(-)-Neocaryachine, an Antiproliferative Pavine Alkaloid from Cryptocarya laevigata, Induces DNA Double-Strand Breaks

Twelve benzylisoquinoline alkaloids, including pavine and phenanthroindolizidine types, were isolated from a MeOH/CH₂Cl₂ extract of Cryptocarya laevigata (stem bark) through bioactivity-guided fractionation for antitumor effects. Selected compounds were evaluated for antiproliferative activity against five human tumor cell lines, including a multidrug-resistant subline. Since more common 2,3,8,9-tetrasubstituted pavine alkaloids, such as crychine (3), exhibit very mild or no cytotoxicity, this compound type has not been well investigated for antitumor activity. Thus, this report is the first discovery of a 7-hydroxylated pavine alkaloid, (-)-neocaryachine (1), to demonstrate strong antiproliferative activity, with IC₅₀ values of 0.06 to 0.41 μM against five tested tumor cell lines, including an MDR subline. Further mechanism of action studies revealed that 1 impacts the cellular S-phase by inducing DNA double-strand breaks.

New Perspectives in the Chemistry of Marine Pyridoacridine Alkaloids

Secondary metabolites from marine organisms are a rich source of novel leads for drug development. Among these natural products, polycyclic aromatic alkaloids of the pyridoacridine type have attracted the highest attention as lead compounds for the development of novel anti-cancer and anti-infective drugs. Numerous sophisticated total syntheses of pyridoacridine alkaloids have been worked out, and many of them have also been extended to the synthesis of libraries of analogues of the alkaloids. This review summarizes the progress in the chemistry of pyridoacridine alkaloids that was made in the last one-and-a-half decades.

Hispidacine, an unusual 8,4'-oxyneolignan-alkaloid with vasorelaxant activity, and hispiloscine, an antiproliferative phenanthroindolizidine alkaloid, from Ficus hispida Linn

Hispidacine, an 8,4'-oxyneolignan featuring incorporation of an unusual 2-hydroxyethylamine moiety at C-7, and hispiloscine, a phenanthroindolizidine alkaloid, were isolated from the stem-bark and leaves of the Malaysian Ficus hispida Linn. Their structures were established by spectroscopic analysis. Hispidacine induced a moderate vasorelaxant activity in rat isolated aorta, while hispiloscine showed appreciable antiproliferative activities against MDA-MB-231, MCF-7, A549, HCT-116 and MRC-5 cell lines.

Additional cytotoxic pyridoacridine alkaloids from the ascidian Cystodytes violatinctus and biogenetic considerations

The extraction and purification of the bioactive extract of Cystodytes violatinctus (Solomon Islands) led to the isolation and identification of six pyridoacridine alkaloids. The structures of four new members of this family, shermilamine F (1), dehydrokuanoniamine F (2), and arnoamines C (3) and D (4), were elucidated on the basis of NMR and MS data and by comparison with data of known compounds isolated from this genus. A general hypothetical biogenetic pathway is then proposed for pyridoacridine alkaloids that contain a fused pyrrole ring. Comparison of the biological properties of the isolated alkaloids is also discussed.

First discovery and stucture-activity relationship study of phenanthroquinolizidines as novel antiviral agents against tobacco mosaic virus (TMV)

A series of phenanthroquinolizidine alkaloids 1-24 were prepared and first evaluated for their antiviral activity against tobacco mosaic virus (TMV). The bioassay results showed that most of these compounds exhibited good to excellent in vivo anti-TMV activity, of which compounds 1, 2, 15 and 16 displayed significantly higher activity than (R)-antofine and commercial Ningnanmycin at the same test condition. The substituents on the phenanthrene moiety play an important role for maintaining high in vivo antiviral activity. The introduction of 6-hydroxyl, which is proposed to interact with TMV RNA, did increased anti-TMV activity. The 14aR-configuration was confirmed to be the preferred antiviral configuration for phenanthroquinolizidine alkaloids. Introduction of hydroxy group at 15-position of phenanthroquinolizidine alkaloids increased activity for S-configuration but decreased activity for R-configuration. Present study provides fundamental support for development and optimization of phenanthroquinolizidine alkaloids as potential inhibitors of plant virus.

Extract of Salvia miltiorrhiza (Danshen) induces Nrf2-mediated heme oxygenase-1 expression as a cytoprotective action in RAW 264.7 macrophages

ETHNOPHARMACOLOGICAL RELEVANCE

Danshen (Salvia miltiorrhiza) is widely used in traditional herbal medicines for relief of a variety of symptoms related to complications arising from vascular diseases such as hypertension, diabetes, and atherosclerosis. Induction of heme oxygenase-1 (HO-1) expression protects against oxidative stress-induced cell damage, which plays an important role in cytoprotection in a variety of pathological models.

MATERIALS AND METHODS

In the present study, we investigated the effect of Danshen on the up-regulation of HO-1, an inducible and cytoprotective enzyme in RAW 264.7 macrophages. Molecular mechanisms underlying the effects, especially protective effects, was elucidated by analyzing the activation of transcription factors and their upstream signalling, and by evaluating the inhibitory effect of HO-1 on ROS production.

RESULTS

Danshen induced HO-1 mRNA expression and protein production, and nuclear translocation of NF-E2-related factor 2 in RAW 264.7 macrophages. Pharmacological inhibitors of PI3K/Akt and MEK1 attenuated HO-1 induction in Danshen-stimulated RAW 264.7 macrophages. Furthermore, Danshen pretreatment reduced intracellular production of reactive oxygen species after stimulation with hydrogen peroxide; this effect was reversed by the HO-1 inhibitor ZnPP.

CONCLUSION

Danshen induced HO-1 expression through PI3K/Akt-MEK1-Nrf2 pathway and reduced intracellular production of reactive oxygen species via induction of HO-1 expression. The results support a role of HO-1 in the cytoprotective effect of Danshen.

Isolation and biological activities of phenanthroindolizidine and septicine alkaloids from the Formosan Tylophora ovata

An investigation of alkaloids present in the leaves and stems of Tylophora ovata led to the isolation of two new septicine alkaloids and one new phenanthroindolizidine alkaloid, tylophovatines A, B, C (1, 2, and 5), respectively, together with two known septicine and six known phenanthroindolizidine alkaloids. The structures of the new alkaloids 1, 2, and 5 were established by means of spectroscopic analyses. These eleven alkaloids show in vitro anti-inflammatory activities with IC₅₀ values ranging from 84 nM to 20.6 μM through their suppression of nitric oxide production in RAW264.7 cells stimulated by lipopolysaccharide and interferon-γ. Moreover, these substances display growth inhibition in HONE-1, NUGC-3, HepG2, SF-268, MCF-7, and NCI-H460 cancer cell lines, with GI₅₀ values ranging from 4 nM to 24.2 μM. In addition, tylophovatine C (5) and 13a(S)-(+)-tylophorine (7) were found to exhibit potent in vivo anti-inflammation activities in a rat paw edema model. Finally, structure–activity relationships were probed by using the isolated phenanthroindolizidines and septicines. Phenanthroindolizidines are suggested to be divided into cytotoxic agents (e.g., 10 and 11) and anti-inflammation based anticancer agents (e.g., 5–9).

Anticancer effect and neurotoxicity of S-(+)-deoxytylophorinidine, a new phenanthroindolizidine alkaloid that interacts with nucleic acids

Phenanthroindolizidine alkaloids are a family of plant-derived compounds with significant antineoplastic activity as well as other effects like antiamebicidal, antiviral, and anti-inflammatory activities. The specific biomolecular targets of these compounds have not yet been clearly identified. S-(+)-Deoxytylophorinidine (CAT) is a new phenanthroindolizidine alkaloid, originally extracted from the roots of Tylophora atrofolliculata and Tylophora ovata. Potent anticancer activity was observed in vitro and in vivo. Neurotoxicity of CAT was also studied and it was far less serious than that of vinblastine. Interactions between this compound and DNA had been studied in detail in our laboratory previously, and we further studied its interactions with RNA.

Identification of phenanthroindolizines and phenanthroquinolizidines as novel potent anti-coronaviral agents for porcine enteropathogenic coronavirus transmissible gastroenteritis virus and human severe acute respiratory syndrome coronavirus

The discovery and development of new, highly potent anti-coronavirus agents and effective approaches for controlling the potential emergence of epidemic coronaviruses still remains an important mission. Here, we identified tylophorine compounds, including naturally occurring and synthetic phenanthroindolizidines and phenanthroquinolizidines, as potent in vitro inhibitors of enteropathogenic coronavirus transmissible gastroenteritis virus (TGEV). The potent compounds showed 50% maximal effective concentration (EC₅₀) values ranging from 8 to 1468 nM as determined by immunofluorescent assay of the expression of TGEV N and S proteins and by real time-quantitative PCR analysis of viral yields. Furthermore, the potent tylophorine compounds exerted profound anti-TGEV replication activity and thereby blocked the TGEV-induced apoptosis and subsequent cytopathic effect in ST cells. Analysis of the structure-activity relations indicated that the most active tylophorine analogues were compounds with a hydroxyl group at the C14 position of the indolizidine moiety or at the C3 position of the phenanthrene moiety and that the quinolizidine counterparts were more potent than indolizidines. In addition, tylophorine compounds strongly reduced cytopathic effect in Vero 76 cells induced by human severe acute respiratory syndrome coronavirus (SARS CoV), with EC₅₀ values ranging from less than 5 to 340 nM. Moreover, a pharmacokinetic study demonstrated high and comparable oral bioavailabilities of 7-methoxycryptopleurine (52.7%) and the naturally occurring tylophorine (65.7%) in rats. Thus, our results suggest that tylophorine compounds are novel and potent anti-coronavirus agents that may be developed into therapeutic agents for treating TGEV or SARS CoV infection.

Mechanisms of the relaxant effect of a danshen and gegen formulation on rat isolated cerebral basilar artery

AIM OF THE STUDY

Danshen (root of Salvia miltiorrhiza) and gegen (root of Pueraria lobata) are two herbs used in traditional Chinese medicine, most commonly for their putative cardioprotective and anti-atherosclerotic effects. In this study, the actions of a danshen and gegen formulation (DG; ratio 7:3) were investigated on rat-isolated cerebral basilar artery.

MATERIALS AND METHODS

Rat basilar artery rings were precontracted with 100 nM U46619. Involvement of endothelium-dependent mechanisms was investigated by mechanical removal of the endothelium; K(+) channels were investigated by pretreatment of the artery rings with various K(+) channel inhibitors, and Ca(2+) channels were investigated in artery rings incubated with Ca(2+)-free buffer and primed with 100 nM U46619 for 5 min prior to adding CaCl(2) to elicit contraction.

RESULTS

DG produced concentration-dependent relaxation of the artery rings with an IC(50) of 895±121 μg/ml. Mechanical removal of the endothelium or pretreatment with the BK(Ca) channel inhibitor iberiotoxin (100 nM), the K(V) channel inhibitor 4-aminopyridine (1 mM), or the K(IR) channel inhibitor barium chloride (100 μM), all had no effect on the DG-induced response (P>0.05 for all). However, pretreatment with the K(ATP) channel inhibitor glibenclamide (1 μM), the non-selective K(+) channel inhibitor tetraethylammonium (TEA, 100 mM), or a combination of all the K(+) channel inhibitors (iberiotoxin+4-aminopyrindine+barium chloride+glibenclamide+TEA) produced significant inhibition on the DG-induced response (P<0.01 for all); its maximum vasorelaxant effect (Imax) was reduced by 37, 24, and 30%, respectively. Preincubation of the artery rings with DG for 10 min produced concentration-dependent (1, 3 and 7 mg/ml) and total inhibition on the CaCl(2)-induced vasoconstriction.

CONCLUSIONS

These findings suggest the vasorelaxant effect of DG on rat basilar artery is independent of endothelium-derived mediators, whereas, inhibition of Ca(2+) influx in the vascular smooth muscle cells is important, and a minor component is mediated by the opening of K(ATP) channels. DG could be a useful cerebroprotective agent in some patients with occlusive cerebrovascular disease.

Structures and antimicrobial activities of pyridoacridine alkaloids isolated from different chromotypes of the ascidian Cystodytes dellechiajei

Three new pentacyclic alkaloids were isolated from different chromotypes of the western Mediterranean ascidian Cystodytes dellechiajei. The purple color morph collected in Catalonia contained the known compounds kuanoniamine D (1), shermilamine B (2), N-deacetylkuanoniamine D (3), and styelsamine C (4) and a new alkaloid named N-deacetylshermilamine B (5). The green color morph collected in the Balearic Islands contained the known compounds 11-hydroxyascididemin (6) and 8,9-dihydro-11-hydroxyascididemin (7) and two new alkaloids named cystodimine A (8) and cystodimine B (9). The blue color morph collected in Catalonia yielded the known compound ascididemin (10). The structures of all compounds were elucidated on the basis of spectroscopic data, mainly 1D and 2D NMR data. The antimicrobial potential of the pyridoacridine alkaloids isolated from each color morph was evaluated and compared.

Evaluation of pyridoacridine alkaloids in a zebrafish phenotypic assay

Three new minor components, the pyridoacridine alkaloids 1-hydroxy-deoxyamphimedine (1), 3-hydroxy-deoxyamphimedine (2), debromopetrosamine (3), and three known compounds, amphimedine (4), neoamphimedine (5) and deoxyamphimedine (6), have been isolated from the sponge Xestospongia cf. carbonaria, collected in Palau. Structures were assigned on the basis of extensive 1D and 2D NMR studies as well as analysis by HRESIMS. Compounds 1–6 were evaluated in a zebrafish phenotype-based assay. Amphimedine (4) was the only compound that caused a phenotype in zebrafish embryos at 30 μM. No phenotype other than death was observed for compounds 1–3, 5, 6.

Complete assignments of (1)H and (13)C NMR data of three new dihydrophenanthrofurans from Pleione yunnanensis

Three new dihydrophenanthrofurans, pleionesins A-C (1-3), together with two known dihydrophenanthrenes (4-5) were isolated from the tubers of Pleione yunnanensis (Rolfe). The complete (1)H and (13)C NMR spectra assignments of these compounds were carried out using 1D and 2D NMR experiments ((1)H, (13)C, selective 1D NOE, HSQC and HMBC).

Effects of major tanshinones isolated from Danshen (Salvia miltiorrhiza) on rat CYP1A2 expression and metabolism of model CYP1A2 probe substrates

This study explored the effects of Danshen on metabolism/pharmacokinetics of model CYP1A2 substrates and hepatic CYP1A2 expression in rats. The effects of Danshen and tanshinones on CYP1A2 activity was determined by metabolism of model substrates in vitro (phenacetin) and in vivo (caffeine). HPLC was used to determine model substrates/metabolites. The effect of Danshen on CYP1A2 expression was determined by Western blot. Tanshinones (1.25-50 microM) competitively inhibited phenacetin O-deethylation in vitro. Inhibition kinetics studies showed the K(i) values were in the order: dihydrotanshinone (3.64 microM), cryptotanshinone (4.07 microM), tanshinone I (22.6 microM) and tanshinone IIA (23.8 microM), furafylline (35.8 microM), a CYP1A2 inhibitor. The Ki of Danshen extract (mainly tanshinones) was 72 microg/ml. Acute Danshen extract treatment (50-200mg/kg, i.p.) decreased metabolism of caffeine to paraxanthine, with overall decrease in caffeine clearance (14-22%); increase in AUC (11-25%) and plasma T(1/2) (12-16%). Danshen treatment with (100mg/kg/day, i.p. or 200mg/kg/day, p.o.) for three or fourteen days showed similar pharmacokinetic changes of the CYP1A2 probe substrate without affecting CYP1A2 expression. This study demonstrated that major tanshinones competitively inhibited the metabolism of model CYP1A2 probe substrates but had no effect on rat CYP1A2 expression.

Enhanced antioxidant bioactivity of Salvia miltiorrhiza (Danshen) products prepared using nanotechnology

The traditional Chinese medicine, Salvia miltiorrhiza (Danshen), promotes blood circulation and relieves blood stasis, also demonstrating good antioxidant activity. In the present study, therefore, the antioxidant activities of medicinal plant materials prepared using nanotechnology or traditional grinding methods were compared using three biological assays. It was found that the nanotechnology preparation had stronger antioxidant bioactivities. Complementary quantitative analysis of four active constituents, salvianolic acid B, cryptotanshinone, tanshinone I and tanshinone IIA, by HPLC revealed only marked differences for salvianolic acid B. The results indicate that the polar active constituent in the nanotechnology samples was released faster compared to the traditionally powdered samples.

Development and Validation of a HPLC Method for 4,7-Phenanthroline-5,6-Dione I and Identification of Its Major Impurity by HPLC-MS-APCI

In this study, the development and validation of an analytical method for the assay of 4,7-phenanthroline-5,6-dione I (dione I) using high-performance liquid chromatography (HPLC) and the determination of its synthetic impurities by employing the method in HPLC-mass spectrometry with atmospheric-pressure chemical ionization and photodiode-array UV detection is reported. The results show that dione I is eluted as a spectrally pure peak resolved from its impurities. 5-Bromo,4-7-phenanthroline is identified as the main impurity. This is supported by elemental analysis of the dione I, which demonstrated the presence of bromine. Validation parameters such as specificity and selectivity, linearity, accuracy, precision, limit of detection (LOD), limit of quantitation (LOQ), ruggedness, stability, and system suitability, which are evaluated for this method. The LOD and LOQ are 2.0 microg/mL and 50 microg/mL with a 0.50% relative standard deviation (%RSD), respectively. The calibration curves showed good linearity over the concentration range of 0.05-1.50 mg/mL. The correlation coefficient is > 0.9991 in each case. The %RSD values for intra- and interday precision studies are < 0.40%.

[Identification of Panax notoginseng and its preparations by LC/MS]

AIM

To develop a method of identifying the existing of Panax notoginseng in products of traditional Chinese medicine compound Danshen.

METHODS

Total ion chromatograms (TIC) of Panax notoginseng, P. ginseng, and P. quinquefolius were obtained by means of LC/MS. Extracted ion chromatograms (EIC) posses m/z of 770, 800, 932, 946 and 1,108 of above-mentioned three herbs was compared between species. EIC 800 and 946 were selected as differentiation marks to distinguish P. notoginseng from the other two species. The EIC 800 and 946 of P. notoginseng were also compared to the EICs obtained by the same method from Chinese patent medicines of compound Danshen pellet, compound Danshen tablet, and compound Danshen injection. EIC 800 and 946 of P. notoginseng and its products possess similar peaks, relative retention time, and relative integral areas. Main chemical constitutes of P. notoginseng were also identified by using LC/MS/MS.

RESULTS

EIC 800 and 946 were obviously different between P. notoginseng, P. ginseng, and P. quinquefolius. Patent medicines of compound Danshen pellet, compound Danshen tablet, which consist of extractions from P. notoginseng, possess the characteristic EICs. The selected EICs were stable and reproductive.

CONCLUSION

EIC 800 and 946, which correspond to ginsenoside Rg1, Re, and their isomers, can be used as identifying mark of P. notoginseng to differentiate it from other herbs, and also can be used to tell apart P. notoginseng from other herb extractions in Chinese patent medicines of compound Danshen.

Pyridoacridine alkaloids inducing neuronal differentiation in a neuroblastoma cell line, from marine sponge Biemna fortis

A new and three known pyridoacridine alkaloids were isolated from the Indonesian marine sponge Biemna fortis as neuronal differentiation inducers against a murine neuroblastoma cell line, Neuro 2A. The chemical structure of the new compound, labuanine A (1), was determined by spectroscopic study and chemical conversion. These pyridoacridine alkaloids induced multipolar neuritogenesis in more than 50% of cells at 0.03-3 micro M concentration. Compound 3, which showed the strongest neuritogenic activity among them, also induced increase of acetylcholinesterase, a neuronal marker in Neuro 2A and arrested cell cycle at the G2/M phase.

Cytotoxic activity and G2/M cell cycle arrest mediated by antofine, a phenanthroindolizidine alkaloid isolated from Cynanchum paniculatum

Starting with an extract derived from the root of Cynanchum paniculatum Kitagawa (Asclepiadaceae) that was active in the process of inhibiting the growth of human cancer cells in culture, a phenanthroindolizidine alkaloid antofine was isolated and identified as an active principle (IC50 = 7.0 +/- 0.2 ng/ml for A549, human lung cancer cells; IC50 = 8.6 +/- 0.3 ng/ml for Col2, human colon cancer cells). Prompted by the high potency of cancer cell growth inhibition, additional action mechanism studies were performed with antofine. Utilizing cultured Col2 cells as a model, antofine induced arrest in the G2/M phase of the cell cycle after 48 h of incubation. With wash-out experiment, colony formation was also inhibited in a dose-dependent manner. These data suggest the potential of antofine to serve as a cancer chemotherapeutic agent by virtue of arresting the cell cycle.

Probing nucleic acid structure with shape-selective rhodium and ruthenium complexes

In this unit, transition metal complexes are used as photochemical probes for the structure of RNA and DNA. The transition metal ion provides a rigid substitutionally inert framework and an octahedral geometry for ligand coordination. The complexes can be constructed to define shapes, symmetries, and functionalities that complement those of the nucleic acid target. Complex formation is easily detected by light-induced nucleic acid cleavage. The modular construction of the complexes makes it possible to generate probes to examine a wide variety of structural characteristics of nucleic acids.