A relatively stable antifungal peptide from buckwheat seeds with antiproliferative activity toward cancer cells.

An antifungal peptide with a molecular mass of approximately 4 kDa was isolated from buckwheat seeds by using ion-exchange chromatography on SP-Sepharose and Q-Sepharose, and gel filtration on Superdex peptide. The peptide was adsorbed on SP-Sepharose in 10 mM NH(4)OAc buffer (pH 4.5) and on Q-Sepharose in 10 mM NH(4)HCO(3) buffer (pH 9.4), and appeared to be highly purified after these two steps. It inhibited mycelial growth in Fusarium oxysporum and Mycosphaerella arachidicola with an IC(50) of 35 and 40 microM, respectively. Its antifungal activity was stable between 0 and 70 degrees C, and between pH 1.0/2.0 and 13. It inhibited proliferation of Hep G2 (hepatoma) cells, L1210 (leukemia) cells, breast cancer (MCF-7) cells, and liver embryonic WRL 68 cells with an IC(50) of 33, 4, 25, and 37 microM, respectively. On the other hand, the peptide was unable to evoke a mitogenic response from splenocytes or induce nitric oxide production by macrophages. It inhibited HIV-1 reverse transcriptase with an IC(50) of 5.5 microM.