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This study evaluated the interaction of Chrysanthemum indicum (CI) flavonoids (luteolin, acacetin, and buddleoside) with α‐amylase. Surface plasmon resonance (SPR) assay showed their equilibrium dissociation constants (KD) are 1.9695 ± 0.12, 2.9240 ± 0.20, and 3.2966 ± 0.08 mM at pH 6.0, respectively. Furthermore, their binding affinities were influenced by KCl, MgCl2, and CaCl2. Enzymatic kinetic studies revealed that three flavonoids exhibited noncompetitive α‐amylase inhibitory activity. The inhibitory sequence is luteolin > acacetin > buddleoside, which was in accordance with the results of binding affinity from SPR. 1,1‐diphenyl‐2‐picryl hydrazyl radical assay demonstrated that antioxidant activities of three flavonoids were inhibited significantly with α‐amylase. Meanwhile, the study reveals that hydroxyl on C′‐4, C′‐5, and C‐7 of flavonoids play an important role on the interaction of three flavonoids with α‐amylase. Also, SPR could be used as sensor for rapid screening inhibitors of α‐amylase and provide useful information for the application of C. indicum flavonoids in food and pharmaceutical area. [ABSTRACT FROM AUTHOR]

Summary: In this work, the effects of three Citrus flavonoids (naringin, neohesperidin and hesperidin) on α‐amylase catalysed starch digestion were investigated. An inhibitory kinetics experiment demonstrated that they noncompetitively inhibit the activity of α‐amylase with Ki values of, respectively, 25.21 μ m, 40.26 μ m, 40.69 μ m. Surface plasmon resonance assay showed three Citrus flavonoids can bind with starch with KD values of, respectively, 3.98 ± 0.20 m m, 4.92 ± 0.15 m m and 5.07 ± 0.17 m m. Scanning electron microscopy indicated they can delay the retrogradation of starch. The results of 1, 1‐diphenyl‐2‐picryl hydrazyl radical assay indicate that the antioxidant activities of three Citrus flavonoids are significantly decreased by interacting with starch. These results illustrated three Citrus flavonoids that retard the digestion of starch not only through interaction with α‐amylase, but also through interaction with starch. [ABSTRACT FROM AUTHOR]

Flavonoids, a class of natural drugs with broad biological activity, exhibit inhibitory effect on α-amylase. Citrus peel is a good source of flavonoids. The real-time interactions between three Citrus flavonoids (naringin, neohesperidin, hesperidin) and α-amylase were investigated by surface plasmon resonance biosensor, and were compared with the α-amylase inhibitors, acarbose. These results showed the binding affinities of naringin, neohesperidin and hesperidin with α-amylase reach the highest at pH 6 with K D values of 2.27 ± 0.18 mM, 3.09 ± 0.20 mM and 3.51 ± 0.09 mM, and can be reinforced with 0.2 M NaCl and 0.1 M CaCl 2 , respectively. The results of 1, 1-diphenyl-2-picryl hydrazyl radical assay indicate that the antioxidant activities of naringin, neohesperidin and hesperidin are significantly inhibited by interacting with α-amylase, and the inhibition percentage are 47.61 ± 0.034%, 22.81 ± 0.037% and 21.01 ± 0.051%, respectively. Additionally, it is found that both the number and the position of hydroxyl group play an important role in the interaction of three Citrus flavonoids and α-amylase. These results provide useful information for rapid screening inhibitors of α-amylase from plant-based food. [ABSTRACT FROM AUTHOR]