ABSTRACT
Alzheimer's disease(AD)is a common degenerative disease of the central nervous system in which neuropathological changes precede cognitive dysfunction and behavioral impairment. Currently, early diagnosis of AD is based on invasive and expensive testing techniques that are difficult to use widely in the clinical setting. Therefore, there is an urgent need for new markers to detect AD at an early stage. The eye, as an extension of the brain, has been found to show earlier onset of ocular pathologic changes in patients with AD compared to brain pathologic changes, such as retinal structural abnormalities, visual dysfunction, retinal abnormal protein accumulation, choroidal thickness changes, decreased corneal nerve fiber density, deposition of abnormal Aβ proteins in the lens, and pupillary light decreased sensitivity of response, etc. This article reviews the ocular pathologic changes in AD patients in recent years to provide new ideas for the early clinical diagnosis of AD.
ABSTRACT
OBJECTIVE To establish a method for simultaneous determination of zeaxanthin ，β-carotene，β-cryptoxanthin palmitate and zeaxanthin dipalmitate in Lycium barbarum . METHODS L. barbarum was extracted with n-hexane-anhydrous ethanol-acetone-toluene（10∶6∶7∶7，V/V/V/V）by ultrasonic method. High performance liquid chromatography （HPLC）method was adopted. The determination was performed on YMC C 30 column with mobile phase A consisted of methanol-acetonitrile-water （81∶ 14 ∶ 5，V/V/V）and mobile phase B consisted of dichloromethane （gradient elution ）at the flow rate of 1.0 mL/min. The column temperature was set at 20 ℃. The detection wavelength was set at 450 nm，and sample size was 20 μL. Using zeaxanthin as control，the relative correction factors （RCFs）of β-carotene，β-cryptoxanthin palmitate and zeaxanthin dipalmitate were calculated ， and then the content of each component was calculated according to RCFs and compared with the results of external standard method（ESM）. RESULTS The linear range of zeaxanthin ，β-carotene，β-cryptoxanthin palmitate and zeaxanthin dipalmitate were 0.119 4-2.983 8，0.121 7-1.521 6，0.285 9-5.718 8，8.460 5-211.513 3 μg/mL（all R2＞0.999）. RSDs of precision ，repeatability and stability（16 h）tests were all less than 4％. The average recoveries were 103.34％，107.37％，105.64％，96.16％（RSD＜5％，n＝ 9）. The average RCFs of β-carotene，β-cryptoxanthin palmitate and zeaxanthin dipalmitate were 1.109，1.390，1.158. The relative errors of the content determination results by quantitative analysis of multi-components by singer marker （QAMS）and ESM were within ±1％. CONCLUSIONS The established HPLC-QAMS method is accurate and stable ，which can be used for the content determination and quality control of 4 carotenoids in L. barbarum .