Ultrastructural analysis of Leishmania infantum chagasi promastigotes forms treated in vitro with usnic acid

In Vitro Anthelminthic Activity and Ultrastructural Analysis of Barbatic Acid against Schistosomulae and Juvenile Worms of Schistosoma mansoni

Schistosomiasis affects about 260 million people worldwide and the search for new schistosomicidal compounds is urgent. In this study we evaluated the in vitro effect of barbatic acid against schistosomulae and young worms of Schistosoma mansoni. The barbatic acid was evaluated through the bioassay of motility and mortality, cellular viability and ultrastructural analysis of juvenile stages through Scanning Electron Microscopy. Barbatic acid showed a schistosomicidal effect against schistosomulae and young worms of S. mansoni after 3 h of exposure. At the end of 24 h, barbatic acid showed 100 %, 89.5 %, 52 % and 28.5 % of lethality for schistosomulae at the concentrations of 200, 100, 50 and 25 μM, respectively. For young worms, barbatic acid showed 100 % and 31.7 % of lethality at the concentrations of 200 and 100 μM, respectively. Motility changes were observed at all sublethal concentrations. There was a significant reduction in the viability of young worms after exposure to barbatic acid at 50, 100 and 200 μM. Extensive damage to the schistosomulae and young worm's tegument, was observed from 50 μM. This report provides data showing the schistosomicidal effect of barbatic acid on schistosomulae and young worms of S. mansoni, causing death, motility changes and ultrastructural damage to worms.

In vitro and in vivo Anti-leishmanial Potential of [Ag (PTA) 4 ]BF 4 and [Ag(HBPz 3 )(PPh 3 )] Silver Complexes

BACKGROUND

American tegumentary leishmaniasis is a parasitic disease known for being difficult to treat; therefore, the search for more effective therapeutic methods is necessary. The objective of this study was to evaluate the in vitro and in vivo antileishmanial activity of silver complexes [Ag(PTA)4]BF4 (Ag1) and [Ag(HBPz3)(PPh3)] (Ag2) against Leishmania (Leishmania) amazonensis [L. (L.) amazonensis] and Leishmania (Viannia) guyanensis.

METHODS

In vitro bioassays were performed to evaluate the activity of the complexes against promastigote and amastigote forms and evaluate their cytotoxicity. In vivo experiments were performed with hamsters (Mesocricetus auratus) infected and treated topically with two gels containing each metallic complex.

RESULTS

Both complexes reduced the number of viable parasites against the promastigote forms of L. (L.) amazonensis. Ag2 was mainly effective against the amastigote forms. The Ag2 complex did not present cellular cytotoxicity, and regarding the selectivity index, both complexes were considered acceptable, with Ag2 having the best selectivity index in murine peritoneal macrophages in relation to L. (L.) amazonensis. Ag2 showed better results in the topical treatment against infections caused by L. (L.) amazonensis, with a small reduction in the lesion volume after the 14th day of treatment and less parasitic load at the lesion site.

CONCLUSIONS

Ag2 was more effective than Ag1 against L. (L.) amazonensis.

The Natural Compound Hydrophobic Usnic Acid and Hydrophilic Potassium Usnate Derivative: Applications and Comparisons

Usnic acid is the best-studied lichen metabolite, presenting several biological activities, such as antibacterial, immunostimulating, antiviral, antifungal, anti-inflammatory, and antiparasitic agents; despite these relevant properties, it is a hydrophobic and toxic molecule. In this context, scientific research has driven the development of innovative alternatives, considering usnic acid as a source of raw material in obtaining new molecules, allowing structural modifications (syntheses) from it. The purpose is to optimize biological activities and toxicity, with less concentration and/or response time. This work presents a literature review with an analogy of the hydrophobic molecule of usnic acid with its hydrophilic derivative of potassium usnate, emphasizing the elucidation and structural characteristics, biological activities, and toxicological aspects of both molecules, and the advantages of using the promising derivative hydrophilic in different in vitro and in vivo assays when compared to usnic acid.

Antimicrobial and antioxidant activity of Evernia prunastri extracts and their isolates

Lichens are symbiotic organisms formed by a fungus and one or more photosynthetic partners which are usually alga or cyanobacterium. Their diverse and scarcely studied metabolites facilitate adaptability to extreme living conditions. We investigated Evernia prunastri (L.) Ach., a widely distributed lichen, for its antimicrobial and antioxidant potential. E. prunastri was sequentially extracted by hexane (Hex), dichloromethane (DCM) and acetonitrile (ACN) that were screened for their antioxidant and antimicrobial (against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli and Candida albicans) activities. The Hex extract possessed the highest antioxidant capacity (87 mg ascorbic acid/g extract) corresponding to the highest content of phenols (73 mg gallic acid/g extract). The DCM and Hex extracts were both active against S. aureus (MICs of 4 and 21 µg/ml, respectively) but were less active against Gram-negative bacteria and yeast. The ACN extract exhibited activity on both S. aureus (MIC 14 µg/ml) and C. albicans (MIC 38 µg/ml) and was therefore further fractionated by silica gel column chromatography. The active compound of the most potent fraction was subsequently characterized by 1H and 13C-NMR spectroscopy and identified as evernic acid. Structural similarity analyses were performed between compounds from E. prunastri and known antibiotics from different classes. The structural similarity was not present. Antioxidant and antimicrobial activities of E. prunastri extracts originate from multiple chemical compounds; besides usnic acid, most notably evernic acid and derivatives thereof. Evernic acid and its derivatives represent possible candidates for a new class of antibiotics.

In-vitro and In-vivo Antileishmanial Activity of a Compound Derived of Platinum, Oxaliplatin, against Leishmania Major

This study aimed to evaluate the antileishmanial efficacy of oxaliplatin against Leishmania major (L. major) both in-vitro and in-vivo. The IC50, CC50, and SI of oxaliplatin against promastigotes, murine macrophages, Raw 264.7 cells, and intramacrophage amastigotes of L. major were investigated in-vitro. The effects of this drug on intracellular amastigotes were also assayed, and the percentage of infectivity and IIR were calculated. Flow cytometry was performed to assay apoptosis, using 50 and 100 µg/mL of oxaliplatin in the promastigotes and macrophages. In-vivo, the BALB/c mice were classified into three groups, receiving oxaliplatin, glucantime, and phosphate-buffered saline for one month, respectively. The lesion size, IFN-γ, and IL-4 levels, and parasite burden were also evaluated in the animals. After 72 h, the IC50 and CC50 of oxaliplatin against promastigotes and macrophages were respectively 0.5 and 66.78 µg/mL. The apoptosis of promastigotes and macrophages using 50 µg/mL of oxaliplatin was 7.25% and 2.14%, respectively, while apoptosis induced at 100 µg/mL was 15.48% and 2.80%, respectively. Similar to the glucantime group, the mice treated with oxaliplatin showed a lower parasite burden and smaller lesions, compared with the PBS group (p < 0.01). Furthermore, higher IFN-γ levels were reported in mice receiving oxaliplatin in comparison with those receiving PBS (p < 0.01). The current findings indicated the efficacy of oxaliplatin against promastigote and amastigote forms of Leishmania and L. major-induced leishmaniasis.

Usnic acid causes apoptotic-like death in Leishmania major, L. infantum and L. tropica

Leishmaniasis, a deadly parasitic infection, threatens many people worldwide. Since the high cost, toxicity, and resistance are drawbacks of current treatment options, it is necessary to find safer and more effective new antileishmanial drugs. The aim of this study was to determine the antileishmanial activity of usnic acid and its apoptotic mechanism on Leishmania spp. promastigotes. The antileishmanial activity was evaluated by MTT assay and apoptosis-related gene expression was investigated by qRT-PCR. Usnic acid was to be effective against Leishmania major, L. infantum, and L. tropica promastigotes at IC₅₀ = 10.76 µg/ml, 13.34 µg/ml, and 21.06 µg/ml, respectively. We also demonstrated a novel mechanism by which usnic acid inhibited proliferation and caused apoptosis; usnic acid upregulated p53, Bax, Casp-3, and Casp-9 gene expression and downregulated the level of Bcl-2 gene expression. Accordingly, the expression level of the P53 gene increased in L. major, L. infantum and L. tropica by 14.4-, 11.8-, and 9.5-fold, respectively, and in contrast, the Bcl-2 gene expression decreased in all three leishmaniasis by 0.8-, 0.8-, and 0.7-fold, respectively. The present study, therefore, revealed that usnic acid played a critical role in the usnic acid-induced apoptotic process in Leishmania species. Usnic acid is easily accessible and an inexpensive agent, and can be considered as an alternative therapeutic agent for Leishmania infections subject to further tests in animal models.

Toxicity of Usnic Acid from Cladonia substellata (Lichen) to embryos and adults of Biomphalaria glabrata

This study reports the molluscicidal activity of usnic acid isolated from Cladonia substellata Vanio (lichen) on embryos at various stages of development and in adult mollusks of Biomphalaria glabrata. The toxicity of usnic acid was also evaluated through Artemia salina larvae mortality. Usnic acid was extracted with diethyl ether, isolated, purified, and its structure confirmed by analyzing the spectra of proton nuclear magnetic resonance. LC₉₀ for 24 h of exposure were 1.62, 4.45, 5.36, and 4.49 μg mL^-1 for blastula, gastrula, trocophore, and veliger embryonic stages, respectively, and 3.45 μg mL^-1 for adult snails; LC₅₀ of usnic acid against A. salina was 2.46 μg mL^-1. LC₉₀ assessed 7 days after exposure was 2.56 μg mL^-1 for adult mollusks. In conclusion, these findings demonstrate that under laboratory conditions usnic acid has teratogenic and molluscicide potential to control the aquatic snail B. glabrata and may prove to be a promising candidate in the search for new molluscicide agents, but further detailed studies on its molluscicidal effect and possible environmental effects are needed.