Atividade antimicrobiana do extrato de Punica granatum L. in vitro e in vivo contra cepas de bactérias fitopatogênicas

Abstract

Phytopathogenic bacteria constitute one of the main threats to agricultural production on a global scale. The use of synthetic agricultural and antimicrobial pesticides is a commonly strategy for the control of phythopathogens in agriculture. However, the indiscriminate use of these substances is related to problems such as contamination of soil and water, induction of bacterial resistance and toxic effects for humans and other animals. Medicinal plants with antimicrobial activity have been investigated as an effective component in integrated disease management. The products extracted from these plants have low or no phytotoxicity, fast biodegradation and a renewable source. Punica granatum L. is a plant known worldwide for different medicinal properties. This species presents several compounds with antimicrobial and antioxidant activity and is beneficial in the treatment of various pathologies. The aim this study was to investigate the antimicrobial activity of P. granatum fruit peel hydroalcoholic extract and Punicalagin compound on phytopathogenic bacteria isolates and its potential in the treatment of infected seeds as an alternative to the use of synthetic pesticides. In vitro assays consisted of the agar diffusion method (concentrations of 100; 50; 25; 1.25; 6.25; 3.125 mg/mL) and minimum inhibitory concentration with P. granatum crude extract (concentrations of 500; 250; 125; 62.5 ; 31.25 g/mL) and Punicalagin compound (250; 125; 62.5; 31.25 g/mL). Data were taken according to inhibition zone (mm), percentage of cell viability measurements and qualitative analysis of bacterial growth in culture plates with solid medium. In vivo assays included the treatment of Eruca vesicaria L. seeds artificially inoculated with X. campestris pv. campestris with crude extract of P. granatum (500 ug/mL and 250 ug/mL). The results indicate antimicrobial effect of P. granatum extract on the tested isolates (inhibition zone between 35,33±1.2 5,11±5.11 mm). Microdilution assays indicated bacteriostatic and bactericide effect of the extract with minimum inhibitory concentration (MIC) value of 125 ug/mL. The treatment of E. vesicaria seeds with P. granatum extract indicated beneficial effects such as inhibition of the disease symptoms caused by the pathogen, increase of the the germination percentage and seedling survival rate in relation to the control. These results supported the proposal of the bioproduct for the control of plant diseases based on the pomegranate peel extract described in the patent entitled: "COMPOSITION BASED ON POMEGRANATE (PUNICA GRANATUM L.) AND ITS USE AS A PESTICIDE AGAINST BACTERIAL PHYTOPATOGENS".