Open AccessA new estimation of the total flavonoids in silkworm cocoon sericin layer through aglycone determination by hydrolysis-assisted extraction and HPLC-DAD analysis
Author(s) -
Jinge Zhao,
Yuqing Zhang
Publication year - 2016
Publication title -
food and nutrition research/food and nutrition research. supplement
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.041
H-Index - 37
eISSN - 1654-6628
pISSN - 1654-661X
DOI - 10.3402/fnr.v60.30932
Subject(s) - sericin , kaempferol , quercetin , chromatography , chemistry , aglycone , hydrolysis , extraction (chemistry) , polyphenol , high performance liquid chromatography , glycoside , antioxidant , food science , silk , biochemistry , organic chemistry , materials science , composite material
Background Silk sericin and a few non-protein components isolated from the cocoon layer including two silk proteins in silkworm Bombyx mori has many bioactivities. The dietary sericin possess antinatural oxidation, anticancer, antihyperlipidemic, and antidiabetic activities. The non-protein components surrounding the sericin layer involve in wax, pigments mainly meaning flavonoids, sugars, and other impurities. However, very few investigations have reported the estimation of the total flavonoids derived from the cocoon layer. The flavonoids are commonly present in their glycosylated forms and mostly exist as quercetin glycosides in the sericin layers of silkworm cocoons. Objective The aim of this study was to find a more accurate method to estimate the level of the total flavonoids in silkworm cocoons. Design An efficient procedure of hydrolysis-assisted extraction (HAE) was first established to estimate the level of the total flavonoids through the determination of their aglycones, quercetin, and kaempferol. Then, a comparison was made between traditional colorimetric method and our method. In addition, the antioxidant activities of hydrolysis-assisted extract sample were determined. Results The average contents of quercetin and kaempferol were 1.98 and 0.42 mg/g in Daizo cocoon. Their recoveries were 99.56 and 99.17%. The total sum of quercetin and kaempferol was detected to be 2.40±0.07 mg/g by HAE-HPLC, while the total flavonoids (2.59±0.48 mg/g) estimated by the traditional colorimetric method were only equivalent to 1.28±0.04 mg/g of quercetin. The HAE sample also exhibits that IC 50 values of scavenging ability of diphenyl picryl hydrazinyl (DPPH) radical and hydroxyl radical (HO·) are 243.63 µg/mL and 4.89 mg/mL, respectively. Conclusions These results show that the HAE-HPLC method is specificity of cocoon and far superior to the colorimetric method. Therefore, this study has profound significance for the comprehensive utilization of silkworm cocoon and also may be applied to the estimation of total flavonoids in other functional foods.