Elicited cell suspension cultures of apple (Malus x domestica) cv. Liberty produce biphenyl phytoalexins

Yeast extract treated cell suspension cultures from a scab (Venturia inaequalis) resistant apple cultivar, Malus x domestica cv. Liberty produce dibenzofuran and biphenyl compounds as part of their defense system against fungal invasion. We have isolated and identified three biphenyl derivatives, 4-hydroxy-3,5-dimethoxybiphenyl (aucuparin), 2',4,-dihydroxy-3,5- dimethoxybiphenyl (2'-hydroxy-aucuparin) and 2'-O-β-D-glucopyranosyl-4- hydroxy-3,5-methoxybiphenyl (2'-o-β-D-glucopyranosylaucuparin) from the cells and the medium and show here their chemical properties. Although this is the first identification of 2'-glucopyranosylaucuparin, its aglycone, 2'- hydroxyaucuparin, and aucuparin have been reported previously [Kokubun, T., Harborne, J.B., Phytochemistry, 1995, 40, 1649-1654.] from fungus infected wood of Malus species. Production of an array of dibenzofuran and biphenyl derivatives in response to fungal attack may be an important part of the disease resistance mechanism of scab resistant apple cultivars.