Viscum album L. homeopathic mother tinctures: Metabolome and antitumor activity

Background: Viscum album L. is a semi-parasitic plant with antitumor activity attributed to the aqueous extracts. However, European V. album ethanolic extracts (VAE) have also demonstrated in vitro activity in tumor models. Aims: Evaluate the metabolic profiles of fifty VAE harvested during summer and winter seasons and their antitumor activity through 2D and 3D models. Methodology: VAE were prepared by maceration from: V. album subsp. album growing on Malus domestica, Quercus sp.     and Ulmus sp.; V. album subsp. austriacum from Pinus sylvestris; V. album subsp. abietis from Abies alba. Chemical analyses were performed through liquid chromatography coupled with high resolution mass spectrometry and Partial Least Squares Discriminant Analysis (PLS-DA) was performed in the Metaboanalyst 4.0. The antitumor potential of the selected VAE was evaluated in 2D and 3D models (MDA-MB-231 cancer cells) by MTT, crystal violet and glycolytic pathway analysis. Results and discussion: The first 3 principal components in PLS-DA explained 60% and 40% of data variation in positive and negative modes respectively. Three groups were formed and showed chemical similarity among V. album subspecies. The compounds responsible for group separation were tentatively identified as: pinobankasin or naringenin hexoside; isorhamnetin-3-hexoside, meglutol and different amino acids. The summer VAE at 0.5% v/v induced higher cytotoxic damage than the winter preparations, and Abies alba and Quercus sp. VAE promoted 49% and 42% reduction of tumor viability in 3D model (72h incubation), respectively. MDA-MB-231 glycolytic pathway in 2D model showed a decrease in the glucose consumption and extracellular lactate production. Also, PFK (6- phosphofructo-1-kinase) and PK (Pyruvate kinase) activities were inhibited by Abies alba and Quercus sp. VAE at 48h of incubation. Conclusion: VAE extracts showed different metabolomes and the glycolytic pathway should be an important target involved in the inhibition of tumor growth by these extracts.