Extraction of Flavonoids and Polyphenols from Coronatinetreated Mulberry Leaves and Evaluation of Their Antibacterial Activity against Pseudomonas syringae

Flavonoids and polyphenols are the main secondary metabelites in mulberry leaves, which have multiple biological functions such as antibacterial activity, free radical scavenging activity and antioxidant activity. In this paper, the parameters for the extraction of flavonoids and palyphenols from eoronatine （ COR）- treated mulberry leaves were optimized, and the components of the extracts were analyzed by high performance liquid chromatography （ HPLC）, and their antibacterial activity against Pseudomonas syringae, which causes mulberry bacterial blight, was evaluated in vitro to explore the mechanism how COR acted as a plant immune elicitor to improve the resistance of mulberry to bacterial blight. The results showed that ethanol concentration of 70%, extraction temperature of 80 ℃, extraction duration of 6 h and solid-liquid ratio of 1 ： 40 were the optimal parameters for the extraction of flavonoids and polyphenols from mulberry leaves. Flavonoids and polyphenols were mostly distributed in ethyl acetate and n-butyl alcohol fractions which showed better antibacterial activity than petroleum ether, dichloromethane and water fractions. Meanwhile, the antibacterial activity of ethyl acetate and n-butyl alcohol fractions of COR-treated mulberry leaves were more evident than that of water-treated mulberry leaves. Scanning electron microscopy showed that flavonoids and pelyphenols inhibited the growth of pathogenic bacteria by changing cell morphology, damaging cell wall structure and unbalancing cell osmotic pressure. HPLC analysis confirmed the contents of morin, quercetin, quereitrin, kaempferol, chlorogenic acid and rutin were increased to a different extent in COR-treated mulberry leaves. So it can be concluded that the increased contents of flavonoids and polyphenols induced by COR may be one of the reasons for the enhanced resistance to mulberry bacterial blight.

A comparison of cross-correlation-based and phasecorrelation-based image registration algorithms for optical coherence tomographic angiography

A large field of view is in high demand for disease diagnosis in clinical applications of optical coherence tomography(OCT)and OCT angiography(OCTA)imaging.Due to limits on the optical scanning range,the scanning speed,or the data processing speed,only a relatively small region could be acquired and processed for most of the current clinical OCT systems at one time and could generate a mosaic image of multiple adjacent small-region images with registration algorithms for disease analysis.In this work,we investigated performing cross-correlation(instead of phase-correlation)in the workflow of the Fourier–Mellin transform(FMT)method(called dual-cross-correlation-based translation and rotation registration,DCCTRR)for calculating translation and orientation offsets and compared its performance to the FMT method used on OCTA images alignment.Both phantom and in vivo experiments were implemented for comparisons,and the results quantitatively demonstrate that DCCTRR can align OCTA images with a lower overlap rate,which could improve the scanning efficiency of large-scale imaging in clinical applications.

Low-cost spectrometer design for ultra-high resolution spectral domain optical coherence tomography

In this Letter,we present a low-cost,high-resolution spectrometer design for ultra-high resolution optical coherence tomography(UHR-OCT),in which multiple standard achromatic lenses are combined to replace the expensive F-theta lens to achieve a comparable performance.For UHR-OCT,the spectrometer plays an important role in high-quality 3D image reconstruction.Typically,an F-theta lens is used in spectrometers as the Fourier lens to focus the dispersed light on the sensor array,and this F-theta lens is one of the most expensive components in spectrometers.The advantage of F-theta lens over the most widely used achromatic lens is that the aberrations(mainly spherical aberration,SA)are corrected,so the foci of the dispersed optical beams(at different wavelengths)with different incident angles could be placed on the sensor array simultaneously.For the achromatic lens,the foci of the center part of the spectrum are farther than those on the side in the longitudinal direction,causing degradations of the spectral resolution.Furthermore,in comparison with the achromatic lens with the same focal length,those with smaller diameters have stronger SA,but small lenses are what we need for making spectrometers compact and stable.In this work,we propose a simple method of using multiple long-focal-length achromatic lenses together to replace the F-theta lens,which is>8-fold cheaper based on the price of optical components from Thorlabs,US.Both simulations and in vivo experiments were implemented to demonstrate the performance of the proposed method.