Mentha villosa Hubs., M. x piperita and their bioactives against gastrointestinal nematodes of ruminants and the potential as drug enhancers.

Parasitic diseases caused by gastrointestinal nematodes (GIN) are responsible for a major impact on ruminant welfare. Although the available anthelmintics have a safe margin of toxicity to the animals, their indiscriminate use has increased the selection of resistant parasite populations. In this scenario, essential oils (EO) stand out as a promising ecofriendly therapeutic alternative against GIN. The objective of this work was to determine the effect of the EO of Mentha villosa Hubs (MVEO) collected in 2017 and 2018, M. x piperita (MPEO) and their main components, carvone and limonene, against the third stage larvae (L3) of Haemonchus spp. and Trichostrongylus spp. The solutions, including in nanoemulsion preparations, were tested in a range of concentrations using the larval migration inhibition test (LMIT). The EO and carvone were also tested in combination with nitroxynil (NTX) to determine their effect as drug enhancers (additive or synergy). MVEO/2017, MVEO/2018, MPEO and carvone showed 70.6 (73.4 mg/mL), 86.3 (74.9 mL/mL), 95.5 (143.6 mg/mL), and 88.2 % (38.3 mg/mL) efficacy against L3, respectively. Carvone alone had approximately a 3-fold higher efficacy when compared to its concentration in each EO: 68.8 % in MVEO/2017 and 83.9 % in MVEO/2018. Limonene did not show any significant effect on inhibiting L3 migration. The combination of MPEO and NTX, and carvone and NTX showed a statistically significantly (P <  0.05) synergic and additive effect, respectively, when compared to the isolated treatment. The nanoemulsion of MVEO/2017 at 0.367 mg/mL, inhibited L3 migration by 83.1 %, demonstrating to be highly effective (concentration ratio of 1:0.004), when compared to the MVEO/2017 (70.6 % at 73.4 mg/mL) extraction. The in vitro data from the combination of MPEO or carvone plus NTX suggest that these products can be considered for in vivo experiments against the most important GIN of ruminants as drug enhancers, possibly reducing the final concentration of NTX`. The efficacy of carvone was higher (EC50 = 1.96 mg/mL) than its expected efficacy, based on its concentrations on both EO. Therefore, this component does not need the entire EO composition to exert its L3 motility action. The remarkable efficacy demonstrated by the MVEO/2017/nanoemulsion (EC50 = 0.10 mg/mL), supports its potential to be a candidate to the next-generation therapy to alleviate clinical parasite infections and combat GIN resistant populations.

Antiparasitic effect of Mentha × villosa hydrolate against monogenean parasites of the Nile tilapia / Efeito antiparasitário do hidrolato de Mentha × villosa contra parasitas monogenéticos para Tilápia-do-nilo

ABSTRACT: This paper o evaluated different concentrations and exposure times of Mentha × villosa hydrolate for the control of monogeneans in Nile tilapia (Oreochromis niloticus). Mentha × villosa leaves (150 g) were homogenized and the hydrolate was obtained by hydrodistillation for 4 h in a Clevenger apparatus. Fifty tilapia were then divided into ten groups (five fish each) and subjected to therapeutic baths for 15 minutes in five different hydrolate concentrations (0, 10, 20, 40, and 80 ml.L-1;× 2 replicates). After a suitable hydrolate concentration was identified, another 50 tilapia were divided into ten groups (five fish each) and subjected to therapeutic baths at the identified hydrolate concentration for five different durations (0, 15, 30, 45, and 60 minutes;× 2 replicates). In both steps, the mucus and gills were analyzed to determine parasitological indices. The hydrolate concentration of 20 ml.L-1 showed an efficacy of 59.9% and the biggest decrease in pathogen prevalence, average abundance, and average infection compared to the control and the lowest concentration (10 ml.L-1). For duration, the best antiparasitic effects were achieved with the 60-minute therapeutic bath, as it resulted in 89.28% antiparasitic efficacy. Therefore, it was concluded that therapeutic baths of M. × villosa hydrolate at a concentration of 20 ml.L-1 for 60 minutes have satisfactory antiparasitic effects and could be used to control monogenetic infestations in the gills and mucus of Nile tilapia (O. niloticus).

RESUMO: Este trabalho teve como objetivo avaliar diferentes concentrações e tempos de exposição do hidrolato de Mentha × villosa para o controle de monogenéticos em Tilápia-do-nilo (Oreochromis niloticus). Folhas de Mentha × villosa (150 g) foram homogeneizadas e o hidrolato foi obtido por hidrodestilação por 4 h em aparelho de Clevenger. Em seguida, 50 tilápias foram divididas em dez grupos (cinco peixes cada) e submetidas a banhos terapêuticos por 15 minutos em cinco diferentes concentrações de hidrolato (0, 10, 20, 40 e 80 ml.L-1; × 2 repetições). Após a identificação de uma concentração de hidrolato adequada, outras 50 tilápias foram divididas em dez grupos (cinco peixes cada) e submetidas a banhos terapêuticos na concentração de hidrolato identificada por cinco durações diferentes (0, 15, 30, 45 e 60 minutos; × 2 repetições). Em ambas as etapas, o muco e as guelras foram analisados para determinar os índices parasitológicos. A concentração de hidrolato de 20 ml.L-1 apresentou eficácia de 59,9% e a maior redução na prevalência do patógeno, abundância média e infecção média em relação ao controle e a menor concentração (10 ml.L-1). Para a duração, os melhores efeitos antiparasitários foram alcançados com o banho terapêutico de 60 minutos, uma vez que resultou em 89,28% de eficácia antiparasitária. Portanto, concluiu-se que banhos terapêuticos de hidrolato de M. × villosa na concentração de 20 ml.L-1 por 60 minutos têm efeitos antiparasitários satisfatórios e podem ser usados para controlar infestações monogenéticas nas brânquias e muco da Tilápia-do-nilo (O. niloticus).

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.

Insecticide activity of Baccharis dracunculifolia essential oil against Cochliomyia macellaria (Diptera: Calliphoridae).

The ethnobotanical uses of Brazilian plants for different injuries and diseases conjoined with local rich biodiversity represent an important resource for research and development. This study aimed to characterise BDEO and its in vitro activity on the third instar larvae (L3) of Cochliomyia macellaria. Groups of 20 L3 were placed on filter paper impregnated with increasing concentrations of 5-30% (v/v), equivalent to 0.79-4.77 µL/cm2, solubilised in ethanol or acetone. The major constituents of BDEO were ß-pinene (9.94%), D-limonene (9.59%), ß-nerolidol (7.93%), caryophyllene (7.69%), spathulenol (6.69), α-muurolene (6.74%) and α-pinene (5.31%). Lethal concentrations of 50% for BDEO on C. macellaria (LC50) after 24 and 48 h of exposure were 2.63 and 2.47 µL/cm2 for ethanol and 9.58 and 8.11 µL/cm2 for acetone, respectively. Furthermore, larvae cuticle abnormalities and adult deformity were observed. Our data confirm the effectiveness of BDEO as an ecofriendly product against blowflies.