Abstract
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.
Highlights
Carica papaya is a fast growing, soft-wooded, herbaceous plant reaching 3–10 m in height
To evaluate and compare the effect of leaf juice (LJ), brewed leaf juice (BLJ), and leaf decoction (LD) on cancer cell viability, the MTT assay was performed on human squamous cell doi:10.1371/journal.pone.0147956.g001
After treatment with leaf juice at a concentration equivalent to original leaf of 20 mg/mL, only approximately 20% of SCC25 cells survived, whereas leaf decoction showed a weaker effect by reducing cell viability to a constant 60% for much of the range of tested concentrations from 2 to 20 mg/mL
Summary
Carica papaya is a fast growing, soft-wooded, herbaceous plant reaching 3–10 m in height. An Australian Aboriginal remedy, has been reported widely for its healing capabilities against cancer, with numerous anecdotal reports [8]. The heating process to prepare the decoction can potentially affect temperature-sensitive compounds, leading to possible changes in bioactivity. This type of effect has been reported for other herbal medicines such as ginseng root and ginger, where steaming preparation has been observed to increase the antiproliferative effect compared to unprocessed materials [11,12,13]. We conducted a study to test the hypothesis that the preparation of Carica papaya leaves following an Aboriginal remedy alters the chemical pattern and the anticancer effect of Carica papaya leaf
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
