Phenolic profile, bioactivity and cytotoxicity of plant extracts from thyme, ginger, garlic, ground roasted coffee and coffee silverskin

We evaluated selected biological properties of extracts from thyme (THY) (Thymus vulgaris L.), ginger (GNG) (Zingiber officinale Roscoe), garlic (GLC) (Allium sativum L.), ground roasted coffee (GRC), and coffee silverskin (CS) (Coffea sp. L.). The extraction was carried out sequentially with water and ethanol, ultrasonic bath, and solvent evaporation. The phenolic composition was evaluated by modified Folin Ciocalteu, Ultra-performance liquid chromatography with photodiode array detection (UPLC-PDA) and Ultra-performance liquid chromatography-mass spectrometry (UPLC-MS). The antioxidant activity was assessed using FRAP, DDPH, ABTS and ORAC assays, while the potential toxicity was investigated by Tetrazolium dye assays MTT and supercoiled DNA. Several important phenolic compounds were identified, including ellagic acid (23.28 µg EAG/mL in garlic), rutin (25.88 µg EAG/mL in thyme) and caffeine (660–203.3 µg/mL in coffee extracts). The MTT results showed that the highest concentrations of THY and GLC exhibited cytotoxic activity in colon carcinoma cells (Caco-2), reducing cell viability to below 50%. All extracts showed a protective effect on DNA and prevented damage caused by the oxidant AAPH (2,2-Azobis(2-methylpropionitrile)) in the supercoil test. These results demonstrate the bioactive composition of the plant extracts, while also indicating that their toxic potential should be evaluated at higher concentrations.