Production of bioactive cyclotides in somatic embryos of Viola odorata

Viola odorata L. (Violaceae), an Indian medicinal plant, contains a plethora of cyclotides, which are a class of cyclic peptides derived from plants, possessing several applications. Somatic embryo culture of V. odorata was developed, via indirect somatic embryogenesis, to serve as an alternative to natural plant biomass for sustainable and continuous production of its bioactive ingredients, such as cyclotides. Among the various combinations of phytohormones tested, Murashige and Skoog medium supplemented with 1 mg/l thidiazuron gave rise to the maximum frequency of induction (86.7%) and a high number of somatic embryos (3) from an embryogenic callus. Identification and characterization of cyclotides in the somatic embryos were carried out using a Fourier transform mass spectrometer coupled with liquid chromatography (LC-FTMS). Among the cyclotides identified in the study, few were found to be exclusively present in the somatic embryo culture. Furthermore, the relative abundance of the cyclotides was higher in somatic embryo extract than in the natural plant extract. The biological activities (cytotoxic, haemolytic and antimicrobial) of the somatic embryos and the parent plant were compared. Unlike the natural plants, the somatic embryo extracts demonstrated specificity i.e. they were found to be potent against cancerous cells but not against non-cancerous cell line or red blood cells. In contrast to the plant extract, the somatic embryos extracts were found to be potent against Escherichia coli and Staphylococcus aureus. These results suggest that somatic embryos of V. odorata (rich in cyclotides) can be used as an alternative to plant biomass for its therapeutic applications and germplasm conservation.