Mitsuru Watanabe1, Jun Ayugase1. 1. Agro-Production Technologies and Management Research Division, NARO Tohoku Agricultural Research Center, Shimokuriyagawa, Morioka, 020-0198, Japan.
Abstract
BACKGROUND: Winter sweet treatment (WST) has been established for cultivating high-quality leafy vegetables during the winter. Although it is known that chilling stress during cold acclimation induces oxidative damage by reactive oxygen species in plant tissues, knowledge about changes in antioxidant activity and compounds during WST in spinach is superficial. We investigated changes in flavonoids, total ascorbic acid, carotenoids and hydrophilic oxygen radical absorbance capacity (H-ORAC) along with components in three spinach varieties during low-temperature treatment by exposure to cold air in winter. RESULTS: The H-ORAC values increased substantially together with total flavonoids and total ascorbic acid concentration. In addition, WST increased mono- and diglucosylated flavonoid derivatives with an ortho-dihydroxy (catechol) structure of lower molecular weight in spinach. These results suggest that WST contributes to the prevention of low-temperature-induced oxidative damage by increasing the level of antioxidant compounds, thereby improving antioxidant activity. Although sucrose concentrations were increased by WST, nitrate and oxalate concentrations did not increase in any variety. CONCLUSION: WST can contribute to the increase in antioxidant compounds such as flavonoids and ascorbic acids, antioxidant activity and sucrose without increasing in nitrate and oxalate of spinach.
BACKGROUND: Winter sweet treatment (WST) has been established for cultivating high-quality leafy vegetables during the winter. Although it is known that chilling stress during cold acclimation induces oxidative damage by reactive oxygen species in plant tissues, knowledge about changes in antioxidant activity and compounds during WST in spinach is superficial. We investigated changes in flavonoids, total ascorbic acid, carotenoids and hydrophilic oxygen radical absorbance capacity (H-ORAC) along with components in three spinach varieties during low-temperature treatment by exposure to cold air in winter. RESULTS: The H-ORAC values increased substantially together with total flavonoids and total ascorbic acid concentration. In addition, WST increased mono- and diglucosylated flavonoid derivatives with an ortho-dihydroxy (catechol) structure of lower molecular weight in spinach. These results suggest that WST contributes to the prevention of low-temperature-induced oxidative damage by increasing the level of antioxidant compounds, thereby improving antioxidant activity. Although sucrose concentrations were increased by WST, nitrate and oxalate concentrations did not increase in any variety. CONCLUSION: WST can contribute to the increase in antioxidant compounds such as flavonoids and ascorbic acids, antioxidant activity and sucrose without increasing in nitrate and oxalate of spinach.