Phenolic extracts of strawberry fruits, leaves and cell cultures - analysis and biological activities

Berry fruits are rich in phenolic compounds, such as flavonoids, phenolic acids, lignans and complex polymeric tannins, with wide variation in their contents depending on the plant species and environmental factors. The main phenolics in strawberry fruits are anthocyanins and ellagitannins. We have shown earlier that ellagitannins possess strong antimicrobial properties against human gastrointestinal pathogens. As an alternative to use of strawberry fruits, plant leaves and cell cultures are interesting choice for production of strawberry phenolics, as well as other, potentially novel secondary metabolites with interesting biological effects. As far as we know, strawberry cell cultures have not been used for production of berry and plant phenolics earlier. In this study, sterile in vitro strawberry plants were germinated from sterilized seeds. Cuts of the in vitro leaves were treated with plant growth hormones for production of callus, and the most productive calli were used for establishment of strawberry cell cultures. Analysis of phenolic extracts of strawberry fruits, leaves and cell cultures were performed using HPLC-DAD and LC-MS, and comparison of phenolic compound patterns of in vivo strawberry fruits and leaves to those of in vitro leaves and cell cultures revealed interesting differences. Also antimicrobial activities against selected human pathogenic bacteria and anti-oxidative activities, measured as radical scavenging activity, varied depending on the origin of the material of phenolic extract. These results showed that strawberry leaves are interesting and rich sources of bioactive phenolic compounds.