11,13-dihydro-dehydroleucodine, a derivative of dehydroleucodine with an inactivated alkylating function conserves the anti-proliferative activity in G2 but does not cause cytotoxicity

Effect of dehydroleucodine (DhL) on the acrosome reaction in sperm of Chinchilla lanigera: signalling pathways involved

The secondary metabolites of several plant species, particularly sesquiterpenic lactones (SLs) have been studied by different research groups for over 30 years. This group of metabolites presents numerous biological activities such as antibacterial, antiviral, antiulcer, cell proliferation inhibitor, and oocyte activator with participation in exocytosis processes. This study aims to assess some sperm parameters in epididymal gametes of Chichilla lanigera exposed to increasing concentrations (0 to 2 mM) of DhL for various incubation times from 10 to 40 minutes. We determined the participation of different cell signalling pathways in the induced acrosome reaction. Our results showed an alteration in the progressive motility pattern and cell viability depending on DhL concentration and exposure time of gametes. When analyzing acrosomal status, higher percentages than the negative control were obtained in all tested doses. Both isolated and joint inhibition tests of PKA and phospholipases (PLC and PLA2) showed a greater participation of PI-PLC. This is the first report concerning the effects of this lactone on the medium of sperm incubation. Consequently, further studies will be necessary to determine the molecular implications of this lactone on the fertilizing potential of the sperm.

Azido derivatives of sesquiterpene lactones: Synthesis, anticancer proliferation, and chemistry of nitrogen-centered radicals

Sesquiterpene lactones (SLs) such as parthenolide (PTL) and dehydroleucodine (DhL) selectively kill cancer cells without exerting normal tissue toxicity, potentially due to presence of α-methylene-γ-lactone (αMγL) fragment. We hypothesize that the addition of an azido group to the αMγL fragment of PTL or DhL further augments their anticancer properties as well as radiation sensitivity of cancer cells. Azido-SLs containing the azido group at the C14 methyl position of PTL (i.e., azido-melampomagnolide B, AzMMB) while preserving the mechanistically crucial exomethylene unit of αMγL fragment were also prepared. Sham-irradiated (i.e., unirradiated control) or irradiated human breast cancer cells (MCF7) were treated with different concentrations of azido-PTL (AzPTL) or azido-DhL (AzDhL) along with parental SLs. Proliferation rate of MCF7 cells were measured by MTT-assay, and their colony forming ability was determined by colony formation assay. Both AzPTL and AzDhL significantly suppress proliferation rate and colony forming ability of MCF-7 cells. AzPTL suppressed colony forming ability, not cellular proliferation, following irradiation to a greater extent than PTL at lower concentrations (5 and 10 μM). Electron spin resonance (ESR) studies were performed employing gamma-irradiated homogeneous supercooled aqueous solutions to investigate radical formation through addition of radiation-mediated prehydrated electrons to the azide group of AzPTL and AzDhL and to follow subsequent reactions of these radicals. In AzPTL, formation of a tertiary carbon-centered radical plausibly via a metastable aminyl radical was observed, whereas AzDhL produced both π-aminyl and α-azidoalkyl radicals. These radicals may contribute to the antitumor activities of AzPTL and AzDhL.

Design, Synthesis, and Anti-Hepatocellular Carcinoma Evaluation of Sesquiterpene Lactone Epimers Trilobolide-6-O-isobutyrate Analogs

Hepatocellular carcinoma (HCC), one of the most common malignant cancers with a low 5-year survival rate, is the third leading cause of cancer-related deaths worldwide. The finding of novel agents and strategies for the treatment of HCC is an urgent need. Sesquiterpene lactones (SLs) have attracted extensive attention because of their potent antitumor activity. In this study, a new series of SL derivatives (3-18) were synthesized using epimers 1 and 2 as parent molecules, isolated from Sphagneticola trilobata, and evaluated for their anti-HCC activity. Furthermore, the structures of 4, 6, and 14 were confirmed by X-ray single-crystal diffraction analyses. The cytotoxic activities of 3-18 on two HCC cell lines, including HepG2 and Huh7, were evaluated using the CCK-8 assay. Among them, compound 10 exhibited the best activity against the HepG2 and Huh7 cell lines. Further studies showed that 10 induced cell apoptosis, arrested the cell cycle at the S phase, and induced the inhibition of cell proliferation and migration in HepG2 and Huh7. In addition, absorption, distribution, metabolism, and excretion (ADME) properties prediction showed that 10 may possess the properties to be a drug candidate. Thus, 10 may be a promising lead compound for the treatment of HCC.

Structure modification and anti-tumor activity evaluation on sesquiterpene lactones TBA and TBB from Sphagneticola trilobata

Thirteen sesquiterpene lactone derivatives were designed and synthesised using the sesquiterpene lactone epimers TBA and TBB as the parent molecules, isolated from Sphagneticola trilobata. Their structures were elucidated by extensive spectroscopic studies and chemical evidence. Furthermore, the structures of 1a, 4b and 5a were confirmed by X-ray single-crystal diffraction analyses. All of the compounds were further examined for their in vitro antiproliferative activity against human cancer cell lines HeLa and MCF-7. Unfortunately, the activity of all derivatives were weaker than that of the parental compounds.

Synthesis and biological evaluation of α-santonin derivatives as anti-hepatoma agents

A series of α-santonin-derived compounds as potentially anti-hepatoma agents were designed and synthesized in an effort to find novel therapeutic agents. Among them, derivative 5h was more potent than the positive control 5-fluorouracil (5-Fu) on HepG-2, QGY-7703 and SMMC-7721 with IC₅₀ values of 7.51, 3.06 and 4.08 μM, respectively. The structure-activity relationships (SARs) of these derivatives were discussed. In addition, flow cytometry and western blot assay revealed that the derivatives induced hepatoma cells apoptosis by facilitating apoptosis-related proteins expressions. Our findings suggested that these α-santonin-derived analogues hold promise as chemotherapeutic agents for the treatment of human hepatocellular cancer.

Biomedical Properties and Origins of Sesquiterpene Lactones, with a Focus on Dehydroleucodine

Dehydroleucodine, a sesquiterpene lactone, belongs to the terpenoid class of secondary metabolites. Dehydroleucodine and other Artemisia-derived phytochemicals evolved numerous biodefenses that were first co-opted for human pharmacological use by traditional cultures in the Middle East, Asia, Europe and the Americas. Later, these phytochemicals were modified through the use of medicinal chemical techniques to increase their potency. All sesquiterpene lactones contain an α-methylene-γ-lactone group, which confers thiol reactivity, which is responsible, in part, for their therapeutic effects. A wide range of therapeutic uses of sequiterpene lactones has been found, including anti-adipogenic, cytoprotective, anti-microbial, anti-viral, anti-fungal, anti-malarial and, anti-migraine effects. Dehydroleucodine significantly inhibits differentiation of murine preadipocytes and also significantly decreases the accumulation of lipid content by a dramatic down regulation of adipogenic-specific transcriptional factors PPARγ and C-EBPα. Dehydroleucodine also inhibits secretion of matrix metalloprotease-2 (MMP-2), which is a known protease involved in migration and invasion of B16 cells. In addition to these anti-adipogenic and anti-cancer effects, dehydroleucodine effectively neutralizes several bacterial species, including Bacillus cereus, Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Helicobacter pylori, methicillin resistant Staphylococcus aueus (MRSA) and S. epidermis (MRSE). The compound also inhibits the growth and secretion of several toxins of Pseudomonas aeruginosa, possesses gastro-protective qualities and possesses anti-parasitic properties against Trypanosoma cruzi, responsible for Chagas disease. Other sesquiterpene lactones, such as parthenolide, costunolide, and helanin, also possess significant therapeutic utility.

Covalent Modifiers: A Chemical Perspective on the Reactivity of α,β-Unsaturated Carbonyls with Thiols via Hetero-Michael Addition Reactions

Although Michael acceptors display a potent and broad spectrum of bioactivity, they have largely been ignored in drug discovery because of their presumed indiscriminate reactivity. As such, a dearth of information exists relevant to the thiol reactivity of natural products and their analogues possessing this moiety. In the midst of recently approved acrylamide-containing drugs, it is clear that a good understanding of the hetero-Michael addition reaction and the relative reactivities of biological thiols with Michael acceptors under physiological conditions is needed for the design and use of these compounds as biological tools and potential therapeutics. This Perspective provides information that will contribute to this understanding, such as kinetics of thiol addition reactions, bioactivities, as well as steric and electronic factors that influence the electrophilicity and reversibility of Michael acceptors. This Perspective is focused on α,β-unsaturated carbonyls given their preponderance in bioactive natural products.

Phytometabolite Dehydroleucodine Induces Cell Cycle Arrest, Apoptosis, and DNA Damage in Human Astrocytoma Cells through p73/p53 Regulation

Accumulating evidence supports the idea that secondary metabolites obtained from medicinal plants (phytometabolites) may be important contributors in the development of new chemotherapeutic agents to reduce the occurrence or recurrence of cancer. Our study focused on Dehydroleucodine (DhL), a sesquiterpene found in the provinces of Loja and Zamora-Chinchipe. In this study, we showed that DhL displayed cytostatic and cytotoxic activities on the human cerebral astrocytoma D384 cell line. With lactone isolated from Gynoxys verrucosa Wedd, a medicinal plant from Ecuador, we found that DhL induced cell death in D384 cells by triggering cell cycle arrest and inducing apoptosis and DNA damage. We further found that the cell death resulted in the increased expression of CDKN1A and BAX proteins. A marked induction of the levels of total TP73 and phosphorylated TP53, TP73, and γ-H2AX proteins was observed in D384 cells exposed to DhL, but no increase in total TP53 levels was detected. Overall these studies demonstrated the marked effect of DhL on the diminished survival of human astrocytoma cells through the induced expression of TP73 and phosphorylation of TP73 and TP53, suggesting their key roles in the tumor cell response to DhL treatment.

Chemical activation in Rhinella arenarum oocytes: effect of dehydroleucodine (DhL) and its hydrogenated derivative (2H-DhL)

Mature oocytes are arrested in metaphase II due to the presence of high levels of active maturation promoting factor (MPF). After fertilization, active MPF levels decline abruptly, enabling oocytes to complete meiosis II. One of the first and universal events of oocyte activation is an increase in cytosolic Ca2+ that would be responsible for MPF inactivation. Mature oocytes can also be activated by parthenogenetic activation. The aims of this work are to test the ability of dehydroleucodine (DhL) and its hydrogenated derivative 11,13-dihydro-dehydroleucodine (2H-DhL) to induce chemical activation in amphibian oocytes and to study the participation of calcium in the process. Results indicated that DhL and 2H-DhL induced oocyte activation in a dose-dependent manner. After 90 min of treatment, DhL 36 μM was able to induce 95% activation, while 2H-DhL 36 μM was less active, with only 40% activation. Our results suggest that DhL induced the inhibition of MPF activity, probably by an increase in intracellular Ca2+ concentration. Extracellular Ca2+ would not be significant, although Ca2+ release from intracellular stores is critical. In this sense, IP3Rs and RyRs were involved in the Ca2+ transient induced by lactones. In this species, RyRs appears to be the largest contributor to Ca2+ release in DhL-induced activation. Although more studies are needed on the mechanism of action through which these lactones induce oocyte activation in Rhinella arenarum, the results of this research provide interesting perspectives for the use of these lactones as chemical activators in in vitro fertilization and cloning.

Ethanolic Extracts of California Mugwort (Artemisia douglasiana Besser) Are Cytotoxic against Normal and Cancerous Human Cells

California mugwort (Artemisia douglasiana Besser) is used by many tribes throughout California to treat a variety of conditions, including colds, allergies, and pain. California mugwort is also utilized as women's medicine. Its use is on the rise outside of Native communities, often without the guidance of a traditional healer or experienced herbalist. Because it has been shown to have antiproliferative activity against plant and animal cells, we investigated whether California mugwort extracts have an effect on normal human cells as well as estrogen receptor positive (ER⁺) and estrogen receptor negative (ER^-) human breast cancer cells. Ethanolic and aqueous extracts of A. douglasiana leaves were tested for cytotoxicity against unstimulated normal human peripheral blood mononuclear cells (hPBMC), as well as against an ER⁺ human breast cancer cell line (BT-474) and an ER^- human breast cancer cell line (MDA-MB-231). An ethanolic leaf extract killed hPBMC, BT-474, and MDA-MB-231 cells with IC₅₀ values of 23.6 ± 0.3, 27 ± 5, and 37 ± 4 μg/ml, respectively. An aqueous extract killed hPBMC with an IC₅₀ value of 60 ± 10 μg/ml, but had no effect on the two cancer cell lines at concentrations up to 100 μg/ml. The results of this study indicate that the cytotoxicity of California mugwort extends to normal human cells, as well as cancerous cells. Therefore, until further is known about the safety of this medicine, caution should be taken when consuming extracts of California mugwort, whether as a tincture or as a tea.

The sesquiterpene lactone dehydroleucodine triggers senescence and apoptosis in association with accumulation of DNA damage markers

Sesquiterpene lactones (SLs) are plant-derived compounds that display anti-cancer effects. Some SLs derivatives have a marked killing effect on cancer cells and have therefore reached clinical trials. Little is known regarding the mechanism of action of SLs. We studied the responses of human cancer cells exposed to various concentrations of dehydroleucodine (DhL), a SL of the guaianolide group isolated and purified from Artemisia douglasiana (Besser), a medicinal herb that is commonly used in Argentina. We demonstrate for the first time that treatment of cancer cells with DhL, promotes the accumulation of DNA damage markers such as phosphorylation of ATM and focal organization of γH2AX and 53BP1. This accumulation triggers cell senescence or apoptosis depending on the concentration of the DhL delivered to cells. Transient DhL treatment also induces marked accumulation of senescent cells. Our findings help elucidate the mechanism whereby DhL triggers cell cycle arrest and cell death and provide a basis for further exploration of the effects of DhL in in vivo cancer treatment models.

The effect of dehydroleucodine in adipocyte differentiation

Dehydroleucodine (DhL) is a sesquiterpene lactone of the guaianolide group with gastric cytoprotective activity. Recent studies have also demonstrated that DhL inhibits the proliferation of vascular smooth muscle cells. In this study we examined the effect of DhL in the differentiation of 3T3-L1 preadipocytes. The addition of DhL significantly inhibited the differentiation of 3T3-L1 preadipocytes along with a significant decrease in the accumulation of lipid content by a dramatic downregulation of the expression of adipogenic-specific transcriptional factors PPARγ and C-EBPα. However, phosphorylation of AMPKα, Erk1/2 and Akt1 was not inhibited by DhL treatment. Interestingly, we also found that 11,13-dihydrodehydroleucodine, a derivative of DhL with inactivated α-methylene-γ-lactone function, also inhibited the differentiation of 3T3-L1 preadipocytes. Taken together, these data suggest that DhL has an important inhibitory effect in cellular pathways regulating adipocyte differentiation by modulating the PPARγ expression, which is known to play a pivotal role during adipogenesis.