Essential oils of Lippia gracilis and Lippia sidoides chemotypes and their major compounds carvacrol and thymol: nanoemulsions and antifungal activity against Lasiodiplodia theobromae

Abstract

The aim of this work was to evaluate the antifungal activity of essential oils (EOs) of Lippia gracilis and Lippia sidoides accessions, their major compounds and nanoemulsions. Nanoemulsions with 18% of EO or major compound were produced by spontaneous emulsification method. The EO of two L. gracilis accessions (LGRA-106 and LGRA-109) and two L. sidoides accessions (LSID-102 and LSID-104) were extracted by hydrodistillation and the major compounds thymol and carvacrol were purchased commercially. Antifungal activity was tested against Lasiodiplodia theobromae by calculating the percentage of inhibition of mycelial growth caused by different concentrations (0.1, 0.5, 1.0, 5.0, and 10.0 mL.L-1), in relation to the control. The EOs and their respective nanoemulsions presented as major compounds thymol (LGRA-106: 61.84% and Nano-106: 63.43%; LSID-102: 64.07% and Nano-102: 83.03%) or carvacrol (LGRA-109: 54.56% and Nano-109: 45.63%; LSID-104: 69.06% and Nano-104: 38.66%). Nano-104 presented 35.91% of an unidentified compound. The fungicidal activity of the EOs was similar to that of the major compounds, with a minimum fungicidal concentration of 1.0 mL.L-1 for LGRA-106, LSID-102 as well as for thymol, and 0.5 mL.L-1 for LGRA-109, LSID-104 as well as for carvacrol. The nanoemulsions were only able to reduce the mycelial growth of the fungus except for Nano-104 that exhibited fungicidal activity at the concentration of 10 ml.L-1. It was possible to observe that the EOs exhibited greater toxicity against L. theobromae than the nanoemulsions. These results can help in the development of products for the control of this important phytopathogen.

Antifungal Activity of Thymol against Aspergillus awamori and Botrytis aclada Isolated from Stored Onion Bulbs

“…Essential oils from various host plants have been tested against several plant pathogens because plant-derived essential oils exhibit environmentally friendly control characteristics [ 17 , 18 , 20 , 35 ]. In a previous study, Rasooli et al.…”

“…Recently, De Melo et al. [ 35 ] reported that essential oils of Lippia gracilis and Lippia sidoides exhibited significant, antifungal activity against Lasiodiplodia theobromae , the causal fungus of diplodia pod rot of cocoa.…”

Chemical composition of the essential oil of Eucalyptus genotypes susceptible or resistant to the gall-forming wasp Leptocybe invasa Fisher & La-Salle, 2004 (Hymenoptera: Eulophidae)

“…Separations were performed on a Rtx ® -5MS Restek (5%-diphenyl-95%-dimethylpolysiloxane) fused silica capillary column (30 m x 0.25 mm i.d. x 0.25 µm film thickness), Helium as carrier gas at a constant flow of 1.0 mL min -1 [17].…”

“…Molecules in the GC/MS were ionized by electron ionization at 70 eV. Fragments were analyzed by a quadrupole system programmed to filter fragments/ions at m/z from 40 to 500 Da and detected by an electron multiplier [17].…”

Condições ambientais e horário da coleta influenciam na produção do óleo essencial das folhas de Lippia sidoides no litoral cearense

“…Suas folhas e flores formam a fração medicinal desta planta. Utilizado de diferentes formas e contendo até 4,5% de óleo essencial (OE) abundante em timol e carvacrol, o alecrim-pimenta apresenta fortíssima atividade antimicrobiana e antifúngica (Matos;Lorenzi, 2008;Monteiro et al, 2020;Melo et al, 2022).…”