DIFFERENCES IN ANTIOXIDATIVE POLYPHENOLS CONTENTS OF ASPARAGUS RELATED TO CULTIVARS AND SEASONAL CHANGE UNDER VARIOUS CULTURAL CONDITIONS OF THE MOTHER-FERN CULTURE

To obtain the basic knowledge about antioxidative activities of asparagus, differences in cultivars and seasonal changes of rutin and total polyphenols contents under different cultural conditions of mother-fern culture were determined. Significant differences were observed both in rutin and total polyphenols contents among 20 cultivars. Rutin contents of the spears varied from 763 to 1,550 mg/kg fw. Total polyphenols contents varied from 771 to 1,026 mg quercetin/kg fw. The differences became smaller, however, when mother stalks had grown in July. DPPH radical absorbing activity was also getting weaker in summer. Rutin contents showed a greater range of seasonal change than polyphenols contents and DPPH radical absorbing activity. The comparison between the two years investigations of 2003 and 2004 showed different patterns of the seasonal change of rutin and polyphenols contents. Rutin and polyphenols contents had constantly decreased from April to August in 2003, whereas they increased again in July 2004. However, this re-increase was only observed in the outdoor spears. These results might be due to the difference in weather condition in summer of these years. Outdoor spears generally showed greater contents of rutin and polyphenols than of greenhouse spears except for early spring harvest. These results suggest that not only rutin but also combination or synergism of antioxidative polyphenols might contribute to the antioxidative activity of asparagus, and the weather and cultural condition, especially light condition, might have great influence on rutin and polyphenols contents.