The effect of purified extract of Fagopyrum esculentum (buckwheat) on protein kinases involved in signal transduction pathways.

The effect of a purified extract of the flowering herb of Fagopyrum esculentum (buckwheat) on various protein kinases involved in signal transduction was examined. We observed that buckwheat contains red fluorescent compounds having photosensitizing properties. Spectrophotometric analysis of the extract has indicated structural similarity to hypericin. Dose- and light-dependent inhibition of various protein kinases was observed. The purified buckwheat extract strongly inhibited two receptor-associated protein tyrosine kinases (EGF-R and Ins-R) and a Ser/Thr kinase (PK-C) at an ng/ml concentration range. Selectivity was exhibited as a decreased sensitivity to cytosolic PTKs and protein kinase CK-2. The protein kinases are important components of the signal transduction pathway. Aberration of signal transduction is a hallmark of several proliferative diseases. Our results indicate that photosensitizing compounds in buckwheat are potential antiproliferative agents.