Plant essential oils (EOs) can potentially replace synthetic fungicides in the management of postharvest fruit and vegetable diseases. The aim of this study was to evaluate in vitro and in vivo effectiveness of thymol, carvacrol, linalool, and trans-caryophyllene, single constituents of the EO of Origanum vulgare L. ssp. hirtum against Monilinia laxa, M. fructigena, and M. fructicola, which are important phytopathogens and causal agents of brown rot of pome and stone fruits in pre- and postharvest. Moreover, the possible phytotoxic activity of these constituents was assessed and their minimum inhibitory concentration (MIC) was determined. In vitro experiment indicated that thymol and carvacrol possess the highest antifungal activity. Results of in vivo trials confirmed the strong efficacy of thymol and carvacrol against brown rot of peach fruits. The thymol MIC resulted to be 0.16 μg/μL against M. laxa and M. fructigena and 0.12 μg/μL against M. fructicola, whereas for carvacrol they were 0.02 μg/μL against the first two Monilinia species and 0.03 μg/μL against the third. Results of this study indicated that thymol and carvacrol could be used after suitable formulation for controlling postharvest fruit diseases caused by the three studied Monilinia species.

Three novel mixed ligand metal complexes have been synthesized by the reaction of Zn(II), Sn(II), and Ce(III) with gemifloxacin (GMFX) in the presence of glycine (Gly) (1:1:1 molar ratio). The coordination possibility of the two ligands toward metal ions has been proposed in the light of elemental analysis, molar conductance, spectral infrared (IR), ultraviolet-visible (UV-Vis) and proton-nuclear magnetic resonance (¹H NMR), and magnetic studies. Results suggest that GMFX and Gly interact with the metal ions as bidentate ligands. Electronic and magnetic data proposed the octahedral structure for all complexes under investigation. Antibacterial screening of the compounds was carried out in vitro against two Gram-positive bacteria, Clavibacter michiganensis and Bacillus megaterium, and two Gram-negative bacteria, Escherichia coli and Xanthomonas campestris. Antifungal activity was performed in vitro against Rhizoctonia solani, Sclerotinia sclerotiorum, Aspergillus niger, Botrytis cinerea, and Penicillium digitatum. The ligands and their complexes were also screened for their antioxidant activity. Results showed that some metal complexes showed more biological efficiency than the parent GMFX drug.

Bacillus mojavensis is an endophytic bacterium which has been reported to have fungicidal effect against some phytopathogens. Bioactive secondary metabolites produced by B. mojavensis could have promising applications in agricultural, food industry and clinical fields. The current research has been conducted to: i) evaluate the antagonistic effect of B. mojavensis isolate against some phytopathogens; ii) characterize chemically the principal bioactive substances produced by the studied isolate of B. mojavensis using Gas Chromatography-Mass Spectroscopy (GC-MS); iii) evaluate its ability to produce a biofilm using ELISA technique. Results showed that the studied isolate has an antagonistic activity against the majority of tested microorganisms. Results showed also that the studied isolated produced a biofilm in Supplemented Luria-Bertani Casamino acid (SLB) and Minimal Mineral (MM) medium. The substantial attached growth in SLB was significantly higher than MM media. GC-MS analysis revealed the presence of 9 compounds accounting 87.8% of the total extract, where oxygenated monoterpenes are the main constituents.

Pomegranate (Punica granatum L.) fruits are important sources of vitamins and minerals and widely used in the dietary supplement industry. An aqueous extract of its leathery exocarp (LEP) was obtained by a solid-phase micro-extraction method. The antifungal activity was examined against the phytopathogenic fungi, Fusarium oxysporum, Phytophthora cinnamomi, Penicillium digitatum and Botrytis cinerea, and the antibacterial activity was evaluated against Escherichia coli, Xanthomonas campestris,Bacillus megaterium and Clavibacter michiganensis. The antimicrobial assays showed, in some cases, a promising antimicrobial effect compared to the synthetic drugs. The possible anti-acetylcholinesterase and antioxidant activities of the LEP extract were investigated by the Ellman’s assay and 2,2-diphenyl-1-picrylhydrazyl (DPPH) test, respectively, and their results showed that the LEP extract has an effective anti-acetylcholinesterase inhibitory effect and an antioxidant activity. Thus, the LEP extract could be valid as a candidate for further studies on the use of pomegranate in neurodegenerative diseases as a food preservative and a suitable substitute to control several phytopathogens.

There is a great interest in discovering new microbial natural biocides such as microbial secondary metabolites to reduce the environmental pollution due to the excessive use of synthetic pesticides. Verticillium wilt, caused by the soil-borne Verticillium dahliae, is a widespread disease in tomato growing in many parts of the world. Burkholderia gladioli pv. agaricicola produces some antimicrobial substances and extracellular hydrolytic enzymes which exhibited promising antimicrobial activity towards several phytopathogens. The aims of the current research are to assess in vitro fungicidal effect of 4 strains of B. gladioli pv. agaricicola (ICMP11096, 11097, 12220 and 12322) against V. dahliae using culture or cell-free culture filtrate. In situ assay was performed to evaluate the biocontrol effect of the most efficient bacterial strain on wilt disease caused by V. dahliae in tomato plants. Results demonstrated that the studied bacterial strain ICMP12322 exerted the highest in vitro antifungal activity against V. dahliae which correlated with its ability to produce extracellular hydrolytic enzymes. Furthermore, in situ results showed that the selected bacterial strain significantly minimized the disease incidence.

There is a growing interest in essential oils (EOs) as possible alternatives for traditional chemical pesticides. This study was carried out to characterize the chemical composition of the three EOs extracted from Verbena officinalis, Majorana hortensis, and Salvia officinalis using gas chromatography (GC) and GC-mass spectrometry (GC-MS) and to evaluate in vitro their efficacy against some phyto or human pathogens. The antifungal activity was investigated against Colletotrichum acutatum and Botrytis cinerea in comparison with Azoxystrobin as a large spectrum fungicide. Antibacterial activity was evaluated against Bacillus megaterium, Bacillus mojavensis, and Clavibacter michiganensis (G+ve) and Escherichia coli, Xanthomonas campestris, Pseudomonas savastanoi, and P. syringae pv. phaseolicola (G−ve) compared to a synthetic antibiotic tetracycline. Minimum inhibitory concentration was evaluated against the above tested fungi using 96-well microplate method. Results showed that the chemical structure of the three studied EOs was mainly composed of monoterpene compounds and all oils belong to the chemotype carvacrol/thymol. Results of GC analysis identified 64 compounds, which were identified based on their mass to charge ratio. Furthermore, the different concentrations of studied EOs inhibited the growth of tested microorganism in a dose-dependent manner.