José Eduardo Gonçalves

Antifungal activity, yield, and composition of Ocimum gratissimum essential oil

Ocimum gratissimum L. or clove basil, belongs to the Lamiaceae family, has various desirable uses and applications. Beyond its aromatic, seasoning, and medicinal applications, this plant also has antimicrobial activity. This study was aimed at assessing the antifungal activity, yield, and composition of the essential oil (EO) of O. gratissimum. The species was cultivated in garden beds with dystrophic red latosol soil type containing high organic-matter content. The EO was obtained by hydrodistillation of dried leaves in a modified Clevenger apparatus, followed by determination of its content. Chemical characterization was carried out by gas chromatography-mass spectrometry (GC-MS). Microbial activity was assessed using the broth microdilution method, by determining the minimum inhibitory concentration (MIC), in order to compare the antimicrobial effect of EO in 10 isolates-Fusarium oxysporum f. sp tracheiphilum (CMM-0033), F. oxysporum f. sp. cubense (CMM-0813 and CMM-2819), F. oxysporum f. sp lycopersici (CMM-1104), F. solani (CMM-3828), Rhizoctonia solani (CMM-3274), and Macrophomina phaseolina (CMM-2715, CMM-3875, CMM-3615, and CMM-3650). The EO was a highly effective inhibitor of the studied phytopathogenic fungi, with MICs varying from 31.25 to 125 µg/mL. F. oxysporum f. sp lycopersici and R. solani were the most sensitive; both were inhibited at an MIC of 31.25 µg/mL. The EO content in the plant extract was 0.18%. Thirty chemical compounds were detected via GC-MS, with linalool (32.9%) being the major compound followed by 1,8-cineole (21.9%), both oxygenated monoterpenes. It can be concluded that clove basil EO is a highly effective antifungal agent, and therefore, a potential alternative for the control of plant pathogenic diseases.

Larvicidal activity against Aedes aegypti of essential oil of Laurus nobilis leaves obtained at different seasons

Abstract Aedes aegypti is a mosquito and vector of dengue, chikungunya and Zika virus making it a serious global health problem. We aimed to evaluate the chemical composition of the essential oil (EO) of Laurus nobilis leaves obtained at different seasons and its A. aegypti larvicidal activity. The EO was obtained from fresh leaves by hydrodistillation. Larvicidal activity was determined by the larval immersion test. It was identified 37 EO chemical compounds and the major ones were 1,8-cineole and linalool. Seasonal variations affected EO larvicidal activity: spring LC50 was 0.41 mg/mL and LC99 0.77 mg/mL, autumn LC50 was 0.60 mg/mL and LC99 1.37 mg/mL, winter LC50 was 0.66 mg/mL and LC99 3.19 mg/mL and summer LC50 was 0.91 mg/mL and LC99 2.50 mg/mL. The EO extracted during spring showed the highest larvicidal activity on A. aegypti larvae. Our results present a new perspective of L. nobilis EO use as a larvicidal agent.

Antifungal activity of Gallesia integrifolia fruit essential oil

Gallesia integrifolia (Phytolaccaceae) is native to Brazil and has a strong alliaceous odor. The objective of this study was to identify the chemical composition of G. integrifolia fruit essential oil and evaluate fungicidal activity against the main food-borne diseases and food spoilage fungi. The essential oil was extracted by hydrodistillation and identified by GC–MS. From 35 identified compounds, 68% belonged to the organosulfur class. The major compounds were dimethyl trisulfide (15.49%), 2,8-dithianonane (52.63%) and lenthionine (14.69%). The utilized fungi were Aspergillus fumigatus, Aspergillus niger, Aspergillus ochraceus, Aspergillus versicolor, Penicillium funiculosum, Penicillium ochrochloron, Penicillium verrucosum var. cyclopium, and Trichoderma viride. Minimal fungicidal concentration for the essential oil varied from 0.02 to 0.18 mg/mL and bifonazole and ketoconazole controls ranged from 0.20 to 3.50 mg/mL. The lower concentration of the essential oil was able to control P. ochrochloron, A. fumigatus, A. versicolor, A. ochraceus and T. viride. This study shows a high fungicidal activity of G. integrifolia fruit essential oil and can support future applications by reducing the use of synthetic fungicides.

Antimicrobial activity and chemical composition of Brunfelsia uniflora flower oleoresin extracted by supercritical carbon dioxide

Brunfelsia genus is traditionally utilized in popular medicine due to its antibacterial and antifungal properties to name but a few. However, studies on the antimicrobial activity of Brunfelsia uniflora flower oleoresin have not been found yet. This study aimed to evaluate the chemical composition and antimicrobial activity of B. uniflora flower oleoresin obtained by supercritical carbon dioxide. Oleoresin from the plant dried flowers was obtained by carbon dioxide, and the chemical composition was analyzed by gas chromatographic-mass spectrometry. The minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and minimum fungicidal concentration (MFC) of this oleoresin for seven bacteria and eight fungi were determined using 96-well microtiter plates. The oleoresin MBC for Bacillus cereus, Enterobacter cloacae, Escherichia coli, Listeria monocytogenes, Pseudomonas aeruginosa, Salmonella enterica, and Staphylococcus aureus ranged from 0.01 to 0.08 mg/mL, whereas the controls streptomycin and ampicillin varied from 0.1 and 0.5 mg/mL. The oleoresin MFC for Aspergillus fumigatus, Aspergillus niger, Aspergillus ochraceus, Aspergillus versicolor, Penicillium funiculosum, Penicillium ochrochloron, Penicillium verrucosum var. cyclopium, and Trichoderma viride varied from 0.01 to 0.08 mg/mL, whereas the controls bifonazole and ketoconazole ranged from 0.2 to 3.5 mg/mL. The oleoresin obtained by supercritical carbon dioxide presented bacteriostatic, bactericidal, fungistatic, and fungicidal activities that were higher than the positive controls streptomycin, ampicillin, bifonazole, and ketoconazole. The high antimicrobial activity was related to the high content of (E, E)-geranyllinalool that composes 21.0% of the oleoresin and a possible synergic action with fatty acid esters that made up 50.5% of the oleoresin. The oleoresin antimicrobial activity against common multiresistant bacteria in severe infectious processes as P. aeruginosa or against toxin-producing fungi such as P. ochrochloron or fungi that are difficult to control such as T. viride suggests the development of promising applications of this product in the food, farming, livestock, and pharmaceutical industry.