Letícia Teixeira Nunes

In vitro growth-inhibitory effect of Brazilian plants extracts against Paenibacillus larvae and toxicity in bees

American foulbrood (AFB) is a serious worldwide spreading disease in bees caused by Paenibacillus larvae. Plants extracts are known to decrease or inhibit the growth of these bacteria. The purpose of this study was to evaluate the antimicrobial activity of Calendula. officinalis, Cariniana domestica, and Nasturtium officinale extracts against the P. larvae and to evaluate the toxicity of the extracts in bees. In vitro activity against P. larvae of the extracts was evaluated by micro dilution method and the minimal inhibitory concentrations (MICs) were also determined. The concentrations used in the toxicity test were established based on the MIC values and by the spraying application method. The P. larvae was susceptible to the evaluated crude extract of C. officinalis and N. officinale. To C. domestica, only the ethyl acetate (EtAc) fraction and n-butanol (BuOH) fractions had activity against P. larvae. Toxicity analysis in bees showed no toxicity for N. officinale crude extract and for C. domestica BuOH fraction during 15 days of treatment, however, some deaths of bees occurred during the first three days of treatment with C. officinalis and C. domestica EtAc fraction. The results with these species were firstly described and showed that N. officinale crude extract and C. domestica BuOH fraction both presented not toxic effects in the concentration tested by the spraying application method, and can be a useful alternative for treatment or prevention of AFB.

Chemical Composition, Antioxidant and Antimicrobial Activities of the Essential Oil of Scutia buxifolia Reissek Leaves

The chemical composition, antioxidant and antibacterial activities of essential oil isolated by hydrodistillation from the leaves parts of Scutia buxifolia were evaluated. The chemical composition was analyzed by gas chromatography (GC-FID) and gas chromatography-mass spectrometry (GC-MS). Twenty-five substances were identified, consisting of a complex mixture of sesquiterpenes (73.69%) and monoterpenes (18.74%). The main components in the oil were spathulenol (27.09%), β-cubebene (11.26%), germacrene D (9.81%), carvacrol (7.01%), globulol (5.36%), α-copaene (4.17%), γ-eudesmol (3.59%), thymol (3.27%), 1,8-cineol (3.08%), p-cymene (2.56%), α-eudesmol (2.34%), β-elemene (2.04%), butylated hydroxytoluene (2.00%) along with eugenol acetate, n-hexanol, α-pinene, α-humulene, eugenol, humulene epoxide, phytol as minor constituents. The antioxidant property of the oil was assessed by free radical scavenging (DPPH) assay. S. buxifolia essential oil presented interesting radical scavenging activity (IC50=13.62 ± 0.17 μg/mL). The antibacterial properties of the oils also was tested by broth microdilution method and was effective only against S. aureus and E. coli (MIC=500 and 750 μg/mL, respectively). To the best of our knowledge, this is the first study of the composition, antioxidant and antimicrobial activities of essential oil from the S. buxifolia collected from Brazil.

Potential Use of Buddleja Thyrsoides for the Control and Prevention of American Foulbrood Disease in Honey Bees

Abstract Paenibacillus larvae is the causative agent of American Foulbrood (AFB ), a severe disease that affects the larvae of the honeybees. The use of plant extracts are considered to be an alternative way of controlling the disease. In this study, the in vitro antimicrobial activity of Buddleja thyrsoides Lam. against the Paenibacillus species, including P. larvae, was evaluated. In Mueller-Hinton broth, the minimal inhibitory concentration (MI C) was assessed using the microdilution method. All Paenibacillus species were sensitive to the crude extract and the fractions of B. thyrsoides. The ethyl acetate (EA ) fraction showed a better result with MI C values of 1.68 - 3.36 mg/mL, followed by butanolic (BU) (MI C = 2.18 - 6.54 mg/mL), dichloromethane (DCM) (7.40 - 14.80 mg/mL), and crude extract (CE) (7.51 - 16.90 mg/mL). The toxic effect of the CE and fractions of B. thyrsoides against bees were also evaluated using the spraying application method with the same concentrations of MI Cs. Bee mortality was evident in treatment with DCM fractions only, while CE, EA , and BU extracts showed no toxic effects after 15 days of observation. Furthermore, phenolic acids, tannins, and flavonoids were identified and quantified by highperformance liquid chromatography (HPLC), and may be partially responsible for the antimicrobial properties observed. These results show, for the first time, that B. thyrsoides might be a natural alternative for the prevention/control of AFB .