Synthesis of Linear Geranylphenols and Their Effect on Mycelial Growth of Plant Pathogen Botrytis cinerea

Abstract

Natural geranyl compounds are known to exhibit important biological activities. In this work a series of geranylphenols were synthesized to evaluate their effect on the mycelial growth of Botrytis cinerea. Geranyl derivatives were synthesized by direct geranylation reactions between the corresponding phenol derivatives and geraniol, using BF 3 . OEt 2 as catalyst and AgNO 3 as secondary catalyst. Previously reported molecules [geranylhydroquinone (2), geranylhydroquinone diacetate (6) and geranylphloroglucinol (9)], and new substances [(E)-4-(3,7-dimethylocta-2,6-dienyl)benzene-1,2,3-triol (geranylpyrogallol, 7), (E)-4-(3,7-dimethylocta-2,6-dienyl)benzene-1,2,3-triyl triacetate (8), (E)-2-(3,7-dimethylocta-2,6-dienyl)benzene-1,3,5-triyl triacetate geranylphloroglucinol triacetate (10), 2,4-bis((E)-3,7-dimethylocta-2,6-dienyl)benzene-1,3,5-triyl triacetate (11), 2,6-bis((E)-3,7-dimethylocta-2,6-dienyl)-3,5-dihydroxyphenyl acetate (12)], were obtained. All compounds were characterized by IR, HRMS and NMR spectroscopic data. The inhibitory effect of the synthesized compounds on the mycelial growth of Botrytis cinerea was tested in vitro. Excepting compound 11, all substances constrained the mycelial growth of Botrytis cinerea. The antifungal activity depends on the chemical structure of geranylphenol derivatives. Compounds 2 and 9 were the more effective substances showing inhibition degrees higher than those obtained with the commercial fungicide Captan, even at lower concentrations. Monosubstitution on the aromatic nucleus by a geranyl chain seems to be OPEN ACCESSMolecules 2014, 19 1513 more effective for the inhibition of mycelial growth than a double substitution. These results suggest that the new derivatives of geranylphenols have the ability to block the mycelial development of the plant pathogen B. cinerea and that this capacity depends strongly on the structural features and lipophilicity of the compounds.

Antiphytopathogenic activity ofPsoralea glandulosa(Fabaceae) againstBotrytis cinereaandPhytophthora cinnamomi

“…Furthermore, the semi-synthetic derivatives bakuchiol acetate (5) and bakuchiol methyl eter (6) obtained from bakuchiol were not active against P. cinnamomi; in addition, only compound 5 decreased the mycelial growth of B. cinerea up to 57% at a concentration of 150 mg/L, as reported by Espinoza et al (2014). The antifungal activity is assumed to be associated with the presence of strong electrophilic or nucleophilic systems; other authors have supported this hypothesis, since the presence of free hydroxyl groups in the aromatic ring increases biological activity against mycelial growth of fungus tested in vitro (Bajwa et al 2007).…”

Synthesis and in Vitro Antifungal Activity against Botrytis cinerea of Geranylated Phenols and Their Phenyl Acetate Derivatives

“…This reaction was chosen, between many different synthetic pathways for obtaining prenylated compounds [ 1 , 11 , 12 , 13 , 14 ], because it has been previously used to synthesize a series of synthetic analogs of 3-demethylubiquinone ( 3 ) having one, two, or three methoxy groups in different positions of the quinone moiety [ 6 ]. Alternatively, the reaction was also carried out in acetonitrile instead of dioxane, using AgNO 3 as a secondary catalyst [ 9 ]. The results indicate that both yields and products depend on the solvent.…”

“…In a previous work, we have found that the inhibitory effect of Captan changed more deeply with concentration, i.e. , 40%, 60% and 80% at 50, 150 and 250 mg/L, respectively [ 9 ]. Both sets of experiments were carried out under the same conditions and, therefore, this remarkable difference is difficult to explain.…”

“…Based on these antecedents, we have undertaken a study of the effect of a series of geranylphenols on the mycelial growth inhibition of plant pathogen Botrytis cinerea as a function of molecular structure [ 9 ]. This knowledge might be useful to design and synthesize new substances to control such kinds of pathogens.…”

Cytotoxic Effect of Geranylphenol Derivatives in the Human Breast Cancer Cell Line MDA-MB-231 and Gastric Cancer Cell Line MKN74

“…Other synthetic geranylphenols, such as 2-geranyl-5methyl resorcinol and 4-geranyl-5-methyl resorcinol ( Figure 1A), showed antimicrobial and antifungal activities [16][17][18][19] . Recently, our research group has developed the synthesis, structural determination and antifungal activity of a series of linear geranylphenols derivatives of 2-geranylhydroquinones, such 2-geranylphloroglucinol ( Figure 1A) [20][21][22][23][24][25][26] .…”