Breast Cancer Migration and Proliferation Inhibitory and Antibiotic Secondary Metabolites from The Egyptian Olive Tree Endophytic Fungus Penicillium citrinum

Objectives: The main aim of this study is to discover fungal endophytes associated with the Egyptian native olive tree Olea europaea as new sources for breast cancer control and investigate the chemistry and bioactivity of the fermentation metabolites of the identified active fungal species. Methods: Screening of multiple cultured Egyptian olive tree-associated fungal endophyte extracts identified Penicillium citrinum extract in breast cancer proliferation assays. Bioassay-guided isolation of the fungus P. citrinum extract identified four known metabolites 1-4. Their structure identity was established by different 1D and 2D NMR analyses. Compounds were tested for antiproliferative activity against the human breast cancer cell lines BT-474, MDA-MB-231 and MDA-MB-468using MTT assay and antimigratory activity against the human breast cancer cell lines MDA-MB-231 using wound healing assay. The antimicrobial activity of 1-3 was assessed using modified Kirby-Bauer disc diffusion method against multiple Gram positive and negative bacteria and fungi. Results:NMR analyses identified 1 as the known mycotoxin citrinin and the three different pyrrolidine alkaloids: 2-(hept-5-enyl)-3-methyl-4-oxo-6,7,8,8a-tetrahydro-4H-pyrrolo[2,1-b]-1,3-oxazine (2), scalusamide A (3) and perinadine A (4). Compounds 2-4 showed significant antiproliferative activity against the human triple negative breast cancer cell line MDA-MB-231 with IC50 values of 10.6, 14.8 and 17.7 µM, respectively. Prerinadine (3) significantly suppressed the HGF-induced cell migration in a dose dependent manner with IC50 9.7. Citrinin (1) exerted remarkable antibiotic activity against Gram (+) and Gram (-) bacteria and was even up to several-fold those of tetracycline standard. Conclusion:Egyptian olive tree endophytes are valuable sources for biologically active natural products.