Nitrogen effects on total flavonoids, chlorogenic acid, and antioxidant activity of the medicinal plant Chrysanthemum morifolium

Chrysanthemum morifolium (Ramat.) has a long history of cultivation and use as a traditional medicine and tea plant in China. A greenhouse experiment with potted soil-quarz mixture studied the effects of nitrogen supply (0, 56, 112, 167, 224, 334, 501, 556, and 668 mg N kg(-1)) on concentrations and ratios of total flavonoids and chlorogenic acid in the flowers of C. morifolium using spectrophotometric and HPLC methods. The antioxidant activity of the flowers was determined as the radical scavenging activities of hydroxyl, superoxide anion, and 2,2-diphenyl-1-picrylhydrazyl hydrate (DPPH) free radicals. A high N supply decreased the concentrations of total flavonoids by 18%-35% and that of chlorogenic acid by 8%-60% compared to a low N-supply rate. At the same time, increasing N supply significantly decreased the antioxidant activity of the flowers. The antioxidant activity of C. morifolium flowers was significantly positively correlated with the concentrations of total flavonoids and chlorogenic acid. We conclude that an N supply in excess of 300 mg (kg soil)(-1) will negatively affect the antioxidant activity and thereby reduce the quality of C. morifolium flowers.