Chemical constituents of Coccoloba peltata Schott leaves and their cytotoxic activities.

Chromatographic fractionation of CH2Cl2:MeOH (1:1) extract of Coccoloba peltata Schott cultivated in Egypt afforded four compounds, lupeol acetate (1), ent-13-epi-manoyl oxide (2), 5-methoxymethyl-7,8-dimethyltocol (3), and α-tocopherol quinone (4). The planar structures of the isolated compounds were concluded based on HRESIMS and NMR spectroscopy. X-ray crystallography of 2 is reported herein for the first time and its unambiguous absolute configuration was deduced from anomalous dispersion. To the best of our knowledge, this is the first known report on the isolation of compounds 1-4 from this species. Among the isolated compounds, only compound 4 showed a moderate level of cytotoxic activity against six cancer cell lines out of seven cell lines tested.

Prenylated xanthones from mangosteen (Garcinia mangostana) target oxidative mitochondrial respiration in cancer cells.

Mangosteen (Garcinia mangostana) is well-known for its nutritional value and health benefits. Breast cancer is the most common cancer and the leading cause of cancer-related mortality among females worldwide. Here we show that the prenylated xanthones, α-mangostin, γ-mangostin, 9-hydroxycalabaxanthone (9-HCX), and garcinone E from the mangosteen pericarp exhibit cytotoxicity against a panel of human cancer cell lines including lung adenocarcinoma (A549), cervical carcinoma (HeLa), prostatic carcinoma (DU 145), pancreatic carcinoma (MIA PaCa-2), hepatocellular carcinoma (Hep G2), bladder urothelial cancer (5637), as well as the triple-negative breast cancer cells MDA-MB-231. In line with its higher predicted bioactivity score compared to other prenylated xanthones, 9-HCX induced the strongest antiproliferative and proapoptotic effects in MDA-MB-231 breast cancer xenografts in vivo. In different in vitro models, we demonstrate that prenylated xanthones from G. mangostana target mitochondria in cancer cells by inhibition of the mitochondrial respiratory chain complex II (α-mangostin, γ-mangostin, and garcinone E) and complex III (9-HCX) as shown in isolated mitochondria. Accordingly, oxidative mitochondrial respiration (OXPHOS) was inhibited, mitochondrial proton leak increased, and adenosine triphosphate (ATP) synthesis decreased as analyzed by Seahorse assay in MDA-MB-231 cells. Hence, the prenylated xanthones increased mitochondrial superoxide levels, induced mitochondrial membrane permeabilization, and initiated caspase 3/7-mediated apoptosis in MDA-MB-231 triple-negative breast cancer cells. Thus, prenylated xanthones from Garcinia mangostana exhibit anticancer activity based on interference with the mitochondrial respiration.

Cannabinoid-like meroterpenoids from Peperomia incana.

Ten previously undescribed metabolites were isolated from Peperomia incana (Haw.) A. Dietr. (Piperaceae), among which four contained a chromene moiety, two were identified as meroterpene lactones, and four were cannabinoid-like compounds. While the chemical structures of the compounds were assigned based on HRESIMS and 1D and 2D-NMR spectra analyses, the relative and absolute configurations were assigned from NOE correlations and a combination of ECD data and X-ray single crystal analyses, respectively. In a cytotoxic assay against a panel of seven human cancer cell lines (A549, MDA-MB-231, HeLa, DU 145, 5637, Hep G2, and MIA PaCa-2, which represent non-small cell lung cancer, as well as breast, cervical, prostate, bladder, liver, and pancreas carcinomas, respectively) most of the isolated compounds showed promising cytotoxic activities. The incanachromenes B, and incanabinoids A and C exhibited the highest cytotoxicity toward all tested cancer cell lines with IC50 values in the range of 5.0-10.0 µM, whereas incanolides A, B, and incanabinoid B showed the lowest cytotoxic activity. In addition, incanachromene C and incanabinoid C produced a significant antibacterial effect toward planktonic cells and biofilms of multidrug-resistant Staphylococcus aureus strains.

Arglabin, an EGFR receptor tyrosine kinase inhibitor, suppresses proliferation and induces apoptosis in prostate cancer cells.

Evidence for clinical efficacy of a semisynthetic derivative of arglabin in anticancer treatment prompted us to examine molecular mechanisms and cellular targets of arglabin. Arglabin, a sesquiterpene lactone isolated from Artemisia glabella was cytotoxic to different human cancer cell lines including those derived from advanced triple-negative breast, lung, androgen-dependent and androgen-independent prostate carcinomas. Noteworthy, arglabin was less toxic to non-neoplastic prostate epithelial cells indicating selectivity for cancer cells. At the molecular level, prior to any biochemical signs of cellular toxicity, arglabin reduced levels of cell-surface sulphanyl groups and inhibited phosphorylation of the redox-sensitive receptor tyrosine kinase EGFR, the only active RTK in PC-3 prostate cancer cells among 49 TRKs analyzed by the assay. Henceforth, arglabin inhibited the EGFR downstream signaling pathways mTORC1 and mTORC2. Accordingly, arglabin induced autophagosome formation and autophagic flux, inhibited phosphorylation of ribosomal protein S6 kinase beta-1 (S6K1) and eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1), and impeded cell cycle progression and proliferation of PC-3 cells. In agreement with inhibition of the mTORC2 pathway, arglabin induced sustained actin polymerization, inhibited cell migration, and triggered apoptosis in vitro in 2D cell culture and colony formation assay and in vivo in prostate cancer xenografts grown on chick chorioallantoic membranes. Under physiological conditions, arglabin rapidly formed adducts with reduced glutathione (GSH). Moreover, thiol-based antioxidants GSH and ß-mercaptoethanol abolished arglabin-induced cancer cell toxicity, whereas the non-thiol antioxidant trolox was ineffective pointing to a crucial role of interaction with cell-surface sulphanyl groups for arglabin cytotoxic activity against cancer cells.

Phytochemical Composition of Commiphora Oleogum Resins and Their Cytotoxicity against Skin Cancer Cells.

Oleogum resins of the genus Commiphora have been used in traditional medicines for centuries. More than 200 Commiphora species exhibit highly variable phytochemical compositions. A novel highly selective, sensitive, accurate HPLC-MS/MS method was developed and validated to quantify five characteristic phytosteroids and furanosesquiterpenoids, namely (E)-guggulsterone, (Z)-guggulsterone, curzerenone, furanoeudesma-1,3-diene, and myrrhone. The resulting contents and additionally GC analysis were used to classify and differentiate Commiphora oleogum resins of the species C. myrrha, C. erythraea, C. mukul, C. holtziana, C. confusa, and C. kua, as well as unspecified resins. Interestingly, a Commiphora sample from Ogaden, Ethiopia, comprised 446 ng/mg guggulsterones presumed to be unique to C. mukul from the Indian subcontinent. However, Commiphora from Ogaden differed considerably from C. mukul in respect to guggulsterones isomer's ratio. Moreover, the cytotoxicity of Commiphora extracts, essential oils, botanical drugs containing Commiphora, and pure compounds against the epidermoid carcinoma A431, malignant melanoma RPMI-7951 and SK-MEL-28 cells was investigated in vitro. Thereby, especially C. mukul extract and C. myrrha essential oil exhibited high cytotoxicity against skin cancer cells with IC50 of 2.9-10.9 µg/mL, but were less toxic to normal keratinocytes. In summary, Commiphora oleogum resins and its phytochemicals warrant further investigation aiming at chemotaxonomical classification as well as application in skin cancer treatment.

The SC cell line as an in vitro model of human monocytes.

In vitro analysis of human macrophages is generally hampered by the necessity to differentiate them from peripheral blood monocytes. We have analyzed to which extent noncancerous SC monocytes could be used as an in vitro macrophage model. Macrophages differentiated from peripheral monocytes using standard CSF1 and CSF2 protocols for M2 and M1 precursors, respectively, were compared with THP-1-derived macrophages treated with PMA and with SC-derived macrophages differentiated either by CSF1, CSF2, or PMA according to different protocols. The optimal condition for generation of SC macrophages was treatment with PMA for 3 days, followed by 5-days culture without PMA and 24-h polarization with LPS/IFN-γ or IL-4/IL-13. Similar to THP-1, SC cells do not express the monocyte marker CD14 and differentiation to macrophages results neither in CD68 nor in CD14 expression, both of which were expressed by monocyte-derived macrophages. Similar to THP-1-macrophages, a proportion of SC macrophages can be polarized to the M1-like subtype that is characterized by higher expression of CD38, CD86, CD80, TNF-α, and IL-1ra, whereas treatment with IL4/IL13 did not lead to expression of the M2-associated receptors CD163, CD206, and only slightly increased the CD200R expression. Still, SC-M1 express much lower levels of the M1-associated markers compared with monocyte-derived M1 and no IL-1ß. The data demonstrate that SC-derived macrophages differ from monocyte-derived macrophages in respect of their morphology, expression of important macrophage markers, phagocytosis. Yet, polarized SC-M1-like cells may with restrictions serve as a model for M1 macrophages, though this model does not provide significant advantages over already well-described THP-1-M1-like cells.

The phloroglucinol calcitrinone A, a novel mitochondria-targeting agent, induces cell death in breast cancer cells.

Breast cancer is the most common cancer and the leading cause of cancer-related mortality among females worldwide. From the leaves of Callistemon citrinus, we have isolated a novel phloroglucinol dimer, calcitrinone A, and analyzed its potential anticancer activity using the triple-negative breast cancer cell line MDA-MB-231. Calcitrinone A decreased the total intracellular ATP levels, inhibited proliferation, and induced apoptosis in MDA-MB-231 cells, but was less toxic to peripheral blood mononuclear cells. The antiproliferative and apoptosis-inducing effects of calcitrinone A were confirmed in vivo using breast cancer xenografts grown on chick chorioallantoic membranes. Mechanistic analysis showed mitochondrial membrane-potential dissipation and interference with energy-yielding processes resulting in cell accumulation in the S phase of the cell cycle. Seahorse assay analysis revealed an early inhibition of mitochondrial oxidative phosphorylation (OXPHOS). At the molecular level, calcitrinone A inhibited activity of the succinate-coenzyme Q reductase (SQR) (mitochondrial complex II). In silico docking identified the coenzyme Q binding pocket as a possible high affinity binding site for calcitrinone A in SQR. Inhibition of complex II was accompanied by strong elevation of mitochondrial superoxide and cytoplasmic ROS. Calcitrinone A might be a promising anticancer lead compound acting through the interference with the mitochondrial complex II activity.

Chrysosplenol d, a Flavonol from Artemisia annua, Induces ERK1/2-Mediated Apoptosis in Triple Negative Human Breast Cancer Cells.

Triple negative human breast cancer (TNBC) is an aggressive cancer subtype with poor prognosis. Besides the better-known artemisinin, Artemisia annua L. contains numerous active compounds not well-studied yet. High-performance liquid chromatography coupled with diode-array and mass spectrometric detection (HPLC-DAD-MS) was used for the analysis of the most abundant compounds of an Artemisia annua extract exhibiting toxicity to MDA-MB-231 TNBC cells. Artemisinin, 6,7-dimethoxycoumarin, arteannuic acid were not toxic to any of the cancer cell lines tested. The flavonols chrysosplenol d and casticin selectively inhibited the viability of the TNBC cell lines, MDA-MB-231, CAL-51, CAL-148, as well as MCF7, A549, MIA PaCa-2, and PC-3. PC-3 prostate cancer cells exhibiting high basal protein kinase B (AKT) and no ERK1/2 activation were relatively resistant, whereas MDA-MB-231 cells with high basal ERK1/2 and low AKT activity were more sensitive to chrysosplenol d treatment. In vivo, chrysosplenol d and casticin inhibited MDA-MB-231 tumor growth on chick chorioallantoic membranes. Both compounds induced mitochondrial membrane potential loss and apoptosis. Chrysosplenol d activated ERK1/2, but not other kinases tested, increased cytosolic reactive oxygen species (ROS) and induced autophagy in MDA-MB-231 cells. Lysosomal aberrations and toxicity could be antagonized by ERK1/2 inhibition. The Artemisia annua flavonols chrysosplenol d and casticin merit exploration as potential anticancer therapeutics.

A comparative study on root and bark extracts of Eleutherococcus senticosus and their effects on human macrophages.

BACKGROUND: Eleutherococcus senticosus or Siberian ginseng is a medicinal plant containing adaptogenic substances believed to regulate immune responses. Both, the root and stem bark are commonly used in traditional medicines. PURPOSE: The purpose of the present study is to chemically characterize E. senticosus root and bark extracts and to compare their effects on functions of human primary macrophages. STUDY DESIGN AND METHODS: HPLC-DAD-MS analysis was used to characterize chemical constituents of alcoholic extracts from E. senticosus root and bark. The data obtained and available databases were combined for network pharmacology analysis. Involvement of predicted pathways was further functionally confirmed by using monocyte-derived human macrophages and endotoxin-free E. senticosus root and bark extracts. RESULTS: Chemical analysis showed that the root extract contained more syringin, caffeic acid, and isofraxidin than the bark extract. At variance, bark extract contained more sesamin and oleanolic acid. Coniferyl aldehyde and afzelin were below the limit of quantification in both extracts. Network pharmacology analysis indicated that constituents of E. senticosus might affect the immune cell phenotype and signaling pathways involved in cell metabolism and cytoskeleton regulation. Indeed, both extracts promoted actin polymerization, migration, and phagocytosis of E. coli by macrophages pointing to macrophage polarization towards the M2 phenotype. In addition, treatment with E. senticosus root and bark extracts decreased phosphorylation of Akt on Ser473 and significantly reduced expression of the hemoglobin scavenger receptor CD163 by macrophages. Neither extract affected expression of CD11b, CD80, or CD64 by macrophages. In addition, macrophages treated with the bark extract, but not with the root extract, exhibited activated p38 MAPK and NF-κB and released increased, but still moderate, amounts of proinflammatory TNF-α and IL-6, anti-inflammatory IL-10, and chemotactic CCL1, which all together point to a M2b-like macrophage polarization. Differently, the root extract increased the IL-4-induced expression of anti-inflammatory CD200R. These changes in monocytes are in agreement with an increased M2a macrophage polarization. CONCLUSION: The ability of E. senticosus root and bark extracts to promote polarization of human macrophages towards anti-inflammatory M2a and M2b phenotypes, respectively, might underlay the immunoregulatory activities and point to potential wound healing promoting effects of this medicinal plant.

A Novel Polyhalogenated Monoterpene Induces Cell Cycle Arrest and Apoptosis in Breast Cancer Cells.

Breast cancer is the most common cancer type and a primary cause of cancer mortality among females worldwide. Here, we analyzed the anticancer efficacy of a novel bromochlorinated monoterpene, PPM1, a synthetic analogue of polyhalogenated monoterpenes from Plocamium red algae and structurally similar non-brominated monoterpenes. PPM1, but not the non-brominated monoterpenes, decreased selectively the viability of several triple-negative as well as triple-positive breast cancer cells with different p53 status without significantly affecting normal breast epithelial cells. PPM1 induced accumulation of triple-negative MDA-MB-231 cells with 4N DNA content characterized by decreased histone H3-S10/T3 phosphorylation indicating cell cycle arrest in the G2 phase. Western immunoblot analysis revealed that PPM1 treatment triggered an initial rapid activation of Aurora kinases A/B/C and p21Waf1/Cip1 accumulation, which was followed by accumulation of polyploid >4N cells. Flow cytometric analysis showed mitochondrial potential disruption, caspase 3/7 activation, phosphatidylserine externalization, reduction of the amount polyploid cells, and DNA fragmentation consistent with induction of apoptosis. Cell viability was partially restored by the pan-caspase inhibitor Z-VAD-FMK indicating caspase contribution. In vivo, PPM1 inhibited growth, proliferation, and induced apoptosis in MDA-MB-231 xenografted onto the chick chorioallantoic membrane. Hence, Plocamium polyhalogenated monoterpenes and synthetic analogues deserve further exploration as promising anticancer lead compounds.

Acovenoside A Induces Mitotic Catastrophe Followed by Apoptosis in Non-Small-Cell Lung Cancer Cells.

We investigated the cytotoxic potential of the cardenolide glycoside acovenoside A against non-small-cell lung cancer cells. Lung cancer is the leading cause of cancer-related mortality and the second most common cancer diagnosed. Epidemiological studies revealed a direct correlation between the regular administration of cardiac glycosides and a lower incidence of various cancers. Acovenoside A, isolated from the pericarps of Acokanthera oppositifolia, potently inhibited proliferation and induced cytotoxicity in A549 non-small-cell lung cancer cells with an IC50 of 68 ± 3 nM after 48 h of exposure. Compared to the antineoplastic agent doxorubicin, acovenoside A was more potent in inhibiting the viability of A549 cancer cells. Moreover, acovenoside A exhibited selectivity against cancer cells, being significantly less toxic to lung fibroblasts and nontoxic for peripheral blood mononuclear cells. Analysis of the cell cycle profile in acovenoside A-treated A549 cells revealed mitotic arrest, due to accumulation of the G2/M regulators cyclin B1 and CDK1, and cytokinesis failure. Furthermore, acovenoside A affected the mitochondrial membrane integrity and induced production of radical oxygen species, which resulted in induction of canonical apoptosis, manifested by caspase 3 activation and DNA fragmentation. Based on our results, acovenoside A warrants further exploration as a potential anticancer lead.

The Cardenolide Glycoside Acovenoside A Affords Protective Activity in Doxorubicin-Induced Cardiotoxicity in Mice.

The current study aimed to investigate the protective effect of the cardenolide glycoside acovenoside A (AcoA) against doxorubicin-induced cardiotoxicity in mice. AcoA was isolated from the pericarps of Acokanthera oppositifolia to chemical homogeneity and characterized by means of one- and two-dimensional nuclear magnetic resonance spectroscopy. AcoA exhibited relatively low toxicity in mice (LD50 = 223.3 mg/kg bw). Repeated administration of doxorubicin induced cardiotoxicity manifested by reduced activity of myocardial membrane-bound ion pumps and elevated serum biomarkers of myocardial dysfunction, oxidative stress, and inflammation. Pretreatment of doxorubicin-exposed mice with AcoA (11.16 or 22.33 mg/kg bw, i.p.) for 2 weeks after 2 weeks of combined administration of AcoA and doxorubicin protected the animals dose dependently against doxorubicin-induced cardiotoxicity as indicated by normalization of the levels of different myocardial markers of oxidative stress (malondialdehyde, nitric oxide, total antioxidant capacity, and cardiac glutathione), serum myocardial diagnostic marker enzymes (serum cardiac troponin T, creatine kinase isoenzyme MB, aspartate aminotransferase, and lactate dehydrogenase), and inflammatory markers (c-reactive protein, tumor necrosis factor-α, and interleukin-6), as well as myocardial Na(+)/K(+)-ATPase activity. These effects were attributed to the negative impact of AcoA on transcription factors nuclear factor κB and interferon regulatory factor 3/7. Thus acovenoside A might act as a cardioprotective agent to prevent doxorubicin-induced cardiotoxicity.

Anti-inflammatory and antiatherogenic effects of the NLRP3 inflammasome inhibitor arglabin in ApoE2.Ki mice fed a high-fat diet.

BACKGROUND: This study was designed to evaluate the effect of arglabin on the NLRP3 inflammasome inhibition and atherosclerotic lesion in ApoE2Ki mice fed a high-fat Western-type diet. METHODS AND RESULTS: Arglabin was purified, and its chemical identity was confirmed by mass spectrometry. It inhibited, in a concentration-dependent manner, interleukin (IL)-1ß and IL-18, but not IL-6 and IL-12, production in lipopolysaccharide and cholesterol crystal-activated cultured mouse peritoneal macrophages, with a maximum effect at ≈50 nmol/L and EC50 values for both cytokines of ≈ 10 nmol/L. Lipopolysaccharide and cholesterol crystals did not induce IL-1ß and IL-18 production in Nlrp3(-/-) macrophages. In addition, arglabin activated autophagy as evidenced by the increase in LC3-II protein. Intraperitoneal injection of arglabin (2.5 ng/g body weight twice daily for 13 weeks) into female ApoE2.Ki mice fed a high-fat diet resulted in a decreased IL-1ß plasma level compared with vehicle-treated mice (5.2±1.0 versus 11.7±1.1 pg/mL). Surprisingly, arglabin also reduced plasma levels of total cholesterol and triglycerides to 41% and 42%, respectively. Moreover, arglabin oriented the proinflammatory M1 macrophages into the anti-inflammatory M2 phenotype in spleen and arterial lesions. Finally, arglabin treatment markedly reduced the median lesion areas in the sinus and whole aorta to 54% (P=0.02) and 41% (P=0.02), respectively. CONCLUSIONS: Arglabin reduces inflammation and plasma lipids, increases autophagy, and orients tissue macrophages into an anti-inflammatory phenotype in ApoE2.Ki mice fed a high-fat diet. Consequently, a marked reduction in atherosclerotic lesions was observed. Thus, arglabin may represent a promising new drug to treat inflammation and atherosclerosis.

An α-acetoxy-tirucallic acid isomer inhibits Akt/mTOR signaling and induces oxidative stress in prostate cancer cells.

Here we provide evidence that αATA(8,24) (3α-acetyloxy-tir-8,24-dien-21-oic acid) inhibits Akt/mammalian target of rapamycin (mTOR) signaling. αATA(8,24) and other tirucallic acids were isolated from the acetylated extract of the oleo gum resin of Boswellia serrata to chemical homogeneity. Compared with related tirucallic acids, αATA(8,24) was the most potent inhibitor of the proliferation of androgen-insensitive prostate cancer cells in vitro and in vivo, in prostate cancer xenografted onto chick chorioallantoic membranes. αATA(8,24) induced loss of cell membrane asymmetry, caspase-3 activation, and DNA fragmentation in vitro and in vivo. These effects were selective for cancer cells, because αATA(8,24) exerted no overt toxic effects on peripheral blood mononuclear cells or the chick embryo. At the molecular level, αATA(8,24) inhibited the Akt1 kinase activity. Prior to all biochemical signs of cellular dysfunction, αATA(8,24) induced inhibition of the Akt downstream target mTOR as indicated by dephosphorylation of S6K1. This event was followed by decreased expression of cell cycle regulators, such as cyclin D1, cyclin E, and cyclin B1, as well as cyclin-dependent kinases CDK4 and CDK2 and phosphoretinoblastoma protein, which led to inhibition of the cell-cycle progression. In agreement with the mTOR inhibition, αATA(8,24) and rapamycin increased the volume of acidic vesicular organelles. In contrast to rapamycin, αATA(8,24) destabilized lysosomal and mitochondrial membranes and induced reactive oxygen species production in cancer cells. The ability of αATA(8,24) to inhibit Akt/mTOR signaling and to induce simultaneously oxidative stress could be exploited for the development of novel antitumor therapeutics with a lower profile of toxic side effects.