Abstract
Flavonoids are secondary metabolites of plants that often have medical applications. The influences of different sample drying pretreatments on flavonoids and antioxidant activity of ferns have not studies. Dryopteris erythrosora leaves used to analyze flavonoid alterations resulting from drying pretreatments. The total flavonoid content of D. erythrosora leaves exposed to different pretreatments was significantly different. The total flavonoid content of samples initially air-dried in shade and then oven-dried at 75°C were the highest (7.6%), while samples initially dried at 75°C had the lowest content (2.17%). Antioxidant activities of D. erythrosora leaves with different pretreatments varied. Group B first air-dried in the shade and then oven-dried at 75°C and group C first air-dried in the sun and then oven-dried at 75°C, both showed relatively stronger antioxidant activity. The best pretreatment for preserving the flavonoids was to first dry the plant material in the shade and then complete the drying process in an oven at 75°C. It was tentatively identified 22 flavonoids among the four different pretreatments by HPLC-ESI-TOF-MS.
Highlights
Flavonoids are plant secondary metabolites with medical applications [1]
The total flavonoid content of extracts from group B, which were first dried about one day completely oven-dried at 75 ̊C was the highest
The process of drying in the shade produced a slow rate of water loss.which might result in the increasing of total flavonoid content
Summary
Some factors influenced flavonoid levels, such as harvest time [2,3,4], shade netting, planting time [5], development [6], and using the light transmittance paper bags [7]. The flavonoid content of fresh mulberry leaves was highest and the content in leaves that were oven-dried at 100–105 ̊C was lowest [11]. DPPH scavenging activity, and reducing power of Salvia officinalis L. leaves dried in the shade were higher than levels in leaves oven-dried at 65 ̊C [12]. Paramignya trimera dried in an oven at 25 ̊C had a higher flavonoid content than samples dried in an oven at 100 ̊C [8].
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