Tissue damage and cytotoxic effects of Tagetes minuta essential oil against Lucilia cuprina.

The blowfly Lucilia cuprina has great medico-sanitary and veterinary importance due to the ability of its larval form to develop in decaying organic matter, parasitizing vertebrates. Fly eradication is challenging and the essential oil (EO) of Tagetes minuta (TMEO) have been reported to have therapeutic properties. This study aimed to determine the activity of EO from the aerial parts of T. minuta against third instar larvae (L3) of L. cuprina. Groups of 20 L3 were placed on filter paper, which were impregnated with varying concentrations (0.19; 0.39; 0.79; 1.59; 2.38; 3.18; 4.77; and 6.36 µL/cm2) of TMEO solubilized in acetone, ethanol or Tween 20. Histological tissue damage of TMEO was measured in L3 after 24, 48 and 96 h of exposure. Dihydrotagetone (67.64%), trans-ocimene (16.23%), trans-tagetone (10.14%) and verbenone (2.98%) were obtained as major compounds of TMEO. Lethal concentrations of 50%, 24 and 48 h after TMEO exposure were 1.02 and 0.73 µL/cm2 for acetone; 3.37 and 1.75 µL/cm2 for ethanol; and 7.46 and 6.11 µL/cm2 for Tween 20, respectively. TMEO had a significant L3 mortality of 96.6% in acetone, 48 h after contact. Cuticle abnormalities were observed, as well as the loss of digestive tract architecture and vacuolization in fat bodies. TMEO presented time and concentration-dependent effects against L. cuprina. As our study demonstrated a strong insecticide activity of TMEO, we consider that it could be developed into an ecofriendly product against L. cuprina.

Seasonal variation of vegetative growth, essential oil yield and composition of menthol mint genotypes at southern Brazil / Variação sazonal do crescimento vegetativo, produtividade e composição de óleo essencial em genótipos de menta no sudeste brasileiro

Menthol has economic importance to the flavor, food and pharmaceutical industries. Ten menthol mint (Mentha spp) genotypes were assessed for essential oil content and composition at Southern Brazil environmental conditions at two harvest times (February and May). The experimental design was in completely randomized blocks with a 10 x 2 factorial for genotypes and harvest time. The essential oil was obtained by hydrodistillation in a Clevenger apparatus. The essential oil content varied from 0.8 to 5.3% and was greater in February for all the investigated genotypes. The main constituents identified in the essential oil samples were menthol (12 - 92.7%), mentone (2.2 - 56.9%), and neomenthol (2.9 - 12.1%). Menthol levels were superior in May and showed a negative correlation with mentone and neomenthol, which in turn were higher in February. Menthol levels were positively correlated with menthyl acetate. Pulegone, 1.8 cineol, and limonene were also detected in lower concentrations in some genotypes. Thirteen other essential oil constituents were identified as trace elements in essential oil. Mentha canadensis L. showed the highest essential oil content (5.3 % - February and 3.5% - May) as well as the highest menthol content (89.6% - February, 92.7% - May) in both harvests. From the analyzed results, Southern Brazil local environmental conditions are appropriated for menthol production, with two harvests and M. canadensis L. can be recommended as a promising genetic source. The summer harvest (February) favored oil yield, although with a slight decrease in menthol content. The challenge of achieving higher essential oil and menthol yields depends on strategies to increase herb yield by developing innovative agronomic practices.

O mentol, constituinte majoritário do óleo essencial de menta é usado nas indústrias farmacêutica, alimentícia e de aromas. Onze genótipos de Mentha sp. foram estudados em relação ao desenvolvimento vegetativo, rendimento, produtividade e composição de óleo essencial nas condições edafoclimáticas do litoral Norte Catarinense, em duas épocas (fevereiro e maio). O trabalho foi conduzido em delineamento experimental de blocos ao acaso, em esquema fatorial 10 x 2 para genótipos e épocas de colheita. A extração do óleo essencial foi realizada por hidrodestilação em aparelho graduado Clevenger. O teor de óleo essencial variou entre 0,8 e 5,3%, sendo maior em fevereiro para todos os genótipos. Os constituintes majoritários identificados foram mentol (12 ­ 92,7%), mentona (2,2 ­ 56,9%), e neomentol (2,9 ­ 12,1). Os maiores teores de mentol foram observados em maio, apresentando correlação negativa com mentona e neomentol, os quais foram superiores em fevereiro. Os teores de acetato de metila apresentaram correlação positiva com os de mentol. Pulegona, 1,8 cineol, e limoneno foram identificados em menores concentrações e outros treze constituintes foram detectados como elementos traço em alguns genótipos. Mentha canadensis L. apresentou os maiores teores de óleo essencial, (5,3 % - Fevereiro e 3,5% - Maio) e mentol (89,6% - Fevereiro, 92,7% - Maio) em ambas as colheitas. Os resultados obtidos permitem concluir que as condições edafoclimáticas do litoral Norte Catarinense são adequadas para a produção de mentol, com duas colheitas, recomendando-se o genótipo M. canadensis L. A colheita de verão (fevereiro) favorece a produtividade de óleo essencial reduzindo o teor de mentol. O desafio para aumentar a produtividade de óleo essencial e de mentol depende de estratégias que aumentem a produção de biomassa através do desenvolvimento de práticas agronômicas inovativas.