Nguyen Thao T, Parat Marie-Odile, Shaw Paul N, Hewavitharana Amitha K, Hodson Mark P
School of Pharmacy, The University of Queensland, Brisbane, Queensland, Australia.
Metabolomics Australia, Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Brisbane, Queensland, Australia.
PLoS One. 2016 Feb 1;11(2):e0147956. doi: 10.1371/journal.pone.0147956. eCollection 2016.
Carica papaya leaf decoction, an Australian Aboriginal remedy, has been used widely for its healing capabilities against cancer, with numerous anecdotal reports. In this study we investigated its in vitro cytotoxicity on human squamous cell carcinoma cells followed by metabolomic profiling of Carica papaya leaf decoction and leaf juice/brewed leaf juice to determine the effects imparted by the long heating process typical of the Aboriginal remedy preparation. MTT assay results showed that in comparison with the decoction, the leaf juice not only exhibited a stronger cytotoxic effect on SCC25 cancer cells, but also produced a significant cancer-selective effect as shown by tests on non-cancerous human keratinocyte HaCaT cells. Furthermore, evidence from testing brewed leaf juice on these two cell lines suggested that the brewing process markedly reduced the selective effect of Carica papaya leaf on SCC25 cancer cells. To tentatively identify the compounds that contribute to the distinct selective anticancer activity of leaf juice, an untargeted metabolomic approach employing Ultra High Performance Liquid Chromatography-Quadrupole Time of Flight-Mass Spectrometry followed by multivariate data analysis was applied. Some 90 and 104 peaks in positive and negative mode respectively were selected as discriminatory features from the chemical profile of leaf juice and >1500 putative compound IDs were obtained via database searching. Direct comparison of chromatographic and tandem mass spectral data to available reference compounds confirmed one feature as a match with its proposed authentic standard, namely pheophorbide A. However, despite pheophorbide A exhibiting cytotoxic activity on SCC25 cancer cells, it did not prove to be the compound contributing principally to the selective activity of leaf juice. With promising results suggesting stronger and more selective anticancer effects when compared to the Aboriginal remedy, Carica papaya leaf juice warrants further study to explore its activity on other cancer cell lines, as well as investigation to confirm the identity of compounds contributing to its selective effect, particularly those compounds altered by the long heating process applied during the traditional Aboriginal remedy preparation.
番木瓜叶煎剂是一种澳大利亚原住民疗法，因其对癌症的治疗能力而被广泛使用，有大量轶事报道。在本研究中，我们研究了其对人鳞状细胞癌细胞的体外细胞毒性，随后对番木瓜叶煎剂和叶汁/冲泡叶汁进行代谢组学分析，以确定原住民疗法制备中典型的长时间加热过程所产生的影响。MTT 试验结果表明，与煎剂相比，叶汁不仅对 SCC25 癌细胞表现出更强的细胞毒性作用，而且对非癌性人角质形成细胞 HaCaT 细胞的测试表明，叶汁还产生了显著的癌症选择性作用。此外，在这两种细胞系上测试冲泡叶汁的证据表明，冲泡过程显著降低了番木瓜叶对 SCC25 癌细胞的选择性作用。为了初步鉴定导致叶汁具有独特选择性抗癌活性的化合物，采用了一种非靶向代谢组学方法，即超高效液相色谱 - 四极杆飞行时间质谱联用，随后进行多变量数据分析。分别从叶汁的化学图谱中选择了约 90 个和 104 个正、负离子模式下的峰作为区分特征，并通过数据库搜索获得了超过 1500 个假定的化合物 ID。将色谱和串联质谱数据与现有参考化合物直接比较，确认一个特征与拟议的真实标准品相符，即脱镁叶绿酸 A。然而，尽管脱镁叶绿酸 A 对 SCC25 癌细胞表现出细胞毒性活性，但它并不是导致叶汁选择性活性的主要化合物。与原住民疗法相比，番木瓜叶汁显示出有前景的结果，表明其具有更强和更具选择性的抗癌作用，因此值得进一步研究以探索其对其他癌细胞系的活性，同时进行研究以确认导致其选择性作用的化合物的身份，特别是那些在传统原住民疗法制备过程中因长时间加热而改变的化合物。
