Involvement of p21 and FasL in induction of cell cycle arrest and apoptosis by neochamaejasmin A in human prostate LNCaP cancer cells

Biflavonoids: Preliminary Reports on Their Role in Prostate and Breast Cancer Therapy

Dimeric flavonoids, also called biflavonoids, are bioactive compounds that exhibit various activities described in the literature, including antibacterial, antifungal, antiviral, anti-inflammatory, analgesic, antioxidant, vasorelaxant, and anticancer properties. This work focuses on the anticancer action of naturally occurring dimeric flavonoids against prostate and breast cancer, as well as on the mechanisms of action involved in their activity and presents the most current information on this subject in the literature. In the present review, we summarize the latest findings on the antiproliferative activity of 33 dimeric flavonoid-based compounds selected from recently published studies. The tests conducted were in silico and in vitro and demonstrated the cytotoxic activity potential of biflavonoids against prostate and breast tumor cells. Biflavonoids were capable of interfering with the migration and replication of cancer cells and their mechanism of action is related to cell death pathways, especially apoptosis, necrosis, and ferroptosis. These compounds decreased mitochondrial membrane potential and significantly increased intracellular levels of reactive oxygen species (ROS). Additionally, they significantly upregulated the expression of p21, Bax, and cleaved caspase-3, while downregulating Bcl-2 and caspase-3 levels, indicating their cell death mechanism of action is through the Bcl-2/Bax/cleaved caspase-3 pathway and cell cycle arrest. The biflavonoids here related have shown promising anticancer activity and are considered potential drug candidates for prostate and breast cancer treatment.

Natural products target glycolysis in liver disease

Mitochondrial dysfunction plays an important role in the occurrence and development of different liver diseases. Oxidative phosphorylation (OXPHOS) dysfunction and production of reactive oxygen species are closely related to mitochondrial dysfunction, forcing glycolysis to become the main source of energy metabolism of liver cells. Moreover, glycolysis is also enhanced to varying degrees in different liver diseases, especially in liver cancer. Therefore, targeting the glycolytic signaling pathway provides a new strategy for the treatment of non-alcoholic fatty liver disease (NAFLD) and liver fibrosis associated with liver cancer. Natural products regulate many steps of glycolysis, and targeting glycolysis with natural products is a promising cancer treatment. In this review, we have mainly illustrated the relationship between glycolysis and liver disease, natural products can work by targeting key enzymes in glycolysis and their associated proteins, so understanding how natural products regulate glycolysis can help clarify the therapeutic mechanisms these drugs use to inhibit liver disease.

Ethnopharmacology, phytochemistry, pharmacology, clinical applications and toxicology of the genus Stellera Linn.: A review

ETHNOPHARMACOLOGICAL RELEVANCE

The genus Stellera Linn. consists of species of perennial herbs and shrubs, and is mainly distributed in the temperate regions of east Asia to west Asia. There are 10∼12 species in the world, two species in China: Stellera chamaejasme Linn. and Stellera formosana Hayata ex Li. As recorded, the roots of Stellera species are used to dissipate phlegm and relieve pain. The roots and the barks can be used for papermaking.

AIM OF THIS REVIEW

This review aims to summarize the ethnopharmacological uses, chemical constituents, pharmacological activities, clinical applications and toxicology of the genus Stellera to better understand their therapeutic potential in the future.

MATERIALS AND METHODS

The relevant information of the genus Stellera was collected from scientific databases (Pubmed, ACS website, SciFinder Scholar, Elsevier, Google Scholar, Web of Science and CNKI). Information was also gathered from 'Flora Republicae Popularis Sinicae (〈〈〉〉)', folk records, conference papers on ethnopharmacology, Ph.D. and Masters' Dissertation.

RESULTS

Stellera plants have been studied as traditional folk medicines all around the world. The chemical constituents of Stellera species mainly comprise terpenoids, flavonoids, coumarins, lignans, and so on. Extracts and compounds of Stellera species exhibit extensive pharmacological activities, such as anti-tumor, anti-viral, anti-convulsive, anti-epileptic, anti-bacterial and anti-insect activities, etc. Clinical applications have suggested that the genus Stellera has the effects in treating several skin diseases and cancers, however, the results should be further verification. The genus Stellera plants are toxic and should be used reasonable.

CONCLUSION

This paper reviewed the ethnopharmacological uses, chemical constituents, pharmacology, clinical applications and toxicology of the genus Stellera. The genus Stellera has broad application prospects. However, further in-depth studies are needed to determine the medical uses of the genus and its chemical constituents, pharmacological activities, clinical applications and toxicology.

Neochamaejasmin A Induces Mitochondrial-Mediated Apoptosis in Human Hepatoma Cells via ROS-Dependent Activation of the ERK1/2/JNK Signaling Pathway

The botanical constituents of Stellera chamaejasme Linn. exhibit various pharmacological and medicinal activities. Neochamaejasmin A (NCA), one main active constituent of S. chamaejasme, inhibits cell proliferation and induces cell apoptosis in several types of tumor cells. However, the antitumor effect of NCA on hepatocellular carcinoma cells is still unclear. In this study, NCA (36.9, 73.7, and 147.5 μM) significantly inhibited hepatoblastoma-derived HepG2 cell proliferation in a concentration-dependent manner. Hoechst 33258 staining and flow cytometry showed that apoptotic morphological changes were observed and the apoptotic rate was significantly increased in NCA-treated HepG2 cells, respectively. Additionally, the levels of Bax, cleaved caspase-3, and cytoplasmic cytochrome c were increased, while the level of Bcl-2 was decreased in NCA-treated HepG2 cells when compared with the control group. Moreover, we found that the reactive oxygen species (ROS) level was significantly higher and the mitochondrial membrane potential was remarkably lower in NCA-treated HepG2 cells than in the control group. Further studies demonstrated that the levels of p-JNK and p-ERK1/2 were significantly upregulated in NCA-treated HepG2 cells, and pretreatment with JNK and ERK1/2 inhibitors, SP600125 and PD0325901, respectively, suppressed NCA-induced cell apoptosis of HepG2 cells. In addition, NCA also significantly inhibited human hepatoma BEL-7402 cell proliferation and induced cell apoptosis through the ROS-mediated mitochondrial apoptotic pathway. These results implied that NCA induced mitochondrial-mediated cell apoptosis via ROS-dependent activation of the ERK1/2/JNK signaling pathway in HepG2 cells.

Neochamaejasmin A extracted from Stellera chamaejasme L. induces apoptosis involving mitochondrial dysfunction and oxidative stress in Sf9 cells

To explore the toxicity mechanisms of neochamaejasmin A (NCA), extracted from Stellera chamaejasme L., we first evaluated its cytotoxicity on the Spodoptera frugiperda (Sf9) cell line. The results confirmed that NCA inhibited Sf9 cell survival in both a dose- and time-dependent manner. Then, intracellular biochemical assays showed that NCA induced apoptosis in Sf9 cells. Evidence of apoptosis was confirmed by morphological changes and the activation of caspases-3/9. We also observed that NCA induced apoptosis via mitochondrial-dependent intrinsic apoptotic pathway by upregulating cytochrome c and proapoptotic protein (Bax) and downregulating the mitochondrial membrane potential (MMP) and antiapoptotic protein (Bcl-2). Moreover, we found a dose-dependent increase in reactive oxygen species (ROS), accumulation of lipid peroxidation product and an inactivation of the antioxidant enzymes in treated cells. Additionally, the cleavage of PARP and G2/M arrest were also detected in Sf9 cells exposed to NCA. These findings provide critical information that NCA effectively induced apoptosis in Sf9 cells through mitochondrial pathways.

The Ethyl Acetate Extract of Gynura formosana Kitam. Leaves Inhibited Cervical Cancer Cell Proliferation via Induction of Autophagy

Gynura formosana Kitam. belongs to the Compositae family and has been traditionally used for the prevention of cancer, diabetes, and inflammation in China. Previous studies had indicated that the ethyl acetate extract of Gynura formosana Kitam. leaves (EAEG) exhibited antioxidant and anti-inflammatory activity. In this report, we demonstrated that EAEG possessed potent anticancer activity through autophagy-mediated inhibition of cell proliferation. EAEG induced a strong cytostatic effect towards HeLa cells and, to a lesser extent, HepG2 and MCF-7 cells. This cytostatic effect of EAEG was not a consequence of increased apoptosis, as neither DNA fragmentation nor change in protein expression level for a number of apoptosis-related genes including Bid, Bax, Bcl-2, and caspase-3 was observed after EAEG treatment, and the apoptosis inhibitor Z-VAD-FMK did not inhibit the EAEG-elicited cytostatic effect. On the other hand, EAEG induced autophagy in a dose-dependent fashion, as shown by increased GFP puncta formation, enhanced conversion of the microtubule-associated protein light chain LC3-I to LC3-II, and downregulation of the p62 protein. Treating the HeLa cells with EAEG together with Chloroquine (CQ) further accelerated LC3 conversion and p62 clearance, indicating that EAEG induced complete autophagy flux. Importantly, the autophagy inhibitor 3-methyladenine (3MA) significantly abrogated the cytostatic effect of EAEG, strongly suggesting that EAEG inhibited HeLa cell proliferation through the induction of autophagy rather than apoptosis. Our results provided a novel and interesting mechanistic insight into the anticancer action of EAEG, supporting the traditional use of this plant for the treatment of the cancer.

Simultaneous determination of isochamaejasmin, neochamaejasmin A and aphnoretinin rat plasma by UPLC-MS/MS and its application to a pharmacokinetic study of Stellera chamaejasme L. extract

Isochamaejasmin, neochamaejasmin A and daphnoretin derived from Stellera chamaejasme L. are important because of their reported anticancer properties. In this study, a sensitive UPLC-MS/MS method for the determination of isochamaejasmin, neochamaejasmin A and daphnoretin in rat plasma was developed. The analyte and IS were separated on an Acquity UPLC HSS T3 column (100 × 2.1 mm, 1.8 μm) using gradient elution with the mobile phase of aqueous solution (methanol-water, 1:99, v/v, containing 1 mm formic acid) and organic solution (methanol-water, 99:1, v/v, containing 1 mm formic acid) at a flow rate of 0.3 mL/min. Multiple reaction monitoring mode with negative electrospray ionization interface was carried out to detect the components. The method was validated in terms of specificity, linearity, accuracy, precision, stability, etc. Excellent linear behavior was observed over the certain concentration ranges with the correlation coefficient values >0.99. Intra- and inter-day precisions (RSD) were <6.7% and accuracy (RE) ranged from -7.0 to 12.0%. The validated method was successfully applied to investigate the pharmacokinetics of three chemical ingredients after oral administration of S. chamaejasme L. extract to rats.

Chamaejasmin B exerts anti-MDR effect in vitro and in vivo via initiating mitochondria-dependant intrinsic apoptosis pathway

Multidrug resistance (MDR) is the main obstacle limiting the efficacy of cancer chemotherapy. Looking for novel anti-MDR agents is an important way to conquer cancer drug resistance. We recently established that chamaejasmin B (CHB), a natural biflavone from Stellera chamaejasme L., is the major active component. However, its anti-MDR activity is still unknown. This study investigated the anti-MDR effect of CHB and the underlying mechanisms. First, it was found that CHB inhibited the growth of both sensitive and resistant cell lines in vitro, and the average resistant factor (RF) of CHB was only 1.26. Furthermore, CHB also displayed favorable anti-MDR activity in KB and KBV200 cancer cells xenograft mice. Subsequent study showed that CHB induced G0/G1 cell cycle arrest as well as apoptosis both in KB and in resistant KBV200 cancer cells. Further studies showed that CHB had no influence on the level of Fas/FasL and activation of procaspase 8. However, CHB-induced apoptosis was dependent on the activation of caspase 9 and caspase 3. Moreover, CHB treatment resulted in the elevation of the Bax/Bcl-2 ratio, attenuation of mitochondrial membrane potential (ΔΨ_m), and release of cytochrome c and apoptosis-inducing factor from mitochondria into cytoplasm both in KB and KBV200 cells. In conclusion, CHB exhibited good anti-MDR activity in vitro and in vivo, and the underlying mechanisms may be related to the activation of mitochondrial-dependant intrinsic apoptosis pathway. These findings provide a new leading compound for MDR therapy and supply a new evidence for the potential of CHB to be employed in clinical trial of MDR therapy in cancers.

Altered profile of gut microbiota after subchronic exposure to neochamaejasmin A in rats

Neochamaejasmin A, isolated from Stellera chamaejasme L., has been widely used in China. Gut microbiota represent the first barrier against xenobiotics. This study aimed to evaluate the effects of subchronic exposure to neochamaejasmin A on the composition of gut microbiota. We found that neochamaejasmin A altered 21 OTUs in female rats and 46 OTUs in male rats. Among these OTUs, OTU86, OTU338 and OTU482 were shared in neochamaejasmin A-fed groups in both genders, implying that neochamaejasmin A might promote the growth of these three genera. In contrast, little or no effect on 226 OTUs was observed at all doses in both genders, suggesting their resistance to neochamaejasmin A. These findings could help improve our understanding of the health effects of neochamaejasmin A and provide an example of the risk assessment of pharmaceuticals or food contaminants on the gut microbiota composition.

Potential ecological roles of flavonoids from Stellera chamaejasme

Stellera chamaejasme L. (Thymelaeaceae), a perennial weed, distributes widely in the grasslands of Russia, Mongolia and China. The plant synthesizes various secondary metabolites including a group of flavonoids. To our knowledge, flavonoids play important roles in the interactions between plants and the environment. So, what are the benefits to S. chamaejasme from producing these flavonoids? Here, we discuss the potential ecological role of flavonoids from S. chamaejasme in protecting the plant from insects and other herbivores, as well as pathogens and competing plant species, and new data are provided on the phytotoxicity of flavonoids from S. chamaejasme toward Poa annua L.

Phytotoxic flavonoids from roots of Stellera chamaejasme L. (Thymelaeaceae)

Allelopathy, the negative effect on plants of chemicals released to the surroundings by a neighboring plant, is an important factor which contributes to the spread of some weeds in plant communities. In this field, Stellera chamaejasme L. (Thymelaeaceae) is one of the most toxic and ecologically-threatening weeds in some of the grasslands of north and west China. Bioassay-guided fractionation of root extracts of this plant led to the isolation of eight flavonoids 1-8, whose structures were elucidated by spectroscopic analysis. All compounds obtained, except 7-methoxylneochaejasmin A (4) and (+)-epiafzelechin (5), showed strong phytotoxic activity against Arabidopsis thaliana seedlings. Seedling growth was reduced by neochamaejasmin B (1), mesoneochamaejasmin A (2), chamaejasmenin C (3), genkwanol A (6), daphnodorin B (7) and dihydrodaphnodorin B (8) with IC50 values of 6.9, 12.1, 43.2, 74.8, 7.1 and 27.3μg/mL, respectively, and all of these compounds disrupted root development. Endogenous auxin levels at the root tips of the A. thaliana DR5::GUS transgenic line were largely reduced by compounds 1, 2 and 6-8, and were increased by compound 4. Moreover, the inhibition rate of A. thaliana auxin transport mutants pin2 and aux1-7 by compounds 1-8 were all lower than the wild type (Col-0). The influence of these compounds on endogenous auxin distribution is thus proposed as a critical factor for the phytotoxic effect. Compounds 1, 2, 4 and 8 were found in soils associated with S. chamaejasme, and these flavonoids also showed phytotoxicity to Clinelymus nutans L., an associated weed of S. chamaejasme. These results indicated that some phytotoxic compounds from roots of S. chamaejasme may be involved in the potential allelopathic behavior of this widespread weed.

Ligustrum lucidum Ait. fruit extract induces apoptosis and cell senescence in human hepatocellular carcinoma cells through upregulation of p21

Nü-zhen-zi, the fruit of Ligustrum lucidum Ait., is one of the most frequently used liver Yin tonifying Chinese herbs for the treatment of liver cancer. However, the effect of Ligustrum lucidum fruit on hepatocarcinoma cells remains unknown. In the present study, we evaluated the effects of a Ligustrum lucidum fruit extract (LLFE) on human hepatocellular carcinoma Bel-7402 cells. The results showed that LLFE inhibited the proliferation of the Bel-7402 cells in a dose- and time-dependent manner. LLFE induced apoptosis in Bel-7402 cells accompanied by activation of caspase-3, -8 and -9. LLFE-induced apoptosis was completely abrogated by a pan caspase inhibitor, Z-VAD-FMK. LLFE treatment also caused a large and flat morphologic cellular change, positive SA-β-gal staining, and G0/G1 phase cell cycle arrest in the Bel-7402 cells, accompanied by upregulation of p21 and downregulation of RB phosphorylation. Specific knockdown of p21 expression by RNA interference partially abrogated LLFE-induced apoptosis, and significantly abrogated LLFE-induced cell senescence. These observations suggest that Nü-zhen-zi is a potential anticancer herb and support the traditional use of Nü-zhen-zi for hepatocarcinoma treatment.

Emblica officinalis extract induces autophagy and inhibits human ovarian cancer cell proliferation, angiogenesis, growth of mouse xenograft tumors

Patients with ovarian cancer (OC) may be treated with surgery, chemotherapy and/or radiation therapy, although none of these strategies are very effective. Several plant-based natural products/dietary supplements, including extracts from Emblicaofficinalis (Amla), have demonstrated potent anti-neoplastic properties. In this study we determined that Amla extract (AE) has anti-proliferative effects on OC cells under both in vitro and in vivo conditions. We also determined the anti-proliferative effects one of the components of AE, quercetin, on OC cells under in vitro conditions. AE did not induce apoptotic cell death, but did significantly increase the expression of the autophagic proteins beclin1 and LC3B-II under in vitro conditions. Quercetin also increased the expression of the autophagic proteins beclin1 and LC3B-II under in vitro conditions. AE also significantly reduced the expression of several angiogenic genes, including hypoxia-inducible factor 1α (HIF-1α) in OVCAR3 cells. AE acted synergistically with cisplatin to reduce cell proliferation and increase expression of the autophagic proteins beclin1 and LC3B-II under in vitro conditions. AE also had anti-proliferative effects and induced the expression of the autophagic proteins beclin1 and LC3B-II in mouse xenograft tumors. Additionally, AE reduced endothelial cell antigen – CD31 positive blood vessels and HIF-1α expression in mouse xenograft tumors. Together, these studies indicate that AE inhibits OC cell growth both in vitro and in vivo possibly via inhibition of angiogenesis and activation of autophagy in OC. Thus AE may prove useful as an alternative or adjunct therapeutic approach in helping to fight OC.

Anticancer effect of Tamarix gallica extracts on human colon cancer cells involves Erk1/2 and p38 action on G2/M cell cycle arrest

Taking into account that oxidative stress is among the factors causing cancer-related death; chemoprevention which consists in using antioxidant substances such as phenolics could prevent cancer formation and progression. In the present study, phenolic contents and antioxidant activities of methanolic extracts from the halophyte Tamarix gallica shoots were determined. Moreover, the anticancer effect of this species on human colon cancer cells and the likely underlying mechanisms were also investigated. Shoot extracts showed an appreciable total phenolic content (85 mg GAE/g DW) and a high antioxidant activity (IC50 = 3.3 μg/ml for DPPH test). At 50 and 100 μg/ml, shoot, leaf, and flower extracts significantly inhibited Caco-2 cell growth. For instance, almost all plant part extracts inhibited cell growth by 62 % at the concentration 100 μg/ml. DAPI staining results revealed that these extracts decrease DNA synthesis and confirm their effect on Caco-2 cells proliferation, principally at 100 μg/ml. More importantly, cell mitosis was arrested at G2/M phase. The changes in the cell-cycle-associated proteins (cyclin B1, p38, Erk1/2, Chk1, and Chk2) are correlated with the changes in cell cycle distribution. Taken together, our data suggest that T. gallica is a promising candidate species to be used as a source of anticancer biomolecules.

In vitro inhibitory and pro-apoptotic effect of Stellera chamaejasme L extract on human lung cancer cell line NCI-H157

OBJECTIVE

To investigate the inhibitory and pro-apoptotic effect of Stellera Chamaejasme L extract (ESC) in vitro.

METHODS

ESC was first extracted with ethanol, and then washed using a polyamide column with 60% ethanol. ESC was then decompressively recycled and vacuum dried at room temperature to obtain active fractions. Subsequently, the cytotoxic and apoptotic effects of ESC on NCI-H157 human lung cancer cells were determined.

RESULTS

The results showed that ESC was rich in isomers of Chamaejasminor, neochamaejasmine and Sikokianin. ESC had significant cytotoxicity against NCI-H157 cells, with an IC50 of approximately 18.50 microg x mL(-). ESC caused significant increase in total apoptotic rate, the activity of caspase 3 and 8,

CONCLUSION

The inhibitory effect of ESC on NCI-H157 tumor cells might partly be attributed to its apoptotic induction through activation of the Fas death receptor pathway.

Sikokianin D, a new C-3/C-3"-biflavanone from the roots of Wikstroemia indica

A new 3,3′′-biflavanone, sikokianin D (1), was isolated from the roots of Wikstroemia indica, together with two known compounds. Their structures were elucidated by chemical evidence and spectral analyses, including HR-ESI-MS, and 1D- and 2D-NMR techniques.

Fighting fire with fire: poisonous Chinese herbal medicine for cancer therapy

ETHNOPHARMACOLOGICAL RELEVANCE

Following the known principle of "fighting fire with fire", poisonous Chinese herbal medicine (PCHM) has been historically used in cancer therapies by skilled Chinese practitioners for thousands of years. In fact, most of the marketed natural anti-cancer compounds (e.g., camptothecin derivatives, vinca alkaloids, etc.) are often known in traditional Chinese medicine (TCM) and recorded as poisonous herbs as well. Inspired by the encouraging precedents, significant researches into the potential of novel anticancer drugs from other PCHM-derived natural products have been ongoing for several years and PCHM is increasingly being recognized as a gathering place for promising anti-cancer drugs. The present review aimed at giving a rational understanding of the toxicity of PCHM and, especially, providing the most recent developments on PCHM-derived anti-cancer compounds.

MATERIALS AND METHODS

Information on the toxicity and safety control of PCHM, as well as PCHM-derived anti-cancer compounds, was gathered from the articles, books and monographs published in the past 20 years.

RESULTS

Based on an objective introduction to the CHM toxicity, we clarified the general misconceptions about the safety of CHM and summarized the traditional experiences in dealing with the toxicity. Several PCHM-derived compounds, namely gambogic acid, triptolide, arsenic trioxide, and cantharidin, were selected as representatives, and their traditional usage and mechanism of anti-cancer actions were discussed.

CONCLUSIONS

Natural products derived from PCHM are of extreme importance in devising new drugs and providing unique ideas for the war against cancer. To fully exploit the potential of PCHM in cancer therapy, more attentions are advocated to be focused on their safety evaluation and mechanism exploration.

Guanosine supplementation reduces the antiproliferative and apoptotic effects of the IMPDH inhibitor gnidilatimonoein in K562 cells

IMPDH (inosine 5'-monophosphate dehydrogenase) is the rate-limiting enzyme in the de novo biosynthetic pathway of guanine nucleotides, which is usually up-regulated in human leukaemia cell lines. Our previous studies have classified gnidilatimonoein, isolated from Daphne mucronata, as an IMPDH inhibitor and a strong antiproliferative agent among several types of leukaemia cells. In the present study, we investigated the effects of gnidilatimonoein on intracellular GTP pool size and its link to differentiation and apoptosis of K562 cells. It was found that gnidilatimonoein inhibited cell proliferation and induced G0/G1 cell cycle arrest in K562 cells after 24 h exposure to a single dose of gnidilatimonoein (1.5 μM), while no significant effects were observed on unstimulated and phytohaemagglutinin-stimulated peripheral blood lymphocyte cells at the gnidilatimonoein dose (1.5 μM) used. Based on the morphological changes, Wright-Giemsa staining, benzidine assay and the expression of cell surface markers [GPIIb (glycoprotein IIb) and glycophorin A], as analysed by flow cytometry, we found that K562 cells had differentiated towards megakaryocytic lineage. In addition, gnidilatimonoein induced apoptosis among K562 cells based on Acridine Orange/ethidium bromide and annexin V/propidium iodide double-staining observations. These changes, which were abrogated by the addition of guanosine, became evident when the intracellular GTP level decreased to approx. 20-35% of the untreated control level. Based on these findings, it can be concluded that gnidilatimonoein induces differentiation and apoptosis in K562 cells through perturbation of GTP metabolism, as one of its routes of action.

Proteasome-inhibitory and cytotoxic constituents of Garcinia lateriflora: absolute configuration of caged xanthones

A new biflavonoid (1), a new xanthone enantiomer (2), five new caged xanthones (3-7), and several known compounds were isolated from the stem bark of Garcinia lateriflora, collected in Indonesia. The structures of the new compounds were determined by analysis of spectroscopic data, and the absolute configuration of the caged xanthones was shown for the first time at carbons 5, 7, 8, 8a, 10a, and 27, by analysis of COSY and NOESY NMR and ECD spectra. The biflavonoids exhibited proteasome inhibitory activity, and the known compound, morelloflavone (8) was found to have the greatest potency (IC(50) = 1.3 muM). The caged xanthones were cytotoxic towards HT-29 cells, with the known compound, morellic acid (10) being the most active (ED(50) = 0.36 muM). However, when tested in an in vivo hollow fiber assay, it was inactive at the highest dose tested (20 mg/kg).