Three new flavans, (2S)-7-O-galloyl-5,3',4'-trihydroxyflavan (1), (2S)-7,3'-O-digalloyl-5,4'-dihydroxyflavan (2), and (2S)-7,4'-O-digalloyl-5,3'-dihydroxyflavan (3), together with four known compounds, (2S)-5,7,3',4'-tetrahydroxyflavan (4), (-)-epicatechin (5), (-)-syringaresinol (6), and methyl gallate (7) have been isolated from the EtOAc extract of the stems of Helixanthera parasitica. Compounds 2 and 3 were obtained as a mixture of positional isomers. The structures of the isolated compounds were established using extensive spectroscopic data. Compound 1 and the mixture of 2 and 3 exhibited significant antimalarial activity against Plasmodium falciparum, with IC50 values of 0.59 and 1.38 μM, respectively. In addition, flavans 1-3 showed cytotoxicity against KB, MCF-7, and NCI-H187 cancer cell lines, with IC50 values in the range of 11.1-30.0 μM.

中文翻译：

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寄生螺旋虫茎中的生物活性没食子黄酮。

三个新的黄酮，（2S）-7-O-galloyl-5,3'，4'-三羟基黄烷（1），（2S）-7,3'-O-二戊酰基-5,4'-二羟基黄烷（2）， （2S）-7,4'-O-二甘氨酰-5,3'-二羟基黄烷（3）以及四种已知化合物（2S）-5,7,3'，4'-四羟基黄烷（4），（从副产螺旋藻的茎的EtOAc提取物中分离了-）-表儿茶素（5），（-）-丁香脂醇（6）和没食子酸甲酯（7）。获得化合物2和3为位置异构体的混合物。分离的化合物的结构使用广泛的光谱数据建立。化合物1以及2和3的混合物显示出对恶性疟原虫的显着抗疟活性，IC50值分别为0.59和1.38μM。此外，黄烷1-3对KB，MCF-7和NCI-H187癌细胞系显示出细胞毒性，