Bioassay-guided fractionation of Euphrasia pectinata Ten. and isolation of iridoids with antiproliferative activity

The use of aerial parts of Euphrasia pectinata Ten. usually known as Eyebright, is one of the commonest folk remedy in many European and Asian countries to treat eye problems. By a bioassay-guided fractionation of the dichloromethane fraction of E. pectinata methanolic extract, following the antiproliferative activity on different cancer cell lines (MCF-7, HeLa, LNCaP, ACHN and C32), the new iridoid euphrasin (1), and the known campsinol (2), artselaenin A (3), and artselaenin B (4) were isolated. The structure of euphrasin (1) was determined by spectroscopic methods. All compounds screened by SRB assay exhibited antiproliferative activity in a concentration dependent-manner. In particular, euphrasin (1) showed a promising activity against LNCaP and HeLa cells with IC50 values of 0.1 and 0.2 μM, respectively. Signficative results were also obtained with campsinol (2) with IC50 value of 1.9 μM on endometrial cancer cells.     

Inhibitory effects of metachromins L–Q and its related analogs against receptor tyrosine kinases EGFR and HER2

Metachromins are a series of sesquiterpenoid quinones isolated from Okinawan marine sponges. Inhibitory effects of metachromins L–Q (1–6), sesquiterpenoid quinones with an amino acid residue, and their related analogs (7–18) prepared from metachromins A (19) and C (20) against receptor tyrosine kinases EGFR and HER2 were investigated. Two analogs 11 and 12 showed relatively stronger inhibitory activity against EGFR, while metachromins L–Q (1-6) and seven analogs (8, 10, 11, and 15–18) showed inhibitory activities against HER2.     

Carandinol: First isohopane triterpene from the leaves of Carissa carandas L. and its cytotoxicity against cancer cell lines

A new triterpene carandinol (1) was isolated from the leaves of Carissa carandas L., along with five known compounds, betulinic acid (2), β-sitosterol-3-O-β-d-glucopyranoside (3), oleanolic acid (4), ursolic acid (5) and 4-hydroxybenzoic acid (6). The structure of compound 1 was deduced as 3β,21α-dihydroxyisohopane by exhaustive spectroscopic analyses. The known compounds 2–6 were identified by comparison with the reported spectral data. Compound 1 was evaluated for cytotoxicity, immunomodulatory, antiglycation, antioxidant and enzyme inhibition activity. It exhibited significant in vitro cytotoxicity to every cell line tested (HeLa, PC-3 and 3T3) and was relatively more toxic to human cervical cancer (HeLa) cell line. This is the first report of the isolation of an isohopane triterpene from the genus Carissa. Carandinol also represents the first example of a cytotoxic isohopane.     

Fluorescence kinetics in HeLa cells after treatment with cell cycle arrest inducers visualized with Fucci (fluorescent ubiquitination-based cell cycle indicator)

Fucci (fluorescent ubiquitination-based cell cycle indicator) is able to visualize dynamics of cell cycle progression in live cells; G1- and S-/G2-/M-phase cells expressing Fucci emit red and green fluorescence, respectively. This system could be applied to cell kinetic analysis of tumour cells in the field of cancer therapy; however, it is still unclear how fluorescence kinetics change after various treatments, including exposure to anticancer agents. To explore this, we arrested live HeLa cells expressing the Fucci probes at various cell cycle stages and observed the fluorescence, in conjunction with flow cytometric analysis. X-irradiation, HU (hydroxyurea) and nocodazole arrest cells at G2/M boundary, early S-phase and early M-phase, respectively. Although X-irradiation and HU treatment induced similar accumulation kinetics of green fluorescent cells, nocodazole treatment induced an abnormal red fluorescence at M phase, followed by accumulation of both red and green fluorescent cells with 4N DNA content. We conclude that certain agents that disrupt normal cell cycle regulation could cause unexpected fluorescence kinetics in the Fucci system.     

Fucci2a: A bicistronic cell cycle reporter that allows Cre mediated tissue specific expression in mice

Markers of cell cycle stage allow estimation of cell cycle dynamics in cell culture and during embryonic development. The Fucci system incorporates genetically encoded probes that highlight G1 and S/G2/M phases of the cell cycle allowing live imaging. However the available mouse models that incorporate Fucci are beset by problems with transgene inactivation, varying expression level, lack of conditional potential and/or the need to maintain separate transgenes—there is no transgenic mouse model that solves all these problems. To address these shortfalls we re-engineered the Fucci system to create 2 bicistronic Fucci variants incorporating both probes fused using the Thosea asigna virus 2A (T2A) self cleaving peptide. We characterize these variants in stable 3T3 cell lines. One of the variants (termed Fucci2a) faithfully recapitulated the nuclear localization and cell cycle stage specific florescence of the original Fucci system. We go on to develop a conditional mouse allele (R26Fucci2aR) carefully designed for high, inducible, ubiquitous expression allowing investigation of cell cycle status in single cell lineages within the developing embryo. We demonstrate the utility of R26Fucci2aR for live imaging by using high resolution confocal microscopy of ex vivo lung, kidney and neural crest development. Using our 3T3 system we describe and validate a method to estimate cell cycle times from relatively short time-lapse sequences that we then apply to our neural crest data. The Fucci2a system and the R26Fucci2aR mouse model are compelling new tools for the investigation of cell cycle dynamics in cell culture and during mouse embryonic development.     

Supercritical fluid extraction assisted isolation of sesquiterpene lactones with antiproliferative effects from Centipeda minima

Pseudoguaianolide sesquiterpene lactones minimolides A (1), B (2), C (3) and D (4) and two guaianolide sesquiterpene lactones minimolides E (5) and F (6), along with seven known ones (7–13), were isolated from the supercritical fluid extract of Centipeda minima. The structures of these compounds were elucidated by extensive spectroscopic methods (IR, UV, HRESIMS, 1D-NMR and 2D-NMR), and the complete structure and stereochemistry of 1 was further confirmed by X-ray diffraction analysis. Compounds 1, 5–8, 11 and 13 displayed inhibitory activity against human nasopharyngeal cancer cells (CNE) with IC₅₀ values ranging from 1.1 to 20.3 μM. Compound 13 containing both α-methylene-γ-lactone and α, β-unsaturated cyclopentenone moieties exhibited even stronger inhibitory activity than that of cisplatin (positive control) through cell cycle arrest at G2/M phase. Isolation of six sesquiterpene lactones from Centipeda minima highlighted the potential of supercritical fluid extraction for enrichment of minor constituents for phytochemical study.     

Pentacyclic hemiacetal sterol with antifouling and cytotoxic activities from the soft coral Nephthea sp.

A novel unusual pentacyclic hemiacetal sterol nephthoacetal (1), was isolated from soft coral Nephthea sp. The structure of this sterol was inferred from its two acetyl derivatives (2) and (3), by means of spectroscopic methods, and quantum chemical calculations. Anti-fouling activity of compounds 1–3 against Bugula neritina larvae was evaluated, sterol (1) exhibited significant inhibitory effect with EC₅₀ value of 2.5 μg/mL, while having low toxicity with LC₅₀ >25.0 μg/mL. The in vitro cytotoxic activity of compounds 1–3 against HeLa cells was also evaluated, all of them exhibited moderate cytotoxicity with IC₅₀ values of 12.3 (1), 10.1 (2), and 19.6 μg/mL (3), respectively.     

Decaturenol A and known oxalicine related meroterpenoids isolated from Penicillium decaturense RO050, and their new biological activities

Decaturenol A (1), a new oxalicine related meroterpenoid, has been isolated from Penicillium decaturense RO050 along with seven known compounds (2–8). The structure of 1 was elucidated by spectroscopic data. The effects of isolated compounds (1–8) on endoplasmic reticulum (ER) stress-induced cell death in HT22 hippocampal nerve cells and on the interleukin 10 (IL-10)-induced expression of CD163, a M2 phenotype marker, in human monocyte-derived macrophages were evaluated. While decaturenol A (1) exhibited a protective effect on ER stress-induced cell death in HT22 cells at 10 µM, on the other hand oxalicine A (7) showed cytotoxic activity (IC₅₀ = 5.9 µM). Additionally, decaturenol A (1), decaturins D (2), E (3), and B (4) inhibited the IL-10-induced expression of CD163 each at a concentration of 20 µg/mL.     

Two new butanolides from the roots of Litsea acuminata

Two new butanolides, licunolides A (1) and B (2), were isolated from the roots of Litsea acuminata, together with three known compounds: isolancifolide (3), longifolin (4), and sesquirose furan (5). The structures of compounds 1 and 2 were determined by spectroscopic studies (IR, MS, 1D and 2D NMR) and chemical evidence. This is the first report of 4-hydroxy-5-methylbutanolides with a C₁₀-side chain from a natural source. Longifolin (4) and sesquirose furan (5) showed a significant cytotoxicity against HeLa cell lines in vitro.     

Four new phenylpropanoid glycosides from Clausena dunniana var. robustaand their antiinflammatory activities

Four new phenylpropanoid glycosides, clausenaglycosides A–D (1–4), along with fourteen known compounds (5–18) were isolated from the leaves and twigs of Clausena dunniana var. robusta. The structures of the isolated compounds were determined by a combination of 1D and 2D NMR, MS, and CD spectroscopic data. The NF-κB inhibitory activity was evaluated in HeLa cells. Compound 17 displayed a moderate inhibition against NF-κB activation.     

The synthesis of ursolic acid derivatives with cytotoxic activity and the investigation of their preliminary mechanism of action

Nineteen ursolic acid derivatives (15 novel compounds) modified at the C-3 and the C-28 positions were synthesized. The cytotoxic activity of the derivatives was evaluated against HeLa, BGC-823 and SKOV3 cells by MTT assay. Inducing apoptosis and affecting cell cycle distribution by the derivatives in HeLa cells were assessed by flow cytometry and DNA fragmentation. Compounds 10b and 11b were particularly active to inhibit HeLa cells growth through inducing apoptosis and arresting cell cycle progression. The typical ‘sub-G1 peak’ and DNA ladder formation were checked and cell cycle was arrested at the S phase in a dose-dependent manner.     

Alkene lactones from Persea fulva (Lauraceae): Evaluation of their effects on tumor cell growth in vitro and molecular docking studies

The new alkene lactone, (3E)-5,6-dihydro-5-(hydroxymethyl)-3-docdecylidenefuran-3(4H)-one (1), named majoranolide B, and three alkene lactones known as majorenolide (2), majoranolide (3) and majorynolide (4) were obtained from the aerial parts of Persea fulva (Lauraceae). The structures were elucidated in light of extensive spectroscopic analysis, including 1D, 2D NMR (¹H, ¹³C, ¹H-¹H-COSY, HMBC and HSQC) and HR-ESI-MS. These compounds were screened for their in vitro antiproliferative activity in rat C6 glioma and astrocyte cells using MTT assay and in silico by molecular docking against targets that play a central role in controlling glioma cell cycle progression. Majoranolide (3) is the most active compound with IC₅₀ 6.69 µM against C6 glioma cells, followed by the compounds 1 (IC₅₀ 9.06 µM), 2 (IC₅₀ 12.04 µM) and 4 (IC₅₀ 41.90 µM). The alkene lactones 1–3 exhibited lower toxicity in non-tumor cells when compared to glioma cells. Molecular docking results showed that majoranolide establishes hydrogen bonds with all targets through its α,β-unsaturated-γ-lactone moiety, whereas the long-chain alkyl group binds by means of several hydrophobic bonds. In the present study, it can be concluded from the anti-proliferative activity of isolates against C6 glioma cells that lactone constituents from P. fulva could have a great potential for the control of C6 glioma cells.     

New tirucallane triterpenoids from Picrasma quassioides with their potential antiproliferative activities on hepatoma cells

Seven new tirucallane-type triterpenoids (1–7), kumuquassin A-G, along with 20 known analogues (8–27) were isolated from the stems of Picrasma quassioides. The structures and the absolute configurations of new compounds were elucidated by spectroscopic data, electronic circular dichroism (ECD) spectroscopic analyses and quantum ECD calculations. Notably, kumuquassin A (1) contains a rare Δ^{17, 20} double bond, kumuquassin B (2) is the first example of tirucallane triterpenoid possessing a 5/3 biheterocyclic ring system at the side chain. All the compounds were screened for the cytotoxicity against two human hepatoma cell lines, HepG2 and Hep3B, and several compounds exhibited promising activity. The most potential compound 3 was selected for cell cycle analysis, which showed that 3 could cause an accumulation of HepG2 cells at subG1 peak. Annexin V-FITC/PI staining further confirmed that compound 3 caused death of hepatoma cells through apoptosis induction.     

A new cytotoxic apotirucallane from the roots of Walsura trichostemon

A new apotirucallane, trichostemonate (1), was isolated from the roots of Walsura trichostemon. The complete structural assignment of this new compound was elucidated from spectroscopic methods and the stereochemistry of 1 was confirmed by X-ray crystallographic analysis. Moreover, this new compound was evaluated for its cytotoxicity (KB and HeLa cells), and showed significant cytotoxicity against both KB and HeLa cell lines with IC₅₀ values of 3.28 and 0.93 μg/mL, respectively.     

Tomensides A–D,new antiproliferative phenylpropanoid sucrose esters from Prunus tomentosa leaves

To search for novel cytotoxic constituents against cancer cells as lead structures for drug development, four new 3-phenylpropanoid-triacetyl sucrose esters, named tomensides A–D (1–4), and three known analogs (5–7) were isolated from the leaves of Prunus tomentosa. Their structures were elucidated by spectroscopic analyses (1D, 2D NMR, CD and HRESIMS). The cytotoxic activities of all isolates against four human cancer cell lines (MCF-7, A549, HeLa and HT-29) were assayed, and the results showed that these isolates displayed stronger inhibitory activities compared with positive control 5-fluorouracil. Tomenside A (1) was the most active compound with IC₅₀ values of 0.11–0.62 μM against the four tested cell lines. The structure–activity relationship (SAR) of the isolates was also discussed. The primary screening results indicated that these 3-phenylpropanoid-triacetyl sucrose esters might be valuable source for new potent anticancer drug candidates.     

A novel prenylated C6–C3 compound with estrogen-like activity from the fruits of Illicium arborescens

A novel C₆–C₃ prenylated compound, illicarborene A (1), together with illioliganfunone D (2), 1-allyl-3,5-dimethoxy-4-(3-methylbut-2-enyloxy)benzene (3), (?)-illicinone A (4), (?)-illicinone B (5) and (?)-illicinone A derivative (6) was isolated and characterized from the fruits of Illicium arborescens Hayata. Compound 1 possesses a new class of tricyclic 6/6/5 ring system. The structure of 1 was determined by spectroscopic analysis such as ¹H–¹H COSY, HMQC, HMBC, and NOESY, and confirmed by chemical reaction to yield 7. Compounds 1–5 were found to increase proliferative activity in primary cell culture of osteoblast cells.     

Cytotoxic diterpenoids as potential anticancer agents from the twigs of Casearia kurzii

A search for bioactive natural products as anticancer lead compounds has led to the isolation of five new clerodane diterpenoids (1–5) from the twigs of Casearia kurzii. Their structures were elucidated by extensive analysis of their NMR, IR, and HRESIMS data, and the absolute configurations were determined by experimental and calculated electronic circular dichroism (ECD) data analysis. The isolates were biologically evaluated and showed cytotoxic activities toward human lung cancer cells (A549), human cervical cancer cells (HeLa), and human hepatocellular carcinoma cells (HepG2). The most active compound (5) with an IC₅₀ value of 5.3 μM against HeLa cells, was found to induce apoptosis and arrest the HeLa cell cycle at G0/G1 stage to exert cytotoxic effects.     

Xanthones and a benzophenone from the roots of Pentadesma butyracea and their antiproliferative activity

A new xanthone, 3,4-dihydro-8,10,12-trihydroxy-2,2-dimethylpyrano[2,3-b]xanthen-11(2H)-one or butyraxanthone E (1), along with the known compounds 30-epi-cambogin (2), 1,7-dihydroxyxanthone (3) and 1,5-dihydroxyxanthone (4) were isolated from the roots of Pentadesma butyracea. Their structures were elucidated by spectroscopic means and comparison with published data. Their antiproliferative activities were evaluated against Drosophila S2 cells and two human cancer cell lines, THP-1 (leukemia) and HCT116 (colon cancer). Compounds 1 and 2 showed moderate antiproliferative activity against Drosophila S2 cells and the HCT116 cell line, respectively. Compound 2 was active against Drosophila S2 cells.     

Two new coumarins and a new xanthone from the leaves of Rhizophora mucronata

Two new coumarins (1, 2) and a new xanthone (3), together with 14 known compounds—eight coumarins (4, 5, 9, 10, 12–15), three xanthones (11, 16, 17), a benzoic acid (6) and two flavonones (7, 8)—were isolated from the leaves of Rhizophora mucronata. The structures of the compounds were elucidated by spectroscopic (IR, MS, and NMR) analyses. The isolated compounds were tested for cytotoxicity against human cancer cell lines HL-60 and HeLa. Among these compounds, only compound 16 inhibited the growth of both HeLa (IC₅₀?=?4.8?μM) and HL-60 (IC₅₀?=?1.0?μM) cells. Compounds 4, 7, 10, and 12 exhibited moderate activity against HeLa cells (IC₅₀?=?3.8–8.3?μM). Compounds 5, 9, 11, and 17 showed moderate activity against HL-60 cells (IC₅₀?=?2.2–6.3?μM). Higher selectivity against HL-60 cell lines was observed for compounds 5, 9, 11, and 16 with SI values (NIH 3T3/HL-60) of 8.6, 19.2, 9.4, and 10.2, respectively.     

Ring A rearranged limonoids from the fruits of Aphanamixis grandifolia and their cytotoxicity evaluation

Two new limonoids aphanamolides C (1) and D (2), together with two known limonoids aphanamolide A (3) and aphapolynin A (4), were isolated from the fruits of Aphanamixis grandifolia. Their structures were assigned on the basis of spectroscopic data, with the absolute configurations of 1 and 2 being established by electronic circular dichroism (ECD) spectroscopic analyses. Those limonoids varied in the ring A: aphanamolide C featured two oxygenated bridges, and aphanamolide D was the second example containing β-hydroxy-α,β:γ,δ-dienoate moiety. The cytotoxic activities were also evaluated in vitro against four human cancer cell lines (MCF-7, A549, SMMC-7721, and HL-60).