The defensive secretions of five neotropical species of harvestmen (Opiliones: Gonyleptidae) from the Brazilian Atlantic Forest were analyzed and chemically characterized by GC-MS and NMR methods. Three of the species, Cobania picea, Roweria virescens, and Serracutisoma proximum, secrete a mixture of 2,3-dimethyl-1,4-benzoquinone and 2-ethyl-3-methyl-1,4-benzoquinone. The secretions produced by the other two species, Iporangaia pustulosa and Neosadocus maximus, contain 1-hepten-3-one, 5-methyl-1-hexen-3-one, and 1-(6-butyl-3,4-dihydro-2H-pyran-2-yl)pentanone (1) as major components, as well as 2,3-dimethyl-1,4-benzoquinone and 2-ethyl-3-methyl-1,4-benzoquinone as minor constituents. The dihydropyran 1-(6-butyl-3,4-dihydro-2H-pyran-2-yl)pentanone (1) is a new natural product, composed of two 1-hepten-3-one subunits formally linked in a hetero-Diels-Alder reaction. The natural product was proven to be racemic, and its biogenetic origin is discussed.

Four species of gonyleptid harvestmen, Acanthogonyleptes pulcher, Gonyleptes saprophilus (Gonyleptinae), Sodreana barbiellini, and Sodreana leprevosti (Sodreaninae), were examined by GC-MS and ¹³H NMR. All of these species release vinyl ketones, and three of them produce the corresponding pyranyl ketones, which are presumed hetero-Diels-Alder (HDA) dimers. The vinyl ketones 5-methyl-1-hexen-3-one, rac-4-methyl-1-hexen-3-one, and (S)-4-methyl-1-hexen-3-one were synthesized. Natural 4-methyl-1-hexen-3-one is present as a single stereoisomer and has the R-configuration. Vinyl ketone dimers (HDA dimers) were also observed in the scent gland exudate and characterized by HRMS, ¹³C NMR, and ¹H NMR chemical shifts of the pyranyl moiety.

Trypanosoma cruzi antioxidant enzymes are among the factors that guarantee parasite survival and maintain infection, enabling T. cruzi to cope with oxidative stress. Herein, the expression of cytosolic (TcCPx) and mitochondrial (TcMPx) tryparedoxin peroxidases was evaluated in tissue culture-derived trypomastigotes upon incubation with different concentrations of H(2)O(2). TcCPx expression slightly increased (5.4%) in cells submitted to 10 μM H(2)O(2) treatment when compared to the control, but decreased when higher H(2)O(2) concentrations (20-50 μM) were employed. Under these conditions, TcMPx expression increased (∼53%) with 10 μM-treatment compared to the control, followed by a reduction that reached ∼46% of the control when using the highest concentration tested. Interestingly, in the supernatant of the incubations, TcCPx, but not TcMPx, was detected, and its levels increased concomitantly with its decreased expression in the intracellular compartment. Our data show that peroxiredoxins in the tissue culture-derived trypomastigote can be modulated under oxidative stress and are present in higher amounts when compared to the epimastigote stage of T. cruzi. Additionally, due to the different expression patterns observed upon H(2)O(2)-treatment, each peroxiredoxin may play a distinct role in protecting the parasite under oxidative stress conditions.

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