Antifungal Activity of 2-Allylphenol Derivatives on the Botrytis cinerea Strain: Assessment of Possible Action Mechanism.

Botrytis cinerea is a phytopathogenic fungus that causes serious damage to the agricultural industry by infecting various important crops. 2-allylphenol has been used in China as a fungicide for more than a decade, and it has been shown that is a respiration inhibitor. A series of derivatives of 2-allylphenol were synthesized and their activity against B. cinerea was evaluated by measuring mycelial growth inhibition. Results indicate that small changes in the chemical structure or the addition of substituent groups in the aromatic ring induce important variations in activity. For example, changing the hydroxyl group by methoxy or acetyl groups produces dramatic increases in mycelial growth inhibition, i.e., the IC50 value of 2-allylphenol decreases from 68 to 2 and 1 µg mL-1. In addition, it was found that the most active derivatives induce the inhibition of Bcaox expression in the early stages of B. cinerea conidia germination. This gene is associated with the activation of the alternative oxidase enzyme (AOX), which allows fungus respiration to continue in the presence of respiratory inhibitors. Thus, it seems that 2-allylphenol derivatives can inhibit the normal and alternative respiratory pathway of B. cinerea. Therefore, we believe that these compounds are a very attractive platform for the development of antifungal agents against B. cinerea.

Synthesis and In Vitro Growth Inhibition of 2-Allylphenol Derivatives Against Phythopthora cinnamomi Rands.

Phytophthora cinnamomi is a phytopathogen that causes extensive damage in different crops, and therefore, produces important economic losses all around the world. Chemical fungicides are a key factor for the control of this disease. However, ecological and environmental considerations, as well as the appearance of strains that are resistant to commercial fungicides, have prompted the quest for new antifungal agents which are of low ecological impact. In this work, a series of new 2-allylphenol derivatives was synthesized, and their structures were confirmed by FT-IR, NMR, and MS. Some of the synthesized compounds, more specifically nitro derivatives, exhibit strong growth inhibition of P. cinnamomi with EC50 as low as 10.0 µg/mL. This level of activity is similar to that exhibited by METALAXYL MZ 58 WP, a commonly-used commercial fungicide; therefore, these compounds might be of agricultural interest due to their potential use as fungicides against P. cinnamomi. The results indicate that this activity depends on the chemical structures of the 2-allylphenol derivatives, and that it is strongly enhanced in molecules where nitro and hydroxyl groups adopt a -para configuration. These effects are discussed in terms of the electronic distribution of the aromatic ring induced by substituent groups.

Antifungal Activity of Eugenol Derivatives against Botrytis Cinerea.

Botrytis cinerea is a worldwide spread fungus that causes the grey mold disease, which is considered the most important factor in postharvest losses in fresh fruit crops. Consequently, the control of gray mold is a matter of current and relevant interest for agricultural industries. In this work, a series of phenylpropanoids derived from eugenol were synthesized and characterized. Their effects on the mycelial growth of a virulent and multi-resistant isolate of B. cinerea (PN2) have been evaluated and IC50 values for the most active compounds range between 31⁻95 ppm. The antifungal activity exhibited by these compounds is strongly related to their chemical structure, i.e., increasing activity has been obtained by isomerization of the double bond or introduction of a nitro group on the aromatic ring. Based on the relationship between the fungicide activities and chemical structure, a mechanism of action is proposed. Finally, the activity of these compounds is higher than that reported for the commercial fungicide BC-1000 that is currently employed to combat this disease. Thus, our results suggest that these compounds are potential candidates to be used in the design of new and effective control with inspired natural compounds of this pathogen.

Effect of drimenol and synthetic derivatives on growth and germination of Botrytis cinerea: Evaluation of possible mechanism of action.

The aim of this study was to determine the antifungal activity of Drimenol (1) and its synthetic derivatives, nordrimenone (2), drimenyl acetate (3), and drimenyl-epoxy-acetate (4), and to establish a possible mechanism of action for drimenol. For that, the effect of each compound on mycelial growth of Botrytis cinerea was assessed. Our results showed that compounds 1, 2, 3 and 4 are able to affect Botrytis cinerea growth with EC50 values of 80, 92, 80 and 314ppm, respectively. These values suggest that the activity of these compounds is mainly determined by presence of the double bond between carbons 7 and 8 of the drimane ring. In addition, germination of B. cinerea in presence of 40 and 80ppm of drimenol is reduced almost to a half of the control value. Finally, in order to elucidate a possible mechanism by which drimenol is affecting B. cinerea, the determination of membrane integrity, reactive oxygen species production and gene expression studies of specific genes were performed.