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.

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.

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.

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.

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.

Amurensiosides L-P, five new cardenolide glycosides from the roots of Adonis amurensis.

Five new cardenolide glycosides, amurensiosides L-P (1-5), were isolated from the roots of Adonis amurensis. Their structures were determined based on extensive spectroscopic analysis, including two-dimensional (2D) NMR data, and on the results of hydrolytic cleavage. Compounds 1-5 were evaluated for their cytotoxic activities against HL-60 human promyelocytic leukemia and HSC-2 human oral squamous cell carcinoma cell lines.

Steroidal glycosides from the underground parts of Yucca glauca and their cytotoxic activities.

Six steroidal glycosides and 14 known compounds were isolated from the underground parts of Yucca glauca (Agavaceae). Their structures were determined from extensive spectroscopic analysis, including analysis of two-dimensional NMR data, and from chemical transformations. The compounds were also evaluated for cytotoxic activities against HL-60 human leukemia cells and A549 human lung adenocarcinoma cells. Four spirostanol glycosides and three furostanol glycosides exhibited cytotoxic activities against both HL-60 and A549 cells. Two of the compounds induced apoptosis in HL-60 cells.

6-demethoxynobiletin, a nobiletin-analog citrus flavonoid, enhances extracellular signal-regulated kinase phosphorylation in PC12D cells.

We previously demonstrated that nobiletin, a polymethoxylated flavone isolated from citrus peels, has the potential to improve cognitive dysfunction in patients with Alzheimer's disease (AD). Recent studies suggest that the generation of intraneuronal amyloid-beta (Aß) oligomers is an early event in the pathogenesis of AD. Aß oligomers cause deficits in the regulation of the extracellular signal-regulated kinase (ERK) signaling which is critical for consolidation of the memory. Our previous studies revealed that nobiletin activated ERK signaling and subsequent cyclic AMP response element-dependent transcription. In this study, the effects of five nobiletin analogs, 6-demethoxynobiletin, tangeretin, 5-demethylnobiletin, sinensetin, and 6-demethoxytangeretin, isolated from citrus peels were assessed on ERK phosphorylation in PC12D cells, and the structure-activity relationships were examined. PC12D cells were treated with nobiletin or its analogs, and the cell extracts were analyzed by Western blotting using an antibody specific to phosphorylated ERK. 6-Demethoxynobiletin markedly enhanced ERK phosphorylation in a concentration-dependent manner. These results may be useful in developing drugs and functional foods using citrus peels for the treatment of dementia including AD.

Chemical constituents of the leaves of Dracaena thalioides.

Two new furostanol bisdesmosides (1 and 2) and seven known compounds (3-9) were isolated from the leaves of Dracaena thalioides (Agavaceae). The structures of the new compounds were determined on the basis of spectroscopic data and the results of hydrolytic cleavage. The isolated compounds were evaluated for cytotoxic activity against HL-60 human promyelocytic leukemia cells. Compound 5, a glyceroglycolipid-related compound assigned as (2S)-1-O-linoleoyl-3-O-beta-D-galactopyranosylglycerol, was found to induce apoptotic cell death in HL-60 cells with an IC50 value of 25.8 microM.

Nobiletin, a citrus flavonoid, ameliorates cognitive impairment, oxidative burden, and hyperphosphorylation of tau in senescence-accelerated mouse.

Senescence-accelerated mouse prone 8 (SAMP8) is a model of aging characterized by the early onset of learning and memory impairment and various pathological features of Alzheimer's disease (AD). Our recent studies have demonstrated that nobiletin, a polymethoxylated flavone from citrus peels, ameliorates learning and memory impairment in olfactory-bulbectomized mice, amyloid precursor protein transgenic mice, and NMDA receptor antagonist-treated mice. Here, we present evidence that this natural compound improves age-related cognitive impairment and reduces oxidative stress and tau phosphorylation in SAMP8 mice. Treatment with nobiletin (10 or 50mg/kg) reversed the impairment of recognition memory and context-dependent fear memory in SAMP8 mice. Treatment with nobiletin also restored the decrease in the GSH/GSSG ratio in the brain of SAMP8 mice. In addition, increases in glutathione peroxidase and manganese-superoxide dismutase activities, as well as a decrease in protein carbonyl level, were observed in the brain of nobiletin-treated SAMP8 mice. Furthermore, nobiletin reduced tau phosphorylation in the hippocampus of SAMP8 mice. Together, the markedly beneficial effects of nobiletin represent a potentially useful treatment for ameliorating the learning and memory deficits, oxidative stress, and hyperphosphorylation of tau in aging as well as age-related neurodegenerative diseases such as AD.

Potent activity of nobiletin-rich Citrus reticulata peel extract to facilitate cAMP/PKA/ERK/CREB signaling associated with learning and memory in cultured hippocampal neurons: identification of the substances responsible for the pharmacological action.

cAMP/PKA/ERK/CREB signaling linked to CRE-mediated transcription is crucial for learning and memory. We originally found nobiletin as a natural compound that stimulates this intracellular signaling and exhibits anti-dementia action in animals. Citrus reticulata or C. unshiu peels are employed as "chinpi" and include a small amount of nobiletin. We here provide the first evidence for beneficial pharmacological actions on the cAMP/PKA/ERK/CREB cascade of extracts from nobiletin-rich C.reticulata peels designated as Nchinpi, the nobiletin content of which was 0.83 ± 0.13% of the dry weight or 16-fold higher than that of standard chinpi extracts. Nchinpi extracts potently facilitated CRE-mediated transcription in cultured hippocampal neurons, whereas the standard chinpi extracts showed no such activity. Also, the Nchinpi extract, but not the standard chinpi extract, stimulated PKA/ERK/CREB signaling. Interestingly, treatment with the Nchinpi extract at the concentration corresponding to approximately 5 µM nobiletin more potently facilitated CRE-mediated transcriptional activity than did 30 µM nobiletin alone. Consistently, sinensetin, tangeretin, 6-demethoxynobiletin, and 6-demethoxytangeretin were also identified as bioactive substances in Nchinpi that facilitated the CRE-mediated transcription. Purified sinensetin enhanced the transcription to a greater degree than nobiletin. Furthermore, samples reconstituted with the four purified compounds and nobiletin in the ratio of each constituent's content in the extract showed activity almost equal to that of the Nchinpi extract to stimulate CRE-mediated transcription. These findings suggest that above four compounds and nobiletin in the Nchinpi extract mainly cooperated to facilitate potently CRE-mediated transcription linked to the upstream cAMP/PKA/ERK/CREB pathway in hippocampal neurons.

New cholestane glycosides and sterols from the underground parts of Chamaelirium luteum and their cytotoxic activity.

Six new cholestane glycosides (1, 5, 6, 10, 12, and 13) and two new sterols (9 and 11), along with five known compounds (2-4, 7, and 8), were isolated from the underground parts of Chamaelirium luteum (Liliaceae). The structures of these new compounds were determined by spectroscopic analysis and the results of hydrolytic cleavage. The isolated compounds and aglycones were evaluated for their cytotoxic activity against HL-60 human leukemia cells. Compounds 6a, 10a, 12a, 13, and 13a were cytotoxic to HL-60 cells, with IC50 values of 12.8, 9.8, 15.3, 6.2, and 10.2 µM, respectively.

Chemical constituents of Lycoris albiflora and their cytotoxic activities.

An alcoholic extract of Lycoris albiflora (Amaryllidaceae) showed potent cytotoxic activity against HL-60 cells with an IC50 value of 1.7 microg/mL. Phytochemical examination of the extract resulted in the isolation of 15 alkaloids, including two phenanthridine-type alkaloids (1, 2), one benzylphenethylamine-type alkaloid (3), two crinane-type alkaloids (4, 5), one pyrrolophenanthridine-type alkaloid (6), six lycorenan-type alkaloids (7-12), and three galanthamine-type alkaloids (13-15), together with three neolignans (16-18), two flavans (19, 20), and two acetophenone derivatives (21, 22). Compound 3 (hostasinine A) has not been isolated from Amaryllidaceae plants, and 1, 2, 4, 5, 7-9, 11, 12 and 14-22 are the first isolation and identification from L. albiflora. The phenanthridine-type alkaloids (1, 2), as well as the alkaloids (3-5), exhibited potent cytotoxic activities against not only HL-60 cells but also HSC-2 cells, thus leading to the conclusion that these alkaloids are mainly responsible for the cytotoxicity of the L. albiflora extract. Compound 1 (lycoricidinol), with the most potent cytotoxic activities, induced apoptosis in both HL-60 cells and HSC-2 cells. It is notable that 1 induced transient autophagy and morphological changes in mitochondria in the early stages of the apoptotic cell death process in HSC-2 cells.

Cycloartane glycosides from the rhizomes of Curculigo orchioides.

Cycloartane glycosides (1-9) were isolated from rhizomes of Curculigo orchioides (Hypoxidaceae), and this structures were determined by spectroscopic analysis and a few chemical transformations. Cytotoxic activity of glycosides (1-9) and their common aglycone (1a) against HL-60 human promyelocytic leukemia cells was also examined.

Triterpene glycosides from Curculigo orchioides and their cytotoxic activity.

Six new cycloartane glycosides (1-6) were isolated from the rhizomes of Curculigo orchioides. The structures of 1-6 were determined by spectroscopic analyses and the results of hydrolytic cleavage. Compounds 1-6, and their common aglycone (1a), were evaluated for cytotoxic activity against HL-60 human leukemia cells. Compounds 1 and 1a showed cytotoxic activity against HL-60 cells with IC(50) values of 9.0 and 1.8 microM, respectively. The cancer cell growth inhibition of 1a was also examined using a panel of 39 human cancer cell lines in the Japanese Foundation for Cancer Research.

Triterpene glycosides from the whole plant of Anemone hupehensis var. japonica and their cytotoxic activity.

Three new triterpene glycosides (1-3), together with eight known triterpene glycosides (4-11), were isolated from the whole plant of Anemone hupehensis var. japonica (Ranunculaceae). The structures of the new compounds were determined on the basis of spectroscopic analysis and the results of hydrolytic cleavage experiments. The isolated compounds were evaluated for their cytotoxic activities against HL-60 human leukemia cells, HSC-2 human oral squamous carcinoma cells, HSC-4 human oral squamous carcinoma cells, and A549 human lung adenocarcinoma cells.