In this study, natural pigments from the hemp (Datisca cannabina L.) and dyer's oak (Quercus infectoria Oliv.) dye plants were prepared by using KAl(SO4)(2)center dot 12H(2)O (alum) mordant. A reversed-phase high performance liquid chromatography (RP-HPLC) with diode array detection (DAD) method was used in the identification of dyes in the natural pigments. The dye extractions from the natural pigments were carried out with 37% HCl/MeOH/H2O (2:1:1 v/v/v) mixture. Also, antimicrobial activity of crude extracts of plants and pigments were investigated.