Antifungal Resveratrol Derivatives Figure 3. Selected population charge distribution. Compound 1, top left, and its demethoxylated derivative (E)-4,5-dimethoxy,3-hydroxy-b-(2- furyl)-styrene, top right. Compound 3, 2nd group from top, left, and its demethoxylated derivative (E)-3-hydroxy-5-methoxy,b-(2-furyl)-styrene, 2nd group from top, right. Compound 2, 3rd group from top, left, and its demethoxylated derivative (E)-4-hydroxy,b-(2-furyl)-styrene, 3rd group from top, right. Geometry optimized molecular structure of piceatannol, bottom; some atomic separations are also included. doi:10.1371/journal.pone.0025421.g003 based on the higher antifungal activity of compound 3. Another potential mechanism based on quinone formation by laccases, upon hydroxyl formation, may be also expected. Hydrophobicity is also an important factor for effective fungicidal activity that can be evaluated through LogP values. Earlier studies found an apparently optimum hydrophobic effect for antifungal activity as molecules with high and low LogP value were less active [24–26]. In our study, molecules with a LogP value slightly higher than 4.0 showed higher antifungal activities against B. cinerea, compared to resveratrol (logP of 3.0). Table 1 confirms that the presence of two methoxy groups increases the hydropho- bicity of the compounds, compared to resveratrol, which suggests increased possibility of crossing, or at least interaction with, the fungal cytoplasmic membrane. Earlier studies to determine the target of pterostilbene on B. cinerea suggested that the endoplasmic reticulum and mitochon- drial membranes were affected [10]. Our studies with compound 3 show alteration of the plasma membrane after 6 h of incubation. Recently, it was shown that, in Saccharomyces cerevisiae, pterostilbene increased the gene expression involved in mitochondrial functions, drug detoxification and lipid metabolism significantly [27]. Our results show that, at low concentration, compound 3 does not affect the respiratory chain of B. cinerea conidia while at high concentration it could act as an uncoupler. That methoxylated stilbenes can react by other mechanisms, such as inhibition of cytochrome P450 enzymes or apoptosis induction, cannot be discarded. Pterostilbene inhibits human recombinant cytochrome P450, CYP1A1 and CYP1B1 [16], while PLoS ONE | www.plosone.org 4 October 2011 | Volume 6 | Issue 10 | e25421