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Optimization of ultrasonic–microwave synergistic extraction of flavonoids from sweet potato leaves by response surface methodology

Liu, Jiang, Mu, Taihua, Sun, Hongnan, Fauconnier, Marie Laure
Journal of food processing and preservation 2019 v.43 no.5 pp. e13928
Ginkgo biloba, antioxidant activity, caffeic acid, crop production, high performance liquid chromatography, inhibitory concentration 50, isoflavones, isoquercitrin, kaempferol, leaves, livestock feeds, propolis, quercetin, response surface methodology, sweet potatoes, temperature, China
Ultrasonic–microwave synergistic extraction was used to extract flavonoids from sweet potato leaves (SPL) by response surface methodology. The optimal conditions for flavonoids extraction were 1:40 (g/ml) of solid–liquid ratio, 57°C of extraction temperature, 76 s of extraction time, and 72% (v/v) ethanol for 2 times, the highest extraction efficiency was 91.65 ± 3.37%. After purification, the flavonoids purity reached to 76.10 ± 3.11 (%, DW). The result of high‐performance liquid chromatography revealed 11 compounds including astragalin (473.8 ± 7.3 mg/g, DW), quercetrin (86.5 ± 0.7 mg/g, DW), 4,5‐chlorogenic acid (76.4 ± 0.5 mg/g, DW), isoquercitrin (62.4 ± 0.4 mg/g, DW), tiliroside (18.8 ± 0.3 mg/g, DW), quercetin (12.5 ± 0.2 mg/g, DW), 3,4,5‐chlorogenic acid (6.5 ± 0.2 mg/g, DW), caffeic acid (6.1 ± 0.2 mg/g, DW), kaempferol (6.0 ± 0.2 mg/g, DW), myricetrin (5.9 ± 0.1 mg/g, DW), and rhamnetin (4.3 ± 0.1 mg/g, DW) in sweet potato leaf flavonoids, which possessed good antioxidant activity compared to soy isoflavones, ginkgo biloba extract, and propolis flavone. The IC₅₀ value of sweet potato leaf flavonoids was 13.26 ± 0.09 μg/ml in ferric reducing antioxidant power and 5.41 ± 0.21 in 2, 2′‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulphonic acid) scavenging capacity, respectively. PRACTICAL APPLICATIONS: China is the leading country of sweet potato production in the world, but sweet potato leaves (SPL) have been neglected except for a partial use as livestock feed in most parts of China, and detailed reports on the effective components in the leaves are scarce. Ultrasonic–microwave synergistic extraction is an efficient way to select flavonoids from SPL which has a potential to be extended in natural flavonoids industry.