Synthesis and Antiplasmodial Evaluation of Analogues Based on the Tricyclic Core of Thiaplakortones A-D

Thiaplakortone B attenuates RANKL-induced NF-κB and MAPK signaling and dampens OVX-induced bone loss in mice

Osteoclasts play an important role in maintaining the relative stability of bone mass. Abnormal number and function of osteoclasts are closely related to osteoporosis and osteolytic diseases. Thiaplakortone B (TPB), a natural compound derived from the Great Barrier Reef sponge Plakortis lita, has been reported to inhibit the growth of the malaria parasite, Plasmodium falciparum, but its effect on osteoclastogenesis has not been previously investigated. In our study, we found that TPB suppresses the receptor activator of nuclear factor-κB (NF-κB) ligand (RANKL)-induced osteoclast formation and resorption activity by tartrate-resistant acid phosphatase (TRAcP) staining, immunofluorescence staining of F-actin belts and hydroxyapatite resorption assay. Furthermore, using quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting analysis, we discovered that TPB inhibits osteoclast-specific genes and proteins expression. Mechanistically, TPB blocks multiple upstream pathways including calcium oscillation, NF-κB, mitogen-activated protein kinase (MAPK) and nuclear factor of activated T cells 1(NFATc1) signaling pathways. In vivo, TPB could dampen bone loss in an ovariectomy (OVX) mouse model by micro-CT assessment and histological staining. Therefore, TPB may serve as a potential therapeutic candidate for the treatment of osteoporosis and osteolysis.

Regioselective and stereospecific synthesis of functionalized 3,4-dihydro-2H-1,4-thiazines by catalyst-free [3 + 3] annulation of pyridinium 1,4-zwitterionic thiolates and aziridines

An efficient route to 3,4-dihydro-2H-1,4-thiazines was developed though [3 + 3] annulation of pyridinium 1,4-zwitterionic thiolates and aziridines under catalyst-free conditions.

Synthesis and in vitro antileishmanial efficacy of novel benzothiadiazine-1,1-dioxide derivatives

Leishmaniasis is a major vector-borne parasitic disease that affects thousands of people in tropical and subtropical developing countries. In 2019 alone, it killed 26,000-65,000 individuals. Leishmaniasis is curable, yet its eradication and elimination are hampered by major hurdles, such as the availability of only a handful of clinical toxic drugs and the emergence of pathogenic resistance against them. This underscores the imperative need for new and effective antileishmanial drugs. In search for such agents, we synthesized and evaluated the in vitro antileishmanial potential of a small library of benzothiadiazine derivatives by assessing their activity against the promastigotes of three strains of Leishmania and toxicity in healthy cells. The derivatives were found to have no toxicity to the mammalian cells and were, in general, active against all parasites. The benzothiadiazine derivative 1e, 3-methyl-2-[3-(trifluoromethyl)benzyl]-2H-benzo[e][1,2,4]thiadiazine 1,1-dioxide, was found to be the most active (IC₅₀ , 0.2 μM) against Leishmania major, responsible for the most prevalent disease form, cutaneous leishmaniasis. Conversely, benzothiadiazine 2c, 2-(4-bromobenzyl)-3-phenyl-2H-benzo[e][1,2,4]thiadiazine 1,1-dioxide, was the most potent (IC₅₀ , 6.5 μM) against Leishmania donovani, a causative strain of the lethal visceral leishmaniasis. Both compounds stand as antipromastigote hits for further lead investigation into their potential to act as new antileishmanial agents.

Screening a Natural Product-Based Library against Kinetoplastid Parasites

Kinetoplastid parasites cause vector-borne parasitic diseases including leishmaniasis, human African trypanosomiasis (HAT) and Chagas disease. These Neglected Tropical Diseases (NTDs) impact on some of the world's lowest socioeconomic communities. Current treatments for these diseases cause severe toxicity and have limited efficacy, highlighting the need to identify new treatments. In this study, the Davis open access natural product-based library was screened against kinetoplastids (Leishmania donovani DD8, Trypanosoma brucei brucei and Trypanosoma cruzi) using phenotypic assays. The aim of this study was to identify hit compounds, with a focus on improved efficacy, selectivity and potential to target several kinetoplastid parasites. The IC50 values of the natural products were obtained for L. donovani DD8, T. b. brucei and T. cruzi in addition to cytotoxicity against the mammalian cell lines, HEK-293, 3T3 and THP-1 cell lines were determined to ascertain parasite selectivity. Thirty-one compounds were identified with IC50 values of ≤ 10 µM against the kinetoplastid parasites tested. Lissoclinotoxin E (1) was the only compound identified with activity across all three investigated parasites, exhibiting IC50 values < 5 µM. In this study, natural products with the potential to be new chemical starting points for drug discovery efforts for kinetoplastid diseases were identified.

Bioactive Thiazine and Benzothiazine Derivatives: Green Synthesis Methods and Their Medicinal Importance

Thiazines are a group of heterocyclic organic compounds that are still largely unexplored for their pharmacological activities. There are different available methods for the synthesis of thiazine derivatives in the literature. In this review, we discuss available methods of thiazine preparation through green synthesis methods. Beside their synthesis, many thiazine derivatives are biologically active and play an important role in the treatment of various diseases and show promising results of varying degrees, where they act as antibacterial, antifungal, antitumor, antimalarial, antineoplastic, antiviral, anti-inflammatory, analgesic and anticancer agents and thus they represent an interesting class of heterocyclic medicinal compounds worthy of further exploration.