Kinetic study for the optimization of ginsenoside Rg3 production by heat treatment of ginsenoside Rb1

AbstractBackgroundGinsenoside Rg3 is a promising anticancer agent. It is usually produced by heat treatment of ginseng, in which ginsenoside Rb1 is the major ginsenoside. A kinetic study was conducted to optimize ginsenoside Rg3 production by the heat treatment of ginsenoside Rb1.MethodsGinsenoside Rb1 was heated using an isothermal machine at 80°C and 100°C and analyzed using HPLC. The kinetic parameters were calculated from the experimental results. The activation energy was estimated and used to simulate the process. The optimized parameters of ginsenoside Rg3 production are suggested based on the simulation.ResultsThe rate constants were 0.013 h−1 and 0.073 h−1 for the degradation of ginsenosides Rb1 and Rg3 at 80°C, respectively. The corresponding rate constants at 100°C were 0.045 h−1 and 0.155 h−1. The estimated activation energies of degradation of ginsenosides Rb1 and Rg3 were 69.2 kJ/mol and 40.9 kJ/mol, respectively. The rate constants at different temperatures were evaluated using the estimated activation energies, and the kinetic profiles of ginsenosides Rb1 and Rg3 at each temperature were simulated based on the proposed kinetic model of consecutive reaction. The optimum strategies for producing ginsenoside Rg3 from ginsenoside Rb1 are suggested based on the simulation. With increased temperature, a high concentration of ginsenoside Rg3 is formed rapidly. However, the concentration decreases quickly after the reaching the maximal concentration value.ConclusionThe optimum temperature for producing ginsenoside Rg3 should be the highest temperature technically feasible below 180°C, in consideration of the cooling time. The optimum reaction time for heat treatment is 30 min

In vitro antioxidative activity of moss extract, and effect of moss on serum lipid level of mice fed with high-fat diet

Purpose: To evaluate the potential of active compounds derived from moss in the prevention and treatment of various diseases.Methods: Three species of moss were extracted with deionized water at 95 °C, and with 70.5 % ethanol at 85 °C. Analysis of total phenolic contents (TPC) of the extracts were performed by Folin- Ciocalteu (FC) method. The antioxidant activity of the extracts were determined using three methods, namely, by 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic) acid (ABTS), 1,1-diphenyl-2-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP). In vivo effects were evaluated in mice fed high fat diet (HFD) supplemented with 20 % ground moss. Cholesterol levels in HFD were evaluated by ophthalaldehyde method. Serum triglyceride levels were measured using triglyceride (TG) kit, while blood insulin level and leptin concentration were measured by enzyme-linked immunosorbent assay (ELISA) kit.Results: The moss extracts exhibited antioxidative effects, as evidenced of . TPC of 47.20 ± 11.20 to 119.87 ± 11.51 mg GAE/mg, respectively. ABTS scavenging activity was 1078.11 ± 18.95 to 2587.33 ± 46.19 μmol Trolox/mg, DPPH scavenging activity of were 42.11 ± 8.22 to 298.78 ± 20.02 μmol Trolox/mg, and FRAP value of 393.19 ± 24.64 to 1070.14 ± 17.92 μmol Trolox/mg, respectively. Mice fed with 20 % ground moss did not show any significant effect (p < 0.05) on visceral weight and blood lipid levels of HFD, while leptin concentrations reduced significantly to 4.74 ± 0.00 and 0.20 ± 0.00 ng/dL) relative to HFD alone (26.72 ± 6.53 ng/dL).Conclusion: Moss can potentially be used as an antioxidative ingredient, for the improvement of overall human health, suggesting that important medical benefits associated with moss consumption. However, further investigations are required to ascertain this.Keywords: Moss, total phenolic content, antioxidant activity, insulin, lepti

Trans-reflective color filters based on a phase compensated etalon enabling adjustable color saturation

Trans-reflective color filters, which take advantage of a phase compensated etalon (silver-titania-silver-titania) based nano-resonator, have been demonstrated to feature a variable spectral bandwidth at a constant resonant wavelength. Such adjustment of the bandwidth is presumed to translate into flexible control of the color saturation for the transmissive and reflective output colors produced by the filters. The thickness of the metallic mirror is primarily altered to tailor the bandwidth, which however entails a phase shift associated with the etalon. As a result, the resonant wavelength is inevitably displaced. In order to mitigate this issue, we attempted to compensate for the induced phase shift by introducing a dielectric functional layer on top of the etalon. The phase compensation mediated by the functional layer was meticulously investigated in terms of the thickness of the metallic mirror, from the perspective of the resonance condition. The proposed color filters were capable of providing additive colors of blue, green, and red for the transmission mode while exhibiting subtractive colors of yellow, magenta, and cyan for the reflection mode. The corresponding color saturation was estimated to be efficiently adjusted both in transmission and reflection.This work was supported by a National Research Foundation of Korea grant funded by the Korean government (MSIP) (No. 2011-0030079), and by a research grant from Kwangwoon University in 2016. The work was partly supported by the Australian Research Council Future Fellowship (FT110100853, Dr. Duk-Yong Choi) and was performed in part at the ACT node of the Australian National Fabrication Facility

Angle-tolerant linear variable color filter based on a tapered etalon

We propose and fabricate a linear variable color filter (LVCF) that possesses an enhanced angular tolerance in conjunction with a wide linear filtering range (LFR) by taking advantage of an Ag-TiO2-Ag configuration. The TiO2 cavity is tapered in thickness along the device so that the resonance wavelength can be continuously tuned according to the position. In addition, the metal-dielectric-metal structure is overlaid with a pre-designed graded anti-reflection coating in SiO2 to complete the etalon, thereby maximizing the transmission efficiency across the entire device. The tapered dielectric layers in the proposed filter were fabricated via glancing angle deposition without the help of any mask or moving parts. The center wavelength was scanned from 410 nm to 566 nm, resulting in an LFR of 156 nm, and the overall spectra exhibited an approximate peak transmission of 40% and spectral bandwidth of 68 nm. The angular tolerance was as large as 45°, incurring a fractional wavelength shift below 4.2%. The resonance wavelength was verified to be linearly dependent on the position, providing a linearity beyond 99%. The proposed LVCF will thus be actively utilized in a portable micro-spectrometer and spectral scanning device.National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIP) (No. 2016R1A2B2010170); ARC Future Fellowship FT110100853

Omnidirectional color filters capitalizing on a nano-resonator of Ag-TiO2-Ag integrated with a phase compensating dielectric overlay

We present a highly efficient omnidirectional color filter that takes advantage of an Ag-TiO2-Ag nano-resonator integrated with a phase-compensating TiO2 overlay. The dielectric overlay substantially improves the angular sensitivity by appropriately compensating for the phase pertaining to the structure and suppresses unwanted optical reflection so as to elevate the transmission efficiency. The filter is thoroughly designed, and it is analyzed in terms of its reflection, optical admittance, and phase shift, thereby highlighting the origin of the omnidirectional resonance leading to angle-invariant characteristics. The polarization dependence of the filter is explored, specifically with respect to the incident angle, by performing experiments as well as by providing the relevant theoretical explanation. We could succeed in demonstrating the omnidirectional resonance for the incident angles ranging to up to 70°, over which the center wavelength is shifted by below 3.5% and the peak transmission efficiency is slightly degraded from 69%. The proposed filters incorporate a simple multi-layered structure and are expected to be utilized as tri-color pixels for applications that include image sensors and display devices. These devices are expected to allow good scalability, not requiring complex lithographic processes.This work was supported by a National Research Foundation of Korea grant funded by the Korean government (MEST) (No. 2013-008672 and 2013-067321), and also by a research grant from Kwangwoon University in 2014. The work was partly supported by the Australian Research Council Future Fellowship (FT110100853, Dr. Duk-Yong Choi) and was performed in part at the ACT node of the Australian National Fabrication Facilit

Structural color filters based on an all-dielectric metasurface exploiting silicon-rich silicon nitride nanodisks

An all-dielectric metasurface is deemed to serve a potential platform to demonstrate spectral filters. Silicon-rich silicon nitride (SRN), which contains a relatively large portion of silicon, can exhibit higher refractive indices, when compared to silicon nitride. Meanwhile, the extinction coefficient of SRN is smaller than that of hydrogenated amorphous silicon, leading to reduced absorption loss in the shorter wavelength. SRN is therefore recommended as a scattering element from the perspective of realizing all-dielectric metasurfaces. In this work, we propose and embody a suite of highly efficient structural color filters, capitalizing on a dielectric metasurface that consists of a two-dimensional array of SRN nanodisks that are embedded in a polymeric layer. The SRN nanodisks may support the electric dipole (ED) and magnetic dipole (MD) resonances via Mie scattering, thereby leading to appropriate spectral filtering characteristics. The ED and MD are identified from field profile observation with the assistance of finite-difference time-domain simulations. The manufactured color filters are observed to produce various colors in both transmission and reflection modes throughout the visible band, giving rise to a high transmission of around 90% in the off-resonance region and a reflection ranging up to 60%. A variety of colors can be realized by tuning the resonance by adjusting the structural parameters such as the period, diameter, and height of the SRN nanodisks. The spectral position of resonances might be flexibly tuned by tailoring the polymer surrounding the SRN nanodisks. It is anticipated that the proposed coloring devices will be actively used for color displays, imaging devices, and photorealistic color printing.National Research Foundation of Korea (NRF) funded by the Korean government (No.2016R1A2B2010170 and 2018R1A6A1A03025242); Australian Research Council Future Fellowship (FT110100853, Dr. Duk-Yong Choi)