In a method for preparing a composition including a compound mixture and a carrier agent, the compound mixture is obtained by pulverizing the wood material and/or by extracting the wood material so that the compound mixture contains at least two different compounds, selected from a first specified group, at least one compound selected from a second specified group, the compound mixture is mixed with the carrier agent, the amount of the compound mixture is kept in a range of 0.1-5 wt % from the total weight of the composition, providing that the range is also such that the total cytotoxicity of compound mixture dissolved in ethanol, measured for a HaCat cell culture after 24 h incubation period, is lower than the cytotoxicity of 0.02-0.1 wt % butylated hydroxy toluene (BHT) dissolved in ethanol for a HaCat cell culture after 24 h incubation period.