In vitro apoptotic effect of cassaine-type diterpene amides from Erythrophleum fordii on PC-3 prostate cancer cells

Cytotoxic activity-guided fractionation of Erythrophleum fordii led to the isolation of two new cassaine diterpenoid–diterpenoid amide dimers, erythrophlesins H–I (1, 2). Spectral data indicated that they consist of asymmetrical dimeric structure via an ester bond between two cassaine diterpenoids. MTT assay confirmed that compound 1, erythrophlesin H, had the strongest cytotoxic effect toward the human prostate cancer cell line, PC-3. The molecular mechanism by which this compound induced apoptosis cell in prostate cancer remains unknown. Erythrophlesin H induced apoptosis in a dose-dependent manner. Acridine orange and annexin V-FITC/PI double staining confirmed that erythrophlesin H effectively induces apoptosis in PC-3 cells.     

(−)-9′-O-(α-l-Rhamnopyranosyl)lyoniresinol from Lespedeza cuneata suppresses ovarian cancer cell proliferation through induction of apoptosis

Lespedeza cuneata (Dum. Cours.) G. Don. (Fabaceae), known as Chinese bushclover or sericea lespedeza, has been used in traditional medicine to treat diabetes, hematuria, and insomnia, and it has been reported that bioactive compounds from L. cuneata possess various pharmacological properties. However, there has been no study to determine the active compounds from L. cuneata with potential activity against ovarian cancer. This study aimed to isolate cytotoxic compounds from L. cuneata and identify the molecular mechanisms underlying the apoptosis pathway in ovarian cancer cells. Based on cytotoxic activity identified in the screening test, chemical investigation of the active fraction of L. cuneata led to the isolation of nine compounds including four lignanosides (1–4), three flavonoid glycosides (5–7), and two phenolics (8–9). Cytotoxicity and the molecular mechanism were examined by methyl thiazolyl tetrazolium (MTT) assay and Western blot analysis. Of the isolated compounds, (?)-9′-O-(α-l-rhamnopyranosyl)lyoniresinol (3) demonstrated the strongest effect in suppressing A2780 human ovarian carcinoma cell proliferation in a dose-dependent manner, with an IC₅₀ value of 35.40?±?2.78?μM. Control A2780 cells had normal morphology, whereas cell blebbing, shrinkage, and condensation were observed after treatment with compound 3. Western blotting analysis showed that compound 3 inhibited A2780 human ovarian cancer cell viability by activating caspase-8, caspase-3, and PARP, which contributed to apoptotic cell death. These results suggest that (?)-9′-O-(α-l-rhamnopyranosyl)lyoniresinol (3) has potent anticancer activities against A2780 human ovarian carcinoma cells through the extrinsic apoptotic pathway. Therefore, (?)-9′-O-(α-l-rhamnopyranosyl)lyoniresinol is an excellent candidate for the development of novel chemotherapeutics.     

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.     

New monoterpenes from stalks and infructescence of Sibiraea leavigata

Chemical investigation of the ethanol extract of the stalks and infructescence of Sibiraea leavigata led to the isolation of two new monoterpenes named (4R)-2-(2-hydroxy-4-methyl-3-pentenyl)furan-2(5H)-one (1) and (2R,4R)-2-(2-hydroxyethyl)-4-(2-methyl-1-propenyl)furan-5H-2-one (2) along with eight known phenylpropanoids (3–10). Their structures were established on the basis of the interpretation of spectroscopic data and electronic circular dichroism (ECD) calculations. In addition, all of these isolates were evaluated for their cytotoxic activity. The results showed that compound 3 displayed moderate cytotoxicity with IC₅₀ values ranging from 10.8 to 49.2 μg mL⁻¹ against five cell lines. While 1 showed selective promotion effects on proliferation of gastric cancer MGC803 and RSC96 cell lines.     

Meeting organometallic chemistry with drug discovery: CH activation enabled discovery of a new ring system of 12H-Indazolo[2,1-a]cinnolin-12-ones with anti-proliferation activity

A diverse library of new ring system 12H-indazolo[2,1-a]cinnolin-12-ones have been synthesized efficiently via Ru (II) and Rh (III) catalyzed tandem CH alkylation/[4 + 2] annulation with diazo compounds in high to excellent yields. For the first time, we evaluated the biological activity of these compounds with this new skeleton and found some compounds exhibited high cytotoxic activity against human PC-3 and PANC-1 tumor cell lines with nanomolar IC₅₀. Among them, the most potent compound 36 showed broad-spectrum cytotoxic activities against a series of human tumor cell lines derived from different organs (IC₅₀ ~ 41 to 197 nM). Moreover, preliminary mechanistic studies indicated that 36 could inhibit the colony formation, cause cell cycle arrest and induce apoptosis of PC-3 cancer cells in a dose-dependent manner. Further intracellular mechanisms investigation found that 36 treatments could dose-dependently decrease the levels of caspase-3 and PARP and up-regulate the level of cleaved PARP. These results suggested that 36 is a novel compound with good potential in the treatment of human cancers and worthy of further investigation.     

Discovery and development of 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid derivatives as Bcl-2/Mcl-1 inhibitors

Bcl-2 family proteins play a vital role for cancer cell in escaping apoptosis, and small-molecule anti-apoptotic Bcl-2 protein inhibitors have been developed as new anticancer therapies. In current study, a series of substituted 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid derivatives were developed based on the lead compound 1 (K_i = 5.2 µM against Bcl-2 protein). The fluorescence polarization assays suggested that active compounds possessed potent binding affinities to both Bcl-2 and Mcl-1 protein, but had minor or no binding affinities to Bcl-X_L protein. MTT assays showed that these compounds had certain anti-proliferative activities against cancer cells. Furthermore, it was found that active compound 11t could induce cell apoptosis and caspase-3 activation in a dose-dependent manner in Jurkat cells.     

Synthesis of quercetin glycosides and their melanogenesis stimulatory activity in B16 melanoma cells

4′-O-β-d-Glucopyranosyl-quercetin-3-O-β-d-glucopyranosyl-(1→4)-β-d-glucopyra-noside (3) was isolated from Helminthostachys zeylanica root extract as a melanogenesis acceleration compound and was synthesized using rutin as the starting material. Related compounds were also synthesized to understand the structure–activity relationships in melanin biosynthesis.Melanogenesis activities of the glycosides were determined by measuring intracellular melanin content in B16 melanoma cells. Among the synthesized quercetin glycosides, quercetin-3-O-β-d-glucopyranoside (1), quercetin-3-O-β-d-glucopyranosyl-(1→4)-β-d-glucopyranoside (2), and 3 showed more potent intracellular melanogenesis acceleration activities than theophyline used as positive control in a dose-dependent manner with no cytotoxic effect.     

Flavonoids and anthraquinones from Murraya tetramera C. C. Huang (Rutaceae)

Phytochemical investigation of Murraya tetramera C. C. Huang led to the isolation of ten flavonoids (1−10) and three anthraquinones (11−13). Their structures were determined on the basis of MS, NMR, specific optical rotation, and CD spectroscopic data analysis, and by comparison of the obtained data with those reported in the literature. This is the first report for the occurrence of compounds 2, 4–7, and 11–13 in the Murraya species, and all the compounds were isolated from M. tetramera for the first time with the exception of compound 3. The chemotaxonomic significance of these compounds was also discussed.     

Design,synthesis and biological evaluation of novel β-pinene-based thiazole derivatives as potential anticancer agents via mitochondrial-mediated apoptosis pathway

A series of novel β-pinene-based thiazole derivatives were synthesized and characterized by HRMS, ¹H NMR, and ¹³C NMR analyses as potential antineoplastic agents. Derivatives were evaluated for their anticancer activities in vitro, and the data manifested that most target compounds showed potent anti-proliferative activities against three human cancer cell lines. Especially, compound 5g displayed excellent cytotoxic activity against Hela, CT-26, and SMMC-7721 cell lines with IC₅₀ values of 3.48 ± 0.14, 8.84 ± 0.16, and 6.69 ± 0.15 µM, respectively. To determine the underlying mechanism of compound 5g on cell viability, DAPI staining, Annexin-V/PI staining, JC-1 staining, DCFDA staining, and Western blot analysis were performed. Our data showed that compound 5g inhibited cell proliferation by inducing apoptosis and cell cycle arrest of Hela cells at the G0/G1 phase in a dose dependent manner. Further studies revealed that compound 5g enhanced levels of reactive oxygen species (ROS), caused a decrease in mitochondrial membrane potential, increased the release of mitochondrial cytochrome C, and affected the expression of Bax, Bcl-2, caspase-3 and caspase-9. Thus, our findings indicated that compound 5g induced apoptosis in Hela through ROS-mediated mitochondrial dysfunction signaling pathways.     

New polyoxygenated cyclohexenes isolated from Uvaria rufa and cinnamtannin B1 isolated from Nephelium hypoleucum with TRAIL-resistance-overcoming activity

Bioactivity-guided isolation of Uvaria rufa leaves and Nephelium hypoleucum bark resulted in the successful isolation of nine compounds (1–9) bearing a new polyoxygenated cyclohexene scaffold: zeylenol-6-shikimate (1), (−)-zeylenol (2), microcarpin A (3), uvarigranol F (4), quercetin (5), kaempferol (6), and p-coumaric acid (7) from U. rufa, and epicatechin (8) and cinnamtannin B1 (9) from N. hypoleucum. The structures of the isolated compounds were elucidated using various spectroscopic techniques. All compounds, except for 7, exhibited weak-to-strong TRAIL-resistance-overcoming activity and an increased gastric cancer cell line (AGS) inhibition by 17–32% as compared to the treatment with the compounds alone. Compounds 3 and 9 were studied for their ability to overcome TRAIL resistance using western blot analysis, which indicated that they sensitised AGS cells to apoptosis via both extrinsic and intrinsic pathways by increasing the expression of several proapoptotic proteins (cleaved caspase-3, −8, and −9) and by decreasing the expression of anti-apoptotic protein Bcl-2.     

Two new polycyclic polyprenylated acylphloroglucinols from Hypericum curvisepalum N. Robson

Phytochemical investigation of the whole plant of Hypericum curvisepalum led to the isolation of nine polycyclic polyprenylated acylphloroglucinols (1–9). Among them, curvisepalumiones A (1) and B (2) are two new compounds and their structures were elucidated based on extensive spectroscopic data analysis combined with Rh₂(OCOCF₃)₄-induced electronic circular dichroism experiment. Cytotoxic assay showed that all the tested compounds except for 1 was moderately cytotoxic against human hepatocarcinoma cell line SMMC-7721 cell line, while compounds 3 and 4 also exhibited cytotoxicity toward MGC-803 cells. In addition, compound 2 exhibited weak inhibitory activity against Bacillus subtilis.     

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.     

Discovery of novel 4(1H)-quinolone derivatives as potential antiproliferative and apoptosis inducing agents

A series of novel 4(1H)-quinolone derivatives was synthesized and evaluated for antiproliferative activity in vitro. The results showed that these compounds exhibited more potent antiproliferative effect against a panel of human tumor cell lines than the lead compound 7-chloro-4(1H)-quinolone 1. Compound 7e was found to be the most potent antiproliferative agent and to exhibit selective cytotoxic activity against HepG2 cell lines with IC₅₀ value lower than 1.0 μM. Annexin V/FITC-PI assay showed that compound 7e induced apoptosis in HepG2 cells with a dose-dependent manner. Western blotting analysis indicated that compound 7e induced cell cycle arrest in G2/M phase by p53-depedent pathway.     

Pro-apoptotic activity of acylated triterpenoid saponins from the stem bark of Albizia chevalieri harms

As a continuation of our interest in apoptosis-inducing triterpenoid saponins from Albizia genus, phytochemical investigation of the stem bark of Albizia chevalieri led to the isolation of three new oleanane-type saponins, named chevalierosides A–C (1–3). Their structures were established on the basis of extensive analysis of 1D and 2D NMR (¹H-, ¹³C NMR, DEPT, COSY, TOCSY, ROESY, HSQC and HMBC) experiments, HRESIMS studies, and by chemical evidence. The pro-apoptotic effect of the three saponins was evaluated on two human cell lines (pancreatic carcinoma AsPC-1 and hematopoietic monocytic THP-1). Cytometric analyses showed that saponins 1–3 induced apoptosis of both human cell lines (AsPC-1 and THP-1) in a dose-dependent manner.     

Two new rocaglamide derivatives from twigs of Aglaia odorata var. microphyllina

Phytochemical investigation of Aglaia odorata var. microphyllina led to the isolation of two new rocaglamide derivatives and three known ones. The structures of the two new compounds were elucidated as 8b-methoxy-desmethylrocaglamide (1) and 3′-hydroxy-8b-methoxy-rocaglamide (2) by spectroscopic techniques (IR, MS, 1D and 2D NMR) and comparing with published data. All the five compounds were evaluated for cytotoxic activity against K562 cell line by MTT method. The results indicated that the OH at 8b position was a decisive group for cytotoxic activity.     

Design,synthesis and evaluation of structurally diverse chrysin-chromene-spirooxindole hybrids as anticancer agents

A series of structurally diverse chrysin-chromene-spirooxindole hybrids were designed, synthesized via a Knoevenagel/Michael/cyclization of chrysin and isatylidene malononitrile derivatives through utilizing a hybrid pharmacophore approach. The newly synthesized compounds were evaluated for their in vitro anticancer activity, and most of the compounds showed stronger anti-proliferative activity than parent compound chrysin. In particular, compound 3e had the highest cytotoxicity towards A549 cells (IC₅₀ = 3.15 ± 0.51 μM), and had better selectivity in A549 cells and normal MRC-5 cells. Furthermore, compound 3e could significantly inhibit the proliferation and migration of A549 cells in a dose-dependent manner, as well as induce the apoptosis possibly through mitochondria-mediated caspase-3/8/9 activation and multi-target co-regulation of the p53 signaling pathway. Thus, our results provide in vitro evidence that compound 3e may be a potential candidate for the development of new anti-tumour drugs.     

Two new compounds from Trigonostemon heterophyllus

Phytochemical investigation on the stems of Trigonostemon heterophyllus led to the isolation of a new diterpene, trigonoheterene (1), and a new naphthoquinone, trigonoheterone (2), together with two known compounds, 3,4-seco-sonderianol, (3) and trigonochinene E, (4). Their structures were determined by spectroscopic techniques (UV, IR, MS, 1D and 2D NMR). All compounds were evaluated for cytotoxic activities and antibacterial activities.     

Bioactivity of prenylated hydroxybenzoic acids from Piper garagaranum C. DC

A bio-assay guided fractionation of Piper garagaranum C. DC. led to the isolation of two prenylated hydroxybenzoic acids (1-2) with anti-inflammatory and cytotoxic activities. The anti-inflammatory action was determined in an LPS stimulated RAW 264.7 murine macrophage assay with IC50 values for inhibition of NO production of (18 ± 3) and (26 ± 5) μM, for 1 and 2, respectively. These compounds do not inhibit NO production by a competitive inhibition of the iNOS enzyme and show anti-inflammatory properties by lowering the expression of pro-inflammatory genes (TNF-α, IL-1β, CXCL2 and CCL2), as determined by qRT-PCR. Electrochemical measurements using cyclic voltammetry (CV) show that compound 1 exhibits anti-oxidant properties. This is the first phytochemical study of this plant, and we report a preliminary study of the biological activity of the isolated compounds.