Ying-Chi Du

Cytotoxic Triterpenoids from the Stems of Microtropis japonica

Bioassay-guided fractionation of a methanol extract obtained from stems of Microtropis japonica led to the isolation of six new ursane-type triterpenoids (1-6) and a new 2,3-seco-oleanane-type triterpenoid (7), together with seven known compounds. The structures of the new compounds were elucidated using spectroscopic data analysis. Among the known compounds isolated, the main component, 8 (ursolic acid), was active for HL60 cells, and its effects on histone hyperacetylation and the inhibition of histone deacetylase (HDAC) activity were investigated.

Towards the small and the beautiful: a small dibromotyrosine derivative from Pseudoceratina sp. sponge exhibits potent apoptotic effect through targeting IKK/NFκB signaling pathway.

A dibromotyrosine derivative, (1′R,5′S,6′S)-2-(3′,5′-dibromo-1′,6′-dihydroxy-4′-oxocyclohex-2′-enyl) acetonitrile (DT), was isolated from the sponge Pseudoceratina sp., and was found to exhibit a significant cytotoxic activity against leukemia K562 cells. Despite the large number of the isolated bromotyrosine derivatives, studies focusing on their biological mechanism of action are scarce. In the current study we designed a set of experiments to reveal the underlying mechanism of DT cytotoxic activity against K562 cells. First, the results of MTT cytotoxic and the annexin V-FITC/PI apoptotic assays, indicated that the DT cytotoxic activity is mediated through induction of apoptosis. This effect was also supported by caspases-3 and -9 activation as well as PARP cleavage. DT induced generation of reactive oxygen species (ROS) and the disruption of mitochondrial membrane potential (MMP) as indicated by flow cytometric assay. The involvement of ROS generation in the apoptotic activity of DT was further corroborated by the pretreatment of K562 cells with N-acetyl-cysteine (NAC), a ROS scavenger, which prevented apoptosis and the disruption of MMP induced by DT. Results of cell-free system assay suggested that DT can act as a topoisomerase II catalytic inhibitor, unlike the clinical anticancer drug, etoposide, which acts as a topoisomerase poison. Additionally, we found that DT treatment can block IKK/NFκB pathway and activate PI3K/Akt pathway. These findings suggest that the cytotoxic effect of DT is associated with mitochondrial dysfunction-dependent apoptosis which is mediated through oxidative stress. Therefore, DT represents an interesting reference point for the development of new cytotoxic agent targeting IKK/NFκB pathway.

Lupane-Type Triterpenoids from Microtropis fokienensis and Perrottetia arisanensis and the Apoptotic Effect of 28-Hydroxy-3-oxo-lup-20(29)-en-30-al

Seven new lupane triterpenoids were isolated from bioactive methanol extracts of Microtropis fokienensis (1- 4) and Perrottetia arisanensis (4-7), along with 18 known compounds. The structures of the new compounds were elucidated on the basis of spectroscopic data analysis. All triterpenoids were evaluated for their in vitro cytotoxicity toward seven human cancer cell lines. Compound 8 (28-hydroxy-3-oxo-lup-20(29)-en-30-al) was among the most cytotoxic substances obtained and was found to induce apoptosis of human leukemia HL60 cells and mediate cleavage of PARP and up-regulation of Bax proteins.

5-Episinuleptolide Acetate, a Norcembranoidal Diterpene from the Formosan Soft Coral Sinularia sp., Induces Leukemia Cell Apoptosis through Hsp90 Inhibition

5-Episinuleptolide acetate (5EPA), a cytotoxic norcembranoidal diterpene recently identified from the Formosan soft coral Sinularia sp., exhibited potent activity against the K562, Molt 4 and HL 60 cancer cell lines. The antiproliferative assay, as well as the annexin V-FITC/propidium iodide (PI) apoptotic assay, indicated that the HL 60 cell line is the most sensitive one towards 5EPA. This diterpenoid led to caspases -3, -8, and -9 activation as well as PARP cleavage. It also induced ROS generation, calcium accumulation and disruption of mitochondrial membrane potential. Additionally, the expression levels of Hsp90 protein and several client proteins were downregulated in response to 5EPA treatment. These results suggest that 5EPA’s cytotoxic effect on HL 60 cells may be attributed to the inhibition of Hsp90 as well as the induction of mitochondrial stress which finally results in apoptotic cell death.

10-acetylirciformonin B, a sponge furanoterpenoid, induces DNA damage and apoptosis in leukemia cells.

10-Acetylirciformonin B, a furanoterpenoid derived from irciformonin B found in a marine sponge, has been reported to possess potent cytotoxic activity against several cancer cell lines. However, the mechanism of its apoptotic activity against human leukemia cells has never been reported. The purpose of this study was to investigate the cytotoxic effects of 10-acetylirciformonin B and its possible mechanism of action against leukemia HL 60 cells. We found that 10-acetylirciformonin B decreased cell viability through the inhibition of cell growth as well as the induction of DNA damage and apoptosis in a dose-dependent manner. The induction of DNA damage was mediated by the increase of p-CHK2 and γ-H2A.X, which was suggested from the increase of tail movement in the neutral Comet assay. Induction of apoptosis was mediated with the increase in caspases 8, 9 and 3 activation as well as PARP cleavage. In summary, our resultsindicate that 10-acetylirciformonin B treatment causes apoptosis in leukaemia cells; probably through a caspase-dependent regulatory pathway.

Antileukemic Scalarane Sesterterpenoids and Meroditerpenoid from Carteriospongia (Phyllospongia) sp., Induce Apoptosis via Dual Inhibitory Effects on Topoisomerase II and Hsp90

Two new scalarane sesterterpenoids, 12β-(3′β-hydroxybutanoyloxy)-20,24-dimethyl-24-oxo-scalara-16-en-25-al (1) and 12β-(3′β-hydroxypentanoyloxy)-20,24-dimethyl-24-oxo-scalara-16-en-25-al (2), along with one known tetraprenyltoluquinol-related metabolite (3), were isolated from the sponge Carteriospongia sp. In leukemia Molt 4 cells, 1 at 0.0625 μg/mL (125 nM) triggered mitochondrial membrane potential (MMP) disruption and apoptosis showing more potent effect than 2 and 3. The isolates inhibited topoisomerase IIα expression. The apoptotic-inducing effect of 3 was supported by the in vivo experiment through suppressing the volume of xenograft tumor growth (47.58%) compared with the control. Compound 1 apoptotic mechanism of action in Molt 4 cells was further elucidated through inducing ROS generation, calcium release and ER stress. Using the molecular docking analysis, 1 exhibited more binding affinity to N-terminal ATP-binding pocket of Hsp90 protein than 17-AAG, a standard Hsp90 inhibitor. The expression of Hsp90 client proteins, Akt, p70S6k, NFκB, Raf-1, p-GSK3β, and XIAP, MDM 2 and Rb2, and CDK4 and Cyclin D3, HIF 1 and HSF1 were suppressed by the use of 1. However, the expression of Hsp70, acetylated tubulin, and activated caspase 3 were induced after 1 treatment. Our results suggested that the proapoptotic effect of the isolates is mediated through the inhibition of Hsp90 and topoisomerase activities.

Anti-inflammatory triterpenoids from the stems of Microtropis fokienensis.

Three new ursane- and four new oleanane- type triterpenoids 1–7 were isolated, along with six known compounds 8–13, from the methanolic extract of Microtropis fokienensis. All structures were elucidated by mass and NMR spectroscopic methods. The isolates 4–10 and known compounds 14–17 that were previously isolated from this material were evaluated for anti-inflammatory activity based on effects against superoxide anion generation and elastase release by neutrophils in response to fMLP/CB. 11α,30-Dihydroxy-2,3-seco-olean-12-en-2,3-dioic anhydride (7) was the first triterpene anhydride from the genus of Microtropis to have the ring A expanded to a seven-membered ring; it showed significant anti-inflammatory activity against superoxide anion generation and elastase release. Unexpectedly, 30-hydroxy-2,3-seco-lup-20(29)-ene-2,3-dioic acid (17) showed the best effect against superoxide anion generation and elastase release with IC50 values of 0.06 ± 0.01 and 1.03 ± 0.35 µg/mL, respectively. Compound 17 had a dioic acid function, and compound 7 had an anhydride function modification in ring A; both showed promising activity in the target assays.

New cytotoxic lupane triterpenes from Perrottetia arisanensis.

Eight new lupane triterpenes, including 7beta-cis-coumaroylbetulinic acid (1), 7beta-trans-coumaroylbetulinic acid (2), 7beta-cis-coumaroyl-3-epi-betulinic acid (3), 7beta-trans-coumaroyl-3-epi-betulinic acid (4), 7beta-cis-coumaroylbetulonic acid (5), 7beta-trans-coumaroylbetulonic acid (6), 7beta-hydroxybetulinaldehyde (7) and 28-norlup-20(29)-ene-3alpha,17beta-diol (8), together with fifteen known compounds were isolated from the bioactive methanol extract of the stems of Perrottetia arisanensis. The structures of the new compounds were elucidated by spectroscopic and HR-ESI-MS analysis. All new compounds were evaluated for their cytotoxicity against six human cancer cell lines. Among them, lupane triterpene coumaroyl esters 1-6 showed moderate cytotoxicity with IC (50) values ranging from 3.75 to 21.29 microM. This is the first report for lupane triterpenes with a phenylpropane moiety substituted at C-7.

Rapid HPLC Quantification Approach for Detection of Active Constituents in Modern Combinatorial Formula, San-Huang-Xie-Xin-Tang (SHXXT).

San-Huang-Xie-Xin-Tang (SHXXT), one of the most important traditional Chinese medicinal formulas, is comprised by three herbal medicines, the rhizome of Rheum officinale [or Rheum tanguticum (Polygonaceae) (Dahuang in Chinese)], the root of Scutellaria baicalensis (Labiatae) (Huangqin in Chinese), and the rhizome of Coptis chinensis (Ranunculaceae) (Huanglian in Chinese) in the ratios of 2:1:1 or 1:1:1. This study is aimed to quantitate and qualify of SHXXT, by a rapid, convenient, and effective HPLC-PDA approach associated with LC-MS technique. Of which method, nine chosen major bioactive components in SHXXT, including aloe-emodin (Ale), baicalin (Ba), berberine (Be), coptisine (Co), palmatine (Pa), resveratroloside (Res), rhein (Rh), sennoside A (Se-A), and wogonin (Wo), were evaluated within 30 min. The nine chemical markers were monitored in a high sensitivity with a low detection limit of 0.01−0.55 μg/mL and the correlation coefficient of the regression curve revealed a good linearity with R2 > 0.99. Moreover, the extraction solution system and the HPLC elution conditions were also optimized in the present study. This present developed protocol was then successfully applied to quantify nine chemical markers of 10 SHXXT products from eight Taiwanese TCM pharmaceutical companies. In quantitative results, Res was found as the major compound in SHXXT-1~5 and 8 with significantly higher amounts than those in other products, indicating the products SHXXT-1~5 and 8 may use R. tanguticum as the raw material, which possessed a higher concentration of the bioactive composition Res, instead of R. officinale. Simultaneously, Ale, Rh, and Wo were < 2% in these 10 products. Different chemical profiles of commercial products indicated that, probably, each product with the same named formula might be regarded as a sole medicine and need to be investigated individually. Importantly, it is never too much to emphasize the importance of quality control in TCM development.

Heteronemin, a Marine Sesterterpenoid-Type Metabolite, Induces Apoptosis in Prostate LNcap Cells via Oxidative and ER Stress Combined with the Inhibition of Topoisomerase II and Hsp90

Heteronemin, a marine sesterterpenoid-type natural product, possesses diverse bioactivities, especially antitumor effect. Accumulating evidence shows that heteronemin may act as a potent anticancer agent in clinical therapy. To fully understand the antitumor mechanism of heteronemin, we further explored the precise molecular targets in prostate cancer cells. Initially, heteronemin exhibited potent cytotoxic effect against LNcap and PC3 prostate cancer cells with IC50 1.4 and 2.7 μM after 24 h, respectively. In the xenograft animal model, the tumor size was significantly suppressed to about 51.9% in the heteronemin-treated group in comparison with the control group with no significant difference in the mice body weights. In addition, the results of a cell-free system assay indicated that heteronemin could act as topoisomerase II (topo II) catalytic inhibitor through the elimination of essential enzymatic activity of topoisomerase IIα expression. We found that the use of heteronemin-triggered apoptosis by 20.1–68.3%, caused disruption of mitochondrial membrane potential (MMP) by 66.9–99.1% and promoted calcium release by 1.8-, 2.0-, and 2.1-fold compared with the control group in a dose-dependent manner, as demonstrated by annexin-V/PI, rhodamine 123 and Fluo-3 staining assays, respectively. Moreover, our findings indicated that the pretreatment of LNcap cells with an inhibitor of protein tyrosine phosphatase (PTPi) diminished growth inhibition, oxidative and Endoplasmic Reticulum (ER) stress, as well as activation of Chop/Hsp70 induced by heteronemin, suggesting PTP activation plays a crucial rule in the cytotoxic activity of heteronemin. Using molecular docking analysis, heteronemin exhibited more binding affinity to the N-terminal ATP-binding pocket of Hsp90 protein than 17-AAG, a standard Hsp90 inhibitor. Finally, heteronemin promoted autophagy and apoptosis through the inhibition of Hsp 90 and topo II as well as PTP activation in prostate cancer cells. Taken together, these multiple targets present heteronemin as an interesting candidate for its future development as an antiprostatic agent.