Mariana López

Genomic repetitive DNA elements of Trypanosoma cruzi

Repetitive DNA sequences are interspersed throughout the genomes of mammals and other higher eukaryotes, and represent a substantial portion of the genome. Although it has been generally assumed that the redundant DNA is present only in the complex genomes of high order organisms, over the past few years a number of repetitive DNA sequences have been also detected in the protozoan parasite Trypanosoma cruzi. A compilation of the repetitive DNA sequences found in the T. cruzi genome is here presented by Jose Maria Requena, Manuel Carlos López and Carlos Alonso, who also speculate on their possible origin and functional implications regarding retrotransposition and gene regulation.

Ayanin diacetate-induced cell death is amplified by TRAIL in human leukemia cells

Here we demonstrate that the semi-synthetic flavonoid ayanin diacetate induces cell death selectively in leukemia cells without affecting the proliferation of normal lymphocytes. Incubation of human leukemia cells with ayanin diacetate induced G(2)-M phase cell cycle arrest and apoptosis which was prevented by the non-specific caspase inhibitor z-VAD-fmk and reduced by the overexpression of Bcl-x(L). Ayanin diacetate-induced cell death was found to be associated with: (i) loss of inner mitochondrial membrane potential, (ii) the release of cytochrome c, (iii) the activation of multiple caspases, (iv) cleavage of poly(ADP-ribose) polymerase and (v) the up-regulation of death receptors for TRAIL, DR4 and DR5. Moreover, the combined treatment with ayanin diacetate and TRAIL amplified cell death, compared to single treatments. These results provide a basis for further exploring the potential applications of this combination for the treatment of cancer.

Secondary Metabolites from Two Species of Pulicaria and Their Cytotoxic Activity

Two new compounds, the sesquiterpene (1E,5E)‐8β‐acetoxy‐4α‐hydroxy‐7βH‐germacra‐1(10),5‐dien‐14‐oic acid (2), and a nor‐sesquiterpene, (5E)‐8β‐acetoxy‐4α‐hydroxy‐7βH‐germacr‐5‐en‐10‐one (3), were isolated from Pulicaria canariensis ssp. lanata, along with ten known compounds, including the flavonoid 5,3′‐dihydroxy‐3,7,4′‐trimethoxyflavone (4). From Pulicaria burchardii, we isolated seven known compounds; the physical and spectroscopic data of the triterpenoid 3β‐hydroxytaraxaster‐20‐en‐30‐al (1) are reported. The structures of compounds 1–3 were determined on the basis of HR‐MS, and 1D‐ and 2D‐NMR studies. The structure of 2 was corroborated by X‐ray crystal diffraction. Cell viability experiments revealed that the semisynthetic flavonoid 4b was the most cytotoxic compound against human leukemia cells, and the cytotoxicity was caused by induction of apoptosis, as determined by microscopy of nuclear changes.

Secondary Metabolites from Two Species of Tolpis and Their Biological Activities

Phytochemical research of two Tolpis species, T. proustii and T. lagopoda, led to the isolation of three new compounds: 30-chloro-3β-acetoxy-22α-hydroxyl-20(21)-taraxastene (1), 3β,22α-diacetoxy-30-ethoxy-20(21)-taraxastene (2) and 3β,28-dihydroxy-11α-hydroperoxy-12-ursene (3). The structures of the new compounds were elucidated by means of extensive IR, NMR, and MS data and by comparison of data reported in the literature. The in vitro antioxidant activities of the extracts were assessed by the DPPH and ABTS scavenging methods. The cytotoxicity of several known compounds and its derivatives was also assessed against human myeloid leukemia K-562 and K-562/ADR cell lines.