Bioavailability Improvement Strategies for Icariin and Its Derivates: A Review

In recent years, there has been considerable interest in icariin (ICA) and its derivates, icariside II (ICS) and icaritin (ICT), due to their wide range of potential applications in preventing cancer, cardiovascular disease, osteoporosis, delaying the effects of Alzheimer’s disease, treating erectile dysfunction, etc. However, their poor water solubility and membrane permeability, resulting in low bioavailability, dampens their potential beneficial effects. In this regard, several strategies have been developed, such as pharmaceutical technologies, structural transformations, and absorption enhancers. All these strategies manage to improve the bioavailability of the above-mentioned flavonoids, thus increasing their concentration in the desired places. This paper focuses on gathering the latest knowledge on strategies to improve bioavailability for enhancing the efficacy of icariin, icariside II, and icaritin. We conclude that there is an opportunity for many further improvements in this field. To the best of our knowledge, no such review articles scoping the bioavailability improvement of icariin and its derivates have been published to date. Therefore, this paper can be a good starting point for all those who want to deepen their understanding of the field.     

Characterization of black rust staining of unpassivated 55% Al–Zn alloy coatings. Effect of temperature, pH and wet storage

Wet storage staining is a phenomenon that occurs on both zinc coated and 55% Al–Zn coated steel sheets during shipment or storage in damp conditions. Whereas zinc coated sheets form white corrosion products, 55% Al–Zn coated steel sheets form black corrosion products. The effect of temperature, pH and wet storage on the occurrence of black rust staining of unpassivated Aluzink samples has been investigated in the laboratory in terms of corrosion product formation and composition. A characterization of corrosion products formed has been performed mainly based on scanning electron microscopy with X-ray microanalyses (SEM/EDS) for morphological and quantitative analyses and X-ray diffraction techniques (XRD) for crystalline phase identification. Black rust formation is strongly related to alkaline pH regions and is enhanced by the temperature. All black panels show the presence of Bayerite (Al(OH)₃), mainly formed on the aluminum rich dendrite branches and a basic zinc aluminum carbonate (Zn₆Al₂(OH)₁₆CO₃·4H₂O) formed in the zinc rich interdendritic alloy regions in contact with air. Blackening of Aluzink surfaces is connected to differences in optical properties of embedded metallic zinc and/or aluminum particles of different shape and size in the corrosion layer.     

The roles and electrochemical characterizations of activated carbon in zinc air battery cathodes

We prepared cathodes with various types of activated carbon and measured the cathodes’ electrochemical performance according to the kind of activated carbon. Activated carbon supplies airflow channels and reaction sites in the cathode of zinc air batteries. When we use activated carbon with a high specific surface area as the cathode's catalyst substrate, we expect high electrochemical performance because this type of carbon provides more air flow channels and reaction sites.We focused on investigating the relationship between the cathode's pore structure and its electrochemical characterizations. We also studied the effects of the various activated carbon materials on the zinc air batteries’ performance. Increasing the macropores or mesopores in the activated carbon resulted in achieving more power from the battery.     

Removal of Ag(l), Cu(II) and Zn(ll) ions with a supported liquid membrane containing cryptands as carriers

The interface behaviour in the facilitated co-transport of Ag(I), Cu(II) and Zn(II) ions through supported liquid membranes (SLMs) made of a flat-sheet polypropylene membrane support containing cryptands (2.2.2 or 2.2.1) as carriers was studied. The liquid-liquid extraction tests showed a maximum distribution coefficient when the carrier concentration was greaterthan 10⁻⁴M. In transport experiments the transmembrane flux increased with increasing carrier concentration reaching a limiting value at greater than 10⁻³M concentration. The calculation ofthe diffusion coefficients in membranes showed ahigherdiffusivityof2.2.2-metal complexes with respect to 2.2.1-metal complexes for silver ions. A sequence of diffusivity D(Ag+)>D(Cu²⁺)>D(Zn²⁺) was obtained, but carrier 2.2.1 showed a higher selectivity through copper ions. A sequence of diffusivity D(Cu²⁺)>D(Zn²⁺)>D(Ag⁺) was obtained. The diffusivity was significantly higher when using Celgard 2500 support compared to Celgard 2400 or 2402. Variable metal ion concentrations in the feed phase fluxes almost zero, at less than 10⁻² M concentration, were obtained. In the transient state of the transport through the SLM, different molar flow rates at the feed-membrane and membrane-strip interfaces were observed. The selectivity of the interfaces containing 2.2.2 in the separation binary mixtures of ions showed the following separation factors: SF_AgZn = 2.50, SF_AgCu = 1.64, SF_cuZn = 1.42.     

The spatial distribution of Zn during galvanic corrosion of a Zn/steel couple

The spatial distribution of Zn²⁺ during galvanic corrosion of a model Zn/steel couple in 0.01 M NaCl was investigated using a scanning zinc disk electrode. The couple had a coplanar arrangement of a steel substrate with an electroplated zinc layer at the center. During galvanic corrosion, the marked changes in the Zn²⁺ concentration were confined to a thin solution layer ca. 1.0 mm thick above the couple surface. In this thin solution layer above the zinc layer, a higher concentration region of Zn²⁺ in the range of 5-18 mM extended around the zinc layer in the solution during galvanic corrosion. Conversely, above the steel surface distant from the zinc layer, the surface concentration of Zn²⁺ was almost zero during galvanic corrosion. On this surface, the precipitation of zinc corrosion products due to the hydrolysis reaction of Zn²⁺ was observed. The distribution of the Zn²⁺ concentration supported that Zn²⁺ acted as a buffer that suppressed the increased pH due to the cathodic reaction on the steel surface near the zinc layer and almost no corrosion products formed there. The spatial distribution of Zn²⁺ is discussed in relation to the distributions of potential and pH and the surface morphology of the galvanic couple.     

Preparation of zinc ferrite in the presence of carbon material and its application to hot-gas cleaning

In order to develop an efficient absorbent of H₂S in coal gasification, zinc ferrite (ZnFe₂O₄) was prepared in the presence of carbon materials such as activated carbon (AC), activated carbon fiber (ACF), and Yallourn coal (YL). The absorption behavior of absorbents for H₂S was examined using a fixed-bed flow type reactor equipped with a quadrupole mass spectrometer.Carbon material-supported ZnFe₂O₄ exhibited larger desulfurization capacity for H₂S than unsupported ferrites. They could efficiently remove H₂S from 4000 ppm levels in a simulated coal gasification gas to less than 1 ppm at 500 °C. The absorption capacity of H₂S with ZnFe₂O₄/AC, ZnFe₂O₄/ACF, and ZnFe₂O₄/YL exhibited nearly 100% of stoichiometric amount of loaded metal species. They could be regenerated by an air oxidation in O₂-Ar (50 vol%) at 450 °C for 30 min. The regenerated ferrite can be used for repeated absorption of H₂S with a very slight decrease in the absorption capacity.     

Zinc ferrite based gas sensors: A review

Flammable, explosive and toxic gases, such as hydrogen, hydrogen sulfide and volatile organic compounds vapor, are major threats to the ecological environment safety and human health. Among the available technologies, gas sensing is a vital component, and has been widely studied in literature for early detection and warning. As a metal oxide semiconductor, zinc ferrite (ZnFe₂O₄) represents a kind of promising gas sensing material with a spinel structure, which also shows a fine gas sensing performance to reducing gases. Due to its great potentials and widespread applications, this article is intended to provide a review on the latest development in zinc ferrite based gas sensors. We first discuss the general gas sensing mechanism of ZnFe₂O₄ sensor. This is followed by a review of the recent progress about zinc ferrite based gas sensors from several aspects: different micro-morphology, element doping and heterostructure materials. In the end, we propose that combining ZnFe₂O₄ which provides unique microstructure (such as the multi-layer porous shells hollow structure), with the semiconductors such as graphene, which provide excellent physical properties. It is expected that the mentioned composites contribute to improving selectivity, long-term stability, and other sensing performance of sensors at room or low temperature.     

Effect of zinc chloride added to self-etching primer on bond strength to caries-affected dentin and chemical-physical-mechanical properties of adhesives

The aim of this in vitro study was to evaluate the effect over time of zinc chloride (ZnCl₂) incorporated into the primer of a two-step self-etching adhesive system (Clearfil SE Bond, Kuraray - SE) on long-term microtensile bond strength (μTBS) to caries-affected dentin (CAD), and on flexural strength (FS) and conversion degree (CD) of the adhesive. First, the CD of SE with and without 2% (wt) ZnCl₂ solution was evaluated by Fourier transform infrared spectroscopy (FTIR). Then, beam-shaped samples (7 mm × 2 mm x 1 mm) were prepared with the SE primer containing the ZnCl₂ solution, to perform flexural strength (FS) tests. For μTBS testing purposes, CAD surfaces were randomly divided into two groups, according to the presence of ZnCl₂ powder (2 wt%) incorporated into the adhesive system (ZnCl₂), or its absence (NT). An additional group consisting of dentin pretreated with a 2% chlorhexidine digluconate (CHX) solution was proposed as a positive control (n = 10). A two-step self-etching system (SE) was applied following the manufacturer's instructions, and restorations of composite resin were built up on the dentin. After 24 h, the resin-dentin blocks were sectioned into specimens that were submitted to μTBS testing immediately following, or after 12 months of water storage (WS). Both μTBS and FS tests were performed using a universal testing machine (0.5 mm/min). FS and CD data were submitted to the Student t-test, and μTBS data were submitted to two-way ANOVA and Tukey's test (α = 0.05). ZnCl₂ incorporation had no statistically significant influence on flexural strength (p = 0.88) or conversion degree (p = 566). Regarding μTBS, no significant effect of the double interaction of “dentin treatment” versus “WS period” (p = 0.546) was observed. The bond strength was not affected by the WS period (p = 0.805). The highest mean bond strength was observed for the NT group, which did not differ from the ZnCl₂ group. The lowest mean bond strength was observed for the CHX group, which differed statistically from the NT group (p = 0.053). It was concluded that incorporation of ZnCl₂ into the SE self-etching primer did not interfere in the bond strength of caries-affected dentin, in regard to failure mode, flexural strength or CD, and had no other beneficial effects.     

锌精粉中锌、铁含量的连续测定

以硝酸-氯酸钾体系分解样品,以二甲酚橙作指示剂,用EDTA标准溶液作滴定剂测定锌精粉中锌含量;沉淀用盐酸分解,以二苯胺磺酸钠作指示剂,用重铬酸钾标准溶液作滴定剂测定锌精粉中铁含量,实现锌精粉样品中锌、铁含量的连续测定,且RSD均小于3%,试验测定值与标准推荐值相吻合,能满足日常生产要求.     

Pyrolysis of cellulose, xylan and lignin with the K2CO3 and ZnCl2 addition for bio-oil production

The chemical structure of liquid products of the wood biopolymers, i.e. cellulose, xylan and lignin pyrolysis at 450 °C with and without the 10 wt.% addition of potassium carbonate or zinc chloride was investigated. The yield of liquid products of pyrolysis was in the range of 24-44 wt.% and their form was depending on the chemical structure of pyrolyzed material. The potassium carbonate and zinc chloride addition to biopolymers has also influenced the temperature range of samples decomposition as well as the structure of resulted bio-oils. All bio-oils from biopolymer were dark-brown water-oil emulsions. Contrarily, bio-oils obtained from biopolymer with K₂CO₃ or ZnCl₂ addition were orange liquids with well-separated water and oil phases. All analyses proved that the composition and the quality of bio-oil strongly depends on both the nature of the starting sample and the presence of the additive. The FT-IR analyses of oils showed that oxygen functionalities and hydrocarbons contents highly depend on the type of biopolymer. Results confirmed the significant removal and/or transformation of oxygen containing organic compounds due to the zinc chloride and potassium carbonate presence during pyrolysis process.