The Effect of Dihydromyricetin on the Pharmacokinetics of Fluconazole in Sprague-Dawley Rat Plasma, Based on High-Performance Liquid Chromatography-Tandem Mass Spectrometry.

Background: The synergistic effect of dihydromyricetin (DHM) and fluconazole (FLC) can improve the killing effect of FLC-resistant Candida albicans in vitro and in vivo. However, it is not clear whether DHM affects the pharmacokinetic characteristics of FLC. Methods: In this study, 12 Sprague-Dawley (SD) rats were randomly divided into two groups as follows: (1) an FLC group in which rats were administered FLC only (42 mg/kg orally); (2) an FLC with the combined administration of DHM group, in which rats received an equivalent FLC dose immediately following the administration of DHM (100 mg/kg). Blood samples were collected from the ocular choroid vein of rats and converted into plasma. The concentrations of FLC in the rat plasma were then determined by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), and the related pharmacokinetic parameters were analysed. The initial mobile phase included 0.1% acetonitrile and water with gradient elution. Multiple reaction monitoring modes of m/z 307.2→220.1 for FLC, and m/z 237.1→194.2 for carbamazepine, were utilised to conduct quantitative analysis. Results: The calibration curve of FLC in rat plasma demonstrated good linearity in the range of 0.1-30 µg/mL (r > 0.99), and the lower limit of quantification was 0.1 µg/mL. Moreover, the intra- and inter-day precision relative standard deviation of FLC was less than 9.09% and 6.51%, respectively. There were no significant differences in the pharmacokinetic parameters between the two groups. Conclusion: The results showed that DHM administration did not significantly alter FLC pharmacokinetics in SD rat plasma.

Synergistic antifungal effects of curcumin derivatives as fungal biofilm inhibitors with fluconazole.

Lack of novel antifungal agents and severe drug resistance has led to high incidence and associated mortality of invasive fungal infections. To tackle the challenges, novel antifungal agents with anti-resistant potency are highly desirable. Thus, derivatives of curcumin were synthesized to restore the effectiveness of fluconazole (FLC) against FLC-resistant Candida spp. and structure-activity relationships were then discussed. Some novel derivatives showed promising features as novel antifungal lead compounds. Of them, compound 4 showed good alone or synergistic antifungal activity against FLC-resistant Candida spp. Moreover, compound 4 was proven as a potent inhibitor of Candida albicans biofilm formation and yeast-to-hypha morphological transition whether used alone or in combination with FLC, which was further confirmed by the inhibitory effect on cellular surface hydrophobicity of C. albicans. Compound 4 also inhibits intracellular ATP production of C. albicans and disrupts membrane permeability of C. albicans when used in combination with FLC. The results highlighted the potential of curcumin derivatives to overcome fluconazole-related and biofilm-related drug resistance.

Astragaloside IV Promotes Adult Neurogenesis in Hippocampal Dentate Gyrus of Mouse through CXCL1/CXCR2 Signaling.

Astragaloside IV (ASI) has been reported to promote neural stem cells proliferation in vitro and CXCR2 expression on neutrophils. The present study was aimed to investigate the influence of ASI on adult neurogenesis in hippocampal dentate gyrus (DGs) of mouse and to discuss the possible underlying mechanisms. Total number of proliferative cells (BrdU⁺), pre-mature neurons (DCX⁺), early proliferative cells (BrdU⁺/DCX⁺), proliferative radial gila-like cells (BrdU⁺/GFAP⁺) and newly generated neurons (BrdU⁺/NeuN⁺) after ASI or vehicle administration for two weeks were counted, respectively. The results showed that BrdU⁺ cells and DCX⁺ cells were significantly increased in DGs of mice administered with ASI. The numbers of BrdU⁺/DCX⁺, BrdU⁺/GFAP⁺ cells and BrdU⁺/NeuN⁺ cells were also elevated in the ASI group. Correspondingly, ASI increased the protein expression of hippocampal DCX, GFAP and NeuN. Further study disclosed that ASI remarkably up-regulated the mRNA and protein expressions of CXCL1 as well as that of CXCR2 in the hippocampus. The promotive effect of ASI on DCX, GFAP and NeuN protein expression was abolished by SB225002, the inhibitor of CXCR2. Our results indicated that ASI modulated the homeostasis of the CXCL1/CXCR2 signaling pathway, which might be responsible for the increased neurogenesis within the hippocampal DGs of mice.

Synthesis and synergistic antifungal effects of monoketone derivatives of curcumin against fluconazole-resistant Candida spp.

Twenty-three monoketone derivatives of curcumin were synthesized to investigate the synergy with fluconazole against fluconazole-resistant Candida spp. The minimal inhibitory concentration (MIC80) and the fractional inhibitory concentration index (FICI) of the antifungal synergist fluconazole were measured against fluconazole-resistant C. albicans, C. tropicalis and C. krusei in vitro. Most of these compounds showed good synergistic activities against C. tropicalis. Among them, compound 9 exhibited significant synergistic activities against Candida spp. SARs were also discussed. In particular, a cell growth test exhibited that a combination of 1 µg ml-1 fluconazole and 64 µg ml-1 or 128 µg ml-1 compound 9 showed the most potent fungicidal effect against C. tropicalis. The synergistic effect may be associated with the changes of the intracellular ATP content and cell membrane permeability. Our results provided a basis for future evaluation and development of these compounds as leads for therapeutics for fluconazole-resistant candidiasis.

Endogenous nitric oxide accumulation is involved in the antifungal activity of Shikonin against Candida albicans.

The aim of the present study was to investigate the role of nitric oxide (NO) in the antifungal activity of Shikonin (SK) against Candida albicans (C. albicans) and to clarify the underlying mechanism. The results showed that the NO donors S-nitrosoglutathione (GSNO) and L-arginine could enhance the antifungal activity of SK, whereas the NO production inhibitor Nω-nitro-L-arginine methyl ester (L-NAME) attenuated antifungal action. Using the fluorescent dye 3-amino,4-aminomethyl-2', 7-difluorescein, diacetate (DAF-FM DA), we found that the accumulation of NO in C. albicans was increased markedly by SK in a time- and dose-dependent manner. In addition, the results of real-time reverse transcription-PCR (RT-PCR) demonstrated that the transcription level of YHB1 in C. albicans was greatly increased upon incubation of SK. Consistently, the YHB1-null mutant (yhb1Δ/Δ) exhibited a higher susceptibility to SK than wild-type cells. In addition, although the transcription level of CTA4 in C. albicans was not significantly changed when exposed to SK, the CTA4-null mutant (cta4Δ/Δ) was more susceptible to SK. Collectively, SK is the agent found to execute its antifungal activity directly via endogenous NO accumulation, and NO-mediated damage is related to the suppression of YHB1 and the function of CTA4.

The synthesis and synergistic antifungal effects of chalcones against drug resistant Candida albicans.

To identify effective and low toxicity synergistic antifungal compounds, 24 derivatives of chalcone were synthesized to restore the effectiveness of fluconazole against fluconazole-resistant Candida albicans. The minimal inhibitory concentration (MIC80) and the fractional inhibitory concentration index (FICI) of the antifungal synergist fluconazole were measured against fluconazole-resistant Candida albicans. This was done via methods established by the clinical and laboratory standards institute (CLSI). Of the synthesized compounds, 2'-hydroxy-4'-methoxychalcone (8) exhibited the most potent in vitro (FICI=0.007) effects. The structure activity relationship of the compounds are then discussed.