Arctic bramble cell cultures as a source of berry phenolics

Berries are rich in phenolic compounds with beneficial biological properties for human health. Arctic bramble (Rubus arcticus) grows in borealic zone, and its ruby red berries are well known for good taste and flavour. In addition, arctic bramble is rich in bioactive phenolic compounds, especially the complex phenolic polymer ellagitannin, which is reported to have e.g. in vitro anti-oxidant activities and antimicrobial effects against human pathogens. The colour of arctic bramble originates from anthocyanins, which also possess variable beneficial effects on human health. The crop of both wild and cultivated arctic bramble is very low, and therefore cell cultures are the potential choice for production of already characterized and novel secondary metabolites for food and pharmaceutical purposes. Arctic bramble cell cultures were established from cuts of sterile in vitro leaves on medium with plant hormones kinetin and NAA (alpha-Naphtalen-acetic acid). Callus lines were grown on the hormone medium, and good growth and bright colours were used for selection criteria for maintenance and initiation of suspension cultures. Phenolic compounds were measured from stable callus and suspension cultures obtained, and selected culture was used for elicitation experiment aiming to increase production of phenolic secondary metabolites. Elicitors used were methyl jasmonate, ethephon, S-ABA and chitosan, and they were introduced in the cultures in late logarithmic growth phase. Samples collected at different time points were filtered, and the cell mass was freeze-dried and extracted with methanol. Freeze-dried extracts were analysed by HPLC-DAD. In callus and suspension cultures phenolic acids were the main phenolics detected in methanol extracts. Elicitation clearly enhanced the production of some phenolic compounds in suspension cultures, and elicitation with S-ABA also promoted synthesis of a new phenolic compound, which still needs to be characterized.