Shyh-Chyun Yang

Synthesis, anti-inflammatory, and antioxidant activities of 18β-glycyrrhetinic acid derivatives as chemical mediators and xanthine oxidase inhibitors

Twenty 18beta-glycyrrhetic acid (18beta-GA) derivatives 2-21 including 13 new 18beta-GA derivatives were synthesized and evaluated as anti-inflammatory and antioxidant agents. Compounds 7 and 20 with a 3,4-seco-structure and compound 6 with a lactone moiety showed potent inhibitory effect on superoxide anion generation in rat neutrophils response to fMLP/CB and PMA, respectively. Compound 6 with a lactone moiety revealed stronger inhibitory effect on XO activity than those of compounds 13 and 14 with a 3,4-seco-structure. Compound 14, a 30-isoproylcarbamoyl seco-compound exhibited potent inhibitory effect on NO accumulation and iNOS protein expression while compounds 3, 10, 13, 15, 17, and 21 revealed potent inhibitory effect on tumor necrosis factor-alpha (TNF-alpha) formation in RAW 264.7 cells in response to lipopolysaccharide (LPS). The cleavage of ring A of 3 attenuated the inhibitory effect on TNF-alpha formation in RAW 264.7 cells in response to LPS except for 17. The present results suggested these compounds were potential to be served as anti-inflammatory and antioxidant agents.

Ursolic acid derivatives induce cell cycle arrest and apoptosis in NTUB1 cells associated with reactive oxygen species.

Twenty-three ursolic acid (1) derivatives 2-24 including nine new 1 derivatives 5, 7-11, 20-22 were synthesized and evaluated for cytotoxicities against NTUB1 cells (human bladder cancer cell line). Compounds 5 and 17 with an isopropyl ester moiety at C-17-COOH and a succinyl moiety at C-3-OH showed potent inhibitory effect on growth of NTUB1 cells. Compounds 23 and 24 with seco-structures prepared from 1 also showed the increase of the cytotoxicity against NTUB1 cells. Exposure of NTUB1 to 5 (40 microM) and 23 (20 and 50 microM) for 24h significantly increased the production of reactive oxygen species (ROS) while exposure of NTUB1 to 5 (20 and 40 microM) and 23 (20 and 50 microM) for 48 h also significantly increased the production of ROS while exposure of cells to 17 did not increase the amount of ROS. Flow cytometric analysis exhibited that treatment of NTUB1 with 5 or 17 or 23 led to the cell cycle arrest accompanied by an increase in apoptotic cell death after 24 or 48 h. These data suggest that the presentation of G1 phase arrest and apoptosis in 5- and 23-treated NTUB1 for 24 h mediated through increased amount of ROS in cells exposed with 5 and 23, respectively, while the presence of G2/M arrest before accumulation of cells in sub-G1 phase in 5-treated cells for 48 h also due to increased amount of ROS in cells exposed with 5. The inhibition of tubulin polymerization and cell cycle arrest at G2/M following by apoptosis presented in the cell cycle of 23 also mediates through the increase amount of ROS induced by treating NTUB1 with 23 for 48 h.

Secondary metabolites from the roots of Engelhardia roxburghiana and their antitubercular activities

Bioassay-guided fractionation of stems of Engelhardia roxburghiana led to isolation of: four diarylheptanoids, engelheptanoxides A-D (1-4); two cyclic diarylheptanoids, engelhardiols A (5) and B (6); one naphthoquinone dimer, engelharquinonol (7); and one 1-tetralone, (4S)-4,6-dihydroxy-1-tetralone (8), along with 24 known compounds (9-32). The structures of 1-8 were by spectroscopic analysis. Compounds 5, 6, 13, 22, and 23 showed antitubercular activity against Mycobacterium tuberculosis H(37)Rv with MIC values of 72.7, 62.1, 9.1, 15.3, and 70.1μM, respectively.

Phloroglucinols with prooxidant activity from Garcinia subelliptica.

A new phloroglucinol, garcinielliptone HF ( 1), possessing an unprecedented skeleton, and the tautomeric pair of garcinielliptone FC ( 2/ 2a) were isolated from the heartwood and pericarp of Garcinia subelliptica, respectively. Their structures, including relative configurations, were elucidated by means of spectroscopic methods. The ability of compounds 1 and 2/ 2a to induce DNA-cleavage activity was examined using supercoiled plasmid pBR322 DNA. In the presence of Cu(II), compounds 1 and 2/ 2a caused significant breakage of pBR322 DNA. The involvement of H2O2 and O2 (*-), and H2O2, O2 (*-), and OH (*) in 1- and 2/ 2a-mediated scission, respectively, was established by inhibition or no protection of DNA breakage by various oxygen radical scavengers. Thus, in the presence Cu(II), 1 and 2/ 2a may show a prooxidant effect on DNA and induce cell death.

Antioxidant constituents from the stems and fruits of Momordica charantia

A new cucurbitane-type triterpene glycoside taiwacin A (1), a new 23,24,25,26,27-pentanorcucurbitane, taiwacin B (2) and a known cucurbitane-type triterpene glycoside (3), and a known steroid glycoside (4), were isolated from the stems and fruits of Momordica charantia, respectively. The structure of new compound was elucidated by spectroscopic methods. These four compounds, 1, 2, 3 and 4 revealed ABTS radical cation scavenging activity with an IC(50) values of 119.1±4.3, 204.5±1.2, 159.7±11.0 and 98.1±2.4μM, respectively. Compounds 1 and 3 displayed an inhibitory effect on xanthine oxidase (XO) activity with IC(50) values of 24.1±3.4 and 158.3±35.6μM, respectively. Compounds 2-4 significantly displayed O(2)(-) scavenging activity with an IC(50) values of 12.5±2.2, 16.5±0.1 and 27.3±1.4μM, respectively and the relative oxygen radical absorbance capacity (ORAC) values of 2 and 3, using ORAC-pyrogallol red (PGR) assay, were determined to be 0.88±0.02 and 0.55±0.09, respectively. These findings showed that 1-4 may be used as antioxidants.

Antioxidant xanthone derivatives induce cell cycle arrest and apoptosis and enhance cell death induced by cisplatin in NTUB1 cells associated with ROS

In an effort to develop novel antioxidant as anticancer agents, a series of xanthones were prepared. In vitro screening, the synthetic xanthones revealed significant inhibitory effects on xanthine oxidase and ABTS radical-cation scavenging activity. The selective compounds 2 and 8 induced an accumulation of NTUB1 cells in the G(1) phase arrest and cellular apoptosis by the increase of ROS level. The combination of cisplatin and 2 significantly enhanced the cell death in NTUB1 cells. Compounds 2 and 8 did not show cytotoxic activity in selected concentrations against SV-HUC1 cells. The present results suggested that antioxidants 2 and 8 may be used as anticancer agent for enhancing the therapeutic efficacy of anticancer agents and to reduce their side effect.

18β-Glycyrrhetinic acid derivatives induced mitochondrial-mediated apoptosis through reactive oxygen species-mediated p53 activation in NTUB1 cells

Twenty six 18β-glycyrrhetinic acid (GA) (1) derivatives 2-27 including twelve new GA derivatives 10, 11, 13-17, 21-25 were synthesized and evaluated for cytotoxicities against NTUB1 cells (human bladder cancer cell lines). seco-Compounds 9, 25, and 27 are the most potent compounds of this series, inhibiting cell growth of human NTUB1 cells with an IC(50) values of 2.34 ± 0.28, 4.76 ± 1.15, and 3.31 ± 0.61 μM, respectively. Exposure of NTUB1 to 25 for 24h significantly increased the production of reactive oxygen species (ROS). Flow cytometric analysis exhibited that treatment of NTUB1 with 25 did not induce cell cycle arrest but accompanied by an increase of apoptotic cell death in a dose-dependant manner after 24h. Mitochondrial membrane potential (MMP) decreased significantly in a dose-dependant manner when the NTUB1 cells were exposed to 25 for 24h. Marked collapse of the MMP suggested that dysfunction of the mitochondria may be involved in the oxidative burst and apoptosis induced by 25. Western blot analysis shows that NTUB1 cells treated with 25 increased the level of p-p53 in a dose-dependant manner. Further, NAC treatment prevented p53 phosphorylation stimulated by 25. These results suggested that 25 induced a mitochondrial-mediated apoptosis in NTUB1 cells through activation of p53, which are mainly mediated ROS generated by 25.

Xanthine Oxidase Inhibitory Triterpenoid and Phloroglucinol from Guttiferaceous Plants Inhibit Growth and Induced Apoptosis in Human NTUB1 Cells through a ROS-Dependent Mechanism

A known triterpenoid, β-amyrin (1), and a known and a new phloroglucinol, cohulupone (2) and garcinielliptone P (3), were isolated from the pericarp and heartwood and seed of Garcinia subelliptica, respectively. A new xanthonolignoid, hyperielliptone HF (4), was isolated from the heartwood of Hypericum geminiflorum. The new compounds were established by analysis of their spectroscopic data. Compounds 1-3 showed an inhibitory effect on xanthine oxidase (XO). Treatment of NTUB1, a human bladder cancer cell, with 1 or 1 cotreated with cisplatin for 24 h resulted in a decreased viability of cells. Exposure of NTUB1 to 1 or 1 cotreated with cisplatin for 24 h significantly increased the level of production of reactive oxygen species (ROS). Flow cytometric analysis indicated that treatment of NTUB1 with 1 or 1 cotreated with cisplatin led to the cell cycle arrest, accompanied by an increase in the extent of apoptotic cell death in 1 or 1 combined with cisplatin-treated NTUB1 after 24 h. These data suggested that the presentation of cell cycle arrest and apoptosis in 1 or 1 combined with cisplatin-treated NTUB1 for 24 h was mediated through an increased amount of ROS in cells exposed to 1 or 1 cotreated with cisplatin.

Anthraquinone derivatives induce G2/M cell cycle arrest and apoptosis in NTUB1 cells

Thirteen anthraquinone derivatives 5-17 including two 3-(3-alkylaminopropoxy)-9,10-anthraquinone (NHA) derivatives 5 and 6, and 11 1-hydroxy-3-(3-alkylaminopropoxy)-9,10-anthraquinone (MHA) derivatives 7-17 were synthesized, evaluated for cytotoxicities against two cancer cell lines, and assayed the generation of reactive oxygen species (ROS) in NTUB1 cells (a human bladder carcinoma cell line). Compound 9 bearing a pyrrolidinyl group induced the stronger cytotoxic effect than those of other synthesized NHA and MHA derivatives. Exposure of NTUB1 cells to 9, 13, and 17 for 24h significantly increased the production of ROS, respectively. Flow cytometric analysis exhibited that the exposure of NTUB1 cells to the selective 9 led to the G2/M phase arrest accompanied by an increase of apoptotic cell death after the incubation for 24h. Compound 9 induced up-regulation of cyclinB1 and p21 expressions. Biological results suggested that the induction of G2/M arrest, apoptosis, and cell death by 9 may associate with increased expression of p21 and cyclin B1, elevation of Bax and p53 levels, and generation of ROS in the cell. In conclusion, these series of compounds may be used as anticancer agents.

Phloroglucinols with Antioxidant Activity and Xanthonolignoids from the Heartwood of Hypericum geminiflorum

A new phloroglucinol, hyperielliptone HA (1/1a), a new spirophloroglucinol possessing an unprecedented skeleton, hyperielliptone HB (2/2a), and two new xanthonolignoids, hyperielliptones HC (3) and HD (4), were isolated from the heartwood of Hypericum geminiflorum. Compounds 1/1a and 2/2a were obtained as tautomeric pairs. The structures and relative configurations of these compounds were elucidated by spectroscopic methods. In biological testing, compound 2/ 2a revealed significant inhibition of oxidative DNA damage and an inhibitory effect on xanthine oxidase.