CHANGES IN QUERCETIN CONCENTRATION IN ONION (ALLIUM-CEPA L) OWING TO LOCATION, GROWTH STAGE AND SOIL TYPE

A study with onion investigated the variation in the concentration of the potentially anticarcinogenic flavonol, quercetin owing to location, soil type and growth stage. Seven genotypes grown at two locations were analysed for aglycone and total quercetin concentration by reverse-phase high-performance-liquid-chromatography (RP-HPLC). Out of seven genotypes investigated, four showed significant differences (P = 0.05) in total quercetin concentration between two locations. In 1993, 'Texas Grano 1015Y' (TG1015Y) bulbs collected at five growth stages were analysed for quercetin concentration by RP-HPLC. Quercetin concentration in 'TG1015Y' at different growth stages showed slight differences. Furthermore, quercetin concentration in bulbs harvested at second growth stage (23 March) was significantly (P = 0.05) greater than at the first growth stage (9 March). A slight difference in total quercetin concentration due to soil was noticed. This study shows that the site of growth of onion is a major environmental factor in determining quercetin concentration but soil type and growth stage are not important.