The aim of our study was to produce and characterize poly-ε-caprolactone (PCL) nanospheres containing essential oils from Zanthoxylum riedelianum fruit and to evaluate their stability gains as well as their insecticidal and deterrent activities against whitefly (Bemisia tabaci). The PCL nanospheres exhibited a homogeneous spherical morphology, with particle diameters between 106.7 nm and 129.2 nm, pH of approximately 6, zeta potential (ZP) lower than −19.0 mV and encapsulation efficiency higher than 98%. Only 43% of the nanoencapsulated essential oil (NSEO) was degraded in response to ultraviolet light, whereas the essential oil (EO) degraded by 76% over the same period. In a free-choice test, the NSEO and EO reduced the number of whitefly eggs by approximately 70%. NSEO and EO at 1.5% killed 82.87% and 91.23% of 2nd-instar nymphs of whitefly, respectively. Although NSEO displayed lower insecticidal activity, it offers a greater advantage over the free EO, due to protection conferred by polymer against photodegradation. Therefore, its usage may optimize the maintenance of essential oils in the field through photoprotection and controlled release. Our results suggest that the EO of Z. riedelianum fruit can be used for B. tabaci management strategy; nevertheless, the benefits of NSEO require further evaluation at the field level.

Encapsulation via nanotechnology offers a potential method to overcome limited thermal and photo-stability of botanical pesticides. In this study, nanospheres of essential oils (NSEO) derived from Zanthoxylum rhoifolium Lam. fruit were characterized and evaluated for their photostability and insecticidal activity against Bemisia tabaci. Three major compounds of Z. rhoifolium fruits were detected by CG-MS: β-phellandrene (76.8%), β-myrcene (9.6%), and germacrene D (8.3%). The nanoprecipitation method was used to obtain homogeneous spherical NSEO, with ≥98% encapsulation efficiency. Tests with UV/Vis spectrophotometry showed significantly reduced photodegradation from exposed NSEO samples when compared with essential oil (EO) controls. Whitefly screenhouses bioassays with bean plants treated with 0.25, 0.5, 1 and 1.5% suspensions showed EO treatments in both free and nanoencapsulated forms reduced adult whitefly oviposition by up to 71%. In further tests, applications at 1.5% caused ≥64% mortality of second instar nymphs. When the test was conducted under high temperature and light radiation conditions, the insecticidal effect of NSEO treatments was improved (i.e., 84.3% mortality) when compared to the free form (64.8%). Our results indicate the insecticidal potential of EO-derived from Z. rhoifolium fruits with further formulation as nanospheres providing greater photostability and enhanced insecticidal activity against B. tabaci under adverse environmental conditions.

O gênero Ocimum da família Lamiaceae compreende um grupo de plantas bem conhecidas como Ocimum gratissimum L. (alfavaca) e Ocimum basilicum (manjericão). Estudos revelam que essas plantas apresentam atividade antimicrobiana, inseticida, antioxidante, antifúngica, analgésica e imunoestimulante. Neste contexto, o objetivo deste estudo foi analisar a composição química dos óleos essenciais de O. gratissimum e O. basilicum coletadas em diferentes horários e com diferentes tempos de extração, bem como, avaliar sua atividade antioxidante, o teor de fenólicos totais e atividade bactericida sobre Staphylococcus aureus e Escherichia coli. O óleo essencial foi obtido por hidrodestilação em aparelho tipo Clevenger, e a composição química realizada por cromatógrafo gasoso acoplado ao espectrômetro de massas (CG-EM); a análise da atividade antioxidante foi realizada em microplacas de 96 poços com adição de 2,2-difenil-1-picrilhidrazil (DDPH) em metanol; o teor de fenólicos totais foi realizado em microplacas de 96 poços utilizando Folin-Ciocalteu para determinação do teor de ácido gálico; e a atividade bactericida realizada por método de difusão de discos na placa de Petri e método de difusão em meio Muller-Hinton em placas de 96 poços. O maior rendimento do óleo essencial de O. gratissimum foi de 0,44%, quando coletado no período da manhã, enquanto o óleo essencial de O. basilicum teve rendimento de 0,38% quando coletado no período da tarde, ambos, com quatro horas de extração. Os compostos majoritários de O. gratissimum foram eugenol e eucaliptol, enquanto os compostos majoritários do óleo essencial de O. basilicum foram eugenol, β-linalool e muurolol. A atividade antioxidante foi de 100% de sequestro do radical livre DPPH nas maiores concentrações de óleo essencial 15,6 µg mL-1, tanto para O. gratissimum quanto O. basilicum. O teor de compostos fenólicos totais dos óleos essenciais de O. gratissimum e O. basilicum foi = 17,90 e 16,44 mg EAG 100 g-1, respectivamente. Os óleos essenciais de O. gratissimum e O. basilicum apresentaram 100% e 83% de atividade bactericida sobre Staphylococcus aureus e de 100% a 66% sobre Escherichia coli, respectivamente, destacando assim o potencial biotecnológico desses óleos essenciais.

The phytopathogenic fungi Sclerotinia sclerotiorum and Rhizopus stolonifer infect different crop plants. Essential oils have been used as an alternative to chemical control methods. Therefore, the objective of this study was to analyze the essential oil chemical composition of the stem bark of Zanthoxylum riedelianum (ZREO) and evaluate its antifungal potential. The ZREO obtained by hydrodistillation was analyzed using gas chromatography coupled to mass spectrometry and evaluated for in vitro antifungal activity. The major components identified in the chemical analysis were E-nerolidol (67.21%), α-selinene (14.94%), and β-selinene (7.41%). The antifungal potential of ZREO against S. sclerotiorum and R. stolonifer was detected at all concentrations evaluated in a dose-dependent manner. The best results were against R. stolonifer, with the concentration of 150 µLmL⁻¹ inhibiting more than 80% of mycelial growth. On the basis of the current knowledge, this study describes for the first time the chemical composition and their antifungal activity. GRAPHICAL ABSTRACT