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O comportamento eletroquímico em função da estrutura de uma série de derivados dos ácidos cafeico e ferúlico, assim como de seus precursores catecol e guaiacol, eletroquimicamente ativos, foi avaliado por voltametria cíclica. Os resultados revelaram que as condições experimentais são a chave para as mudanças no mecanismo de oxidação do guaiacol e ácido ferúlico. A oxidação eletroquímica dos derivados amida do ácido ferúlico revelou que o átomo de nitrogênio desempenha um papel importante na derivatização da superfície do eletrodo. Além disso, a atividade sequestradora de radicais dos compostos, avaliada através da porcentagem de inibição do radical 2,2'-difenil-1-picril-hidrazila, mostrou uma boa correlação com os potenciais de oxidação.We studied the electrochemical behaviour as a function of the structure of a series of caffeic and ferulic acids derivatives as well as their corresponding redox moieties catechol and guaiacol by cyclic voltammetry. Results revealed that the medium is key for changes in the oxidation mechanism of guaiacol and ferulic acid. Electrochemical oxidation of the ferulic acid amide derivatives revealed that the nitrogen atom plays an important role in the derivatization of the electrode surface. In addition, radical scavenging activity of the compounds evaluated through the percentage of inhibition of the 2,2'-diphenyl-1-picrylhidrazyl radical showed a good relationship with the oxidation potentials.

Biocontrol traits of arbuscular mycorrhizal fungi (AMF), in terms of single and mixed species inoculum, against the root knot nematode Meloidogyne incongita in Impatiens balsamina L., were examined with and without mineral fertilization in a greenhouse pot experiment. At harvest, 60 days after sowing, general plant growth parameters and plant defense response in terms of antioxidant activity and content of phenolic compounds in roots and leaves were measured. Also AMF root colonization and abundance of nematode root-knots were determined. Mineral fertilization increased all plant growth parameters measured, which coincided with an increased disease development caused by M. incognita. Inoculation with AMF mitigated the observed plant growth reduction caused by M.incognita, though, higher abundance of M. incognita root knots was found in mycorrhizal plants. Plant defense responses in terms of antioxidant activity and content of phenolic compounds did not seem to be linked to the observed biocontrol traits of AMF against M. incognita. However, roots inoculated with a consortium of AMF, which presented less nematode root knots than roots with the single species inoculum, had the highest level of phenolic compounds. The results from the present study suggest that AMF induce tolerance in I. balsamina against the root knot nematode M. incognita.

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