Iridoids, triterpenes and other constituents from the trunk bark and flowers of the Tabebuia caraiba

The trunk bark of Tabebuia caraiba Bignoniaceae was found to contain four novel iridoids, 6-O-E-p-coumaroyljioglutin D (2), 6-O-E-p-coumaroyl-3-demethyl-3-O-ethyljioglutin D (3), 6-O-E-p-coumaroyl-1-demethyl-1-O-ethyljioglutin D (4), 7-O-E-p-coumaroyljiofuranaldehyde (5), three known iridoids, including one iridoid glucoside, jioglutin D (1), rehmaglutin D (6), 6-O-E-p-coumaroylcatalpol (7). From the flowers were obtained six triterpenes, betulinic acid (8), olean-12-en-3-one (9), β-amyrin (10), oleanolic acid (11), ursolic acid (12), 3-O-E-p-coumaroylursolic acid (13), 2α-hydroxyursolic acid (14), 6β,19α-dihydroxyursolic acid (15), and one phenylethanoid, tyrosol (16), in addition to β-sitosterol, β-sitosterol-3-O-β-D-glucopyranoside and β-sitosterol-3-O-β-D-(6´-O-acyl)-glucopyranoside and E-p-coumaric acid. The structures of the isolated compounds were established on the basis of 1D and 2D NMR spectroscopic techniques. The chemical profile of the trunk bark of the plant was determined by HPLC/DAD/HRESIMS and did not present a good correlation with the phytochemical study. It did not detect most of the isolated substances and allowed to propose the presence of some non-isolated compounds.

本研究从紫葳科（Bignoniaceae）黄钟木属植物Tabebuia caraiba的树干树皮中分离得到4个新型环烯醚萜（iridoids）类成分，分别为6-O-E-对香豆酰基吉罗鲁丁D（6-O-E-p-coumaroyljioglutin D，编号2）、6-O-E-对香豆酰基-3-去甲基-3-O-乙基吉罗鲁丁D（编号3）、6-O-E-对香豆酰基-1-去甲基-1-O-乙基吉罗鲁丁D（编号4）、7-O-E-对香豆酰基焦呋喃醛（7-O-E-p-coumaroyljiofuranaldehyde，编号5）；此外还得到3个已知环烯醚萜类成分，其中包含1个环烯醚萜苷（iridoid glucoside）：吉罗鲁丁D（jioglutin D，编号1）、地黄鲁丁D（rehmaglutin D，编号6）以及6-O-E-对香豆酰基梓醇（6-O-E-p-coumaroylcatalpol，编号7）。从该植物的花中分离得到6种三萜类成分：白桦酸（betulinic acid，编号8）、齐墩果-12-烯-3-酮（olean-12-en-3-one，编号9）、β-香树脂醇（β-amyrin，编号10）、齐墩果酸（oleanolic acid，编号11）、熊果酸（ursolic acid，编号12）、3-O-E-对香豆酰基熊果酸（3-O-E-p-coumaroylursolic acid，编号13）、2α-羟基熊果酸（2α-hydroxyursolic acid，编号14）、6β,19α-二羟基熊果酸（6β,19α-dihydroxyursolic acid，编号15）；此外还获得1个苯乙醇类成分：酪醇（tyrosol，编号16），以及β-谷甾醇（β-sitosterol）、β-谷甾醇-3-O-β-D-吡喃葡萄糖苷（β-sitosterol-3-O-β-D-glucopyranoside）、β-谷甾醇-3-O-β-D-(6´-O-酰基)-吡喃葡萄糖苷（β-sitosterol-3-O-β-D-(6´-O-acyl)-glucopyranoside）和E-对香豆酸（E-p-coumaric acid）。所有分离得到的化合物的结构均通过一维（1D）和二维（2D）核磁共振（NMR）波谱技术得以确证。本研究采用高效液相色谱-二极管阵列检测器-高分辨电喷雾电离质谱（HPLC/DAD/HRESIMS）对该植物树干树皮的化学特征进行了分析，结果与植物化学研究结果未呈现良好相关性：该检测方法未检出大部分已分离得到的成分，并可推测存在部分未分离的化合物。