Zn2+ reduction induces neuronal death with changes in voltage-gated potassium and sodium channel currents

Effect of Zn2+ on emodin molecules studied by time-resolved fluorescence spectroscopy and quantum chemical calculations

Emodin is a natural drug for treating neurodegenerative diseases and plays a vital role in the mitigation of nerve damage. Metal ions can modify the drug properties of emodin, where Zn²⁺ can synergize with the emodin molecule and enhance the drug effect of emodin. Besides, complex changes can be observed in the fluorescence intensity and fluorescence lifetime of the emodin molecule as the concentration of Zn²⁺ increases. Herein, the synergistic effects of ligand structural in Zn(II)-Emodin complexes and the electronic effects of metal elements on the antioxidant properties of the complexes are discussed in detail based on UV-vis absorption spectroscopy, fluorescence spectroscopy, time-correlated single photon counting (TCSPC) technique and quantum chemical calculations at the B3LYP/6-31G(d) level. The experimental results confirm that Zn²⁺ can coordinate with the hydroxyl groups on the emodin to make the molecule structure more rigid, thus inhibiting the non-radiative processes such as high-frequency vibrations of the emodin molecule in solution. The suppression of non-radiative processes leads to an increase in the average fluorescence lifetime of the emodin molecule, and finally results in the enhanced fluorescence intensity. The chemical softness of Zn(II)-Emodin is then confirmed to be higher than that of emodin by Gaussian calculations, indicating its higher chemical reactivity and lower stability. The stronger electron donating ability of Zn(II)-Emodin compared to emodin may explain the higher antioxidant activity of Zn(II)-Emodin, which gives it a stronger pharmacological activity. The results of this study show that emodin can well complex with Zn²⁺ to remove excess Zn²⁺ in human body and the resulting complex has better antioxidant properties, which helps to understand the role of Zn²⁺ in drug-metal coordination and provides guidance for the design of new drugs.

Two near-infrared fluorescent probes based on dicyanoisfluorone for rapid monitoring of Zn2+and Pb2

Zinc (Zn2+) and lead (Pb2+) ions in the environment have important effects on human health and environmental safety. Therefore, it is of great significance to realize convenient and reliable detection of these two metal ions. In this study, two near-infrared fluorescent probes for the fast detection of Zn2+ and Pb2+ were synthesized by a simple Schiff base reaction between the dicyanoisophorone skeleton and carbohydrazide derivatives. Among them, the probe with the thiophene-2-carbohydrazide group showed a selective fluorescence response to Zn2+ and Pb2+ with a maximum emission wavelength of 670 nm. And the detection limits of the probe for Zn2+ and Pb2+ were 1.59 nM and 1.65 nM, respectively. In contrast the probe modified by the furan-2-carbohydrazide group achieved quantitative detection of Zn2+, with a detection limit of 2.7 nM. These results were attributed to the fact that the probes bind to Zn2+ and Pb2+ in stoichiometric ratios of 1:1, blocking the intramolecular PET effect. Furthermore, these two probes can be recycled through the action of EDTA and have been successfully used to detect Zn2+ and Pb2+ in real water samples.

Exploring the journey of emodin as a potential neuroprotective agent: Novel therapeutic insights with molecular mechanism of action

Emodin is an anthraquinone derivative found in the roots and bark of a variety of plants, molds, and lichens. Emodin has been used as a traditional medication for more than 2000 years and is still common in numerous herbal drugs. Emodin is plentiful in the three plant families, including Polygonaceae (Rheum, Rumex, and Polygonum spp.), Fabaceae (Cassia spp.), and Rhamnaceae (Rhamnus, Frangula, and Ventilago spp.). Emerging experimental evidences indicate that emodin confers a wide range of pharmacological activities; special focus was implemented toward neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, cerebral ischemia, anxiety and depression, schizophrenia, chronic hyperglycemic peripheral neuropathy, etc. Numerous preclinical evidences were established in support of the neuroprotection of emodin. However, this review highlighted the role of emodin as a potent neurotherapeutic agent; therefore, its evidence-based functionality on neurological disorders (NDs).

A 2-Hydroxy-1-naphthaldehyde Schiff Base for Turn-on Fluorescence Detection of Zn2+ Based on PET Mechanism

Zinc ion is closely related to human health. Its content in human body is small, while the effect is large. However, it is not the more the better, must be in a scientific balance. Therefore, it is significant to the rapid detection of Zn²⁺ in the environment and organism. Herein, a fluorescent probe based on 2-hydroxy-1-naphthalene formaldehyde and furan-2-carbohydrazide was conveniently synthesized via Schiff base reaction. And this probe has been successfully applied to the accurate and quantitative detection of Zn²⁺ in real samples, showing turn on fluorescence, good selectivity, very low detection limit, real time response and reusability. In addition, this probe has the potential application to trace Zn²⁺ in living cells with low cytotoxicity.

Emodin inhibits zinc-induced neurotoxicity in neuroblastoma SH-SY5Y cells

Emodin is a natural anthraquinone derivative with numerous beneficial effects, including antioxidant properties, anti-tumor activities, and protecting the nerves. Zinc-induced neurotoxicity plays a crucial role in the pathogenesis of vascular dementia (VD) and Parkinson’s disease (PD). Here, the protective activity of emodin inhibiting zinc-induced neurotoxicity and its molecular mechanisms such as cellular Zn²⁺ influx and zinc-induced gene expression were examined using human neuroblastoma cells (SH-SY5Y cells). Our findings showed that emodin obviously enhanced cell viability and reduced cell apoptosis and lactate dehydrogenase release. Bedsides, we detected a decrease of intracellular Zn²⁺ concentration after SH-SY5Y cells were pretreated with emodin. Simultaneously, the expression of zinc transporter-1, metallothionein-1, and metallothionein-2 were weakened in emodin-pretreated SH-SY5Y cells. In addition, emodin prevented the depletion of NAD+ and ATP induced by zinc. Emodin also reduced intracellular reactive oxygen species and endoplasmic reticulum-stress levels. Strikingly, emodin elevated SH-SY5Y cell viability and inhibited cell apoptosis caused by AMP-activated protein kinase signaling pathway activation. Thus, emodin could protect against neurotoxicity induced by Zn²⁺ in neuroblastoma SH-SY5Y cells. It is expected to have future therapeutic potential for VD or PD and other neurodegenerative diseases.