Phenylethanoid and iridoid glycosides production in Rehmannia elata NE Brown ex Prein. in vitro shoot cultures and their biological activity

The accumulation of highly relevant bioactive phenylethanoid and iridoid glycosides produced in Rehmannia elata N.E. Brown ex Prein. in vitro shoot cultures was evaluated after culturing plant material under different light quality. Shoots of R. elata were cultured on Murashige and Skoog (MS) agar media without plant growth regulators (PGRs) or supplemented with 0.1 mg/L indole-3-acetic acid (IAA) and 0.8 mg/L N-6-(2-isopentenyl) adenine (2iP) in the presence of white or photosynthetically active radiation (PAR) LED spectra. Ultrastructure of organogenic callus tissue, shoots and roots was observed using scanning electron microscopy (SEM). The highest number of regenerated shoots (4.35) were obtained on media supplemented with PGRs under PAR illumination. Phytochemical analysis of selected metabolites were determined using UHPLC technique. One of the iridoid glycoside, harpagide was detected at significantly higher level in shoots cultured under white light compared to PAR (0.66-1.08 mg/g DW and 0.27 0.29 mg/g DW, respectively), whereas larger contents of phenylethanoid glycoside - verbascoside (17.17-22.25 mg/g DW) were found in shoots cultured on PGRs supplemented media under both, white or PAR light conditions. Due to the presence of the biologically active R. elata metabolites, antimicrobial potential of methanolic extracts from shoot cultures against Gram-positive, Gram-negative bacteria and fungi as well as their cytotoxicity were evaluated. Tested extracts showed moderate antifungal activity against Aspergillus brasiliensis and low cytotoxicity against mouse fibroblasts cell line (L929) in MTT assay.