Effect of isoxazole derivatives of tetrahydrofuran neolignans on intracellular amastigotes of Leishmania (Leishmania) amazonensis: A structure-activity relationship comparative study with triazole-neolignan-based compounds.

Isoxazole analogues derived from the neolignans veraguensin, grandisin, and machilin G were previously synthesized with different substitution patterns through the bioisosterism strategy. These compounds were tested on intracellular amastigotes of Leishmania (Leishmania) amazonensis; the derivatives proved to be active against intracellular amastigotes, with IC50 values ranging from 0.4 to 25 µM. The most active analogues were 4', 14', 15', and 18', with IC50 values of 0.9, 0.4, 0.7, and 1.4 µM, respectively, showing high selectivity indexes (SI = 277.0; 625.0; 178.5 and 357.1). Overall, the isoxazole analogues did not induce nitric oxide (NO) production by infected cells; there was no evidence that NO influences the antileishmanial mechanism of action, except for compound 4'. Trimethoxy groups as substituents seemed to be critical for antileishmanial activity. The SAR study demonstrated that the isoxazole compounds were more active than 1,2,3-triazole compounds with the same substitution pattterns, demonstrating the importance of the bioisosterism strategy in drug design.

Antiproliferative Activity of Extracts of Campomanesia adamantium (Cambess.) O. Berg and Isolated Compound Dimethylchalcone Against B16-F10 Murine Melanoma.

Campomanesia adamantium, a native species of the Brazilian Cerrado, is characterized as a natural source of phenolic compounds and has known potential anticancer activities. This study aimed to evaluate the chemical profile of dichloromethane extracts of pulp (DEGPU) and peel (DEGPE) from the fruits of C. adamantium and to identify compounds with antiproliferative effects in vitro against melanoma cells by sulforhodamine B (SRB) assay, apoptosis induction assay, caspase-3 activation assay, nitric oxide (NO) release in coculture of B16-F10 cells and murine peritoneal macrophages. The chemical profiles of DEGPU and DEGPE were analyzed by high performance liquid chromatography coupled to diode array detector and mass spectrometer using the electrospray ionization interface (HPLC-DAD-ESI-MS/MS). Thirteen compounds were identified in both extracts and the chromatographic study of the most active extract in SRB assay DEGPU (GI50 of 16.17 µg/mL) resulted in the isolation of seven compounds. The isolated compound dimethylchalcone (DMC) had the highest antiproliferative activity against B16-F10 with a GI50 of 7.11 µg/mL. DEGPU extract activated caspase-3 in 29% of cells at 25 µg/mL and caused a 50% decrease in NO release in coculture. DEGPU can be characterized as a source of bioactive compounds such as DMC, as seen from its antiproliferative effect in vitro by inducing B16-F10 cells to undergo apoptosis, essential feature in the search for new anticancer drugs.

Antileishmanial Activity and Structure-Activity Relationship of Triazolic Compounds Derived from the Neolignans Grandisin, Veraguensin, and Machilin G.

Sixteen 1,4-diaryl-1,2,3-triazole compounds 4-19 derived from the tetrahydrofuran neolignans veraguensin 1, grandisin 2, and machilin G 3 were tested against Leishmania (Leishmania) amazonensis intracellular amastigotes. Triazole compounds 4-19 were synthetized via Click Chemistry strategy by 1,3-dipolar cycloaddition between terminal acetylenes and aryl azides containing methoxy and methylenedioxy groups as substituents. Our results suggest that most derivatives were active against intracellular amastigotes, with IC50 values ranging from 4.4 to 32.7 µM. The index of molecular hydrophobicity (ClogP) ranged from 2.8 to 3.4, reflecting a lipophilicity/hydrosolubility rate suitable for transport across membranes, which may have resulted in the potent antileishmanial activity observed. Regarding structure-activity relationship (SAR), compounds 14 and 19, containing a trimethoxy group, were the most active (IC50 values of 5.6 and 4.4 µM, respectively), with low cytotoxicity on mammalian cells (SI = 14.1 and 10.6). These compounds induced nitric oxide production by the host macrophage cells, which could be suggested as the mechanism involved in the intracellular killing of parasites. These results would be useful for the planning of new derivatives with higher antileishmanial activities.

In vitro anti-Leishmania infantum activity of essential oil from Piper angustifolium

Abstract Piper angustifolium Lam., Piperaceae, popularly known as "matito", "pimenta-de-macaco", "pimenta-longa" or "jagurandi" in Brazil, has been commonly used in the treatment of cutaneous leishmaniasis-associated lesions, but there are few studies on the activity against visceral leishmaniasis-associated species. This study demonstrates the first in vitro antileishmanial activity of the P. angustifolium essential oil, of which the phytochemical profile showed the presence of sesquiterpenes and monoterpenes. The main compounds were spathulenol (23.8%) and caryophyllene oxide (13.1%). P. angustifolium essential oil was highly active [the half maximum inhibitory concentration = 1.43 μg/ml] against intracellular amastigotes of Leishmania infantum, the etiological agent of visceral leishmaniasis in the New and Old World. Activity was obtained 24 h after addition of the oil (6.25–50 μg/ml), with a reduction of 100% in the infection index at concentrations of 25 and 50 μg/ml. P. angustifolium essential oil showed low cytotoxicity for mammalian fibroblasts and macrophages (the half maximum inhibitory concentration values of 31.67 and 48.22 μg/ml, respectively), and it was 33 and 22 times more toxic to amastigotes than to mammalian cells, as indicated by selectivity indexes. The results demonstrated that P. angustifolium essential oil is a promising alternative for the study of potential drugs for visceral leishmaniasis.