Bioactivity of Fragaria vesca leaves through inflammation, proteasome and autophagy modulation

Abstract

Ethnopharmacological relevance: Fragaria vesca leaves have been used in folk medicine for the treatment of several diseases, namely gastrointestinal, cardiovascular and urinary disorders, which could be related with the potential anti-inflammatory properties of the extract. This work aims to disclose the bioactivity and the underlying action mechanism of an extract from Fragaria vesca leaves in order to support its traditional uses.

Materials and methods: A hydroalcoholic extract was prepared from Fragaria vesca leaves and its anti-inflammatory potential was evaluated through inhibition of nitric oxide production and expression of several pro-inflammatory proteins in lipopolysaccharide-triggered macrophages. Nitric oxide scavenger activity was also assessed using a standard nitric oxide donor. Since numerous inflammatory proteins are tightly regulated by ubiquitination and proteasomal degradation, the putative effect of the extract on these cellular proteolytic pathways was also disclosed. The phytochemical characterization was performed by HPLC-PDA-ESI/MSn and compared with an infusion prepared according to the traditional method.

Results: For non-cytotoxic concentrations (80 and 160µg/mL) the extract inhibited nitrite production, probably due to a direct nitric oxide scavenging. Furthermore, inhibition of proteasome activity was verified, leading to accumulation of ubiquitinated proteins. The extract also increased the conversion of the microtubule-associated protein light chain LC3-I to LC3-II, a marker of autophagy. Polyphenols, namely ellagitannins, proanthocyanidins, and quercetin and kaempferol glucuronide derivatives were identified in Fragaria vesca leaves extract. Most of the identified phenolic compounds matched with those found in traditional preparation, the infusion.

Conclusions: The extract has a direct nitric oxide scavenging activity giving support to the traditional use of this plant for the treatment of inflammatory disorders. Furthermore, the extract affects the proteolytic systems but its role in cancer treatment requires further studies.

Keywords: Autophagy; Fragaria vesca leaves; Inflammation; Nitric oxide scavenger; Polyphenols; Ubiquitin-Proteasome system.