Modulation of the Antimelanoma Activity Imparted to Artemisinin Hybrids by the Monoterpene Counterpart.

Molecular hybridization is a widely used strategy in drug discovery and development processes that consists of the combination of two bioactive compounds toward a novel entity. In the current study, two libraries of hybrid derivatives coming from the linkage of sesquiterpene counterparts dihydroartemisinin and artesunic acid, with a series of monoterpenes, were synthesized and evaluated by cell viability assay on primary and metastatic melanoma cell lines. Almost all the obtained compounds showed micromolar antimelanoma activity and selectivity toward the metastatic form of this cancer. Four hybrid derivatives containing perillyl alcohol, citronellol, and nerol as monoterpene counterpart emerged as the best compounds of the series, with nerol being active in combination with both sesquiterpenes, dihydroartemisinin and artesunic acid. Preliminary studies on the mechanism of action have shown the dependence of the pharmacological activity of newly synthesized hybrids on the formation of carbon- and oxygen-centered radical species. This study demonstrated the positive modulation of the pharmacodynamic effect of artemisinin semisynthetic derivatives dihydroartemisinin and artesunic acid due to the hybridization with monoterpene counterparts.

In vitro and in vivo evaluation of six artemisinin derivatives against Schistosoma mansoni.

Schistosomiasis is a tropical neglected disease whose socioeconomic impact is surpassed only by malaria. Until recently, praziquantel (PZQ) has been the only available drug, raising concerns that tolerant/resistant strains may appear. Since the discovery of the schistosomicidal potential of artemisinin (ART), new derivatives have been produced and evaluated. In this work, we evaluated the activity of ART derivatives against Schistosoma mansoni, both in vitro and in vivo. In the in vitro assay, worm survival, oviposition, and morphological alterations were evaluated. Further analysis of morphological alterations and membrane integrity was conducted using scanning electron microscopy and a cell-permeable, benzimidazole dye (Hoescht 33258) that binds to the minor groove of double stranded DNA. For the in vivo assay, artesunic acid (AcART) and dihydroartemisinin acetate (AcDQHS) were selected, since they showed the best in vitro results. Infected mice treated 21, 45, or 60 days post-infection (dpi), with a concentration of 100 mg/kg of either AcART or AcDQHS, showed a significant worm reduction (particularly in females), fewer eggs eliminated in feces, and a decrease of immature eggs in the intestinal tissues. Our results indicate that AcART and AcDQHS have some schistosomicidal activity against juvenile and adult stages of S. mansoni.

Synthesis of new betulinic acid/betulin-derived dimers and hybrids with potent antimalarial and antiviral activities.

Severe malaria and viral infections cause life-threatening diseases in millions of people worldwide every year. In search for effective bioactive hybrid molecules, which may possess improved properties compared to their parent compounds, a series of betulinic acid/betulin based dimer and hybrid compounds carrying ferrocene and/or artesunic acid moieties, was designed and, synthesized de novo. Furthermore, they were analyzed in vitro against malaria parasites (growth inhibition of 3D7-strain P. falciparum-infected erythrocytes) and human cytomegalovirus (HCMV). From this series of hybrids/dimers, the betulinic acid/betulin and artesunic acid hybrids 11 and 12 showed the most potent activities against P. falciparum and HCMV. On the strength of results, additive and/or synergistic effects between the natural or semisynthetic products, such as betulinic acid-/betulin- and artesunic acid-derived compounds, are suggested on the basis of putatively complex modes of antimicrobial action. This advantage may be taken into account in future drug development.

Cytotoxic profiling of artesunic and betulinic acids and their synthetic hybrid compound on neurons and gliomas.

Gliomas are brain-born tumors with devastating impact on their brain microenvironment. Novel approaches employ multiple combinations of chemical compounds in synthetic hybrid molecules to target malignant tumors. Here, we report on the chemical hybridization approach exemplified by artesunic acid (ARTA) and naturally occurring triterpene betulinic acid (BETA). Artemisinin derived semisynthetic compound artesunic acid (ARTA) and naturally occurring triterpene BETA were used to synthetically couple to the hybrid compound termed 212A. We investigated the impact of 212A and its parent compounds on glioma cells, astrocytes and neurons. ARTA and BETA showed cytotoxic effects on glioma cells at micromolar concentrations. ARTA was more effective on rodent glioma cells compared to BETA, whereas BETA exhibited higher toxic effects on human glioma cells compared to ARTA. We investigated these compounds on non-transformed glial cells and neurons as well. Noteworthy, ARTA showed almost no toxic effects on astrocytes and neurons, whereas BETA as well as 212A displayed neurotoxicity at higher concentrations. Hence we compared the efficacy of the hybrid 212A with the combinational treatment of its parent compounds ARTA and BETA. The hybrid 212A was efficient in killing glioma cells compared to single compound treatment strategies. Moreover, ARTA and the hybrid 212A displayed a significant cytotoxic impact on glioma cell migration. Taken together, these results demonstrate that both plant derived compounds ARTA and BETA operate gliomatoxic with minor neurotoxic side effects. Altogether, our proof-of-principle study demonstrates that the chemical hybrid synthesis is a valid approach for generating efficacious anti-cancer drugs out of virtually any given structure. Thus, synthetic hybrid therapeutics emerge as an innovative field for new chemotherapeutic developments with low neurotoxic profile.

Synthesis of Novel Hybrids of Thymoquinone and Artemisinin with High Activity and Selectivity Against Colon Cancer.

Colorectal cancer causes 0.5 million deaths each year. To combat this type of cancer the development of new specific drug candidates is urgently needed. In the present work seven novel thymoquinone-artemisinin hybrids with different linkers were synthesized and tested for their in vitro anticancer activity against a panel of various tumor cell lines. The thymoquinone-artesunic acid hybrid 7 a, in which both subunits are connected via an ester bond, was found to be the most active compound and selectively decreased the viability of colorectal cancer cells with an IC50 value of 2.4 µm (HCT116) and 2.8 µm (HT29). Remarkably, hybrid 7 a was up to 20-fold more active than its parent compounds (thymoquinone and artesunic acid), while not affecting nonmalignant colon epithelial HCEC cells (IC50 >100 µm). Moreover, the activity of hybrid 7 a was superior to that of various 1:1 mixtures of thymoquinone and artesunic acid. Furthermore, hybrid 7 a was even more potent against both colon cancer cell lines than the clinically used drug 5-fluorouracil. These results are another excellent proof of the hybridization concept and confirm that the type and length of the linker play a crucial role for the biological activity of a hybrid drug. Besides an increase in reactive oxygen species (ROS), elevated levels of the DNA-damage marker γ-H2AX were observed. Both effects seem to be involved in the molecular mechanism of action for hybrid 7 a in colorectal cancer cells.

2D Inorganic-Antimalarial Drug-Polymer Hybrid with pH-Responsive Solubility.

Artesunic acid (ASH), an antimalarial drug, has low oral bioavailability due to its low aqueous solubility. To overcome this problem, artesunate (AS) was intercalated into zinc basic salt (ZBS) via co-precipitation. AS was immobilized with a tilted double layer arrangement, which was also confirmed by XRD and 1-D electron density mapping. In order to decrease the release rate of AS under gastrointestinal conditions and to simultaneously increase the release rate of AS under intestinal conditions, ZBS-AS was coated with EUDRAGIT L100 (ZBS-AS-L100). Finally, we performed an in-vivo pharmacokinetic study to compare the oral bioavailability of AS of ZBS-AS-L100 with that of ASH. Surprisingly, it was found that the former is 5.5 times greater than the latter due to an enhanced solubility of AS thanks to the ternary hybridization with ZBS and EUDRAGIT L100. Therefore, the present ZBS-AS-L100 system has a great potential as a novel antimalarial drug formulation with pH selectivity and enhanced bioavailability.

Tegumentary changes in two diferent strains of schistosoma mansoni treated with artemisinin and artesunic acid

Different strains of Schistosoma mansoni can respond differently to conventional and experimental treatments. Therefore, the responses to potential schistosomicidal drugs must be checked with different parasite strains. This work aimed to analyze changes caused by different concentrations of artemisinin or artesunic acid administered on different days in the teguments of adult S. mansoni belonging to two Brazilian strains (BH and SJ), using scanning electron microscopy (SEM). Infected mice were treated with 300 or 500 mg/kg of artemisinin and artesunic acid, 30 or 45 days post infection. Fifteen days after treatment, worms were examined by SEM. Altered teguments were observed in males and females on both days of treatment with both compounds, but the injury with artesunic acid was more intense. The treatment utilizing 500 mg/kg of artesunic acid against the BH strain 30 days after the infection proved to be particularly effective, resulting in erosion, peeling, sensory structure damage, and vesicle formation on the tegument of males and females. It is concluded that artemisinin and artesunic acid showed qualitatively similar tegumentary changes in both genders of the BH and SJ parasite strains. However, changes induced by artesunic acid were more severe for the BH strain, which demonstrates greater susceptibility of this strain to this experimental treatment...

Alterações tegumentares em duas diferentes linhagens de Schistosoma mansoni submetidas a tratamento com artemisinina e ácido artesúnicoDiferentes linhagens de Schistosoma mansoni podem responder de formas distintas a tratamentos experimentais. Portanto, ensaios com potenciais fármacos esquistossomicidas necessitam ser realizados com várias linhagens. Este trabalho visou analisar as alterações causadas por diferentes concentrações de artemisinina e ácido artesúnico, administradas em diferentes dias, sobre o tegumento de adultos de S. mansoni de duas linhagens brasileiras (BH e SJ), utilizando-se microscopia eletrônica de varredura (MEV). Os camundongos infectados foram tratados com 300 e 500 mg/kg de artemisinina ou ácido artesúnico, 30 ou 45 dias após a infecção. Após 15 dias do tratamento, os vermes foram analisados pela MEV. A destruição do tegumento foi observada em machos e fêmeas nos dois dias de tratamento com ambos os compostos, mas observou-se que o ácido artesúnico provocou uma destruição mais intensa. O tratamento realizado com 500 mg/g de ácido artesúnico contra parasitos da linhagem BH, 30 dias após a infecção, mostrou ser o mais efetivo, resultando em erosão, descamação, destruição das estruturas sensoriais e formação de vesículas nos machos e nas fêmeas. Ficou evidenciado que as linhagens BH e SJ apresentaram alterações tegumentares diferentes quanto à intensidade, com ambos os compostos. No entanto, a destruição do tegumento foi mais intensa na linhagem BH, especialmente com o ácido artesúnico, o que demonstrou maior suscetibilidade desta linhagem a esse tratamento experimental...