To our interest, this study aimed to recover DNA from six plant species containing cardiac glycosides commonly found in Thailand, i.e. Calotropis gigantea (L.) R.Br. ex Ait., Cerberaodollam Gaertn., Nerium oleander L., Strophanthus gratus (Wall.& Hook.) Baill., Thevetiaperuviana (Pers.) K. Schum., and Adenium obesum (Forssk.) Roem. & Schult. However, these plant shave thick leaf blades, waxy surface, and exude either clear or milky sap when cut or tear, which can cause difficulties in DNA extraction and affect to the yield and quality of DNA. Our results demonstrated that by conventional CTAB method of DNA extraction, DNA were obtained from young leaf tissue of Ca. gigantea, Ce. odollam, N. oleander and S. gratus, but not T. peruviana and A. obesum. DNA yields were 13.9±5.1, 50.0±35.2,12.6±7.3, and 9.5±5.5 μg/g fresh tissue; the A260/A280 ratios were 1.8±0.04, 1.8±0.07, 1.7±0.25, and 1.8±0.04, respectively.These DNA extracts were PCR amplifiable. However, good quality DNA was successfully extracted from petals of the two problematic species, T. peruviana and A. obesum by two different methods, which were the conventional CTAB method and using the commercial DNA extraction kit, respectively. Total DNA yield were 47.8±12.1 and 2.7±0.6 μg/g fresh tissue; A260/A280 ratios were 1.9±0.05 and 1.8±0.05, respectively.