Cage-Monoterpenoid Quinoline Alkaloids with Neurite Growth Promoting Effects from the Fruits of Melodinus yunnanensis.

Meloyunnanines A-C, three alkaloids with an unprecedented skeleton, were isolated from fruits of Melodinus yunnanensis. The structures featuring a caged-6/6/5/6/5/5 ring system were elucidated by the analysis of comprehensive spectroscopic and X-ray data. Biosynthetically, meloyunnanines A-C were assigned to monoterpenoid quinoline alkaloids (MQAs), derived from monoterpenoid indole alkaloids through oxidation and rearrangement. These compounds together with three known Melodinus MQAs were evaluated for their neurotrophic activity and scandine N4-oxide exhibited significant effect.

[Chemical constituents from roots and rhizomes of Rubia oncotricha and their cytotoxic activities].

Fourteen compounds, including rubiprasin D (1), rubiprasin B (2), rubiprasin C (3), oleanolic acid (4), methyl-5-hydroxy-dinaphtho[1, 2-2'3']furan-7, 12-dione-6-carboxylate (5), rubioncolin C (6), mollugin (7), furomollugin (8), 3-amino-2-methoxycarbonyl-1, 4-naphthoquinone (9), 1-hydroxy-2-methyl-9, 10-anthraquinone (10), 2-hydroxy-6-methyl-9, 10-anthraquinone (11), 1, 4-dihydroxy-2-hydroxymethyl-9, 10-anthraquinone (12), 2-hydroxy-1-methoxy-9, 10-anthraquinone (13), and 1-hydroxy-2-methoxy-6-methyl-9, 10-anthraquinone(14), were isolated from the methanol extract of the roots and rhizomes of Rubia oncotricha using various column chromatographies. Their structures were mainly determined on basis of NMR and MS spectroscopic data analyses. Among them, 1 is a new oleanane triterpene, and compounds 2-5, 9 and 11-13 were obtained from this plant for the first time. Cytotoxic and nematicidal activities of all these compounds were evaluated, and the results showed that only 4, 6, 11 and 12 exhibited cytotoxicities against A549, SGC-7901 and HeLa cancer cell lines. The IC50 of 6 were 19.42, 2.74, 8.07 µmol·L⁻¹, respectively.

Rubipodanones A-D, naphthohydroquinone dimers from the roots and rhizomes of Rubia podantha.

Four previously undescribed naphthohydroquinone dimers named rubipodanones A-D, together with 19 known quinones containing three known napthohydroquinone dimers named rubioncolin C, methyl 5-hydroxy-dinaphtho[1,2-2',3']furan-7,12-dione-6-carboxylate and rubialatin B, were isolated from the roots and rhizomes of Rubia podantha. Their structures and absolute configurations were determined mainly by NMR, X-ray diffraction, and computational methods. Rubipodanones C and D, the glycosides of rubipodanone A and a pair of C-3 epimer, are the first identified dimeric napthohydroquinone glycosides from the Rubia plants. All naphthohydroquinone dimers were evaluated for their cytotoxicities against ten tumor cell lines and effects on the tumor-associated NF-κB signaling pathway, and rubioncolin C showed the best cytotoxicity with IC50 value of 1.53 µM and NF-κB inhibitory activity with IC50 value of 2.97 µM. These results also demonstrated that the key roles of C-3 configuration and sugar group for biological activities of rubipodanone C.

Clausenlanins A and B, Two Leucine-Rich Cyclic Nonapeptides from Clausena lansium.

Two new cyclic nonapeptides, named clausenlanins A (1) and B (2), were isolated from the roots and rhizomes of Clausena lansium. Their structures were elucidated as cyclo-(Gly1-L-Leu2-L-Ile3-L-Leu4-L-Leu5-L-Leu6-L-Leu7-L-Leu8-L-Leu9) (1) and cyclo-(Gly1-L-Leu2-L-Val3-L-Leu4-L-Leu5-L-Leu6-L-Leu7-L-Leu8-L-Leu9) (2) respectively on the basis of extensive spectroscopic analysis, particularly 2D NMR spectra taken at the temperature of 338 or 303 K and MS.

New Labdane diterpenes from Hedychium yunnanense with cytotoxicity and inhibitory effects on nitric oxide production.

Two new labdane diterpenes, hedychenoids A (1) and B (2), were isolated from the rhizomes of Hedychium yunnanense, together with four known ones hedychenone (3), forrestin A (4), villosin (5) and calcaratarin C (6). Their structures were determined on the basis of NMR (1D and 2D) and mass spectroscopic analysis. Compounds 2, 3 and 5 exhibited cytotoxicity against SGC-7901 with IC50 values of 14.88 ± 0.52, 7.08 ± 0.21 and 7.76 ± 0.21 µg/ml, 3 and 5 against HeLa with IC50 values of 9.76 ± 0.48 and 13.24 ± 0.63 µg/ml, respectively. Compounds 2, 5 showed inhibitory effects against nitric oxide production in LPS and IFN-γ-induced RAW 264.7 murine macrophages with IC50 values of 6.57 ± 0.88 and 5.99 ± 1.20 µg/ml, respectively.

Rubipodanin A, the First Natural N-Desmonomethyl Rubiaceae-Type Cyclopeptide from Rubia podantha, Indicating an Important Role of the N9-Methyl Group in the Conformation and Bioactivity.

One new cyclic hexapeptide named rubipodanin A (1), which is the first identified natural N-desmonomethyl Rubiaceae-type cyclopeptide, together with six known Rubiaceae-type cyclopeptides (2-7) were obtained using the TLC cyclopeptide protosite detection method with ninhydrin from the roots and rhizomes of Rubia podantha. The cyclopeptide structures were elucidated by extensive spectroscopic analysis, including 1D-NMR, 2D-NMR, IR, UV and MS. The solution conformation and biological activities of 1 and RA-V (4) were evaluated, and the results demonstrated that the N9-methyl group plays a vital role in the maintenance of the conformation and bioactivity.

RA-XII inhibits tumour growth and metastasis in breast tumour-bearing mice via reducing cell adhesion and invasion and promoting matrix degradation.

Cancer cells acquire invasive ability to degrade and adhere to extracellular matrix (ECM) and migrate to adjacent tissues. This ultimately results metastasis. Hence, the present study investigated the in vitro effects of cyclopeptide glycoside, RA-XII on cell adhesion, invasion, proliferation and matrix degradation, and its underlying mechanism in murine breast tumour cells, 4T1. The effect of RA-XII on tumour growth and metastasis in 4T1-bearing mice was also investigated. Our results showed that RA-XII inhibited tumour cell adhesion to collagen, fibronectin and laminin, RA-XII also reduced the expressions of vascular cell adhesion molecule, intracellular adhesion molecule and integrins, and integrin binding. In addition, RA-XII significantly inhibited breast tumour cell migration via interfering cofilin signaling and chemokine receptors. The activities of matrix metalloproteinase-9 and urokinase-type of plasminogen activator, and the expressions of ECM-associated proteinases were attenuated significantly by RA-XII. Furthermore, RA-XII induced G1 phase arrest and inhibited the expressions of cyclins and cyclin-dependent kinases. RA-XII inhibited the expressions of molecules in PI3K/AKT, NF-kappaB, FAK/pSRC, MAPK and EGFR signaling. RA-XII was also shown to have anti-tumour, anti-angiogenic and anti-metastatic activities in metastatic breast tumour-bearing mice. These findings strongly suggested that RA-XII is a potential anti-metastatic agent for breast cancer.

Cyclopeptide RA-V inhibits cell adhesion and invasion in both estrogen receptor positive and negative breast cancer cells via PI3K/AKT and NF-κB signaling pathways.

Cyclopeptide RA-V has potent anti-tumor and anti-angiogenic activities, but its potential anti-metastatic activity is unknown. Cancer cells acquire invasive ability to degrade and adhere to extracellular matrix (ECM), allowing them to migrate to adjacent tissues and ultimately metastasize. Hence, the present study aimed to investigate the effects of RA-V on cell adhesion, migration, invasion and matrix degradation, and its underlying mechanism in two human breast cancer cell lines MCF-7 (ER-positive) and MDA-MB-231 (ER-negative). Our results demonstrated that RA-V (12.5 nM) can significantly inhibit breast cancer cell adhesion and migration via interfering cofilin signaling and chemokine receptors involved in cell migration. RA-V reduced the expressions of vascular intracellular adhesion molecule (VCAM), intracellular adhesion molecule (ICAM), focal adhesion kinase (FAK) and integrins. The activities and expressions of matrix metalloproteinases (MMPs), tissue inhibitors of matrix metalloproteinases (TIMPs) and urokinase-type of plasminogen activator (uPA) were also inhibited by RA-V. Furthermore, RA-V inhibits the expressions of EGFR, PI3K/AKT and NF-κB signaling molecules, and reduces the binding of ß-estradiol to ER via affecting binding ability of ER in MCF-7 cells. RA-V inhibits breast cancer cell migration, adhesion and ECM degradation in vitro, implying that RA-V is a potential anti-metastatic agent in breast cancer, and likely acts via PI3K/AKT and NF-κB signaling pathways in both ER-positive and ER-negative breast cancer cells.

A pH-responsive natural cyclopeptide RA-V drug formulation for improved breast cancer therapy.

The natural plant cyclopeptide RA-V, which was isolated from the roots of Rubia yunnanensis, was discovered to be a novel anti-cancer candidate. However, the cyclic hexapeptide exhibited poor solubility in physiological conditions, limiting its application for cancer therapy in vivo. To solve this problem, pH-sensitive polymers were developed for targeted RA-V delivery into tumor sites and for acid-triggered drug release. The poly(ß-amino ester)s (PAE) copolymers self-assembled into micelle-like nanoparticles in an aqueous solution at pH 7.4, and the solubility of RA-V was enhanced by loading the drug into the hydrophobic cores of micelles. The near-infrared (NIR) fluorescent probe squaraine (SQ) dye, as an imaging probe, could also be encapsulated into polymer micelles simultaneously. The diameters of the RA-V/SQ loaded micelles were measured by dynamic light scattering (DLS) and transmission electron microscopy (TEM), which proved that the micelles with sizes of 35-60 nm were suitable as anti-cancer drug nano-vehicles. The drug-loading capacity and drug release profiles of RA-V-loaded micelles were calculated and monitored by high performance liquid chromatography (HPLC) measurements. The RA-V/SQ loaded micelles were stable at a neutral pH, and drug release could be greatly accelerated by the acid-triggered ionization of copolymer chains. Similarly, with free RA-V cyclopeptide, the RA-V/SQ loaded micelles exhibited high anti-cancer efficiency toward MCF-7 cells and Hela cells, while the intact polymer micelles and SQ-loaded micelles are non-toxic. Moreover, the endocytosis pathway and mitochondria-regulated apoptosis of RA-V/SQ loaded micelles were proved by lysosome colocalization and JC-1 assay, respectively. Finally, biodistribution and tumor growth inhibition were evaluated in MCF-7 cell-xenografted nude mice, demonstrating that RA-V/SQ loaded micelles could realize tumor imaging and effectively and simultaneously inhibit tumor growth. Therefore, the RA-V/SQ loaded micelles may find use as potential nano-scaled cancer therapeutics and imaging agents.

New cytotoxic naphthohydroquinone dimers from Rubia alata.

Two novel naphthohydroquinone dimers with unprecedented skeletons, rubialatins A (1) and B (2), were isolated from the herbal plant Rubia alata together with their precursor, mollugin (3). The structures were elucidated on the basis of NMR spectra and crystal X-ray diffraction. Compound 1, a racemate, was separated by chiral column chromatography, and the absolute configurations of the enantiomers were determined by the computational methods. Cytotoxicity of 1-3 was evaluated as well as the effect on the NF-κB pathway. Compound (+)-1 showed cytotoxicity and could inhibit NF-κB pathway. Meanwhile, 2 showed cytotoxicity and a synergistic effect with TNF-α on NF-κB activation.

Coumarins from roots of Clausena excavata.

Two new coumarins, clauexcavatins A (1) and B (2), along with seven known ones (3-9), were isolated from the roots of Clausena excavata Burm. f. (Rutaceae). Their structures were elucidated on the basis of spectral data.

[Cyclopeptides from Rubia schumanniana].

OBJECTIVE: To separate and identify cyclopeptides of tubers of Rubia schumanniana. METHOD: The 70% methanol extracts from tubers of Rubia schumanniana were separated and purified by silica gel, RP-18, Sephedax LH-20 and HPLC. Their structures were identified by spectral analysis. RESULT: Nine cyclopeptides were separated and identified as RA- II (1), RA-V (2), RA-VIII (3), rubiyunnanin C (4), RA-X (5), RY-II (6), RA- I (7), RA-XIII (8) and RA-XIII-OMe (9), respectively. CONCLUSION: All of nine cyclopeptides were separated from R. schumanniana for the first time.

[Progress in the study of some important natural bioactive cyclopeptides].

Natural cyclopeptides are hot spots in chemical and pharmaceutical fields because of the wide spreading bio-resources, complex molecular structures and various bioactivities. Bio-producers of cyclopeptides distribute over almost every kingdom from bacteria to plants and animals. Many cyclopeptides contain non-coded amino acids and non-pepditic bonds. Most exciting characteristic of cyclopeptides is a range of interesting bioactivities such as antibiotics gramicidin-S (2), vancomycin (3) and daptomycin (4), immunosuppressive cyclosporin-A (1) and astin-C (8), and anti-tumor aplidine (5), RA-V (6) and RA-VII (7). Compounds 1-4 are being used in clinics; compounds 5-8 are in the stages of clinical trial or as a candidate for drug research. In this review, the progress in chemical and bioactive studies on these important natural bioactive cyclopeptides 1-8 are introduced, mainly including discovery, bioactivity, mechanism, QSAR and synthesis.

Biologically active arborinane-type triterpenoids and anthraquinones from Rubia yunnanensis.

Twelve new arborinane-type triterpenoids (1-12) and four new anthraquinones (13-16), together with 50 known compounds, were isolated from the roots of Rubia yunnanensis. The structures of 1-16 were elucidated by spectroscopic data analysis and chemical methods. All compounds were evaluated for their cytotoxic, antibacterial, and antifungal activities. Rubiyunnanol C (5) is the first example of an arborinane-type triterpenoid with a double bond at C-8-C-9.

Antitumor cyclic hexapeptides from rubia plants: history, chemistry, and mechanism (2005-2011).

Rubiaceae-type cyclopeptides (RAs), cyclic hexapeptides from Rubia plants, have shown potential antitumor activity in vitro and in vivo. Based on the review about plant cyclopeptides (Chem. Rev., 2006, 106: 840), this mini-review will highlight new progress on the discovery, synthesis, and mechanism of RAs isolated during 2005 to 2011, covering recent work in our group.