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Seven new triterpenoids (1-7) and 36 known compounds were isolated from the root bark of Maytenus retusa. Their structures were determined by 1D and 2D spectroscopic studies. Several compounds were evaluated for their cytotoxicity against the human tumor cell lines HL-60 and MCF-7. Some of them were cytotoxic, with IC(50) values ranging between 0.2 and 4.7 μM.

Human Chronic Myelogenous Leukemia (CML) is a hematological stem cell disorder which is associated with activation of Bcr-Abl-Stat5 oncogenic pathway. Direct Bcr-Abl inhibitors are initially successful for the treatment of CML but over time many patients develop drug resistance. In the present study, the effects of CM363, a novel naphthoquinone (NPQ) derivative, were evaluated on human CML-derived K562 cells. CM363 revealed an effective cell growth inhibition (IC50 = 0.7 ± 0.5 μM) by inducing cancer cells to undergo cell cycle arrest and apoptosis. CM363 caused a dose- and time-dependent reduction of cells in G0/G1 and G2/M phases. This cell cycle arrest was associated with increased levels of cyclin E, pChk1 and pChk2 whereas CM363 downregulated cyclin B, cyclin D3, p27, pRB, Wee1, and BUBR1. CM363 increased the double-strand DNA break marker γH2AX. CM363 caused a time-dependent increase of annexin V-positive cells, DNA fragmentation and increased number of apoptotic nuclei. CM363 triggered the mitochondrial apoptotic pathway as reflected by a release of cytochrome C from mitochondria and induction of the cleavage of caspase-3 and -9, and PARP. CM363 showed multikinase modulatory effects through an early increased JNK phosphorylation followed by inhibition of pY-Bcrl-Abl and pY-Stat5. CM363 worked synergistically with imatinib to inhibit cell viability and maintained its activity in imatinib-resistant cells. Finally, CM363 (10 mg/Kg) suppressed the growth of K562 xenograft tumors in athymic mice. In summary, CM363 is a novel multikinase modulator that offers advantages to circumvent imanitib resistance and might be therapeutically effective in Bcrl-Abl-Stat5 related malignancies.

Naphthoquinones are among the most active natural products obtained from plants and microorganisms. Naphthoquinones exert their biological activities through pleiotropic mechanisms that include reactivity against cell nucleophiles, generation of reactive oxygen species (ROS), and inhibition of proteins. Here, we report a mechanistic antiproliferative study performed in the yeast Saccharomyces cerevisiae for several derivatives of three important natural naphthoquinones: lawsone, juglone, and β-lapachone. We have found that (i) the free hydroxyl group of lawsone and juglone modulates toxicity; (ii) lawsone and juglone derivatives differ in their mechanisms of action, with ROS generation being more important for the former; and (iii) a subset of derivatives possess the capability to disrupt mitochondrial function, with β-lapachones being the most potent compounds in this respect. In addition, we have cross-compared yeast results with antibacterial and antitumor activities. We discuss the relationship between the mechanistic findings, the antiproliferative activities, and the physicochemical properties of the naphthoquinones.

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A series of 34 1,2,3-triazole-naphthoquinone conjugates were synthesized via copper-catalyzed cycloaddition (CuAAC). They were evaluated for their in vitro antimalarial activity against chloroquine-sensitive strains of Plasmodium falciparum and against three different tumor cell lines (SKBr-3, MCF-7, HEL). The most active antimalarial compounds showed a low antiproliferative activity. Simplified analogues were also obtained and some structure–activity relationships were outlined. The best activity was obtained by compounds 3s and 3j, having IC50 of 0.8 and 1.2 μM, respectively. Molecular dockings were also carried on Plasmodium falciparum enzyme dihydroorotate dehydrogenase (PfDHODH) in order to rationalize the results.

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Macrophages are immune cells that play crucial roles in host defense against pathogens by triggering their exceptional phagocytic and inflammatory functions. Macrophages that reside in healthy tissues also accomplish important tasks to preserve organ homeostasis, including lipid uptake/efflux or apoptotic-cell clearance. Both homeostatic and inflammatory functions of macrophages require the precise stability of lipid-rich microdomains located at the cell membrane for the initiation of downstream signaling cascades. Caveolin-1 (Cav-1) is the main protein responsible for the biogenesis of caveolae and plays an important role in vascular inflammation and atherosclerosis. The Liver X receptors (LXRs) are key transcription factors for cholesterol efflux and inflammatory gene responses in macrophages. Although the role of Cav-1 in cellular cholesterol homeostasis and vascular inflammation has been reported, the connection between LXR transcriptional activity and Cav-1 expression and function in macrophages has not been investigated. Here, using gain and loss of function approaches, we demonstrate that LXR-dependent transcriptional pathways modulate Cav-1 expression and compartmentation within the membrane during macrophage activation. As a result, Cav-1 participates in LXR-dependent cholesterol efflux and the control of inflammatory responses. Together, our data show modulation of the LXR-Cav-1 axis could be exploited to control exacerbated inflammation and cholesterol overload in the macrophage during the pathogenesis of lipid and immune disorders, such as atherosclerosis.