Evaluation of Phytotoxic and Cytotoxic Effects of Prenylated Phenol Derivatives on Tomato Plants (Solanum lycopersicum L.) and Botrytis cinerea B-05 Spores

The phytopathogenic fungus <i>Botrytis cinerea</i>, which causes gray mold disease, has become a limiting factor on agricultural production. <i>B. cinerea</i> field control is made mainly using chemical fungicides, which has led to the spreading of resistant populations of this fungus. Thus, the quest of new fungicides molecules has been focused on synthesis of natural product-inspired compounds. The main aim of this work is to synthesize prenylated phenol derivatives and to assess their potential application as antifungal agents with minimal phytotoxic effects. Thus, new prenylphenols (<b>4</b>, <b>5</b>, and <b>7</b>) have been obtained by microwave irradiation with yields ranging from 2.4% to 42.9%, whereas compounds <b>8</b> and <b>9</b> were synthesized with yields of 25.6% and 54.1%, respectively. The effect of different concentrations of these compounds on <i>B. cinerea</i> spore germination, and their phytotoxic effect on tomato (<i>Solanum lycopersicum</i> L.) seed germination and root growth, were evaluated. Obtained results indicate that biological activities of all tested compounds are concentration-dependent. Interestingly, compound <b>7</b> exhibits the highest antifungal activity against <i>B. cinerea</i> spores (IC₅₀ < 50 µg/mL) with minimal phytotoxicity on tomato seed germination and root growth. In contrast, compounds <b>2</b> and <b>3</b> are active against spores (IC₅₀ = 461 and 325 µg/mL, respectively) but, at the same time, their phytotoxicity is important at the highest concentrations. These results indicated that the presence of hydroxyl and methyl substituents on the aromatic ring of these compounds induces variations in biological activities, and compound <b>7</b> could be a promising candidate as a sporicidal agent.