Real-time observation of stationary and pulsating noise-like vector pulses in a fiber laser.

Rapid progress in real-time measurement technology has uncovered varieties of transient pulse dynamics. Here, we report the vector nature of noise-like pulse (NLP) in a passive fiber laser based on the nonlinear optical loop mirror (NOLM) as the polarization independent saturable absorber. After achieving the basic operation regime of NLP, various types of vector pulses, namely, the polarization locked noise-like vector pulse (PLNLVP), the group velocity locked noise-like vector pulse (GVLNLVP), and the transitional state of combined characteristics of GVLNLVP and polarization rotation noise-like vector pulse (PRNLVP) are also obtained in the cavity. Besides, by utilizing the Dispersive Fourier transform (DFT) technique, the spectral evolution and the energy vibration of pulsating PLNLVP, GVLNLVP, and the transitional state of combined characteristics of GVLNLVP and PRNLVP are also analyzed in real time. Particularly, the coexisting pulsation vector state of NLP and soliton is also captured. All these findings will help to complement our understanding of noise-like vector pulses (NLVPs) in a fiber laser.

A combined network pharmacology and molecular biology approach to investigate the potential mechanisms of G-M6 on ovarian cancer.

Ginsenoside 3ß,12ß,21α,22ß-Hydroxy-24-norolean-12-ene (G-M6), a phase I metabolite of anti-tumor medication 20(R)-25-methoxyl-dammarane-3ß,12ß,20-triol (AD-1), beats the parent drug in anti-ovarian cancer efficacy. The mechanism of action for ovarian cancer, however, is uncertain. Using network pharmacology, human ovarian cancer cells and nude mouse ovarian cancer xenotransplantation model, the anti-ovarian cancer mechanism of G-M6 was preliminarily explored in this study. The PPAR signal pathway is the key signal pathway of the G-M6 anti-ovarian cancer mechanism, according to data mining and network analysis. Docking tests demonstrated that the bioactive chemical G-M6 was capable of forming a stable bond with the PPARγ target protein capsule. Using human ovarian cancer cells and xenograft model of ovarian cancer to evaluate the anticancer activity of G-M6. The IC50 value of G-M6 was 5.83±0.36, lower than AD-1 and Gemcitabine. The tumor weight of the RSG 80 mg/kg group (C), G-M6 80 mg/kg group (I), and RSG 80 mg/kg + G-M6 80 mg/kg group (J) after the intervention was as follows: C < I < J. The tumor inhibition rates of groups C, I, and J were 28.6%, 88.7%, and 92.6%, respectively. When RSG and G-M6 are combined to treat ovarian cancer, q = 1.00 is calculated according to King's formula, which indicates that RSG and G-M6 have additive effects. Its molecular mechanism may involve the up-regulation of PPARγ and Bcl-2 protein expressions, and the down-regulation of Bax, Cytochrome C (Cyt. C), Caspase-3, and Caspase-9 protein expressions. These findings serve as a reference for further research into the processes behind ginsenoside G-M6's ovarian cancer therapy.

Stereospecificity of Ginsenoside AD-1 and AD-2 Showed Anticancer Activity via Inducing Mitochondrial Dysfunction and Reactive Oxygen Species Mediate Cell Apoptosis.

In this paper, the anti-cancer activity and molecular mechanisms of the isomers of AD-1 and AD-2 (20(R)-AD-1, 20(R)-AD-2, 20(S)-AD-1 and 20(S)-AD-2) were investigated. The results indicated that all of the four compounds obviously suppressed the viability of various cancer cells, and the anti-cancer activity of 20(R)-AD-1 and 20(R)-AD-2 was significantly better than 20(S)-AD-1 and 20(S)-AD-2, especially for gastric cancer cells (BGC-803). Then, the differences in the anti-cancer mechanisms of the isomers were investigated. The data showed that 20(R)-AD-1 and 20(R)-AD-2 induced apoptosis and decreased MMP, up-regulated the expression of cytochrome C in cytosol, transferred Bax to the mitochondria, suppressed oxidative phosphorylation and glycolysis and stimulated reactive oxygen species (ROS) production. Apoptosis can be attenuated by the reactive oxygen species scavenger N-acetylcysteine. However, 20(S)-AD-1 and 20(S)-AD-2 barely exhibited the same results. The results indicated that 20(R)-AD-1 and 20(R)-AD-2 suppressed cellular energy metabolism and caused apoptosis through the mitochondrial pathway, which ROS generation was probably involved in. Above all, the data support the development of 20(R)-AD-1 and 20(R)-AD-2 as potential agents for human gastric carcinoma therapy.

Novel ginsenoside derivatives have shown their effects on PC-3 cells by inducing G1-phase arrest and reactive oxygen species-mediate cell apoptosis.

In this study, piperazine groups were introduced into ginsenoside to enhance its ability to induce Reactive Oxygen Species (ROS) production and apoptosis in cancer cells. In total, 27 ginsenoside piperazine derivatives were synthesized and tested for their anti-proliferative activity in cancer cell lines by MTT assay. The results showed that compounds 4a, 4g, 4f, 4i, 5g, 5i, 6a, 6g, 6f and 6i had significant inhibitory effects on cancer cell growth. Compound 6g showed the strongest anti-proliferative effect on PC-3 cells with an IC50 of 1.98 ± 0.34 µM. Compound 6g could also induce G1-phase arrest and apoptosis in PC-3 cells, with apoptosis rates of 8.1%, 41% and 56.1% observed at 5, 10 and 20 µM, respectively. Compound 6g also significantly enhanced the intracellular fluorescence of ROS sensitive substrates, with a fluorescence intensity ratio of 23.1% observed in treated cells, indicative of ROS production. Following N-acetylcysteine treatment, apoptotic rates of the cancer cell lines decreased from 38.9% to 7.3%, and the expression of Cl-PARP, Cl-Caspase-3 and Cl-Caspase-9 also decreased, confirming that compound 6g induced apoptosis through ROS induction. Compound 6g also stimulated the translocation of Bax from the cytoplasm to the mitochondria, which enhanced Cytochrome C (Cyt C) release, and increased the expression of the apoptotic markers Cl-PARP, Cl-Caspase-3, and Cl-Caspase-9 in PC-3 cells. Taken together, these data reveal the anti-cancer effects of compound 6g that enhance ROS production, and then induce apoptosis through mitochondrial pathway.

Multiple Roles of Black Raspberry Anthocyanins Protecting against Alcoholic Liver Disease.

This study aimed to investigate the protective effect of black raspberry anthocyanins (BRAs) against acute and subacute alcoholic liver disease (ALD). Network analysis and docking study were carried out to understand the potential mechanism. Thereafter, the serum biochemical parameters and liver indexes were measured, the histopathological changes of the liver were analyzed in vivo. The results showed that all tested parameters were ameliorated after the administration of BRAs with alcohol. Meanwhile, there was increased protein expression of NF-κB and TGF-ß in extracted livers, which was associated with hepatitis and hepatic fibrosis. Furthermore, BRAs and cyanidin-3-O-rutinoside exhibited cytotoxic effects on t-HSC/Cl-6, HepG2, and Hep3B and induced the apoptosis of HepG2 cells; downregulated the protein expression level of Bcl-2; upregulated the level of Bax; and promoted the release of cytochrome C, cleaved caspase-9, cleaved caspase-3, and cleaved PARP in HepG2 cells. In addition, the antioxidant activity of BRAs was tested, and the chemical components were analyzed by FT-ICR MS. The results proved that BRAs exert preventive effect on ALD through the antioxidant and apoptosis pathways.

Combination of white tea and peppermint demonstrated synergistic antibacterial and anti-inflammatory activities.

BACKGROUND: White tea, considered to be the oldest form of tea, is becoming a popular beverage for its organoleptic characteristics. Peppermint tea, used as a herbal remedy for centuries, is now also very popular throughout the world as herbal tea. What interested us was that in ancient China, peppermint was used in combination with tea as a detoxification or anti-inflammatory agent. However, there are few reports on the combined use of white tea and peppermint. Therefore, this study aims to investigate the antibacterial and anti-inflammatory activities of white tea in combination with peppermint. RESULTS: A synergistic inhibitory effect against four bacterial strains, especially against Staphylococcus argenteus, was observed in the combination of white tea and peppermint in vitro. In addition, the combined formula demonstrated a stronger anti-inflammatory effect in vivo than either of the two used alone, which was associated with the decrease of the pro-inflammatory cytokines of interleukin-6 (IL-6), interleukin-1beta (IL-1ß), tumor necrosis factor-alpha (TNF-α), cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS). In a further mechanism study, it was found that white tea and peppermint inhibited the phosphorylation of p-IκB-α and mitogen-activated protein kinase (MAPK) at different degrees. While the enhanced anti-inflammatory effect of the combined formula was associated with the combination of NF-κB down-regulation and p-MAPK inhibition. CONCLUSION: In our study, it was for the first time shown that when white tea was combined with peppermint, the antibacterial and anti-inflammatory effects were enhanced. The results suggested an effective application of white tea in combination with peppermint as a potential antibacterial and anti-inflammatory functional food. © 2020 Society of Chemical Industry.

Novel panaxadiol triazole derivatives induce apoptosis in HepG-2 cells through the mitochondrial pathway.

In this study, we introduced 1, 2, 4-triazole groups into panaxadiol (PD) to obtain 18 panaxadiol triazole derivatives. Five cancer cells and one normal cell were evaluated for cytotoxicity by MTT assay. The results showed that most of the derivatives could inhibit cancer cell proliferation, and the anti-proliferative activity of compound A1 was the most significant. For HepG-2 cells, the IC50 value was 4.21 ± 0.54 µM, which was nearly 15 times higher than the activity of PD. Further studies showed that compound A1 could induce apoptosis in HepG-2 cells, and could enhance the expression of Cl-caspase-3, Cl-caspase-9 and Cl-PARP. Moreover, Western blot analysis showed that after treating HepG-2 cells with compound A1, the expression of p53 protein was increased and the ratio of Bax/Bcl-2 was gradually increased. The cytoplasmic Bax is then translocated to the mitochondria, causing the release of Cyt c protein. Therefore, the results indicate that compound A1 induces apoptosis through the mitochondrial pathway and can be used the potential to develop new anti-proliferative agents.

Rational design, synthesis and biological evaluation of triphenylphosphonium-ginsenoside conjugates as mitochondria-targeting anti-cancer agents.

In anti-cancer therapy, targeting a single gene or a single metabolic pathway usually cannot effectively cure cancer, while targeting cellular mitochondria might be effective based on the role of mitochondria in the occurrence and development of cancer. Anti-cancer study on ginsenosides AD-1, AD-2 and PD have proved that they have broad spectrum anti-cancer activities in vitro and in vivo. However, they are not active at sufficiently low concentration, and their lower selectivity and cell permeability hindered therapeutic applications. In the present study, AD-1, AD-2 and PD are incorporated with triphenylphosphonium at the OH group in C-3 position through different length of alkyl chains, with the aim of targeting mitochondria and improving the efficacy and selectivity of parent compounds. Biological studies suggested that most of the conjugates had enhanced anti-proliferative activity, in particular, conjugate 1f had an IC50 value of 0.76 µM against MCF-7 cells while showed a high degree of selectivity to MCF-7 cells. In addition, 1f was obviously increased accumulation in the mitochondria, and induced apoptosis, elevated reactive oxygen species (ROS) level and caused mitochondrial membrane potential collapse in MCF-7 cells. Further study revealed that ROS-related mitochondrial translocation of p53 was also involved in 1f-induced mitochondrial apoptotic pathway. The results demonstrated that 1f could be a promising lead for the development of mitocans. These findings also provide a reference for the development of ginsenoside for mitochondria-targeted anti-cancer drugs.

Synthesis and Cytotoxicity Evaluation of Panaxadiol Derivatives.

In this study, 13 panaxadiol (PD) derivatives were synthesized via reactions with aromatic compounds and amino acids. Following this, the cytotoxicity of these compounds was evaluated against four cancer cell lines (human hepatoma cells HepG-2, human lung cancer cells A549, human breast cancer cells MCF-7, and human colon cancer cells HCT-116) and one normal cell lines (human gastric epithelial cells GES-1). The results showed that the panaxadiol derivatives 3, 12, and 13 showed significant inhibition of cellular proliferation against cancer cells compared with PD, and the panaxadiol derivative 12 had the lowest IC50 value for A549 (IC50 =18.91±1.03 µm). For MCF-7 cells, most compounds exhibited good inhibition of cellular proliferation, and the panaxadiol derivative 13 showed the strongest inhibitory effect (IC50 =8.62±0.23 µm), which significantly increased the cytotoxicity of PD and was stronger than the positive control (mitomycin). For normal cells, all compounds exhibited low or no toxic effects; thus, these derivatives can be used to develop novel antiproliferative agents.

Semi-synthesis and anti-tumor activity of novel 25-OCH3-PPD derivatives incorporating aromatic moiety.

Previously we have reported that 25-OCH3-PPD could suppress the reproduction of cancer cells and cause apoptosis without obvious toxicity. Herein, we aimed to enhance its bioactivity by introducing aromatic groups to its dammarane-type skeleton. These synthesized derivatives were tested for their inhibitory activities against five cancer cell lines. Of them, compounds 3a, 14a and 18a had the strongest antiproliferative activities against tumor cells (IC50 < 15 µM, 5-fold to 10-fold increases than 25-OCH3-PPD). Especially compound 14a displayed the most potent activity against DU145, MCF-7 and HepG2 cells (IC50 = 6.7 ±â€¯0.8, 4.3 ±â€¯0.8 and 5.8 ±â€¯0.6 µM, respectively). Structure-activity relationships demonstrated that having aromatic ester at the C3 position could improve the bioactivity. The data provided new insights into exploring novel antiproliferative lead compounds.

New perspective on the metabolism of AD-1 in vivo: Characterization of a series of dammarane-type derivatives with novel metabolic sites and anticancer mechanisms of active oleanane-type metabolites.

20(R)-25-methoxyl-dammarane-3ß,12ß,20-triol (AD-1, CN Patent: 201010107476.7) is a novel derivative of dammarane-type ginsenoside. AD-1 has been shown to inhibit cancer cell proliferation without significant host toxicity in vivo, and has excellent development potential as a new anti-cancer agent. This study was designed systematically to explore the metabolic pathway of ginseng sapogenins. The metabolism of drugs in the body is a complex biotransformation process where drugs are structurally modified to different molecules (metabolites) through various metabolizing enzymes. The compounds responsible for the effects of orally administered ginseng are believed to be metabolites produced in the gastrointestinal tract, so understanding the metabolism of the drug candidate can help to optimize its pharmacokinetics. In this study, faeces samples were collected and extracted after oral administration of AD-1. The 16 metabolites of AD-1 were isolated and identified for the first time with various chromatographic techniques, including semi-preparative high performance liquid chromatography, nuclear magnetic resonance spectroscopy, and mass spectrometry; of these 16 metabolites, 10 were novel compounds. We first discovered the biotransformation of dammarane-type sapogenins into oleanane-type sapogenins in rats and found a series of metabolites that changed, mainly at C-25 and C-29. This study provides new ideas for the metabolic pathway of ginseng sapogenins. The isolated compounds were screened for their effect on the viability and proliferation against cancer cell lines (Human A549, MCF-7, HELA, HO-8901 and U87). The discovery of novel active metabolites 3ß,12ß,21α,22ß-Hydroxy-24-norolean-12-ene (M6) may lead to a new or improved drug candidate. For one, M6 could inhibit the growth of all the tested cancer cells. Among the tested cell lines, M6 exhibited the most remarkable inhibitory effect on ovarian cancer HO-8901 cells, with IC50 value of 2.086 µM. On this basis, we studied the anticancer mechanisms of M6. The results indicated that the pro-apoptotic feature of M6 acts via a mitochondrial pathway. Our results indicated that M6 exhibited a higher inhibitory effect on cancer-cell proliferation than AD-1 by inducing cell apoptosis. Our work provides data for future investigations on the metabolic mechanism of AD-1 in vivo and the potential for future research on developing a new drug.

Design, characterization, and in vitro antiproliferative efficacy of gemcitabine conjugates based on carboxymethyl glucan.

Gemcitabine (GEM) is widely used in clinical practice in the treatment of cancer and several other solid tumors. Nevertheless, the antitumor effect of GEM is partially prevented by some limitations including short half life, and lack of tumor localizing. Carboxymethyl glucan (CMG), a carboxymethylated derivative of ß-(1-3)-glucan, shows biocompatibility and biodegradability as well as a potential anticarcinogenic effect. To enhance the antiproliferative activity of GEM, four water soluble conjugates of GEM bound to CMG via diverse amino acid linkers were designed and synthesized. 1H NMR, FT IR, elementary analysis and RP-HPLC chromatography were employed to verify the correct achievement of the conjugates. In vitro release study indicated that conjugates presented slower release in physiological buffer (pH 7.4) than acidic buffer (pH 5.5) mimicking the acidic tumor microenvironment. Moreover, A549, HeLa and Caco-2 cancer cell lines were used to evaluate the in vitro cytotoxicity of conjugates and the results showed that binding GEM to CMG significantly enhanced antiproliferative activity of GEM on A549 cells. Therefore, these conjugates may be potentially useful as a delivery vehicle in cancer therapy and worthy of further study on structure-activity relationship and antiproliferative activity in vitro and in vivo, especially for lung tumor.

Polyphenols from Acorn Leaves (Quercus liaotungensis) Protect Pancreatic Beta Cells and Their Inhibitory Activity against α-Glucosidase and Protein Tyrosine Phosphatase 1B.

Acorn leaves, which possess potential pharmacologic effects, are traditionally consumed as food in China. Phytochemical investigations of acorn leaves yielded one new and 25 known polyphenols, and their structures were identified by extensive spectroscopic analysis. Three antidiabetes assays were conducted. Compound 2 considerably increased the survival of pancreatic beta cells by reducing the production of reactive oxygen species and enhancing the activities of superoxide dismutase, catalase, and glutathione in MIN6 cells damaged by H2O2. The preliminary mechanism by which compound 2 protects pancreatic beta cells was through the nuclear factor erythroid-2-related factor 2 (Nrf2)/heme oxygenase-1 HO-1 pathway. Most of the tested isolates showed strong inhibitory activity against α-glucosidase and protein tyrosine phosphatase 1B. The IC50 values of most compounds were much lower than those of the positive control. The results suggest that polyphenols from acorn leaves are potential functional food ingredients that can be used as antidiabetic agents.

Deletion of sigB Causes Increased Sensitivity to para-Aminosalicylic Acid and Sulfamethoxazole in Mycobacterium tuberculosis.

Although the de novo folate biosynthesis pathway has been well studied in bacteria, little is known about its regulation. In the present study, the sigB gene in Mycobacterium tuberculosis was deleted. Subsequent drug susceptibility tests revealed that the M. tuberculosis ΔsigB strain was more sensitive to para-aminosalicylic acid (PAS) and sulfamethoxazole. Comparative transcriptional analysis was performed, and downregulation of pabB was observed in the ΔsigB strain, which was further verified by a quantitative reverse transcription-PCR and Western blot assay. Then, the production levels of para-aminobenzoic acid (pABA) were compared between the sigB deletion mutant and wild-type strain, and the results showed that sigB deletion resulted in decreased production of pABA. In addition, SigB was able to recognize the promoter of pabB in vitro Furthermore, we found that deleting pabC also caused increased susceptibility to PAS. Taken together, our data revealed that, in M. tuberculosis, sigB affects susceptibility to antifolates through multiple ways, primarily by regulating the expression of pabB To our knowledge, this is the first report showing that SigB modulates pABA biosynthesis and thus affecting susceptibility to antifolates, which broadens our understanding of the regulation of bacterial folate metabolism and mechanisms of susceptibility to antifolates.

Deletion of nudB Causes Increased Susceptibility to Antifolates in Escherichia coli and Salmonella enterica.

Co-trimoxazole, a fixed-dose combination of sulfamethoxazole (SMX) and trimethoprim (TMP), has been used for the treatment of bacterial infections since the 1960s. Since it has long been assumed that the synergistic effects between SMX and TMP are the consequence of targeting 2 different enzymes of bacterial folate biosynthesis, 2 genes (pabB and nudB) involved in the folate biosynthesis of Escherichia coli were deleted, and their effects on the susceptibility to antifolates were tested. The results showed that the deletion of nudB resulted in a lag of growth in minimal medium and increased susceptibility to both SMX and TMP. Moreover, deletion of nudB also greatly enhanced the bactericidal effect of TMP. To elucidate the mechanism of how the deletion of nudB affects the bacterial growth and susceptibility to antifolates, 7,8-dihydroneopterin and 7,8-dihydropteroate were supplemented into the growth medium. Although those metabolites could restore bacterial growth, they had no effect on susceptibilities to the antifolates. Reverse mutants of the nudB deletion strain were isolated to further study the mechanism of how the deletion of nudB affects susceptibility to antifolates. Targeted sequencing and subsequent genetic studies revealed that the disruption of the tetrahydromonapterin biosynthesis pathway could reverse the phenotype caused by the nudB deletion. Meanwhile, overexpression of folM could also lead to increased susceptibility to both SMX and TMP. These data suggested that the deletion of nudB resulted in the excess production of tetrahydromonapterin, which then caused the increased susceptibility to antifolates. In addition, we found that the deletion of nudB also resulted in increased susceptibility to both SMX and TMP in Salmonella enterica Since dihydroneopterin triphosphate hydrolase is an important component of bacterial folate biosynthesis and the tetrahydromonapterin biosynthesis pathway also exists in a variety of bacteria, it will be interesting to design new compounds targeting dihydroneopterin triphosphate hydrolase, which may inhibit bacterial growth and simultaneously potentiate the antimicrobial activities of antifolates targeting other components of folate biosynthesis.

Sulfamic and succinic acid derivatives of 25-OH-PPD and their activities to MCF-7, A-549, HCT-116, and BGC-823 cell lines.

In the search for new anti-tumor agents with higher potency than our previously identified compound 1 (25-OH-PPD, 25-hydroxyprotopanaxadiol), 12 novel sulfamic and succinic acid derivatives that could improve water solubility and contribute to good drug potency and pharmacokinetic profiles were designed and synthesized. Their in vitro anti-tumor activities in MCF-7, A-549, HCT-116, and BGC-823 cell lines and one normal cell line were tested by standard MTT assay. Results showed that compared with compound 1, compounds 2, 3, and 7 exhibited higher cytotoxic activity on A-549 and BGC-823 cell lines, together with lower toxicity in the normal cell. In particular, compound 2 exhibited the best anti-tumor activity in the in vitro assays, which may provide valuable data for the research and development of new anti-tumor agents.

Succinylome analysis reveals the involvement of lysine succinylation in metabolism in pathogenic Mycobacterium tuberculosis.

Mycobacterium tuberculosis (Mtb), the causative agent of human tuberculosis, remains one of the most prevalent human pathogens and a major cause of mortality worldwide. Metabolic network is a central mediator and defining feature of the pathogenicity of Mtb. Increasing evidence suggests that lysine succinylation dynamically regulates enzymes in carbon metabolism in both bacteria and human cells; however, its extent and function in Mtb remain unexplored. Here, we performed a global succinylome analysis of the virulent Mtb strain H37Rv by using high accuracy nano-LC-MS/MS in combination with the enrichment of succinylated peptides from digested cell lysates and subsequent peptide identification. In total, 1545 lysine succinylation sites on 626 proteins were identified in this pathogen. The identified succinylated proteins are involved in various biological processes and a large proportion of the succinylation sites are present on proteins in the central metabolism pathway. Site-specific mutations showed that succinylation is a negative regulatory modification on the enzymatic activity of acetyl-CoA synthetase. Molecular dynamics simulations demonstrated that succinylation affects the conformational stability of acetyl-CoA synthetase, which is critical for its enzymatic activity. Further functional studies showed that CobB, a sirtuin-like deacetylase in Mtb, functions as a desuccinylase of acetyl-CoA synthetase in in vitro assays. Together, our findings reveal widespread roles for lysine succinylation in regulating metabolism and diverse processes in Mtb. Our data provide a rich resource for functional analyses of lysine succinylation and facilitate the dissection of metabolic networks in this life-threatening pathogen.

Lysine acetylation regulates the activity of Escherichia coli pyridoxine 5'-phosphate oxidase.

Nɛ-lysine acetylation is one of the most abundant post-translational modifications in eukaryote and prokaryote. Protein acetylome of Escherichia coli has been screened using mass spectrometry (MS) technology, and many acetylated proteins have been identified, including the pyridoxine 5'-phosphate oxidase (EcPNPOx), but the biological roles played by lysine acetylation in EcPNPOx still remain unknown. In this study, EcPNPOx was firstly overexpressed and purified, and two acetylated lysine residues were identified by the subsequent liquid chromatography-tandem mass spectrometry analysis. Site-directed mutagenesis analysis demonstrated that acetylated lysine residues play important roles in the enzymatic activity and enzymatic properties of the protein. EcPNPOx could be non-enzymatically acetylated by acetyl-phosphate and deacetylated by CobB in vitro. Furthermore, enzymatic activities of acetylated and deacetylated EcPNPOx were compared in vitro, and results showed that acetylation led to a decrease of its enzymatic activity, which could be rescued by CobB deacetylation. Taken together, our data suggest that CobB modulates the enzymatic activity of EcPNPOx in vitro.

Mycobacterium tuberculosis Arylamine N-Acetyltransferase Acetylates and Thus Inactivates para-Aminosalicylic Acid.

Mycobacterium tuberculosis arylamine N-acetyltransferase (TBNAT) is able to acetylate para-aminosalicylic acid (PAS) both in vitro and in vivo as determined by high-performance liquid chromatography (HPLC) and electrospray ionization-mass spectrometry (ESI-MS) techniques. The antituberculosis activity of the acetylated PAS is significantly reduced. As a result, overexpression of TBNAT in M. tuberculosis results in PAS resistance, as determined by MIC tests and drug exposure experiments. Taken together, our results suggest that TBNAT from M. tuberculosis is able to inactivate PAS by acetylating the compound.

Synthesis of novel 25-hydroxyprotopanaxadiol derivatives by methylation and methoxycarbonylation using dimethyl carbonate as a environment-friendly reagent and their anti-tumor evaluation.

A previous study involving 25-hydroxyprotopanaxadiol (25-OH-PPD) illustrated that the anti-cancer activity increased by 1-3 times after C-3/C-12-OH was substituted by short-chain fatty acids. In addition, 25-OCH3-PPD was also one of our research interests; the unique difference in structure between 25-OH-PPD and 25-OCH3-PPD is that in C-25, the latter activity was 2-5 times higher than that of 25-OH-PPD. These data serves as the scientific basis of our continuing research. To further confirm the effect of short chain acylated and methylated products on the activity and to identify more potent, higher selectivity compounds, we modified 25-OH-PPD with a green environment-friendly and non-toxic chemical dimethyl carbonate (DMC), which plays the role of both solvent and reagent. This experiment yielded 14 derivatives. Their in vitro anti-tumor activities were tested on two different human tumor cell lines (HeLa and DU145) and one normal cell line (IOSE144) by standard MTT assay. The results showed that compounds 3, 5, 6, 10, 11, 12, and 13 exhibited higher cytotoxic activity on two cell lines, with IC50 values within the range of 1.1-12µM. Compounds 12 and 13 exhibited the highest potent activity, with IC50 values of 1.1 and 1.2µM, respectively, on HeLa cells. Antitumor activity significantly increased after the hydroxyl groups are substituted by methyl. The results of the present study may provide useful data for evaluating the structure-activity relationships of other dammarane-type sapogenins and developing new antitumor agents.