Author: Shuang Peng
Peng, Shuang, 2017 Chemical constituents and cytotoxicity against breast cancer cells of South Australian marine sponge Aplysilla rosea, Flinders University, School of Medicine
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Sponge [Porifera] is the richest source of marine natural products, representing over 30% of all marine natural products discovered by far. In Southern Australia Ocean, it is estimated there are over 800 marine sponge species; however, the discovery of marine natural products from these sponge species are very limited.
The aim of this study was, therefore, to screen untapped marine sponges from South Australian waters to discover sponge derived compounds with potential anti-breast cancer activity. Samples of thirty marine sponge species were collected and subjected to a standardised extraction protocol to produce crude extracts. These extracts were tested their cytotoxicity against three breast cancer cell lines (T47D, MCF7 and MDA-MB-231) and one human non-cancer breast cell line (184B5) using the Crystal Violet assay. 60% of the crude extracts showed cytotoxicity against three breast cancer cell lines with an IC50 value range between 5 mg/ml to 50 μg/ml. Crude extracts from three sponges (Tedania sp, Chondropsis cf. arenifera, and Aplysilla rosea) showed the highest toxic activity against three breast cancer cell lines with IC50 (48 h treatment) value of 4.05 to 6.62 μg/ml, 3.80 to 7.28 μ/ml and 8.31 to 12.57 μg/ml, respectively. The three extracts also had lower cytotoxicity against normal breast cell lines 184B5 with IC50 (48 h treatment) value of 14.59 μg/ml, 11.68 μg/ml and 21.96 μg/ml, respectively. Flow Cytometry was used to assess the ability of these three extracts in the apoptosis induction and cell cycle arrest of the three breast cancer cell lines. Extracts from Tedania sp and Chondropsis cf. arenifera showed the ability to induce cell apoptosis. The only extract from Aplysilla rosea showed activities in both cell cycle arrest and apoptosis induction. Therefore, sponge Aplysilla rosea was chosen for further studies.
Using bioactivity-guided isolation, over 50 pure compounds have been obtained from sponge Aplysilla rosea, and 24 compounds were obtained in this thesis. Four novel aplyroseol-type diterpenes compounds (1, 2, 5, and 6) and seven know diterpenes (3, 4, 7-9, 14, and 16), eleven know steroids (10-13, 17-21, and 23-24) and two know fatty acids (15 and 22) were isolated from sponge Aplysilla rosea. The structures of these 24 compounds were elucidated by spectroscopic data (1D and 2D NMR, and HRESIMS). Compounds 1-7, 9, 13, 16, 19 and 24 showed cytotoxicity against three human breast cancer cell lines (T47D, MCF7 and MDA-MB-231), with IC50 value in the range of 3.3 to 16.2 μg/ml. In contrast, the IC50 value in the range of 5.6 to 18.6 μg/ml was indicated on normal breast cell line 184B5. Compound 7 exerted no cytotoxic effect on 184B5 cells after 48 h treatment, compared with IC50 values of 4.4 mg/ml, 3.5 mg/ml, and 3.3 mg/ml on T47D, MCF7 and MDA-MB-231, respectively. Compound 7 induced apoptosis induction and cell cycle arrest in T47D, MCF7 and MDA-MB-231 cell lines at G0/G1 phase.
In conclusion, this study has isolated and identified twenty-four compounds for sponge Aplysilla rosea, with several compounds demonstrated significant cytotoxicity against breast cancer cells. These results indicated a significant advance in the understanding of chemical constituent of sponge Aplysilla rosea for natural product discovery, with four novel compounds and eighteen known compounds never reported from A. rosea. Additionally, at least another twenty compounds could be further identified, with potentially six new compounds. South Australian marine sponges, represented by Aplysilla rosea in this study is a rich source of marine natural product for anticancer drug discovery. Nearly 50% of these compounds identified in this study showed anti-breast cancer activity. Compound 7 indicated selective cytotoxicity against breast cancer cells over normal cells, which showed high potential for further study of the anti-cancer applications.
Keywords: Breast cancer; marine sponge; Aplysilla rosea; cytotoxicity; apoptosis; marine natural product
Subject: Medicine thesis
Thesis type: Doctor of Philosophy
Completed: 2017
School: School of Medicine
Supervisor: Wei Zhang