Biological properties of aqueous extract and pyranocoumarins obtained from the bark of Brosimum alicastrum tree.

ETHNOPHARMACOLOGICAL RELEVANCE: Brosimum alicastrum is a tree used in Mexican traditional medicine for the treatment of several diseases, including uterine cancer. AIM OF THE STUDY: In this study, the cytotoxic activity of aqueous extract of B. alicastrum bark and isolated compounds xanthyletin (1), luvangetin (2), and 8-hydroxyxanthyletin (3) on three human cancer cell lines was determined. Moreover, the biological effects of 8-hydroxyxanthyletin (3) were investigated. MATERIALS AND METHODS: The aqueous extract was prepared according to the ethnomedical information reported from the bark. The compounds were purified using chromatographic methods and their structures were elucidated by spectroscopic techniques. The antiproliferative effect of aqueous extract and isolates was determined in three human tumor cell lines: HeLa, A2780, and MSTO-211H, and evaluated by trypan blue exclusion assay. The cell cycle and the mitochondrial transmembrane potential (ΔΨ) were measured by flow cytometry, while Reactive Oxygen Species (ROS) levels were determined using 2',7'-dichlorofluorescein diacetate (DCFH-DA) probe. The effect on the relaxation activity, mediated by topoisomerase I and II, was evaluated by electrophoresis, and docking studies were performed using Autodock 4.2 to analyze the interactions. RESULTS: Aqueous extract of B. alicastrum bark showed significant antiproliferative effect on the evaluated cancer cell lines (IC50 = 1.6, 8.5, and 21.4 µg/ml). Four coumarins were identified in the extract and three of them were also evaluated. A2780 cell line exhibited higher sensitivity against pyranocoumarins with IC50 values ranging from 32 to 47 µmol/l. 8-hydroxyxanthyletin (3) exerts an interesting effect on human topoisomerases I and II, by inhibiting the enzymes at concentrations comparable to those obtained in antiproliferative assay. Moreover, 8-hydroxyxanthyletin (3) arrests the cell cycle at G0/G1 phase and induces in A2780 cells a concentration-dependent increase in ROS levels. The results of molecular docking suggest the participation of the hydroxyl group in the interaction between 8-hydroxyxanthyletin (3) and topoisomerase I and II. CONCLUSION: This is the first report that demonstrates the cytotoxic activity of the aqueous extract of B. alicastrum bark, and determines the main metabolites.

Naturally Occurring Calanolides: Occurrence, Biosynthesis, and Pharmacological Properties Including Therapeutic Potential.

Calanolides are tetracyclic 4-substituted dipyranocoumarins. Calanolide A, isolated from the leaves and twigs of Calophyllum lanigerum var. austrocoriaceum (Whitmore) P. F. Stevens, is the first member of this group of compounds with anti-HIV-1 activity mediated by reverse transcriptase inhibition. Calanolides are classified pharmacologically as non-nucleoside reverse transcriptase inhibitors (NNRTI). There are at least 15 naturally occurring calanolides distributed mainly within the genus Calophyllum, but some of them are also present in the genus Clausena. Besides significant anti-HIV properties, which have been exploited towards potential development of new NNRTIs for anti-HIV therapy, calanolides have also been found to possess anticancer, antimicrobial and antiparasitic potential. This review article provides a comprehensive update on all aspects of naturally occurring calanolides, including their chemistry, natural occurrence, biosynthesis, pharmacological and toxicological aspects including mechanism of action and structure activity relationships, pharmacokinetics, therapeutic potentials and available patents.

Synthesis and Evaluation of Anticancer Activity of New 4-Acyloxy Derivatives of Robustic Acid.

In the present study, a series of 4-acyloxy robustic acid derivatives were synthesized and characterized for evaluation of their anti-cancer activity. The structures of these derivatives were elucidated by mass spectra (MS) nuclear magnetic resonance spectra (NMR). The single-crystal X-ray diffraction structure of one of these compounds was obtained, for further validation of the target compound structures. The anticancer activities of the target products were evaluated against human leukemic cells HL-60, human non-small cell lung carcinoma cells A-549, human hepatic carcinoma cells SMMC-7721, human hepatocellular carcinoma cells HepG2, and human cervical carcinoma cells Hela. Three compounds among them exhibited potent in-vitro cytotoxicity and excellent DNA topoisomerase I inhibitory activity, even at 0.1 mM concentrations. The most noteworthy observation was the minor toxicity of two of these compounds to normal cells, with an activity similar to the positive control in cancerous cells. A Surflex-Dock docking study was performed to investigate the topoisomerase I activity of all compounds. Of all the other compounds, the most sensitive compound was selected for further investigation of its effect on apoptosis induction and cell cycle regulation in HL-60 cells. Our results suggest that the anticancer effects of these compounds can be attributed to their pharmacological effects on topoisomerase I, cell apoptosis, and cell cycle. These findings suggest that robustic acid derivatives could be used as potential antitumor drugs.

Anticancer effects of alloxanthoxyletin and fatty acids esters - In vitro study on cancer HTB-140 and A549 cells.

Alloxanthoxyletin, a natural occurring pyranocoumarin isolated from a number of plant sources, such as family of Rutaceae, and its synthetic derivatives show cytotoxic and antitumor activities. In the present study new eleven esters of alloxanthoxyletin and fatty acids were synthesized and evaluated for their anticancer toxicity. The structures of the compounds were confirmed by Proton Nuclear Magnetic Resonance (1H NMR), Carbon-13 Nuclear Magnetic Resonance (13C NMR) and High Resolution Mass Spectrometry (HRMS) analyses. For all compounds 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide (MTT) assay was used to determine the cytotoxic effect on human melanoma cells (HTB-140), human epithelial lung carcinoma cells (A549) and human keratinocyte line (HaCaT). For the most active compounds (8-11) lactate dehydrogenase (LDH) assay to assess the level of cell damage as well as migration inhibition assay were performed. To explain the basic mechanism of cell death induction, the effect of derivatives 8-11 on early and late apoptosis in Annexin V-FITC/7-AAD flow cytometry analysis was investigated. The results indicate that human melanoma cells (HTB-140) and human epithelial lung carcinoma cells (A549) were more sensitive to new alloxanthoxyletin derivatives exposure compared to human keratinocytes (HaCaT). Both, the cytotoxicity and the migration tests showed a concentration-dependent inhibition of cell growth, although with a different degree of efficacy. Tested compounds induced apoptosis in cancer cells, however, derivatives 8, 9, 10 and 11 were found to be much more potent inducers of early apoptosis in HTB-140 cells than in A549 and HaCaT cells. To establish the potent mechanism of action of alloxanthoxyletin derivatives 8, 9, 10 and 11 on HaCaT, A549 and HTB-140 cells, the level of IL-6 was measured. Our results indicate, that tested compounds significantly decrease the release of IL-6 for all cancer cell lines.

Natural Korean Medicine Dang-Gui: Biosynthesis, Effective Extraction and Formulations of Major Active Pyranocoumarins, Their Molecular Action Mechanism in Cancer, and Other Biological Activities.

Angelica gigas Nakai (AGN) is a crucial oriental medicinal herb that grows especially in Korea and the Far-East countries. It contains chemically active compounds like pyranocoumarins, polyacetylenes and essential oils, which might be useful for treatment of several chronic diseases. It has been used for centuries as a traditional medicine in Southeast Asia, but in Western countries is used as a functional food and a major ingredient of several herbal products. The genus Angelica is also known as 'female ginseng' due to its critical therapeutic role in female afflictions, such as gynecological problems. However, it is well-documented that the AGN pyranocoumarins may play vital beneficial roles against cancer, neurodisorders, inflammation, osteoporosis, amnesia, allergies, depression, fungi, diabetes, ischemia, dermatitis, reactive oxygen species (ROS) and androgen. Though numerous studies revealed the role of AGN pyranocoumarins as therapeutic agents, none of the reviews have published their molecular mechanism of action. To the best of our knowledge, this would be the first review that aims to appraise the biosynthesis of AGN's major active pyranocoumarins, discuss effective extraction and formulation methods, and detail the molecular action mechanism of decursin (D), decursinol angelate (DA) and decursinol (DOH) in chronic diseases, which would further help extension of research in this area.

Anticancer effects of O-aminoalkyl derivatives of alloxanthoxyletin and seselin.

Seselin and alloxanthoxyletin, naturally occurring pyranocoumarins, were recently isolated from a number of plant sources, such as family of Rutaceae. It was previously reported that their natural and synthetic derivatives show cytotoxic and antitumor activity. In the present study new series of O-aminoalkyl substituted alloxanthoxyletins and seselins were synthesized and evaluated for their anticancer toxicity. Microwave assisted synthesis was used, and the structures of the compounds were confirmed by 1H NMR, 13C NMR and MS spectroscopic data. The molecular and crystal structure of 3a was analyzed by single crystal X-ray diffraction. Alloxanthoxyletin derivatives 2a, 2b, and 2d showed the highest cytotoxic potential against HTB-140 cells with IC50 of 2.48, 2.80 and 2.98µM, respectively. In vitro drug sensitivity testing in HaCaT, A549 and HTB-140 cells were also performed. Tumor cells showed a higher sensitivity to tested compounds than normal cells. Compounds 2a, 2b and 2d inhibited cell migration and exerted stronger effect on A549 and HTB-140 cells than on HaCaT cells. In order to explain the basic mechanism of cell death induction we have investigated the effect of derivatives 2a, 2b and 2d on early and late apoptosis using annexin V-FITC/7-AAD flow cytometry analysis. Derivatives 2a and 2b were much more potent inducers of early apoptosis in HTB-140 cells compared to HaCaT and A549 cells.

Anti-proliferative activity of CGK012 against multiple myeloma cells via Wnt/ß-catenin signaling attenuation.

The aberrant activation of Wnt/ß-catenin signaling is involved in the development of multiple myeloma; thus, this signaling pathway is a potential target for the development of therapeutics for this malignancy. Here, we performed cell-based chemical screening and found that CGK012, a pyranocoumarin compound, suppressed the Wnt3a-CM-mediated activation of ß-catenin response transcription. CGK012 induced ß-catenin phosphorylation at Ser33/Ser37/Thr41, leading to proteasomal degradation and reducing the level of intracellular ß-catenin. Furthermore, CGK012 consistently decreased the amount of ß-catenin and repressed the expression of cyclin D1, c-myc, and axin-2 (downstream target genes of ß-catenin) in RPMI-8226 multiple myeloma cells. In addition, CGK012 inhibited the proliferation of RPMI-8226 cells and promoted apoptosis, as indicated by the increase in the population of Annexin V-FITC-stained cells and caspase-3/7 activity. These findings suggest that CGK012 could exert antiproliferative activity against multiple myeloma cells by attenuating the Wnt/ß-catenin pathway; thus, it may have potential as a therapeutic agent for multiple myeloma treatment.

An integrated approach of network-based systems biology, molecular docking, and molecular dynamics approach to unravel the role of existing antiviral molecules against AIDS-associated cancer.

A serious challenge in cancer treatment is to reposition the activity of various already known drug candidates against cancer. There is a need to rewrite and systematically analyze the detailed mechanistic aspect of cellular networks to gain insight into the novel role played by various molecules. Most Human Immunodeficiency Virus infection-associated cancers are caused by oncogenic viruses like Human Papilloma Viruses and Epstein-Bar Virus. As the onset of AIDS-associated cancers marks the severity of AIDS, there might be possible interconnections between the targets and mechanism of both the diseases. We have explored the possibility of certain antiviral compounds to act against major AIDS-associated cancers: Kaposi's Sarcoma, Non-Hodgkin Lymphoma, and Cervical Cancer with the help of systems pharmacology approach that includes screening for targets and molecules through the construction of a series of drug-target and drug-target-diseases network. Two molecules (Calanolide A and Chaetochromin B) and the target "HRAS" were finally screened with the help of molecular docking and molecular dynamics simulation. The results provide novel antiviral molecules against HRAS target to treat AIDS defining cancers and an insight for understanding the pharmacological, therapeutic aspects of similar unexplored molecules against various cancers.

Clausenidin induces caspase-dependent apoptosis in colon cancer.

BACKGROUND: Clausena excavata Burm.f. is a shrub traditionally used to treat cancer patients in Asia. The main bioactive chemical components of the plant are alkaloids and coumarins. In this study, we isolated clausenidin from the roots of C. excavata to determine its apoptotic effect on the colon cancer (HT-29) cell line. METHOD: We examined the effect of clausenidin on cell viability, ROS generation, DNA fragmentation, mitochondrial membrane potential in HT-29 cells. Ultrastructural analysis was conducted for morphological evidence of apoptosis in the treated HT-29 cells. In addition, we also evaluated the effect of clausenidin treatment on the expression of caspase 3 and 9 genes and proteins in HT-29 cells. RESULT: Clausenidin induced a G0/G1 cell cycle arrest in HT-29 cells with significant (p < 0.05) dose-dependent increase in apoptotic cell population. The DNA fragmentation assay also showed apoptotic features in the clausenidin-treated HT-29 cells. Clausenidin treatment had caused significant (p < 0.05) increases in the expression of caspase 9 protein and gene in HT-29 cells and mitochondrial ROS and mitochondrial membrane depolarization. The results suggest the involvement of the mitochondria in the caspase-dependent apoptosis in clausenidin-treated colon cancer cells. CONCLUSION: Clausenidin induces a caspase-dependent apoptosis in colon cancers through the stimulation of the mitochondria. The study demonstrates the potential of clausenidin for use in the treatment of colon cancers.

Carbazole-pyranocoumarin conjugate and two carbazole alkaloids from the stems of Clausena excavata.

A carbazole-pyranocoumarin conjugate, carbazomarin B (1), and two carbazole alkaloids, 6-methoxymukonidine (2) and 2-hydroxy-3-methoxycarbazole (3), together with 27 known compounds (4-30), were isolated from the stems of Clausena excavata. Their structures have been elucidated by spectroscopic analyses. Compound 2 showed moderate cytotoxicity to HuCCA-1, MOLT-3 and HepG2 cancer cell lines with IC50 values of 15.09-28.50 µg/mL, but none to A549 cell line. Heptaphylline (6) and nordentatin (23) were found to show moderate cytotoxic activity against HepG2 cell line with IC50 values of 12.33 and 11.33, respectively, while clausine K (27) exhibited strong cytotoxicity with IC50 value of 1.05 µg/mL, better than a standard drug (etoposide, IC50 13.40 µg/mL).

[Effect of angular pyranocoumarin isolated from peucedanum praeruptorum on the proliferation and apoptosis of U266 cells].

OBJECTIVE: To investigate the effects of angular pyranocoumarin (±) -4'-O- acetyl-3'-Oangeloyl- cis- khellactone (APC) extracted from peucedanum praeruptoruon on the proliferation and apoptosis of U266 cells, and to explore its related mechanism. METHODS: APC was extracted by petroleum ether technique, and its purity was tested by high performance liquid chromatography, and its chemical structure was identified by magnetic resonance spectroscopy. U266 cells were treated with APC in various concentrations (0, 10, 20, 30, 40 µg/ml）for different durations（24 and 48 h). The inhibitive effect of APC on cell growth was detected by CCK-8 method. After U266 cells were incubated with APC（0, 10, 20, 30, 40 µg/ml）for 24 h, the apoptosis of cells were observed by flow cytometry stained with Annexin Ⅴ/PI and Hochest33342; the expression levels of caspase-3, 8, ERK, p-ERK, AKT and p-AKT protein were assayed by Western blot; the expression of hTERT mRNA was measured by RT-PCR. RESULTS: The purity of APC identified by magnetic resonance imaging was 98.8%. The proliferation of U266 cells was inhibited, and the apoptosis was induced in a time- and/or dose- dependent manner after treatment with APC. APC could upregulate the caspase- 8, 3 protein expression and downregulate the p- ERK, p-AKT protein expression along with the increase of APC dose. APC also could downregulate the hTERT mRNA expression. CONCLUSION: Angular pyranocoumarin APC could inhibit the proliferation and induce the apoptosis of U266 cells. The probable mechanism might be achieved by upregulating caspase-8, 3 protein expression and downregulating p-ERK, P-AKT protein and the hTERT mRNA expression.

Pyranocoumarins from Root Extracts of Peucedanum praeruptorum Dunn with Multidrug Resistance Reversal and Anti-Inflammatory Activities.

In the search for novel herbal-based anticancer agents, we isolated a new angular-type pyranocoumarin, (+)-cis-(3'S,4'S)-3'-angeloyl-4'-tigloylkhellactone (1) along with 12 pyranocoumarins (2-13), two furanocoumarins (14, 15), and a polyacetylene (16) were isolated from the roots of Peucedanum praeruptorum using chromatographic separation methods. The structures of the compounds were determined using spectroscopic analysis with nuclear magnetic resonance (NMR) and high-resolution-electrospray ionization-mass spectrometry (HR-ESI-MS). The multidrug-resistance (MDR) reversal and anti-inflammatory effects of all the isolated compounds were evaluated in human sarcoma MES-SA/Dx5 and lipopolysaccharide (LPS)-induced RAW 264.7 cells. Among the 16 tested compounds, two (2 and 16) downregulated nitric oxide (NO) production and five (1, 7, 8, 11, and 13) inhibited the efflux of drugs by MDR protein, indicating the reversal of MDR. Therefore, these compounds may be potential candidates for the development of effective agents against MDR forms of cancer.

Phenyl derivative of pyranocoumarin precludes Fusarium oxysporum f.sp. Lycopersici infection in Lycopersicon esculentum via induction of enzymes of the phenylpropanoid pathway.

Binding of phenyl derivative of pyranocoumarin (PDP) modulated activity of fungal endopolygalacturonase in silico. Induced fit docking study of PDP with endopolygalacturonase (1HG8) showed a bifurcated hydrogen bond interaction with the protein at Lys 244 with a docking score of -3.6 and glide energy of -37.30 kcal/mol. Docking with endopolygalacturonase II (1CZF) resulted hydrogen bond formation with Lys 258 with a docking score of -2.3 and glide energy of -30.42 kcal/mol. It was hypothesized that this modulation favors accumulation of cell wall fragments (oligogalacturonides) which act as elicitors of plant defense responses. In order to prove the same, in vivo studies were carried out using a formulation developed from PDP (PDP 5EC) on greenhouse grown Lycopersicon esculentum L. The formulation was effective at different concentrations in reduction of seed infection, improvement of vigor and control of Fusarium oxysporum f.sp. lycopersici infection in L. esculentum. At a concentration of 2 %, PDP 5EC significant reduction in seed infection (95.83 %), improvement in seed vigor (64.31 %) and control of F. oxysporum f.sp. lycopersici infection (96.15 %) were observed. Further application of PDP 5EC to L. esculentum challenged with F. oxysporum f.sp. lycopersici significantly increased the activity of enzymes of the phenylpropanoid pathway, namely, peroxidase (PO), polyphenol oxidase (PPO), phenylalanine ammonia lyase (PAL), and enhanced the total phenolic content when compared to the control.

Pyranocoumarins from Glehnia littoralis inhibit the LPS-induced NO production in macrophage RAW 264.7 cells.

A new dihydropyranocoumarin, (+)-cis-(3'S,4'S)-diisobutyrylkhellactone (1), together with five known compounds, 3'-senecioyl-4'-acetylkhellactone (2), 3'-isovaleryl-4'-acetylkhellactone (3), 3',4'-disenecioylkhellactone (4), 3'-isovaleryl-4'-senecioylkhellactone (5), and 3',4'-diisovalerylkhellactone (6), was isolated from Glehnia littoralis. Their chemical structures were elucidated based on the spectroscopic data interpretation, particularly 1D and 2D NMR data including HMQC and HMBC. All the isolated compounds showed the potential to inhibit LPS-induced nitric oxide production in RAW 264.7 cells with IC50 values ranging from 7.4 to 44.3µM.

Naturally occurring calanolides: an update on their anti-HIV potential and total syntheses.

Calanolides are naturally occurring pyranocoumarins found particularly in Calophyllum species (family Clusiaceae/ Guttiferae), and are well known for their potent anti-human immunodeficiency virus (HIV) activity. Various preclinical and clinical studies with this class of compounds are going on, and the National Cancer Institute (NCI) has been playing an active and supportive role in this regard. The present review covers an up-to-date literature of naturally occurring calanolides in view of their anti-HIV potential and total syntheses including information on related patents.

Anti-cancer and other bioactivities of Korean Angelica gigas Nakai (AGN) and its major pyranocoumarin compounds.

Korean Angelica gigas Nakai (AGN) is a major medicinal herb used in Asian countries such as Korea and China. Traditionally, its dried root has been used to treat anemia, pain, infection and articular rheumatism in Korea, most often through boiling in water to prepare the dosage forms. The pyranocoumarin compound decursin and its isomer decursinol angelate (DA) are the major chemical components in the alcoholic extracts of the root of AGN. The in vitro anti-tumor activities of decursin and/or DA against prostate cancer, lung cancer, breast cancer, colon cancer, bladder cancer, sarcoma, myeloma and leukemia have been increasingly reported in the past decade whereas the in vivo efficacy in mouse models was established only for a few organ sites. Preliminary pharmacokinetic studies by us and others in rodent models indicated that decursinol (DOH), which has much less in vitro direct anticancer activities by itself, is the major and rapid in vivo hydrolysis metabolite of both decursin and DA. Besides decursin, DA and DOH, other chemical components in AGN such as polysaccharides and polyacetylenes have been reported to exert anti-cancer and anti-inflammation activities as well. We systematically reviewed the published literature on the anti-cancer and other bio-activities effects of AGN extract and decursin, DA and DOH, as well as other chemicals identified from AGN. Although a number of areas are identified that merit further investigation, one critical need is first-in-human studies of the pharmacokinetics of decursin/DA to determine whether humans differ from rodents in absorption and metabolism of these compounds.

Pyranocoumarins isolated from Peucedanum praeruptorum Dunn suppress lipopolysaccharide-induced inflammatory response in murine macrophages through inhibition of NF-κB and STAT3 activation.

Praeruptorin C, D, and E (PC, PD, and PE) are three pyranocoumarins isolated from the dried root of Peucedanum praeruptorum Dunn of Umbelliferae. In the present study, we investigated the anti-inflammatory effect of these compounds in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophage cells. Pyranocoumarins significantly inhibited LPS-induced production of nitric oxide, interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α). The mRNA and protein expressions of inducible nitric oxide synthase, IL-6, and TNF-α were also suppressed by these compounds. Both PD and PE exhibited greater anti-inflammatory activities than PC. Further study showed that pyranocoumarins suppressed the cytoplasmic loss of inhibitor κB-α protein and inhibited the translocation of NF-κB from cytoplasm to nucleus. In addition, pyranocoumarins suppressed LPS-induced STAT3 tyrosine phosphorylation. Taken together, the results suggest that pyranocoumarins may exert anti-inflammatory effects in LPS-stimulated RAW 264.7 macrophages through the inhibition of NF-κB and STAT3 activation.

3'-O, 4'-O-aromatic acyl substituted 7,8-pyranocoumarins: a new class of P-glycoprotein modulators.

OBJECTIVES: P-glycoprotein (Pgp) overexpression in tumour cells leads to multidrug resistance (MDR) and causes failure in cancer chemotherapy. We have previously identified (±)-praeruptorin A (PA) as a potential lead compound for Pgp modulators. In this study we investigated the MDR-reversing activities of PA derivatives. METHODS: Series 7,8-pyranocoumarins with various C-3' and C-4' side chains had been semi-synthesized and their MDR-reversing activity was investigated in Pgp-overexpressing MDR tumour cell line HepG2/Dox and in a KB V1 xenograft animal model. KEY FINDINGS: All 7,8-pyranocoumarins exhibited equal or higher activity in modulating Pgp. DCK (12), DMDCK (15), 16, 21, 23 and 24 at 4 µm achieved 91%∼99% decrease in IC50 value (concentration inhibiting cell growth by 50%) of anticancer agents vinblastine, doxorubicin, puromycin and paclitaxel, and were more active than others. DMDCK also remarkably enhanced the growth inhibitory effect of paclitaxel on KB V1 xenografts (P < 0.05), showing a potency required for clinical usage. Mechanistic studies suggested that these 7,8-pyranocoumarins might reverse Pgp-MDR through directly binding to substrate binding site(s) or allosteric site(s) on Pgp therefore impairing Pgp-mediated drug transport. CONCLUSIONS: Results from the study suggested that 3'-O, 4'-O-aromatic acyl substituted 7,8-pyranocoumarins could serve as a new class of Pgp modulator. Acyls play an important role in maintaining and enhancing the Pgp-modulating ability of pyranocoumarins. 3,4-Dimethoxyl substituted aromatic acyls, bearing a methoxy that might interact with Pgp as hydrogen bond accepter, were shown to be the most potent for reversing MDR.

Anti-HBV and cytotoxic activities of pyranocoumarin derivatives.

Four natural pyranocoumarins clausenidin (1), nordentatin (2), clausarin (3), and xanthoxyletin (4) were isolated from the medicinal plant Clausena excavata. Recently, we found that 1 and 2 suppressed hepatitis B virus surface antigen in HepA2 cells, and in addition, 1-3 showed cytotoxic activity against four human cancer cell lines (A549, MCF7, KB, and KB-VIN). To explore the SAR of 1-4, 17 pyranocoumarin analogues (5-21) were designed and synthesized. Among these analogues, 5 and 10 were the most potent against hepatitis B virus with EC(50) values of 1.14 and 1.34microM, respectively. The most interesting result in the cytotoxicity assay was the significant activity of 1, 5, and 6 against the multi-drug resistant cell line, KB-VIN, without activity against the KB cell line. These data suggest that these three compounds could be useful hits for developing MDR-inverse drugs.

Scuteflorins A and B, dihydropyranocoumarins from Scutellaria lateriflora.

Two new dihydropyranocoumarins, scuteflorins A (1) and B (2), together with the known compounds decursin (3), chrysin (4), oroxylin A (5), wogonin (6), 5,7-dihydroxy-8,2'-dimethoxyflavone, dihydrochrysin, dihydrooroxylin A, lupenol, scutellaric acid, pomolic acid, ursolic acid, beta-sitosterol, daucosterol, and palmitic acid, were isolated from the aerial parts of Scutellaria lateriflora, commonly used as a dietary supplement. The structures of 1 and 2 were established by means of 1D and 2D NMR spectra as well as HRMS data. The absolute configuration of coumarins 1 and 2 was determined by comparison of experimental and theoretical calculated CD spectra. The cytotoxicity and antioxidant effects of the methanol extract of this plant and some of the constituent flavonoids were evaluated in vitro.