Spruce and beech bark aqueous extracts: source of polyphenols, tannins and antioxidants correlated to in vitro antitumor potential on two different cell lines

The purpose of the present study was to determine the antioxidant capacity, the total phenol content, tannins, the cytotoxic and antiproliferative activity of some aqueous extracts obtained from spruce bark ( Picea abies L.) and beech bark ( Fagus sylvatica L.). In this regard, two types of extracts were obtained from both species using different methods of extraction: classical water bath extraction and ultrasound-assisted extraction. The antioxidant activity (AOA) was determined by means of DPPH assay and the cytotoxic and antiproliferative effects were determined using Alamar Blue technique and scratch assay. The total phenol content was determined colorimetrically by means of the Folin–Ciocalteu method. In vitro antitumor activity was tested on two different cell lines: A375 (human melanoma) and A549 (lung carcinoma) because of their different origin and metastatic potential. In addition, a non-tumor cell line (HaCaT human keratinocytes) was used in order to evaluate the samples selectivity. The results indicated that the aqueous extracts obtained by classical extraction had a higher antioxidant activity compared to the extracts obtained by ultrasound-assisted extraction. Moreover, the AOA of Picea abies L. bark extracts proved to be superior to those obtained from Fagus sylvatica L. bark extracts. Regarding the effect on cancer cells, the samples elicited a dose-dependent cytotoxic effect on A375 human melanoma cells, while on A549 lung carcinoma cells, the extractive solutions stimulated tumor cells viability, an effect that was reduced by increasing the concentration of the samples. Furthermore, the extractive solutions proved to possess antiproliferative properties when tested at the highest concentration; results that could be correlated with the antioxidant effects. In the case of the non-tumor cell line, the samples did not display a cytotoxic activity and stimulated cells proliferation.