Characterization of Nutritionally Important Carotenoids in Bunching Onion

Members of the Allium genus are consumed for their culinary flavor attributes, but also contain antioxidant and anticarcinogenic phytochemicals. Bunching onions (Allium fistulosum L.) are commonly used in Asian cuisine, in which both leaves and pseudostems are consumed. Carotenoids and chlorophylls are important classes of phytochemicals gaining attention for their health attributes. The goal of our study was to characterize carotenoids and chlorophylls and identify possible genetic and environmental influences on carotenoid concentrations among A. fistulosum accessions. Twelve USDA-ARS accessions were field grown in Knoxville, TN, and Geneva, NY, during the summer of 2007. After harvest, carotenoid and chlorophyll pigments were evaluated in leaf and pseudostem tissues using high-performance liquid chromatography. We were able to identify the presence of antheraxanthin, β-carotene, chlorophyll a and b, lutein, neoxanthin, and violaxanthin in leaf tissues; however, pigments were not found in pseudostem tissues. Carotenoid and chlorophyll concentrations did not differ among accessions or between locations. It is possible that accessions evaluated in this study were a narrow genetic base or were selected based on flavor attributes and not leaf tissue pigmentation.