Attenuation of neuroinflammation in microglia cells by extracts with high content of rosmarinic acid from in vitro cultured Melissa officinalis L. cells

Plant cell culture is a biotechnology cultivation method that permit to cultivate plants in a short period of time and to obtain extracts with a high degree of standardization and high safety profile. The aim of our study was to evaluate the anti-inflammatory and neuroprotective activity of a standardized Melissa officinalis L. phytocomplex extract (MD) obtained with an in vitro plant cell culture. The MD has been chemically characterized and the content of total polyphenols was 5.17 ± 0.1 % w/w, with a content of rosmarinic acid (RA), its main constituent, of 4.02 ± 0.1 % w/w. MD was tested in an in vitro model of neuroinflammation, in which microglia cells (BV2) were stimulated with Lipopolysaccharides (LPS; 250 ng/mL) for 24 h and its pharmacological activity was compared with that of RA. MD (10 µg/mL) and RA (0.4 μg/mL) reduced pro-inflammatory factors (NF-kB, HDAC, IL-1ß) in LPS-stimulated BV2 cells and counteracted the toxic effect produced by activated microglia medium on neuronal cells. This work shows the efficacy of MD on reducing microglia-mediated neuroinflammation and promoting neuroprotection, highlighting the innovative use of in vitro plant cell cultures to obtain contaminant-free extracts endowed with marked activity and improved quali-quantitative ratio in the constituents' content.