Guangdong Provincial Key Laboratory of Applied Botany, Key Laboratory of South China Agricultural Plant Molecular Analysis and Genetic Improvement, and South China Branch of Innovation Academy for Drug Discovery and Development, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Guangdong Provincial Key Laboratory of Applied Botany, Key Laboratory of South China Agricultural Plant Molecular Analysis and Genetic Improvement, and South China Branch of Innovation Academy for Drug Discovery and Development, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China.
Fitoterapia. 2020 Jan;140:104442. doi: 10.1016/j.fitote.2019.104442. Epub 2019 Nov 29.
Averrhoa carambola L. (Oxalidaceae) was widely cultivated for fruits (star fruit), whereas the value of leaves remains to be discovered. Our study on the leaves yielded five flavan-3-ols (1-5) and two 2-diglycosyloxybenzoates. Their structures were determined by spectroscopic and chemical methods. Epicatechin-(5,6-bc)-4β-(p-hydroxyphenyl)-dihydro-2(3H)-pyranone (1) and benzyl 2-β-d-apiofuranosyl-(1 → 6)-β-d-glucopyranosyloxybenzoate (6) were new structures. 6-(S-Pyrrolidinone-5-yl)epicatechin (4) and 6-(R-2-pyrrolidinone-5-yl)epicatechin (5) were obtained as monomeric diastereomer for the first time and their absolute configurations were determined by electronic circular dichroism (ECD) computation. Epicatechin-(7,8-bc)-4α-(p-hydroxyphenyl)-dihydro-2(3H)-pyranone (2), epicatechin-(7,8-bc)-4β-(p-hydroxyphenyl)-dihydro-2(3H)-pyranone (3), and methyl 2-β-d-apiofuranosyl-(1 → 6)-β-d-glucopyranosyloxybenzoate (7) were not previously reported from the genus Averrhoa. Compounds 1-5 showed more potent 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radical cation and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activities and ferric reducing antioxidant power (FRAP) than l-ascorbic acid. Meanwhile 1 and 3 exhibited lipase and α-glucosidase inhibitory activities, respectively. The results clarified the structures of flavan-3-ols and 2-diglycosyloxybenzoates in the leaves and their antioxidant, lipase, and α-glucosidase inhibitory activities.
杨桃（酢浆草科）广泛种植用于果实（杨桃），而其叶子的价值尚未被发现。我们对叶子的研究得到了五个黄烷-3-醇（1-5）和两个 2-二糖基氧基苯甲酸酯。它们的结构通过光谱和化学方法确定。表儿茶素-(5,6-bc)-4β-(对羟基苯基)-二氢-2(3H)-吡喃酮（1）和苄基 2-β-d-阿洛呋喃基-(1 → 6)-β-d-吡喃葡萄糖基氧基苯甲酸酯（6）是新结构。6-(S-吡咯烷酮-5-基）表儿茶素（4）和 6-(R-2-吡咯烷酮-5-基）表儿茶素（5）首次作为单体非对映异构体获得，其绝对构型通过电子圆二色性（ECD）计算确定。表儿茶素-(7,8-bc)-4α-(对羟基苯基)-二氢-2(3H)-吡喃酮（2）、表儿茶素-(7,8-bc)-4β-(对羟基苯基)-二氢-2(3H)-吡喃酮（3）和甲基 2-β-d-阿洛呋喃基-(1 → 6)-β-d-吡喃葡萄糖基氧基苯甲酸酯（7）以前未从杨桃属中报道过。化合物 1-5 对 2,2'-偶氮-双(3-乙基苯并噻唑啉-6-磺酸)（ABTS）自由基阳离子和 2,2-二苯基-1-苦基肼（DPPH）自由基清除活性以及铁还原抗氧化能力（FRAP）的作用强于 l-抗坏血酸。同时，1 和 3 分别表现出脂肪酶和α-葡萄糖苷酶抑制活性。结果阐明了叶子中黄烷-3-醇和 2-二糖基氧基苯甲酸酯的结构及其抗氧化、脂肪酶和α-葡萄糖苷酶抑制活性。
