Identification of purine-derived compounds, ustilagomaydisin A-C, from the plant pathogen Ustilago maydis and their modulating effects on multidrug-resistant (MDR) tumors

Three new purine-derived compounds were isolated from Ustilago maydis. Compounds 4-7 (5 μM) overcame the multidrug-resistance (MDR) with the reversal fold (RF) values ranging from 1.56 to 2.68 for K562/A02 cells, respectively, while compounds 1-3 were weakly active.