throughput fashion with good reproducibility without the requirement of an extra releasing step.

Isolation of α-Amylase Inhibitors from Kadsura longipedunculata Using a High-Speed Counter-Current Chromatography Target Guided by Centrifugal Ultrafiltration with LC-MS

In this study, a high-speed counter-current chromatography (HSCCC) separation method target guided by centrifugal ultrafiltration with high-performance liquid chromatography-mass spectrometry (CU-LC-MS) was proposed. This method was used to analyze α-amylase inhibitors from Kadsura longipedunculata extract. According to previous screening with CU-LC-MS, two screened potential α-amylase inhibitors was successfully isolated from Kadsura longipedunculata extract using HSCCC under the optimized experimental conditions. The isolated two target compounds (with purities of 92.3% and 94.6%) were, respectively, identified as quercetin-3-O-rhamnoside (1) and protocatechuic acid (2) based on the MS, UV, and ¹H-NMR spectrometry data. To verify the inhibition of screened compounds, the inhibitory activities of quercetin-3-O-rhamnoside (1) and protocatechuic acid (2) on α-amylase were tested, and it demonstrated that the experimental IC50 values of quercetin-3-O-rhamnoside (1) and protocatechuic acid (2) were 28.8 and 12.5 μmol/L. These results proved that the hyphenated technique using CU-LC-MS and HSCCC was a rapid, competent, and reproductive method to screen and separate potential active compounds, like enzyme inhibitors from the extract of herbal medicines.

Discrimination of Rhizoma Gastrodiae (Tianma) using 3D synchronous fluorescence spectroscopy coupled with principal component analysis

Rhizoma Gastrodiae (Tianma) of different variants and different geographical origins has vital difference in quality and physiological efficacy. This paper focused on the classification and identification of Tianma of six types (two variants from three different geographical origins) using three dimensional synchronous fluorescence spectroscopy (3D-SFS) coupled with principal component analysis (PCA). 3D-SF spectra of aqueous extracts, which were obtained from Tianma of the six types, were measured by a LS-50B luminescence spectrofluorometer. The experimental results showed that the characteristic fluorescent spectral regions of the 3D-SF spectra were similar, while the intensities of characteristic regions are different significantly. Coupled these differences in peak intensities with PCA, Tianma of six types could be discriminated successfully. In conclusion, 3D-SFS coupled with PCA, which has such advantages as effective, specific, rapid, non-polluting, has an edge for discrimination of the similar Chinese herbal medicine. And the proposed methodology is a useful tool to classify and identify Tianma of different variants and different geographical origins.

One step poly(rutin) particle preparation as biocolloid and its characterization

Poly(rutin) p(RT) particles were prepared for the first time via a simple microemulsion polymerization/crosslinking method using l-α lecithin as surfactant, cyclohexane as organic phase and glycerol diglycidyl ether (GDE) as a crosslinking agent. Highly negatively charged p(RT) particles, -48.2 mV, were obtained due to phenolic groups on the particles. It was also confirmed that p(RT) particles are thermally more stable than RT and degradable in PBS at pH7.4., e.g., 11 wt.% can degrade in 1 day and little further degradation was observed over 9 days. The prepared p(RT) particles showed insignificant antibacterial characteristics against common bacteria such as Escherichia coli ATCC8739, Staphylococcus aureus ATCC6538, and Bacillus subtilis ATCC6633 whereas the RT molecules showed significantly better antibacterial characteristics even at low concentrations. Moreover, p(RT) particles were demonstrated for use as drug delivery devices by loading rosmarinic acid (RA) as model drug and showed release capability for up to 6 days by releasing 85% of the loaded RA. Intriguingly, p(RT) particles illustrated enhanced fluorescent properties providing great potential for fluorescent active antioxidant and antibacterial materials in biomedical use.

Investigation on the interaction between luteolin and calf thymus DNA by spectroscopic techniques

The interaction of luteolin with calf thymus deoxyribonucleic acid (ctDNA) under physiological conditions (Tris-HCl buffer solutions, pH 7.4) was studied by UV-Vis spectroscopy, fluorescence spectroscopy and viscosity measurement method, respectively. The results indicated that a complex of luteolin with ctDNA can be formed. Spectroscopic techniques together with viscosity determination provided evidences of intercalation mode of binding for the interaction between luteolin and ctDNA. The binding constant of luteolin to DNA calculated based on UV-Vis spectroscopy data was found to be 4.52×10(4)L mol(-1) at 310 K. The thermodynamic parameters of the complex were calculated by a double reciprocal method: Δ(r)H(m)(s)=-8.9×10(3)J mol(-1),Δ(r)S(m)(s)=60.5 JK(-1)mol(-1) and Δ(r)G(m)(s)=-2.76×10(4)J mol(-1) (310 K). The interacting forces between luteolin and DNA mainly included hydrophobic interactions and hydrogen bonds. The acridine orange displacement studies revealed that luteolin had significant effect for acridine orange bounded on DNA, which was indicative of intercalation binding.

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.

Astragalin from Cassia alata induces DNA adducts in vitro and repairable DNA damage in the yeast Saccharomyces cerevisiae

Reverse phase-solid phase extraction from Cassia alata leaves (CaRP) was used to obtain a refined extract. Higher than wild-type sensitivity to CaRP was exhibited by 16 haploid Saccharomyces cerevisiae mutants with defects in DNA repair and membrane transport. CaRP had a strong DPPH free radical scavenging activity with an IC₅₀ value of 2.27 μg mL⁻¹ and showed no pro-oxidant activity in yeast. CaRP compounds were separated by HPLC and the three major components were shown to bind to DNA in vitro. The major HPLC peak was identified as kampferol-3-O-β-d-glucoside (astragalin), which showed high affinity to DNA as seen by HPLC-UV measurement after using centrifugal ultrafiltration of astragalin-DNA mixtures. Astragalin-DNA interaction was further studied by spectroscopic methods and its interaction with DNA was evaluated using solid-state FTIR. These and computational (in silico) docking studies revealed that astragalin-DNA binding occurs through interaction with G-C base pairs, possibly by intercalation stabilized by H-bond formation.