Antimicrobial activity of Larrea divaricata alkaloids against olive tree pathogens

BOITEUX, JOANA; FERNÁNDEZ, MARÍA DE LOS ANGELES; ESPINO, MAGDALENA; LUCERO, GABRIELA; SILVA, MARÍA FERNANDA

Simposio; LACE 2017; 2017

Larrea divaricata Cav. (Zygophyllacea) is a perennial woody shrub with a wide distribution in Argentina. In folk medicine, different L. divaricata preparations have been used as antiinflammatory, antirheumatic, dysphoretic, amenagogic and antimicrobial agents.Phytochemical studies have reported the presence of phenolic compounds, such as flavonoids, simple phenols and phenolic acids. In particular, the alkaloids remain undescribed. Alkaloids are versatile heterocyclic nitrogen compounds with reported antimicrobial activity against fungal and bacterial phytopathogens. In this work the alkaloids present in L. divaricata extract were determined by HPLC-MWD and their antimicrobial activity was evaluated against Phytophthora palmivora, P. nicotianae and P. citrophthora. The compounds studied were piperine, theophylline, theobromine, harmaline, caffeine and nicotine. The extraction of alkaloids was performed by a miniaturized solid phase extraction using a homemade minicolumn packed with suitable filtering material (C18, 50 mg).Antimicrobial activity of the extract and their alkaloids were assessed using the agar diffusion method against P. palmivora, P. nicotianae and P. citrophthora. Among the alkaloids evaluated, piperine was detected in L. divaricata extract. Antimicrobial activity assay demonstrated that Phytophthora sp. miceliar growth was inhibited completely by the extract at 5 %. On the other hand, piperine at the concentration found in the extract achieved an inhibition between 74-79 % of the pathogens growth. The results reveal that L. divaricata extract has an outstanding activity against Phytophthora sp. due mainly to the presence of piperine. This extract could be considered as a potential alternative to the use of fungicides in the control of olive tree pathogens.