Abstract: Methods of using a compound, its pharmaceutically acceptable salts, and/or its pro-drug esters, in isolated form, to treat cancer, and methods for isolating, for formulating, and for administering the compound, salt, and/or pro-drug ester as an antitumor agent, wherein the compound, salt, or pro-drug ester has the following structure: wherein: R1, R2, R5, R7, and R8 are each separately selected from the group consisting of a hydrogen atom, a halogen atom, and saturated C1-C24 alkyl, unsaturated C1-C24 alkenyl, cycloalkyl, cycloalkenyl, alkoxy, cycloalkoxy, aryl, substituted aryl, heteroaryl, substituted heteroaryl, amino, substituted amino, nitro, substituted nitro, phenyl, and substituted phenyl groups, R3, R4, and R6 are each separately selected from the group consisting of a hydrogen atom, a halogen atom, and saturated C1-C12 alkyl, unsaturated C1-C12 alkenyl, cycloalkyl, alkoxy, cycloalkoxy, aryl, substituted aryl, heteroaryl, substituted heteroaryl, amino, substituted amino, nitro, and substituted