Effect of supplementation with fructus lycii (kei tze) on blood antioxidant status : implications for age-related changes in macular pigment density

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Effect of supplementation with fructus lycii (kei tze) on blood antioxidant status : implications for age-related changes in macular pigment density


Author: Cheng, Chung-yuen
Title: Effect of supplementation with fructus lycii (kei tze) on blood antioxidant status : implications for age-related changes in macular pigment density
Degree: M.Sc.
Year: 2004
Subject: Hong Kong Polytechnic University -- Dissertations
Retinal degeneration -- Treatment
Lycium chinense -- Therapeutic use
Antioxidants -- Physiological effect
Eye -- Diseases -- Prevention
Department: School of Nursing
Pages: xi, 88 leaves : ill. (some col.) ; 30 cm
Language: English
OneSearch: https://www.lib.polyu.edu.hk/bib/b1749106
URI: http://theses.lib.polyu.edu.hk/handle/200/1893
Abstract: Age-related macular degeneration (AMD) is associated with loss of central vision. It is commonly found in those people over 65 years old. No effective and reliable therapy is available for the treatment of AMD once the vision has been impaired. In terms of preventive eye care, dietary supplementation of food containing high content of lutein and zeaxanthin is believed to be a promising preventive measure for AMD because of the specific accumulation of macular pigment in the macula, which is composed of zeaxanthin and lutein. These carotenoids, particularly zeaxanthin which is concentrated in the central part of the fovea, or yellow spot, may act as a protective filter or an effective antioxidant defense system to meet the continuous oxidative challenge. Scarce research study has been conducted in humans for investigation on the effect of supplementation with Fructus Lycii (Kei Tze) on blood antioxidant or zeaxanthin status. The aims of this study were to investigate the effect of supplementation with Kei Tze on plasma antioxidant status (especially lutein and zeaxanthin). In vitro study of antioxidant content of different Kei Tze products was performed to help guide the choice of supplement used in the in-vivo part supplementation trial. A new High Performance Liquid Chromatography (HPLC) method was set up and evaluated for measuring lutein and zeaxanthin. Result showed that Kei Tze contains a fairly high antioxidant power 373.5 umol/g of dried Kei Tze (expressed as Ferric Reducing Antioxidant Power FRAP value), indicating it is a good source of antioxidants. The new HPLC method for lutein and zeaxanthin is simple, analytically reliable and capable of measuring lutein and zeaxanthin separately and sensitively in human plasma. Precision for plasma lutein and zeaxanthin was good: within-day coefficients of variation (CVs) were 3% at 0.50 ug/ml of lutein (n=6) and 4% at 0.25 ug/ml of zeaxanthin (n=6). Between-day coefficients of variation (CVs) were 5% at 0.40 ug/ml of lutein (n=6) and 6% at 0.20 ug/ml of zeaxanthin (n=6). Recovery of lutein and zeaxanthin were good with overall recovery of at least 90% for both. The linearity was maintained to at least 2.0 ug/ml for lutien and to a least 1.0 ug/ml for zeaxanthin (r=0.999). The minimum detectable limit for lutein and zeaxanthin was found to be 0.3 ng. The concentration of lutein and zeaxanthin in Kei Tze used in our supplementation study was 5.8 ug/g and 194 ug/g of Kei Tze respectively. This provides a good reference for comparison with other research data as scarce scientific data are available for consumer, scientist or healthcare professionals. In the in-vivo study of Kei Tze, we conducted a single-blinded, placebo-controlled, parallel intervention study for 28 days. Fasting blood, urine and saliva were collected from 27 apparently healthy subjects (study group n=14, placebo group n=13) at day 0 for baseline. Repeated fasting samples were collected for the study group and the placebo group at day 28 after supplementation of 15 g /day of dried Kei Tze and placebo respectively. Results showed that 28 days supplementation of Kei Tze maintained the baseline plasma antioxidant capacity (expressed as FRAP) and uric acid in the study group after the supplementation study. No significant change was found for urine FRAP and saliva FRAP before and after the supplementation. However, it is of interest that the plasma FRAP values and uric acid were significantly (p<0.05) lower in the placebo group compared to the treatment group after 28 days. A significant increase (p<0.01) in plasma zeaxanthin was found after Kei Tze supplementation. This has not been previously reported in the literature. No statistically significant changes were seen in any of other variables measured, such as plasma ascorbic acid, lutein, superoxide dismutase (SOD), glutathione peroxidase (GPx) and urine hydrogen peroxide (H2O2), however the pattern of change was interesting. Whole blood GPx concentration tended to increase and urine hydrogen peroxide tended to decrease in the study group after 28 days Kei Tze supplementation. These new data indicate that Kei Tze intake can maintain or replenish the plasma antioxidant capacity. No deleterious effect on measured variables was seen. The data in our supplementation study demonstrated Kei Tze causes a significant increase in plasma zeaxanthin after 28 days supplementation. Hopefully, this increase in plasma zeaxanthin may help to prevent AMD by maintaining the macular pigment density, however this remains to be confirmed in future study.

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