Chemical Constituents of the Leaves of Thujopsis dolabrata and Their Cytotoxicity.

Five podophyllotoxin derivatives (1-5), two diterpenoids (6 and 7), three diterpenoid xylosides (8-10), a flavanonol glycoside (11), flavonol (12), and biflavonoid (13) were isolated from the leaves of Thujopsis dolabrata (Cupressaceae). Compounds 1, 6, and 8 were named (-)-ß-isopeltatin, epi-nootkastatin 2, and acetoxyanticopalol 15-O-ß-D-xylopyranoside, respectively. The structures of the isolated compounds were determined based on a detailed analysis of NMR spectroscopic data and through chromatographic and spectroscopic analyses following specific chemical transformations. The isolated compounds (1-5 and 7-11) were evaluated for their cytotoxicity toward HL-60 human promyelocytic leukemia cells and Caki-1 human kidney carcinoma cells. The podophyllotoxin derivatives (1-5) exhibited cytotoxicity against both HL-60 and Caki-1 cells with IC50 values ranging from 0.00069 to 5.4 µM, and the diterpenoid derivatives (7-10) demonstrated cytotoxicity against HL-60 cells with IC50 values ranging from 4.5 to 11 µM. HL-60 cells treated with 8 exhibited apoptosis characteristics, such as accumulation of sub-G1 cells and nuclear chromatin condensation.

Chemical Components in Hedera rhombea Leaves and Their Cytotoxicity.

Two novel triterpene glycosides (1 and 2), 17 known triterpene glycosides (3-19), two known flavonoid glycosides (20 and 21), and two known norsesquiterpene glucosides (22 and 23) were isolated from Hedera rhombea (Araliaceae) leaves. The structures of 1 and 2 were determined by spectroscopic analysis, including two-dimensional NMR spectroscopy, and chromatographic analysis of the hydrolyzed products. The cytotoxicity of the isolated triterpene glycosides (1-19) against HL-60 human promyelocytic leukemia cells was evaluated. Compounds 9, 10, and 11 were cytotoxic to HL-60 cells with IC50 values of 7.2, 21.9, and 32.8 µM, respectively. Other compounds isolated from the leaves were not cytotoxic at sample concentrations of 50 µM.

Steroidal Glycosides from the Aerial Parts of Avena sativa L. and Their Cytotoxic Activity.

Twelve steroidal glycosides (1-12) were isolated from the aerial parts of Avena sativa L. (Poaceae). Among the isolated compounds, 1 was directly isolated from the plant for the first time, and 2-6 were new steroidal glycosides. The structures of 1-6 were determined by analysis of their spectroscopic data, chemical transformations, and chromatographic and spectroscopic analyses of the hydrolyzed products. Compounds 5 and 6 were novel steroidal glycosides with a B-ring contracted skeleton (B-nor steroid). Compounds 1, 9, 11, and 12 were cytotoxic to HL-60 human promyelocytic leukemia cells, MIA PaCa-2 human pancreatic carcinoma cells, and A549 human lung adenocarcinoma cells with IC50 values ranging from 0.79 to 13.5 µM. HL-60 cells treated with 1 exhibited apoptotic characteristics, namely, condensed nuclear chromatin, accumulation of sub-G1 cells, and activation of caspase-3. Additionally, the loss of the mitochondrial membrane potential and the release of cytochrome c into the cytoplasm in 1-treated HL-60 cells suggested that 1 induced apoptosis through a mitochondrial-dependent apoptotic pathway.

Structure and Cytotoxicity of Novel Lignans and Lignan Glycosides from the Aerial Parts of Larrea tridentata.

Previously, the authors conducted phytochemical investigations of the aerial parts of Larrea tridentata and reported triterpene glycosides and lignan derivatives. In continuation of the preceding studies, 17 lignans and lignan glycosides (1-17) were isolated, including seven new compounds (1-7). Herein, the structure of the new compounds was determined based on spectroscopic analysis and enzymatic hydrolysis. The cytotoxicity of 1-17 against HL-60 human promyelocytic leukemia cells was examined. Compounds 4-11 and 14-16 were cytotoxic to HL-60 cells, with IC50 values in the range of 2.7-17 µM. Compound 6, which was the most cytotoxic among the unprecedented compounds, was shown to induce apoptotic cell death in HL-60 cells.

Bufadienolides and ecdysteroids from the whole plants of Helleborus niger and their cytotoxicity.

A new bufadienolide (1), two new bufadienolide glycosides (2 and 3), a new ecdysteroid (4), and four known compounds (5-8), were isolated from the whole plants of Helleborus niger L. (Ranunculaceae). The structures of the new compounds (1-4) were determined by spectroscopic analysis, including 2D NMR spectral data, and hydrolytic studies. Compounds 1-6 showed cytotoxicity against HL-60 human leukemia cells, A549 human lung adenocarcinoma cells, and SBC-3 human small-cell lung cancer cells, with IC50 values ranging from 0.0055 to 1.9 µM. HL-60 cells treated with either 3 or 4 showed apoptosis characteristics, such as nuclear chromatin condensation, accumulation of sub-G1 cells, and activation of caspase-3/7.

Bufadienolide glycosides and bufadienolides from the whole plants of Helleborus lividus, and their cytotoxic activity.

Cytotoxicity-guided fractionation of the MeOH extract of Helleborus lividus Aiton ex Curtis (Ranunculaceae) resulted in the isolation of five undescribed bufadienolide glycosides and two undescribed bufadienolides, along with three known compounds. Their structures were determined by detailed spectroscopic analysis and hydrolysis studies. The isolated compounds showed cytotoxicity against HL-60 human leukemia cells and A549 human lung adenocarcinoma cells, with IC50 values ranging from 2.20 ± 0.01 nM to 0.77 ± 0.01 µM. The undescribed compound 3ß-[(O-ß-d-glucopyranosyl-(1 â†’ 4)-α-l-rhamnopyranosyl)oxy]-14ß,16ß-dihydroxy-5ß-bufa-20,22-dienolide induced apoptosis in HL-60 cells via a mitochondria-dependent apoptotic pathway. The average IC50 values of bufadienolide monorhamnosides for HL-60 and A549 cells were 10-20 times lower than those for Na+/K+ ATPase, implying that they induce tumor cell death via a mechanism of action other than Na+/K+ ATPase inhibition.

Novel Steroidal Glycosides from the Whole Plants of Helleborus foetidus.

Phytochemical analysis of the whole Helleborus foetidus plants identified 28 steroidal glycosides (1-28), including 20 novel spirostanol glycosides (1-20) and a novel furostanol glycoside (21). The structures of the newly identified compounds were elucidated by two-dimensional NMR spectroscopy and hydrolytic cleavage. Compounds 12, 13, and 15 were determined to be spirostanol trisdesmosides bearing sugar moieties at the C-1, -21, and -24 hydroxy groups of the aglycone unit. The isolated compounds were subsequently evaluated for cytotoxic activity against HL-60 human promyelocytic leukemia cells and A549 human lung carcinoma cells. In particular, 7 showed cytotoxic activity against the HL-60 and A549 cells, with IC50 values of 5.9 and 6.6 µM, respectively, whereas 19 was selectively cytotoxic to A549 cells with an IC50 value of 5.5 µM.

Bufadienolides from the whole plants of Helleborus foetidus and their cytotoxicity.

Two undescribed bufadienolide glucosides and four undescribed bufadienolides were isolated from the whole plants of Helleborus foetidus (Ranunculaceae). Their structures were determined by extensive spectroscopic analysis and the results of hydrolytic cleavage. The isolated compounds exhibited cytotoxic activities against HL-60 and A549 cells with IC50 values ranging from 0.019 to 3.0 µM. The isolated compounds also showed the Na+/K+ ATPase inhibitory activity. The undescribed compound 16ß-formyloxy-10,14-dihydroxy-5ß-[(ß-d-glucopyranosyl)oxy]-19-norbufa-3,20,22-trienolide induced apoptosis in HL-60 cells through a mitochondria-dependent apoptotic pathway.

Triterpene Glycosides from the Seeds of Dolichos lablab.

Two new triterpene glycosides (1 and 2), together with nine known triterpene glycosides (3-11), were isolated from the seeds of Dolichos lablab (Leguminosae). The structures of the new compounds were determined by spectroscopic analysis, including two-dimensional NMR spectroscopy, and chromatographic analysis of the hydrolyzed products. The isolated compounds did not show cytotoxicity against HL-60 human leukemia cells and HepG2 human hepatoma cells at sample concentrations of 20 µM.

Cholestane glycosides from Ornithogalum saundersiae bulbs and the induction of apoptosis in HL-60 cells by OSW-1 through a mitochondrial-independent signaling pathway.

A search for cytotoxic cholestane glycosides from Ornithogalum saundersiae bulbs resulted in the isolation of three new OSW-1 analogues (1-3), a new cholestane bisdesmoside (4), a 5ß-cholestane diglycoside (5), and four new 24(23 → 22)-abeo-cholestane glycosides (6-9), together with 11 known cholestane glycosides (10-20), including OSW-1 (11). The structures of 1-9 were determined based on conventional spectroscopic analysis and chemical evidence. As expected, based on previous data, 1-3 exhibited potent cytotoxic activity against HL-60 human promyelocytic leukemia cells and A549 human lung adenocarcinoma cells. Furthermore, the ability of OSW-1 to induce apoptosis in HL-60 cells was examined. Aggregation of nuclear chromatin, accumulation of the sub-G1 cells, DNA fragmentation, and caspase-3 activation were assessed in HL-60 cells treated with OSW-1, providing evidence for OSW-1-induced apoptosis in HL-60 cells. No mitochondrial membrane potential or release of cytochrome c into the cytoplasm were observed in the OSW-1-treated apoptotic HL-60 cells, indicating that a mitochondria-independent signaling pathway is involved in apoptotic cell death.

Pregnane glycosides from the bark of Marsdenia cundurango and their cytotoxic activity.

Seven new pregnane glycosides (1-7) and eight known compounds (8-15) were isolated from the bark of Marsdenia cundurango (Asclepiadaceae). The structures of 1-7 were determined by spectroscopic analysis, including two-dimension NMR spectroscopy, chemical transformations, and chromatographic analysis of the hydrolyzed products. The isolated compounds 1-15 were evaluated for their cytotoxic activity against HL-60 human leukemia cells, A549 human lung adenocarcinoma cells, and TIG-3 normal human lung cells, including apoptosis-inducing activity of a representative pregnane glycoside in HL-60 cells.

Nobiletin Reduces Intracellular and Extracellular ß-Amyloid in iPS Cell-Derived Alzheimer's Disease Model Neurons.

Alzheimer's disease (AD) is the most common cause of dementia, with progressive memory impairment. Recently, neprilysin, a ß-amyloid (Aß)-degrading enzyme has become featured as a drug target for AD. Previously, we identified nobiletin from citrus peels as a natural compound possessing anti-dementia activity. In addition, we demonstrated that nobiletin improved memory in memory-impaired animals and, further, that Aß levels were markedly decreased in the brains of these animals. We demonstrated in vitro that nobiletin up-regulates neprilysin expression and activity in human neuroblastoma cells. However, the action of nobiletin with regard to Aß degradation under in vitro AD pathological conditions remains unclear. In this study, we examined whether nobiletin could enhance the degradation of intra- and extracellular Aß using human induced pluripotent stem cell-derived AD model neurons, which generate an excess of Aß1-42 due to the familial AD presenilin-1 mutation. The neurons were treated in the presence or absence of nobiletin. The results of real-time quantitative RT-PCR indicated that neprilysin mRNA levels were significantly up-regulated by nobiletin. Furthermore, immunostaining with an anti-Aß antibody revealed that nobiletin substantially reduced the intraneuronal content of Aß. Interestingly, the results of Aß1-42 immunoassays confirmed that nobiletin also significantly decreased the levels of Aß1-42 released into the cellular medium. These results suggest that nobiletin enhanced the reduction of intra- and that extracellular Aß levels under AD pathologic conditions, and this is associated with the up-regulation of neprilysin expression. Collectively, nobiletin appears to be a promising novel prophylactic seed drug or functional food for AD.

AU-1 from Agavaceae plants downregulates the expression of glycolytic enzyme phosphoglycerate mutase.

The spirostanol saponin AU-1 from Agavaceae plants stimulates the expression of the glycolytic enzyme phosphoglycerate mutase (PGAM) in ACHN cells. We hypothesized that this may arise from the downregulation of the NAD+-dependent deacetylase SIRT1. In this article, we showed that, unlike in renal adenocarcinoma cells, AU-1 does not affect the expression of SIRT1 in the normal renal cell-derived cell line HK-2. Consistent with the lack of a downregulation of SIRT1, AU-1 did not upregulate, but rather decreased PGAM expression. Moreover, AU-1 inhibited the increase in PGAM levels that results from the knock-down of SIRT1. Our results suggest that AU-1 may prevent carcinogenesis caused by increased cellular PGAM.

Structural Characterization of Cholestane Rhamnosides from Ornithogalum saundersiae Bulbs and Their Cytotoxic Activity against Cultured Tumor Cells.

Previous phytochemical studies of the bulbs of Ornithogalum saundersiae, an ornamental perennial plant native to South Africa, resulted in the isolation of 29 new cholestane glycosides, some of which were structurally unique and showed potent cytotoxic activity against cultured tumor cell lines. Therefore, we aimed to perform further phytochemical examinations of methanolic extracts obtained from Ornithogalum saundersiae bulbs, isolating 12 new cholestane rhamnosides (1-12) and seven known compounds (13-19). The structures of the new compounds (1-12) were identified via NMR-based structural characterization methods, and through a sequence of chemical transformations followed by spectroscopic and chromatographic analysis. The cytotoxic activity of the isolated compounds (1-19) and the derivatives (1a and 6a) against HL-60 human promyelocytic leukemia cells and A549 human lung adenocarcinoma cells was evaluated. Compounds 10-12, 16, and 17 showed cytotoxicity against both HL-60 and A549 cells. Compound 11 showed potent cytotoxicity with an IC50 value of 0.16 µM against HL-60 cells and induced apoptotic cell death via a mitochondrion-independent pathway.

AU-1 from Agavaceae plants causes transient increase in p21/Cip1 expression in renal adenocarcinoma ACHN cells in an miR-34-dependent manner.

Here, we show that AU-1, spirostanol saponin isolated from Agavaceae plants, causes a transient increase in cyclin-dependent kinase inhibitor (CDKI) p21/Cip1 through the upregulation of miRNAs, miR-34 and miR-21. AU-1 stimulated p21/Cip1 expression without exerting cytotoxicity against different types of carcinoma cell lines. In renal adenocarcinoma ACHN cells, AU-1 transiently elevated the expression level of p21/Cip1 protein without marked increases in p21/Cip1 mRNA levels. Rapid and transient increases in miR-34 and miR-21, both of which are known to upregulate p21/Cip1, were observed in AU-1-treated cells. Inhibitor for miR-34 and for miR-21 significantly blocked the AU-1-caused increase in p21/Cip1, indicating that elevation of p21/Cip1 protein by AU-1 is dependent on these microRNAs. We further clarified that NAD-dependent deacetylase SIRT1, a direct target of miR-34, is decreased by the treatment with AU-1. Furthermore, we found that SIRT1-knockdown increases p21/Cip1 protein levels in an miR-21-dependent manner. On the other hand, ectopic expression of p21/Cip1 resulted in the lowered expression of miR-34 and miR-21, suggesting that reciprocal regulation exists between p21/Cip1 and these miRNAs. We propose that the following feedback network composed of miR-34/SIRT1/miR-21/p21 is triggered by the treatment with AU-1: in cells treated with AU-1, transient elevation of miR-34 leads to the downregulation of SIRT1, thereby miR-21 is freed from SIRT1-dependent suppression. Then, elevated miR-21 upregulates p21/Cip1 protein, followed by the suppression of miR-34 expression.

Chemical Constituents of the Roots and Rhizomes of Saposhnikovia divaricata and their Cytotoxic Activity.

Phytochemical investigation of the MeOH extract of the roots and rhizomes of Saposhnikovia divaricata (Umbelliferae) resulted in the isolation of six chromons (1-6)-and five polyacetylene derivatives (7-11). Compounds 9 and 11 were isolated from S. divaricate for the first time. The chromon derivatives -(1-6) were evaluated for their cytotoxic activity against HL-60 human promyclocytic leukemia cells. Compound 1 (3'-O-angeloylhamaudol) showed the most potent cytotoxic activity with an IC50 value of 4.41 µM and was found to induce apoptotic cell death in HL-60 cells. The loss of mitochondrial membrane potential, release of cytochrome c into the cytoplasm, and activation of caspase-9 in the 1-treated HL-60 cells suggests that I induces apoptosis through the mitochondial-dependent apoptotic pathway.

Stryphnosides G-P, 10 new triterpene glycosides from the pericarps of Stryphnodendron fissuratum.

Ten new triterpene glycosides, stryphnosides G-P (1-10), were isolated from the pericarps of Stryphnodendron fissuratum (Legminosae). The structures of 1-10 were determined based on spectroscopic analyses, including various two-dimensional NMR spectroscopic techniques, and the results of hydrolytic cleavage. The sugar moiety attached to C-3 of the aglycone of 4, 5, and 7-10 is composed of five or six monosaccharides, of which the terminal α-l-arabinosyl unit has a 1C4 conformation. Compounds 2 and 5 differ from the other isolates in having an α-l-rhamnosyl unit at the C-21 hydroxy group. The cytotoxic activity of 1-10, stryphnosides A-F (11-16), and their aglycones (1a, 11a, 14a, and 16a) against HL-60 cells was also examined.

Nerve growth factor enhances the CRE-dependent transcriptional activity activated by nobiletin in PC12 cells.

Prevention and treatment of Alzheimer disease are urgent problems for elderly people in developed countries. We previously reported that nobiletin, a poly-methoxylated flavone from the citrus peel, improved the symptoms in various types of animal models of memory loss and activated the cAMP responsive element (CRE)-dependent transcription in PC12 cells. Nobiletin activated the cAMP/PKA/MEK/Erk/MAPK signaling pathway without using the TrkA signaling activated by nerve growth factor (NGF). Here, we examined the effect of combination of nobiletin and NGF on the CRE-dependent transcription in PC12 cells. Although NGF alone had little effect on the CRE-dependent transcription, NGF markedly enhanced the CRE-dependent transcription induced by nobiletin. The NGF-induced enhancement was neutralized by a TrkA antagonist, K252a. This effect of NGF was effective on the early signaling event elicited by nobiletin. These results suggested that there was crosstalk between NGF and nobiletin signaling in activating the CRE-dependent transcription in PC12 cells.

[Discovery of Novel Biologically Active Compounds of Natural Origin, with a Focus on Anti-tumor Activity].

Numerous clinically valuable medicines, including anticancer drugs, have been developed from biologically active natural compounds and their structurally related derivatives. This review discusses novel natural compounds with promising biological activities and those with novel chemical structures. Glaziovianin A, an isoflavone isolated from the leaves of Ateleia glazioviana (Legminosae), inhibited cell cycle progression at the M-phase with an abnormal spindle structure. AU-1 and YG-1, 5ß-steroidal glycosides isolated from the whole plants of Agave utahensis and the underground parts of Yucca glauca (Agavaceae), induced apoptosis of HL-60 cells via caspase-3 activation. Lycolicidinol, an alkaloid isolated from the bulbs of Lycoris albiflora (Amaryllidaceae), induced transient autophagy and morphological changes in mitochondria in the early stage of the apoptotic cell death process in HSC-2 cells. Taccasterosides isolated from the rhizomes of Tacca chantrieri (Taccaceae) and stryphnosides isolated from the pericarps of Stryphnodendron fissuratum (Legminosae) are steroidal and triterpene glycosides with unique chemical structures having novel sugar sequences.

Chemical Constituents of the Underground Parts of Iris florentina and their Cytotoxic Activity.

Three new isoflavonoid glycosides (1, 5, and 9) and 10 known compounds (2-4, 6-8, and 10-13) were isolated from the underground parts of Iris florentina (Iridaceae). The structures of the new compounds were determined based on extensive spectroscopic data and the results of hydrolytic cleavage. The isolated compounds and the aglycones were evaluated for cytotoxic activity against HL-60 human promyelocytic leukemia cells. Compound 12 induced apoptotic cell death in the HL-60 cells.