Human kidney-type glutaminase (KGA) is an important target that is often over expressed in many cancer cells but very few effective inhibitors of this enzyme have yet reached clinical trials. Caudatan A and caudatan B, two undescribed tetracyclic flavans with an unusual ether bond between the C-4 and C-2' were isolated from the roots of Ohwia caudata (Thunb.) H.Ohashi. Caudatan A exhibited stronger inhibitory activity and caudatan B showed moderate effect from the results of inhibitory activities evaluations on KGA. The molecular docking and primary structure-activity relationship analysis revealed that the less steric hindrance at ring A was necessary to the effect. Therefore, combined its better solubility than that of bis-2-(5-phenylacetimido-1,2,4-thiadiazol-2-yl)ethyl sulfide (BPTES), caudatan A might be the potential candidate as the inhibitor of KGA for further studies.

中文翻译：

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Caudatan A，一种未描述的人肾型谷氨酰胺酶抑制剂，含有来自 Ohwia caudata 的四环黄烷

人肾型谷氨酰胺酶 (KGA) 是一个重要的靶标，通常在许多癌细胞中过度表达，但这种酶的有效抑制剂很少能达到临床试验。Caudatan A 和 caudatan B，两个未描述的四环黄烷，在 C-4 和 C-2' 之间具有不寻常的醚键，是从 Ohwia caudata (Thunb.) H.Ohashi 的根中分离出来的。从对KGA的抑制活性评估结果来看，尾坦A表现出更强的抑制活性，尾坦B表现出中等效果。分子对接和一级构效关系分析表明，A环的空间位阻较小是该效应所必需的。因此，结合其比双-2-(5-苯基乙酰亚胺-1,2,4-噻二唑-2-基)乙基硫醚(BPTES)更好的溶解性，