Dehydrobruceine B (DHB) is a quassinoid isolated from Brucea javanica. We have shown previously that DHB induced apoptosis on two kinds of lung cancer cell lines, A549 and NCI-H292. In the present study, we investigated the interactions of DHB and cisplatin (CDDP) on apoptotic-related cancer cell death. Synergistic effects on cell proliferation and apoptosis were observed when A549 cells were treated with DHB plus CDDP. DHB combined CDDP exposure increased depolarization of mitochondrial membrane potential (MMP) and release of cytochrome c from mitochondria into the cytoplasm. The combination treatment also enhanced protein expression of Bax, reduced the protein levels of Bcl-xL and Bcl-2, and increased the cleavage of caspase-3, caspase-9 and poly (ADP-ribose) polymerase (PARP). These results indicated that DHB sensitized A549 cells to cisplatin by regulating the mitochondrial apoptotic pathway. High constitutive expression of Nrf2 was found in A549 cells, which enhance the resistance of cancer cells to chemotherapeutic agents including cisplatin. DHB reduced the protein levels of Nrf2 and its target genes, which may contribute to the increase of intracellular ROS level, consequently, induced mitochondria apoptosis. These results generated a rationale for further investigation of DHB combined with CDDP as a potential therapeutic strategy in lung cancer.Download high-res image (87KB)Download full-size image

•A group of novel alkaloid-lignan hybrids were isolated from Lobelia chinensis simultaneously.•The compounds were determined to be two diastereomeric pairs of enantiomers by chiral HPLC–CD.•All the four stereoisomers were prepared by chiral HPLC.•CD spectra were used for the determination of the absolute configurations.Four novel alkaloid-lignan hybrids, lobechinenoids A–D (1–4), were isolated as a mixture of two diastereomeric pairs of enantiomers from the aerial parts of Lobelia chinensis. These compounds are constituted of the union of a tetrahydroisoquinoline alkaloid and a dihydrobenzofuran neolignan moiety. The structures were determined by detailed analyses of IR, MS and NMR data. These four compounds were characterized as two pairs of enantiomers by on-line chiral high performance liquid chromatography (HPLC)–circular dichroism (CD) analysis. The chiral HPLC separation was accomplished in the normal-phase mode using Chiralpak AD-H, a polysaccharide-derived chiral stationary phase (CSP) and a hexane-ethanol mobile phase. In order to study the chiroptical properties, all of the four single stereoisomers were successfully prepared on an analytical Chiralpak AD-H column and their stereochemical features were determined tentatively based on their CD spectra.

Chemical examination of aerial parts of Dracocephalum heterophyllum resulted in isolation of phenolic alkaloids, including two flavonoidal alkaloids, drahebephins A and B, one imidazole alkaloid with a phenolic substituent, drahebenine, together with 15 other known compounds. Their structures were established by extensive spectroscopic data analyses. Due to the stereogenic center in the pyrrolidin-2-one ring, the flavonoidal alkaloids are chiral, although they were isolated as racemates. The enantiomers were separated by HPLC using a chiral phase and stereochemically characterized by circular dichroism (CD) spectroscopy. The structure of compound drahebenine was established by X-ray crystallography.Graphical abstractPhenolic alkaloids, including flavonoidal alkaloids and an imidazole alkaloid, were obtained from Dracocephalum heterophyllum. The existence of flavonoidal alkaloids as racemates was demonstrated by HPLC using a chiral phase.Highlights► Phenolic alkaloids were isolated from Dracocephalum heterophyllum. ► The alkaloids, drahebephins A–B, are racemic. ► Racemates were resolved by HPLC using a chiral phase. ► CD spectroscopy was used for determination of absolute configurations.

BackgroundBrucea javanica is an effective traditional medicine listed in Chinese Pharmacopoeia. In China, the seed oil of B. javanica has long been used as commercially available drug for the treatment of tumor in clinic. Dehydrobruceine B (DHB) is a quassinoid isolated from B. javanica.PurposeThe aim of the present study is to investigate the apoptotic effects induced by DHB in human lung cancer A549 and NCI-H292 cells. The involvement of a mitochondria-mediated intrinsic pathway in the pro-apoptotic action of DHB was also investigated.Material and methodsCell viability was determined by MTT assay. Cell cycle and apoptosis were assessed by flow cytometry analysis. Mitochondrial membrane potential (MMP) was examined through JC-1 staining. The protein translocation in cells was examined by immunostaining. The expression levels of proteins which are closely related to mitochondria-mediated apoptosis pathway were measured by immunoblot analysis.ResultsTreatment with DHB decreased cell viability, induced apoptosis and blocked cell cycle at S phase. DHB-induced apoptosis was found to be mediated through mitochondrial intrinsic pathway, evidenced by the loss of MMP, the release of cytochrome c into cytosol, and the cleavage of caspase-9, caspase-3 and poly (ADP-ribose) polymerase (PARP).ConclusionDHB triggers apoptosis in A549 and NCI-H292 cells via mitochondrial pathway, making it a promising candidate as a therapeutic agent for lung carcinoma.Download high-res image (202KB)Download full-size image