Total Chlorophyll As a Rapid Estimation of Lutein In Zucchini Squash

Zucchini squash (Cucurbita pepo) is a rich source of lutein, containing 2.1 mg/100 g.  Lutein is a carotenoid pigment found to be helpful in preventing macular degeneration in the eye, and may also offer antioxidant protection of eyes in those who smoke or are overweight.  Analysis of lutein is tedious and expensive, and requires use of HPLC for identification.  Since lutein is a component of the chloroplast, and used to help prevent photo-oxidation of chlorophyll, we wanted to test the idea that green color or total chlorophyll could be used by breeders as an indirect but rapid and accurate means of screening for lutein content in vegetables.  Zucchini squash, representing 9 selections and ranges of green color (from yellow to dark green) were harvested from plots in Clinton, NC then transported to Kannapolis, NC for green color, chlorophyll and lutein analysis using reflectance colorimetry, ethanol extraction, and HPLC analysis.  Color values hue, chroma, L, and a* yielded a fit of 0.5 with lutein content. Chlorophyll extraction with ethanol was much faster than HPLC analysis and provided a linear correlation with lutein with a fit of 0.8.  Total chlorophyll content in peel ranged from 20 in yellow squash to 72 mg/100 g in dark green selections.  Lutein content in peel ranged from 1 to 8.4 mg/100 g.    These results indicate that breeders may be able to use extracted chlorophyll to estimate lutein content in zucchini.