Department of Organic Chemistry, School of Pharmacy, Second Military Medical University, Shanghai 200433, China.
Department of Pharmacy, the 72nd Group Army Hospital of PLA, Huzhou, Zhejiang Province 313000, China.
Anticancer Agents Med Chem. 2020;20(10):1241-1249. doi: 10.2174/1871520620666200302114550.
Rabdosia japonica has been historically used in China as a popular folk medicine for the treatment of cancer, hepatitis, and gastricism. Glaucocalyxin A (GLA), an ent-kaurene diterpene isolated from Rabdosia japonica, is one of the main active ingredients showing potent inhibitory effects against several types of tumor cells. To the best of our knowledge, studies regarding the structural modification and Structure- Activity Relations (SAR) of this compound have not yet been reported.
The aim of this study was to discover more potent derivatives of GLA and investigate their SAR and cytotoxicity mechanisms.
Novel 7-O- and 14-O-derivatives of GLA were synthesized by condensation of acids or acyl chloride. The anti-tumor activities of these derivatives against various human cancer cell lines were evaluated in vitro by MTT assays. Apoptosis assays of compound 17 (7,14-diacylation product) were performed on A549 and HL-60 cells by flow cytometry and TUNNEL. The acute toxicity of this compound was tested on mice, at the dose of 300mg per kg body weight.
Seventeen novel 7-O- and 14-O-derivatives of GLA (1-17) were synthesized. These compounds showed potent cytotoxicity against the tested cancer cell lines, and almost all of them were found to be more cytotoxic than GLA and oridonin. Of the synthesized derivatives, compound 17 presented the greatest cytotoxicity, with IC50 values of 0.26μM and 1.10μM in HL-60 and CCRF-CEM cells, respectively. Furthermore, this compound induced weak apoptosis of A549 cells but showed great potential in stimulating the apoptosis of HL- 60 cells. Acute toxicity assays indicated that compound 17 is relatively safer.
The results reported herein indicate that the synthesized GLA derivatives exhibited greater cytotoxicity against leukemia cells than against other types of tumors. In particular, 7,14-diacylation product of GLA was found to be an effective anti-tumor agent. However, the cytotoxicity mechanism of this product in A549 cells is expected to be different than that in other tumor cell lines. Further research is needed to confirm this hypothesis.
在中国，夏枯草被作为一种民间药物用于治疗癌症、肝炎和胃病。从夏枯草中分离得到的裂环烯醚萜类化合物——高龙胆苦苷 A（GLA），是对多种肿瘤细胞具有显著抑制作用的主要活性成分之一。据我们所知，目前尚未有关于该化合物的结构修饰及构效关系（SAR）的研究报道。
本研究旨在发现 GLA 的更有效衍生物，并研究其 SAR 和细胞毒性机制。
通过酸或酰氯缩合反应，合成了 GLA 的 7-O-和 14-O-衍生物。采用 MTT 法测定了这些衍生物对多种人癌细胞系的体外抗肿瘤活性。采用流式细胞术和 TUNNEL 法对化合物 17（7,14-二酰化产物）在 A549 和 HL-60 细胞中的凋亡作用进行了检测。以 300mg/kg 体重的剂量对该化合物在小鼠中的急性毒性进行了测试。
合成了 17 种新型 GLA 的 7-O-和 14-O-衍生物（1-17）。这些化合物对所测试的癌细胞系表现出很强的细胞毒性，几乎所有化合物都比 GLA 和冬凌草甲素更具细胞毒性。在所合成的衍生物中，化合物 17 的细胞毒性最大，在 HL-60 和 CCRF-CEM 细胞中的 IC50 值分别为 0.26μM 和 1.10μM。此外，该化合物诱导 A549 细胞弱凋亡，但对 HL-60 细胞有很强的促凋亡作用。急性毒性试验表明，化合物 17 相对安全。
本研究结果表明，所合成的 GLA 衍生物对白血病细胞的细胞毒性大于对其他类型肿瘤的细胞毒性。特别是，GLA 的 7,14-二酰化产物是一种有效的抗肿瘤药物。然而，该产物在 A549 细胞中的细胞毒性机制可能与其他肿瘤细胞系不同。需要进一步的研究来证实这一假设。
