neocryptolepine and cryptolepine

The antiprotozoal activities of three naturally occurring isomeric indoloquinoline alkaloids, i.e., cryptolepine (1), neocryptolepine (2), and isocryptolepine (3), and two dimeric indoloquinoline alkaloids, cryptoquindoline (6) and biscryptolepine (7), originally obtained from the plant Cryptolepis sanguinolenta, were compared with those of a new synthetic indoloquinoline isomer, isoneocryptolepine (4), and a quaternary derivative, N-methyl-isocryptolepinium iodide (5). The latter compounds showed a high antiplasmodial activity against the chloroquine-resistant Plasmodium falciparum strain K1 (IC50 of 0.23 +/- 0.04 and 0.017 +/- 0.004 microM, respectively), while the cytotoxicity (L6 cells) was 4.32 +/- 0.04 and 12.7 +/- 2.0 microM, respectively. Isoneocryptolepine (4) was found to act as an inhibitor of beta-hematin formation and as a DNA-intercalating agent.

Topics: Alkaloids; Animals; Antimalarials; Apocynaceae; Indole Alkaloids; Indoles; Molecular Structure; Plasmodium falciparum; Quinolines; Structure-Activity Relationship

Cryptolepine, the main alkaloid present in the roots of Cryptolepis sanguinolenta, presents a large spectrum of biological properties. It has been reported to behave like a DNA intercalator with a preference for GC-rich sequences. In this study, dialysis competition assay and mass spectrometry experiments were used to determine the affinity of cryptolepine and neocryptolepine for DNA structures among duplexes, triplexes, quadruplexes and single strands. Our data confirm that cryptolepine and neocryptolepine prefer GC over AT-rich duplex sequences, but also recognize triplex and quadruplex structures. These compounds are weak telomerase inhibitors and exhibit a significant preference for triplexes over quadruplexes or duplexes.

Topics: Alkaloids; Animals; Cryptolepis; DNA; Enzyme Inhibitors; Indole Alkaloids; Indoles; Mass Spectrometry; Nucleic Acid Conformation; Protein Binding; Quinolines; Structure-Activity Relationship; Substrate Specificity; Telomerase

Cryptolepine and neocryptolepine are two indoloquinoline alkaloids isolated from the roots of the African plant Cryptolepis sanguinolenta. Both drugs have revealed antibacterial and antiparasitic activities and are strongly cytotoxic to tumour cells. We have recently shown that cryptolepine can intercalate into DNA and stimulates DNA cleavage by human topoisomerase II. In this study, we have investigated the mechanism of action and cytotoxicity of neocryptolepine, which differs from the parent isomer only by the orientation of the indole unit with respect to the quinoline moiety. The biochemical and physicochemical results presented here indicate that neocryptolepine also intercalates into DNA, preferentially at GC-rich sequences, but exhibits a reduced affinity for DNA compared with cryptolepine. The two alkaloids interfere with the catalytic activity of human topoisomerase II but the poisoning activity is slightly more pronounced with cryptolepine than with its isomer. The data provide a molecular basis to account for the reduced cytotoxicity of neocryptolepine compared with the parent drug.

Topics: Alkaloids; Animals; Antineoplastic Agents, Phytogenic; Cattle; Circular Dichroism; DNA; DNA Damage; DNA Footprinting; DNA Topoisomerases, Type II; Humans; Indole Alkaloids; Indoles; Intercalating Agents; KB Cells; Melanoma, Experimental; Mice; Mice, Inbred Strains; Plant Roots; Plants, Medicinal; Quinolines; Substrate Specificity; Topoisomerase II Inhibitors

Cryptolepine and neocryptolepine are two indoloquinoline derivatives isolated from the roots of the african plant Cryptolepis sanguinolenta. These two alkaloids, which only differ by the respective orientation of their indole and quinoline rings, display potent cytotoxic activities against tumour cells and present antibacterial and antiparasitic properties. Our previous molecular studies indicated that these two natural products intercalate into DNA and interfere with the catalytic activity of human topoisomerase II. Here we have extended the study of their mechanism of action at the cellular level. Murine and human leukemia cells were used to evaluate the cytotoxicity of the drugs and their effects on the cell cycle were measured by flow cytometry. Cryptolepine, and to a lesser extent neocryptolepine, provoke a massive accumulation of P388 murine leukemia cells in the G2/M phase. With HL-60 human leukemia cells, the treatment with cryptolepine leads to the appearance of a hypo-diploid DNA content peak (sub-G1) characteristic of the apoptotic cell population. With both P388 and HL-60 cells, cryptolepine proved about four times more toxic than its isomer. But the use of the HL-60/MX2 cell line resistant to the anticancer drug mitoxantrone suggests that topoisomerase II may not represent the essential cellular target for the alkaloids, which are both only two times less toxic to the resistant HL-60/MX2 cells compared to the parental cells. The capacity of the drugs to induce apoptosis of HL-60 human leukemia cells was examined by complementary biochemical techniques. Western blotting analysis revealed that cryptolepine, but not neocryptolepine, induces cleavage of poly(ADP-ribose) polymerase but both alkaloids induce the release of cytochrome c from the mitochondria. The cleavage of poly(ADP-ribose) polymerase observed with cryptolepine correlates with the appearance of a marked sub-G1 peak in the cell cycle experiments. The proteolytic activity of Asp-Glu-Val-Asp- or Ile-Glu-Thr-Asp-caspases was found to be enhanced much more strongly with cryptolepine than with its isomer, as expected from their different cytotoxic potential. Despite the activation of the caspase cascade, we did not detect internucleosomal cleavage of DNA in the HL-60 cells treated with the alkaloids. Altogether, the results shed light on the mechanism of action of these two plant alkaloids.

Topics: Alkaloids; Animals; Antineoplastic Agents, Phytogenic; Apoptosis; Caspase 3; Caspases; Cell Cycle; Cell Survival; DNA Fragmentation; HL-60 Cells; Humans; Indole Alkaloids; Indoles; Leukemia P388; Mitochondria; Mitoxantrone; Poly(ADP-ribose) Polymerases; Quinolines

Three different extracts and four alkaloids from the root bark of Cryptolepis sanguinolenta have been assessed in vitro against Plasmodium falciparum D-6 (chloroquine-sensitive strain), K-1, and W-2 (chloroquine-resistant strains). Cryptolepine (1) and its hydrochloride (2), 11-hydroxycryptolepine (3), and neocryptolepine (5) showed a strong antiplasmodial activity against P. falciparum chloroquine-resistant strains. Quindoline (4) was less active. The highest activity was obtained with compound 1. In vivo tests on infected mice showed that cryptolepine (1), when tested as its hydrochloride (2), exhibited a significant chemosuppressive effect against Plasmodium berghei yoelii and Plasmodium berghei, berghei, while 1 had the same effect against P. berghei yoelii only. Compounds 3 and 4 did not show activity in this in vivo test system.

Topics: Alkaloids; Animals; Antimalarials; Humans; In Vitro Techniques; Indole Alkaloids; Indoles; Mice; Microbial Sensitivity Tests; Plants, Medicinal; Plasmodium berghei; Plasmodium falciparum; Quinolines; Spectrum Analysis