The onion, known as the bulb onion or common onion, is not only a key ingredient in many tasty and healthy vegetarian meals but also many traditional medicines. Nine new flavonoids [cepaflavas A, B (5, 6), cepadials A–D (7–9 and 14), and cepabiflas A–C (10–12)] and six known compounds (1–4, 13, 15) were obtained from the outer skins of Allium cepa L. Among them, compounds 5, 6, and 9 might be artificial products formed during extraction and isolation. New compounds were structurally elucidated using various spectroscopy/spectrometry techniques, including NMR and HRMS, and computational methods. Their absolute configurations were determined using time-dependent density functional theory calculations, combined with ECD spectroscopy, optical rotation calculation, and statistical procedures (CP3 and DP4 analysis). The free radical scavenging assays revealed that the new compounds 10–12 possessed considerable antioxidant activities with IC₅₀ values of 4.25–8.88 and 7.12–8.14 μM against DPPH and ABTS^•+, respectively. Compounds 13–15 showed substantial inhibitory activities against both α-glucosidase and protein tyrosine phosphatase 1B (PTP1B), with IC₅₀ values of 0.89–6.80 and 1.13–6.82 μM, respectively. On the basis of molecular docking studies, 13 and 15 were predicted to have high binding capacity and strong affinity toward the active site of PTP1B.

中文翻译：

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葱属外皮黄酮类衍生物的抗氧化和抗糖尿病活性

洋葱，被称为鳞茎洋葱或普通洋葱，不仅是许多美味健康的素食餐中的关键成分，而且还是许多传统药物。九个新黄酮类化合物[cepaflavas A，B（5，6），cepadials A-d（7 - 9和14），和cepabiflas A-C（10 - 12）]和六个已知化合物（14，13，15）从外皮得到洋葱L.其中化合物5，6，和9可能是提取和分离过程中形成的人工产物。使用各种光谱学/光谱技术，包括NMR和HRMS，以及计算方法，对新化合物进行了结构解析。使用与时间相关的密度泛函理论计算，ECD光谱，旋光度计算和统计程序（CP3和DP4分析）确定其绝对构型。自由基清除测定，发现该新化合物10 - 12具有相当大的抗氧化活性与IC _50个的值4.25-8.88和对DPPH 7.12-8.14μM和ABTS ^•+分别。化合物13 – 15对α-葡萄糖苷酶和蛋白酪氨酸磷酸酶1B（PTP1B）均显示出显着的抑制活性，IC ₅₀值分别为0.89–6.80和1.13–6.82μM。根据分子对接研究，预计13和15具有高结合能力和对PTP1B活性位点的强亲和力。