Abstract
Single-factor experiment and Box-Behnken design were applied to optimize the infrared-assisted extraction (IRAE) of rutin, quercetin, kaempferol, and isorhamnetin from Flos sophorae. Four factors (extract solvent, solid-liquid ration, extraction time, infrared power) affecting the extraction yield of flavonoids were studied. Under optimized conditions the extraction yield was 33.199 ± 0.24 mg/g, which substantially improved, compared with heating reflux extraction (HRE) and ultrasonic-assisted extraction (UAE), while extraction time was only 9 min. The eluents were rich in 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azobis (2-methyl-propionamidine) dihydrochloride radical scavenging potential (IC50 of DPPH: 53.44 ± 0.01 μg/mL, oxygen radical absorbance capacity (ORAC): 3785.83 ± 52 μmol/g) than the extracts obtained by HRE and UAE. In addition, an ultra-high performance liquid chromatography method was optimized for the identification and quantification of the tested flavonoids, and the method was validated based on its correlation coefficient (r), reproducibility (RSD, n = 5), and recovery values, which were 0.9994–0.9998, 0.74–1.83%, and 97.78–102.94%, respectively. These results confirmed that high extraction yield of flavonoids results in stronger antioxidant values and response surface methodology optimization of IRAE is a promising alternative to traditional extraction techniques for flavonoids from medicinal plants.
Highlights
Natural antioxidants derived from medicinal plants have attracted considerable interest during the last decade from researchers working in a variety of different fields because of their beneficial effects for human health
We considered all of the factors that could affect the extraction yield of flavonoids obtained by infrared-assisted extraction (IRAE)
IRAE was performed with a three-variable, three-level Box–Behnken design based on the Response Surface Methodology (RSM)
Summary
Natural antioxidants derived from medicinal plants have attracted considerable interest during the last decade from researchers working in a variety of different fields because of their beneficial effects for human health. Natural antioxidants have been reported to exhibit protective effects against chronic degenerative diseases, such as cancer and cardiovascular diseases, because of their antioxidant activity [1]. Natural antioxidants rarely pose mutagenic/genotoxic risks to human health [2], whereas synthetic antioxidants can be toxic. Flavonoids are found to be the bioactive compounds in Flos sophorae, the flowers and buds of Sophora japonica L. Flos sophorae has been used to treat hematuria, hematemesis, hemorrhinia arteriosclerosis, and cerebral infarction [4]. Higher amounts of flavonoids were isolated from Flos sophorae, such as rutin, quercetin, Molecules 2017, 22, 1000; doi:10.3390/molecules22061000 www.mdpi.com/journal/molecules
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