Isolation and papain digestion of novel antifungal peptides from red radish (raphanus raphanistrum subsp sativus) and analysis of selective cytotoxicity for cancer treatment

Anotace: Treating cancer with chemotherapy is accompanied with side effects and drug resistance by cancer cells which call for alternative anticancer agents such as cationic antimicrobial peptides. In specific, antifungal peptides were chosen for cytotoxicity analysis due to their deteriorating effects on fungi (eukaryotic cells). Novel peptides were isolated and analysed from red radish seeds. Water soaked seeds were ground with phosphate buffer (pH 7) and the antifungal assay was carried out and an inhibition zone of 0.5±0.2 mm was noticed for 50 μl of the extract at 1 mg/ml concentration. The study was extended further, by digestion with papain, trypsin and pepsin with appropriate buffer and pH of which papain digests of red radish seeds produced a zone of inhibition of 1.00±0.2 mm at 500 μg/ml concentration, approximately. This sample was processed with a 3 kDa cut off membrane and the filtrate was confirmed for its antifungal activity (MIC 32 μg/ml). Further, for size confirmation, the sample was subjected to MALDI- TOF-MS analysis, and a peak was obtained at 1680 Da (1.68 kDa). To check the anticancer activity of the antifungal peptides obtained, the sample was tested on HeLa cell lines by method of MTT Assay and significant cell death was obtained at MIC 12.5 μg/ml which increased with higher concentrations of the sample. Thus, it is confirmed that red radish seed extract digested with papain is effective in inhibiting the growth of both fungal and cancer cell lines making them a good therapeutic agent against cancer.