Simple phenols in tropical woods determined by UHPLC-PDA and their antioxidant capacities: an experimental design for Randall extraction using environmentally friendly solvents

A comprehensive experimental design was developed to determine suitable conditions (volume, percentage of solvent, extraction temperature) for the ethanol extraction of phenolic compounds from ten tropical woody plants. Wenge, angelim vermelho, zebrano, merbau, tigerwood, angelim pedra, jatoba, angelim amargoso, massaranduba, and doussie woods were used in experiments. The effects of three independent variables and their interactions on the yields of cinnamic and benzoic acid derivates were analyzed using UHPLC-PDA. The most significant parameters were found to be solvent percentage, extraction volume, and extraction temperature. Optimal conditions for the extraction of phenolic compound contents were an 80 degrees C extraction temperature, a 30 mL extraction volume, and the use of pure water as the extraction solvent. The tested species of woods contained mainly cinnamic acid derivates. Water extracts after hydrolysis contained greater amounts of cinnamic acid derivates than those extracts from non-hydrolyzed material. The total phenolics content was highest in water extracts of tigerwood, wenge and merbau; however, the extract of merbau wood was a stronger radical scavenger in ABTS(+center dot) assays: 34.11 +/- 0.02 mM Trolox equivalents per g of dry extract. The main compounds possessing antioxidant activity in the extracts of vermelho wood assessed by UHPLC analysis were hydroxycinnamic acids.