A DFT study of free radicals formed from artemisinin and related compounds

Perturbation of hyperthermia resistance in gastric cancer by hyperstimulation of autophagy using artemisinin-protected iron-oxide nanoparticles

In a bid to overcome hyperthermia resistance, a major obstacle in cancer treatment, this study explores manipulating autophagy, a cellular recycling mechanism, within the context of gastric cancer. We designed artemisinin-protected magnetic iron-oxide nanoparticles (ART-MNPs) to hyperactivate autophagy, potentially sensitizing cancer cells to hyperthermia. The synthesized ART-MNPs exhibited magnetic properties and the capability of raising the temperature by 7 °C at 580.3 kHz. Importantly, ART-MNPs displayed significant cytotoxicity against human gastric cancer cells (AGS), with an IC50 value of 1.9 μg mL-1, demonstrating synergistic effects compared to either MNPs or ART treatment alone (IC50 for MNPs is 9.7 μg mL-1 and for ART is 9.4 μg mL-1 respectively). Combination index studies further supported this synergy. Mechanistic analysis revealed a significant increase in autophagy level (13.58- and 15.08-fold increase compared to artemisinin and MNPs, respectively) upon ART-MNP treatment, suggesting that this hyperactivation is responsible for hyperthermia sensitization and minimized resistance (as evidenced by changes in viability compared to control under hyperthermic conditions). This work offers a promising strategy to modulate autophagy and overcome hyperthermia resistance, paving the way for developing hyperthermia as a standalone therapy for gastric cancer.

A topological study of the decomposition of 6,7,8-trioxabicyclo[3.2.2]nonane induced by Fe(II): modeling the artemisinin reaction with heme

We report a theoretical study on the electronic and topological aspects of the reaction of dihydrated Fe(OH)(2) with 6,7,8-trioxabicyclo[3.2.2]nonane, as a model for the reaction of heme with artemisinin. A comparison is made with the reaction of dihydrated ferrous hydroxide with O(2), as a model for the heme interaction with oxygen. We found that dihydrated Fe(OH)(2) reacts more efficiently with the artemisinin model than with O(2). This result suggests that artemisinin instead of molecular oxygen would interact with heme, disrupting its detoxification process by avoiding the initial heme to hemin oxidation, and killing in this way the malaria parasite. The ELF and AIM theories provide support for such a conclusion, which further clarifies our understanding on how artemisinin acts as an antimalarial agent.

Quantum chemical study of the intermediate complex required for iron-mediated reactivity and antimalarial activity of dispiro-1,2,4-trioxolanes

Quantum chemical methods were used to obtain a structure for the peroxide-iron intermediate complex required for the inner-sphere reduction of dispiro-1,2,4-trioxolane antimalarials. Investigation of this biologically important interaction with iron(II) allows further understanding of the mechanisms of action and clearance of this promising new class of fully synthetic peroxide antimalarials. UHF, B3LYP and B3LYP//MP2 calculations were undertaken to provide structural and energetic information about the coordination complex of iron(II) with five representative trioxolanes, ranging in both iron-mediated reactivity and antimalarial activity. Significant energy differences were observed between the conformational isomers of these trioxolanes, indicating the importance of steric interactions between the iron complex ligands and the trioxolane substituents. These calculations may explain the slower iron-mediated reaction rates of trioxolanes that preferentially adopt a conformation that sterically shields the peroxide bond. The relationship between antimalarial activity and accessibility of the peroxide bond to iron has also been demonstrated for these trioxolanes.

Interaction between artemisinin and heme. A Density Functional Theory study of structures and interaction energies

Malaria is an infectious disease caused by the unicellular parasite Plasmodium sp. Currently, the malaria parasite is becoming resistant to the traditional pharmacological alternatives, which are ineffective. Artemisinin is the most recent advance in the chemotherapy of malaria. Since it has been proven that artemisinin may act on intracellular heme, we have undertaken a systematic study of several interactions and arrangements between artemisinin and heme. Density Functional Theory calculations were employed to calculate interaction energies, electronic states, and geometrical arrangements for the complex between the heme group and artemisinin. The results show that the interaction between the heme group and artemisinin at long distances occurs through a complex where the iron atom of the heme group retains its electronic features, leading to a quintet state as the most stable one. However, for interaction at short distances, due to artemisinin reduction by the heme group, the most stable complex has a septet spin state. These results suggest that a thermodynamically favorable interaction between artemisinin and heme may happen.

Synthesis of New Artemisinin-Derived Dimers by Self-Cross-Metathesis Reaction

[reaction: see text] New artemisinin-derived dimers, fluorinated or not, have been prepared by a self-cross metathesis reaction in the presence of first- or second-generation ruthenium catalysts without degradation of the endoperoxide bridge and with a good E/Z selectivity (up to 100:0).