Antileishmanial Effects of Acetylene Acetogenins from Seeds of Porcelia macrocarpa (Warm.) R.E. Fries (Annonaceae) and Semisynthetic Derivatives.

As part of our continuous studies involving the prospection of natural products from Brazilian flora aiming at the discovery of prototypes for the development of new antiparasitic drugs, the present study describes the isolation of two natural acetylene acetogenins, (2S,3R,4R)-3-hydroxy-4-methyl-2-(n-eicos-11'-yn-19'-enyl)butanolide (1) and (2S,3R,4R)-3-hydroxy-4-methyl-2-(n-eicos-11'-ynyl)butanolide (2), from the seeds of Porcelia macrocarpa (Warm.) R.E. Fries (Annonaceae). Using an ex-vivo assay, compound 1 showed an IC50 value of 29.9 µM against the intracellular amastigote forms of Leishmania (L.) infantum, whereas compound 2 was inactive. These results suggested that the terminal double bond plays an important role in the activity. This effect was also observed for the semisynthetic acetylated (1a and 2a) and eliminated (1b and 2b) derivatives, since only compounds containing a double bond at C-19 displayed activity, resulting in IC50 values of 43.3 µM (1a) and 23.1 µM (1b). In order to evaluate the effect of the triple bond in the antileishmanial potential, the mixture of compounds 1 + 2 was subjected to catalytic hydrogenation to afford a compound 3 containing a saturated side chain. The antiparasitic assays performed with compound 3, acetylated (3a), and eliminated (3b) derivatives confirmed the lack of activity. Furthermore, an in-silico study using the SwissADME online platform was performed to bioactive compounds 1, 1a, and 1b in order to investigate their physicochemical parameters, pharmacokinetics, and drug-likeness. Despite the reduced effect against amastigote forms of the parasite to the purified compounds, different mixtures of compounds 1 + 2, 1a + 2a, and 1b + 2b were prepared and exhibited IC50 values ranging from 7.9 to 38.4 µM, with no toxicity for NCTC mammalian cells (CC50 > 200 µM). Selectivity indexes to these mixtures ranged from >5.2 to >25.3. The obtained results indicate that seeds of Porcelia macrocarpa are a promising source of interesting prototypes for further modifications aiming at the discovery of new antileishmanial drugs.

Antitrypanosomal Activity of Acetogenins Isolated from the Seeds of Porcelia macrocarpa Is Associated with Alterations in Both Plasma Membrane Electric Potential and Mitochondrial Membrane Potential.

As part of a drug discovery program aimed at the identification of anti- Trypanosoma cruzi metabolites from Brazilian flora, four acetogenins (1-4) were isolated from the seeds of Porcelia macrocarpa and were identified by NMR spectroscopy and HRESIMS. The new compounds 1 and 2 displayed activity against the trypomastigote (IC50 = 0.4 and 3.6 µM) and amastigote (IC50 = 23.0 and 27.7 µM) forms. The structurally related known compound 3 showed less potency to the amastigotes, with an IC50 value of 58 µM, while the known compound 4 was inactive. To evaluate the potential mechanisms for parasite death, parameters were evaluated by fluorometric assays: (i) plasma membrane permeability, (ii) plasma membrane electric potential (ΔΨp), (iii) reactive oxygen species production, and (iv) mitochondrial membrane potential (ΔΨm). The results obtained indicated that compounds 1 and 2 depolarize plasma membranes, affecting ΔΨp and ΔΨm and contributing to the observed cellular damage and disturbing the bioenergetic system. In silico studies of pharmacokinetics and toxicity (ADMET) properties predicted that all compounds were nonmutagenic, noncarcinogenic, nongenotoxic, and weak hERG blockers. Additionally, none of the isolated acetogenins 1-4 were predicted as pan-assay interference compounds.

Structurally Related Monoterpenes p-Cymene, Carvacrol and Thymol Isolated from Essential Oil from Leaves of Lippia sidoides Cham. (Verbenaceae) Protect Mice against Elastase-Induced Emphysema.

BACKGROUND: Chronic obstructive pulmonary disease (COPD) is characterized by irreversible airflow obstruction and inflammation. Natural products, such as monoterpenes, displayed anti-inflammatory and anti-oxidant activities and can be used as a source of new compounds to COPD treatment. Our aim was to evaluate, in an elastase-induced pulmonary emphysema in mice, the effects of and underlying mechanisms of three related natural monoterpenes (p-cymene, carvacrol and thymol) isolated from essential oil from leaves Lippia sidoides Cham. (Verbenaceae). METHODS: Mices received porcine pancreatic elastase (PPE) and were treated with p-cymene, carvacrol, thymol or vehicle 30 min later and again on 7th, 14th and 28th days. Lung inflammatory profile and histological sections were evaluated. RESULTS: In the elastase-instilled animals, the tested monoterpenes reduced alveolar enlargement, macrophages and the levels of IL-1ß, IL-6, IL-8 and IL-17 in bronchoalveolar lavage fluid (BALF), and collagen fibers, MMP-9 and p-65-NF-κB-positive cells in lung parenchyma (p < 0.05). All treatments attenuated levels of 8-iso-PGF2α but only thymol was able to reduced exhaled nitric oxide (p < 0.05). CONCLUSION: Monoterpenes p-cymene, carvacrol and thymol reduced lung emphysema and inflammation in mice. No significant differences among the three monoterpenes treatments were found, suggesting that the presence of hydroxyl group in the molecular structure of thymol and carvacrol do not play a central role in the anti-inflammatory effects.