Large amount of oil cake is generated during
biodiesel production from Jatropha seeds. Although Jatropha oil cake is rich in plant nutrients, presence of toxic
phorbol esters restricts the usage of oil cake as a
fertilizer. The objective of this study is to evaluate the components and
tumor promoting activity of
phorbol esters in Jatropha oil cake-supplemented soil and plants grown in the treated soil. Contents and their
biological activity of Jatropha
phorbol esters in soil and plants were sequentially analyzed by high-performance liquid chromatography (HPLC) and in vitro cell transformation assay, respectively. Disappearance of Jatropha
phorbol-ester-specific peaks were followed with HPLC during incubation of Jatropha oil cake with soil for five weeks. Along with the degradation of Jatropha
phorbol ester in soil,
tumor-promoting activity in the sample was also attenuated and ultimately disappeared. Jatropha
phorbol esters and
tumor promoting activity were not detected from mustard spinach grown in the Jatropha oil cake-supplemented soil. In addition, the
esterase KM109 degrades DHPB (see definition below; Jatropha
phorbol ester) and reduced its
tumor-promoting activity. From these data, we conclude: (1) components and
tumor promoting activity of Jatropha
phorbol esters in the oil cake disappeared completely by incubation with soil for five-week, (2) Jatropha
phorbol esters did not transfer into plants grown in the Jatropha oil cake-supplemented soil, and (3) DHPB can be degraded by
esterase from soil bacterium. These observations are useful for utilization of Jatropha oil cake as a
fertilizer.