Yi Bi

Synthesis and Biological Activity of 23-Hydroxybetulinic Acid C-28 Ester Derivatives as Antitumor Agent Candidates

23-Hydroxybetulinic acid (1) served as the precursor for the synthesis of C-28 ester derivatives. The target compounds were evaluated in vitro for their antitumor activities against five cell lines (A549, BEL-7402, SF-763, B16 and HL-60). Among the obtained compounds, 6i had the most potent antitumor activity, with the IC50 values of 8.35 µM in HL-60 cells and showed similar antitumor activity as cyclophosphamide in H22 liver tumor and as 5-fluorouracil in B16 melanoma in vivo.

Synthesis and biological evaluation of novel ocotillol-type triterpenoid derivatives as antibacterial agents.

A novel class of ocotillol-type triterpenoid derivatives have been synthesized and evaluated for their inxa0vitro antibacterial activity against several representative pathogenic bacterial strains. Compounds 20(S)-protopanaxadiol (PPD), 3, 5, 16 and 24 exhibited potent antibacterial activity against Gram-positive bacteria. Compounds 3 and 5 also displayed promising antibacterial activity against a community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA; strain USA300). Furthermore, compounds PPD, 3 and 16 combined with two commercially available antibiotics kanamycin and chloramphenicol showed strong synergistic inhibitory effects at their sub-MIC concentrations against S.xa0aureus USA300 and Bacillus subtilis 168. Additionally, cytotoxic activity assay showed that the compounds tested did not affect cell viability of the human epithelial kidney (HEK-293) and human cervical (HeLa) cells at their MICs.

Design, synthesis, nitric oxide release and antibacterial evaluation of novel nitrated ocotillol-type derivatives.

Nitric oxide (NO) and its auto-oxidation products are known to disrupt normal bacterial function and NO releasing molecules have the potential to be developed as antibacterial leads in drug discovery. We have designed and synthesized a series of novel nitrated compounds by combining NO releasing groups with ocotillol-type triterpenoids, which have previously demonstrated activity only against Gram-positive bacteria. The inxa0vitro NO release capacity and antibacterial activity were sequentially evaluated and the data showed that most of the synthesized compounds could release nitric oxide. Compound 16a, 17a and 17c, with nitrated aliphatic esters at C-3 position, displayed higher NO release than other analogues, correlating to their good antibacterial activity, in which 17c demonstrated broad-spectrum activity against both Gram positive and -negative bacteria, as well as excellent synergism at sub-minimum inhibitory concentration when using with kanamycin and chloramphenicol. Furthermore, the epifluorescent microscopic study indicated that the ocotillol-type triterpenoid core may induce NO release on the bacterial membrane. Our results demonstrate that nitrated substitutions at C-3 of ocotillol-type derivatives could provide an approach to expand their antibacterial spectrum, and that ocotillol-type triterpenoids may also be developed as appropriate carriers for NO donors in antibacterial agent discovery with low cytotoxicity.

Estimation of elimination half-lives of organic chemicals in humans using gradient boosting machine.

BACKGROUNDnElimination half-life is an important pharmacokinetic parameter that determines exposure duration to approach steady state of drugs and regulates drug administration. The experimental evaluation of half-life is time-consuming and costly. Thus, it is attractive to build an accurate prediction model for half-life.nnnMETHODSnIn this study, several machine learning methods, including gradient boosting machine (GBM), support vector regressions (RBF-SVR and Linear-SVR), local lazy regression (LLR), SA, SR, and GP, were employed to build high-quality prediction models. Two strategies of building consensus models were explored to improve the accuracy of prediction. Moreover, the applicability domains (ADs) of the models were determined by using the distance-based threshold.nnnRESULTSnAmong seven individual models, GBM showed the best performance (R(2)=0.820 and RMSE=0.555 for the test set), and Linear-SVR produced the inferior prediction accuracy (R(2)=0.738 and RMSE=0.672). The use of distance-based ADs effectively determined the scope of QSAR models. However, the consensus models by combing the individual models could not improve the prediction performance. Some essential descriptors relevant to half-life were identified and analyzed.nnnCONCLUSIONSnAn accurate prediction model for elimination half-life was built by GBM, which was superior to the reference model (R(2)=0.723 and RMSE=0.698).nnnGENERAL SIGNIFICANCEnEncouraged by the promising results, we expect that the GBM model for elimination half-life would have potential applications for the early pharmacokinetic evaluations, and provide guidance for designing drug candidates with favorable in vivo exposure profile. This article is part of a Special Issue entitled System Genetics Guest Editor: Dr. Yudong Cai and Dr. Tao Huang.

Novel 3-substituted ocotillol-type triterpenoid derivatives as antibacterial candidates.

Plant‐derived triterpenoid saponins are involved in the plant defense system by targeting bacterial membranes. A series of ocotillol‐type triterpenoid derivatives were synthesized starting from PPD, one of the main components of Panax ginseng and their antibacterial activity against several representative bacteria were evaluated. Compounds 5 and 11 exhibited excellent antibacterial activity with MIC values of 1 μg/mL against Staphylococcus aureus and 8 μg/mL and 4 μg/mL against Bacillus subtilis, respectively. Furthermore, when compounds 5 and 11 were combined with two commercial antibiotics kanamycin and chloramphenicol, they showed strong synergistic activity at sub‐MIC levels against S. aureus USA300 and B. subtilis 168. Moreover, chloramphenicol turned from a bacteriostatic to a bactericidal agent when combined with compound 11 against B. subtilis 168.

Synthesis and biological activity of 28-amide derivatives of 23-hydroxy betulinic Acid as antitumor agent candidates.

Based on the structure of 23-hydroxybetulinic acid (1), a series of 28-amide derivatives were synthesized. Biological evaluation in vitro for their antitumor activities against five cell lines (A549, BEL-7402, SF-763, B16 and HL-60) has indicated that compound 6g possesses the most effective antitumor activity with an IC50 value of 10.47 μM when treated with HL-60 cells. In vivo testing has also shown a comparable activity of 6g to cyclophosphamide against H22 liver tumor in mice and 5-fluorouracil against B16 melanoma, respectively.

H6, a novel hederagenin derivative, reverses multidrug resistance in vitro and in vivo

&NA; Multidrug resistance (MDR) is a serious obstacle encountered in cancer treatment, in which the overexpression of P‐glycoprotein (P‐gp) plays an important role. Here, a novel &agr;‐hederagenin derivative, designated H6, was designed, synthesized and evaluated for its ability to reverse MDR. Our results showed that H6 could sensitize KBV and MCF7/T cells to paclitaxel and vincristine. Meanwhile, H6 could increase both rhodamine 123 and paclitaxel accumulation in MDR cells without affecting the expression of P‐gp. Interestingly, siRNA knockdown of MDR1 further sensitized the cytotoxic activity of paclitaxel when co‐administrated with H6. In addition, H6 could directly stimulate P‐gp ATPase activity in vitro. Importantly, H6 enhanced the efficacy of paclitaxel against KBV cancer cell‐derived xenograft tumors in nude mice. Finally, H6 showed high binding affinity with P‐gp with a high docking score. Overall, we show H6 is a novel and potent MDR reversal agent, which has the potential to be administered in combination with conventional anticancer drugs. Graphical abstract Figure. No caption available. HighlightsH6 is one novel synthesized &agr;‐hederagenin derivative.H6 demonstrates robust reversal activity against MDR in vitro and in vivo.H6 could directly stimulate P‐gp ATPase activity via binding with p‐gp.H6 might be co‐administered against drug resistance in clinic.

Synthesis and Antibacterial Evaluation of Novel 3-Substituted Ocotillol-Type Derivatives as Leads

Due to the rapidly growing bacterial antibiotic-resistance and the scarcity of novel agents in development, bacterial infection is still a global problem. Therefore, new types of antibacterial agents, which are effective both alone and in combination with traditional antibiotics, are urgently needed. In this paper, a series of antibacterial ocotillol-type C-24 epimers modified from natural 20(S)-protopanaxadiol were synthesized and evaluated for their antibacterial activity. According to the screening results of Gram-positive bacteria (B. subtilis 168 and MRSA USA300) and Gram-negative bacteria (P. aer PAO1 and A. baum ATCC19606) in vitro, the derivatives exhibited good antibacterial activity, particularly against Gram-positive bacteria with an minimum inhibitory concentrations (MIC) value of 2–16 µg/mL. The subsequent synergistic antibacterial assay showed that derivatives 5c and 6c enhanced the susceptibility of B. subtilis 168 and MRSA USA300 to chloramphenicol (CHL) and kanamycin (KAN) (FICI < 0.5). Our data showed that ocotillol-type derivatives with long-chain amino acid substituents at C-3 were good leads against antibiotic-resistant pathogens MRSA USA300, which could improve the ability of KAN and CHL to exhibit antibacterial activity at much lower concentrations with reduced toxicity.

Synthesis and biological evaluation of novel H6 analogues as drug resistance reversal agents

Hederagenin is a naturally occurring pentacyclic triterpenoids compound with multiple pharmacological activities. We recently showed that H6, a synthetic derivative of hederagenin, could enhance the anticancer activity of paclitaxel in drug-resistant cells inxa0vitro and inxa0vivo, but showed poor solubility. With the aim of improving the drug resistant reversal activity of H6, here we designed and synthesized a series of novel H6 analogues. Our results showed that compound 10u202fat the concentration of 5u202fμM significantly enhanced the cytotoxicity of paclitaxel to drug-resistant KBV cells and sensitized cells to paclitaxel in arresting cells in G2/M phase and inducing apoptosis. We found that compound 10 might block the drug efflux of P-gp via stimulating P-gp ATPase activity. Importantly, compound 10 enhanced the efficacy of paclitaxel against KBV cancer cell-derived xenograft tumors. Finally, we summarized a preliminary structure-activity relationship of hederagenin by the drug resistant reversal activity of H6 analogues inxa0vitro and compound 10 and H6inxa0vivo. This study highlights the importance of nitrogen-containing derivatives of hederagenin C-28 in the development of novel drug resistance reversal agents.

Design and synthesis of 28-hydroxy protopanaxadiol as a novel probe template

Abstract To explore the antitumour mechanism of 20(S)-protopanaxadiol (PPD) while maintaining its uncovered pharmacological active site 3-hydroxyl, 28-hydroxy protopanaxadiol (17), a small molecular probe template of PPD was first designed and synthesised based on the Baldwin’s reaction. Thus, 28-hydroxyl of 17 was built successfully as a derivatized site of molecular probe’s functional and report groups. The important intermediates and final product were confirmed by ESI-MS and nuclear magnetic resonance spectra with good yield. These studies provided a valuable basis for probe research of PPD.