pH Modulation of Zopfiellin Antifungal Activity to Colletotrichum and Botrytis

Zopfiellin, a novel cyclooctanoid natural product isolated from Zopfiella curvata No. 37-3, was evaluated in a 96-well microtiter assay for fungicidal activity against Botrytis cinerea, Colletotrichum acutatum, Colletotrichum fragariae, Colletotrichum gloeosporioides, and Fusarium oxysporum . Zopfiellin exhibited pH-dependent activity, with the most mycelial growth inhibition demonstrated at pH 5.0. Mass spectrometry and nuclear magnetic resonance spectroscopy studies indicated that zopfiellin undergoes structural changes with changes in pH. At pH 5.0, zopfiellin showed the greatest activity against B. cinerea (IC 80 = 10 μM), C . gloeosporioides (IC 80 = 10 μM), and C. fragariae (IC 80 = 10 μM) and intermediate activity against C. acutatum (IC 80 = 30 μM), and was not active against F. oxysporum (IC 80 > 100 μM). Keywords: Fungicide; natural products; zopfiellin; Zopfiella curvata; Botrytis cinerea; Colletotrichum acutatum; Colletotrichum fragariae; Colletotrichum gloeosporioides; Fusarium oxysporum