Black tea, rich in various and complex polyphenols, is one of the most popular beverages in the world due to its pleasant aroma and health benefits, such as alleviate hyperglycemia and antioxidant. The extensive investigation on the chemical constituents of Yunnan black tea 'Jin-Ya', produced from the leaf buds of Camellia sinensis var. assamica, led to the isolation and identification of 16 flavonoids including three new flavan-3-ols, namely theaflavoids A-C (1–3). Most of the isolates displayed obvious inhibitory activity on α-glucosidase with IC₅₀ values ranging from 1.11 to 24.7 μM. Notably, the new theaflavoids 1–3 showed much stronger inhibitory activity (IC₅₀ = 1.34, 1.11, and 4.57 μM, respectively) than those of the positive controls (acarbose and quercetin, IC₅₀ = 228 and 9.38 μM, respectively). In addition, the isolated flavonol glycosides 5–16 were evaluated for their antioxidant activities by DPPH and ABTS ⁺ radical scavenging assays. Those with galloyl group in molecular exhibited comparable free radical scavenging activities to the positive controls (ascorbic acid and Trolox), while most of the flavonol glycosides showed only moderate activities. The results indicated that Yunnan black tea 'Jin-Ya' is an ideal drink with hypoglycemic and antioxidant property, and is worthy of regular consumption.

红茶富含多种复杂的多酚，因其令人愉悦的香气和健康益处，如缓解高血糖和抗氧化，是世界上最受欢迎的饮料之一。云南红茶'金牙'化学成分的广泛调查，来自茶树的叶芽。assamica导致了 16 种黄酮类化合物的分离和鉴定，其中包括三种新的 flavan-3-ols，即 theaflavoids AC ( 1-3 )。大多数分离物对α-葡萄糖苷酶表现出明显的抑制活性，IC ₅₀值范围为1.11至24.7 μM。值得注意的是，新的 theaflavoids 1 – 3_{显示出比阳性对照（阿卡波糖和槲皮素，IC 50}  = 228 和 9.38 μM，分别）更强的抑制活性（IC ₅₀  = 1.34、1.11 和 4.57 μM ）。此外，通过 DPPH 和 ABTS ⁺ 自由基清除试验评估 了分离的黄酮醇苷5 – 16的抗氧化活性。分子中具有没食子酰基的那些表现出与阳性对照（抗坏血酸和Trolox）相当的自由基清除活性，而大多数黄酮醇苷仅表现出中等活性。结果表明，云南红茶'金牙'是一种理想的降糖抗氧化饮品，值得经常饮用。