Absorption and tissue distribution of zeaxanthin and lutein in rhesus monkeys after taking Fructus lycii (Gou Qi Zi) extract

PURPOSE. To study Serum and tissue levels of zeaxanthin and lutein after fe eding rhesus monkeys an extract of Fructus lycii (gou qi zi). METHODS. A carotenoid-containing fraction (P1) from an extract of F. lycii (equivalent to 2.2 mg zeaxanthin) was fed to three rhesus monkeys for 6 wee ks as a daily dietary supplement through a nasogastric tube. Three other mo nkeys were fed with the vehicle (olive oil) similarly for 4 weeks as a cont rol. Another three animals were fed with normal diet only. All animals were killed 4 hours after the last dose. Samples of serum, liver, spleen, brain , and retina were analyzed for zeaxanthin and lutein by high-pressure liqui d chromatography. RESULTS. The basal levels of zeaxanthin and lutein in the monkey sera were 3.0 +/- 1.6 ng/ml (range, 2.3-4.8) and 31.5 +/- 12.2 ng/ml (range, 22.3-42. 5), respectively. Serum levels of zeaxanthin and lutein in the P1-fed group were significantly higher than those of vehicle control (P < 0.05). Beside s the retina, the liver had the highest zeaxanthin and lutein levels, where as the levels in the brain were undetectable. P1 supplement appeared to ele vate zeaxanthin levels in liver and spleen. The level of lutein was higher than that of zeaxanthin in the maculae of rhesus monkeys. However, there we re no detectable carotenoids in the peripheral and the equatorial regions o f the monkey retina. P1 treatment elevated zeaxanthin density but not lutei n in the macula. CONCLUSIONS. Serum levels and macular density of zeaxanthin was raised by f eeding a carotenoid-containing fraction of F. lycii. Therefore, F. lycii is a good dietary source of zeaxanthin supplement.