75 and 43.5 mg/ml ( Macedo et al., 2009). Ocimum gratissimum essential oil inhibited 100% egg hatching at concentration of 0.5% ( Pessoa et al., 2002). Croton zehntneri and Lippia sidoides essential oils inhibited egg hatching in more than 98% at 1.25 mg/ml and larval development in over 98% INCB024360 cell line at 10 mg/ml ( Camurça-Vasconcelos et al., 2007). Chenopodium ambrosioides essential oil inhibited 100% egg hatching at 1.33 μl/ml ( Ketzis et al., 2002). The LC50 of Eucalyptus staigeriana essential oil in the EHA was 0.324 mg/ml and LC50 in the LDA was 1.702 mg/ml ( Macedo et al., 2010). Those values are higher in comparison to our results that showed LC50 in EHA of 0.04; 0.26 and 0.13 mg/ml and LC50 in LDA of 0.06; 0.26 and 0.15 mg/ml

to C. schoenanthus, M. piperita and C. martinii essential oils, respectively. Terpenes are a chemical class of chemicals found in essential oils. C. schoenanthus had approximately 20 constituents, being rich in geraniol, geranial, and neral. Terpenoid compounds are known to be active against a range of organisms and the synergy of several terpenoids can be effective on several targets because they are a complex mixture of compounds that can interact with multiple molecular targets on various developmental stages of the parasite ( Marie-Magdeleine et al., 2009). So, it is quite reasonable to Apoptosis Compound Library nmr consider that the major constituents of

each plant species, as detected by gas chromatography, had some biological activity in vitro against trichostrongylids in the present study. Because geraniol was the main component in both Cymbopogon species, all which had better anthelmintic effects than Mentha (devoid of geraniol), we can hypothesize that geraniol might be of potential interest for in vivo tests. However, the concentration of geraniol does not preclude the potential synergistic effect of geranial and neral, present at higher concentrations in C. schoenanthus, the essential oil with the best anthelmintic activity. The insolubility of essential oils and many of their constituents in aqueous media is likely to impair their performance in susceptibility tests,

and attempts to overcome this problem have been made by using tensio-active agents such as Tween 20 and Tween 80 (Juven et al., 1994). Although Tween 80 has low toxicity to nematodes (4.79% inhibition hatchability and 3.23% inhibition exsheathment) compared to Tween 20, it caused toxicity on LFIA and LDA assays. DMSO, which is less toxic to L1 larvae than Tween 80, was used for both LFIA (14.53% inhibition feeding activity) and LDA (12.35% inhibition development). Those solvents can work as bioenhancers, as they have the ability to increase the bioavailability of drugs by increasing their transport across membranes, increasing anthelmintic effect. Thus, the type and concentration of solvents required to make an emulsion should be considered before tests are performed. Depending on the organism, the solvents can be highly lethal.