Anti-α-glucosidase and Anti-dipeptidyl Peptidase-IV Activities of Extracts and Purified Compounds from Vitis thunbergii var. <i>taiwaniana</i>

Ethanol extracts (Et) from the stem (S) and leaf (L) of Vitis thunbergii var. <i>taiwaniana</i> (VTT) were used to investigate yeast α-glucosidase and porcine kidney dipeptidyl peptidase-IV (DPP-IV) inhibitory activities. Both VTT-Et showed complete α-glucosidase inhibition at 0.1 mg/mL; VTT-S-Et and VTT-L-Et showed 26 and 11% DPP-IV inhibition, respectively, at 0.5 mg/mL. The VTT-Et interventions (20 and 50 mg/kg) resulted in improvements in impaired glucose tolerance of diet-induced obese rats. (+)-Hopeaphenol, (+)-vitisin A, and (−)-vitisin B were isolated from the ethyl acetate fractions of S-Et and showed yeast α-glucosidase inhibition (IC₅₀ = 18.30, 1.22, and 1.02 μM) and porcine kidney DPP-IV inhibition (IC₅₀ = 401, 90.75, and 15.3 μM) compared to acarbose (6.39 mM) and sitagliptin (47.35 nM), respectively. Both (+)-vitisin A and (−)-vitisin B showed mixed noncompetitive inhibition against yeast α-glucosidase and porcine kidney DPP-IV, respectively. These results proposed that VTT extracts might through inhibitions against α-glucosidase and DPP-IV improve the impaired glucose tolerance in diet-induced obese rats

The Contribution of Antibiotic Resistance Mechanisms in Clinical <i>Burkholderia cepacia</i> Complex Isolates: An Emphasis on Efflux Pump Activity

<div><p>Due to the limited information of the contribution of various antibiotic resistance mechanisms in clinical <i>Burkholderia cepacia</i> complex isolates, Antibiotic resistance mechanisms, including integron analysis, identification of quinolone resistance-determining region mutations, measurement of efflux pump activity, and sequence analysis of efflux pump regulators, were investigated in 66 clinical <i>B. cepacia</i> complex isolates. Species were identified via <i>recA</i>-RFLP and MALDI-TOF. Four genomovars were identified by <i>recA</i>-RFLP. <i>B. cenocepacia</i> (genomovar III) was the most prevalent genomovar (90.1%). Most isolates (60/66, 90.9%) were correctly identified by MALDI-TOF analysis. Clonal relatedness determined by PFGE analysis revealed 30 pulsotypes, including two major pulsotypes that comprised 22.7% and 18.2% of the isolates, respectively. Seventeen (25.8%) isolates harboured class 1 integron with various combinations of resistance genes. Among six levofloxacin-resistant isolates, five had single-base substitutions in the <i>gyrA</i> gene and three demonstrated efflux pump activities. Among the 42 isolates exhibiting resistance to at least one antimicrobial agent, 94.4% ceftazidime-resistant isolates (17/18) and 72.7% chloramphenicol-resistant isolates (16/22) demonstrated efflux pump activity. Quantitation of efflux pump RNA level and sequence analysis revealed that over-expression of the RND-3 efflux pump was attributable to specific mutations in the RND-3 efflux pump regulator gene. In conclusion, high-level expression of efflux pumps is prevalent in <i>B. cepacia</i> complex isolates. Mutations in the RND-3 efflux pump regulator gene are the major cause of efflux pump activity, resulting in the resistance to antibiotics in clinical <i>B. cepacia</i> complex isolates.</p></div

Characteristics of QRDR mutations and efflux pump activity of six fluoroquinolone-resistant <i>B. cepacia</i> complex isolates.

<p>Characteristics of QRDR mutations and efflux pump activity of six fluoroquinolone-resistant <i>B. cepacia</i> complex isolates.</p

Comparison of the BCAL1672 gene (the first 320 bp) in <i>B. cenocepacia</i> isolates.

<p>The arrow (at position 125) indicates the deletion of a guanine nucleotide in <i>B. cenocepacia</i> J2315. Deleted nucleotides (between positions 264 and 268) were identified in clinical isolate No. 27.</p

A dendrogram of pulsotype relationships developed via the unweighted pair group method using arithmetic averages (UPGMA) with BioNumerics software version 6.5 (Applied Maths).

<p>Pulsotypes were assigned to the same clusters if they exhibited 80% similarity in the dendrogram. Species identification was performed by <i>recA</i>-RFLP and MALDI-TOF analysis for 66 <i>B. cepacia</i> complex isolates.</p

Class 1 integron cassette analysis.

<p>Genes are shown as arrows with the direction of transcription indicated by the arrowheads. <i>Int1</i>: class 1 integrase, <i>qacF</i>: quaternary ammonium compound-resistance protein, <i>qacEΔ1</i>: remnants of quaternary ammonium compound resistance protein, <i>sul1</i>: sulphonamides resistance gene, <i>aacA4</i>: aminoglycoside 6′-acetyltransferase, <i>aacA7</i>: aminoglycoside 6′-acetyltransferase, and <i>catB3</i>: chloramphenicol acetyltransferase.</p

Quantitative RNA expression of four RND efflux systems in five selected <i>B. cenocepacia</i> (genomovar IIIA) isolates.

a<p>. Fold change was determined by quantitative reverse transcription-PCR (quantitative RT-PCR).</p>b<p>. No. 30 was a strain with a non-induced efflux pump that was utilised as a reference strain.</p

Among 42 antibiotic-resistant clinical isolates, the efficacy of efflux pumps was tested via antibiotic susceptibilities: ceftazidime (CAZ), meropenem (MEM), minocycline (MI), trimethoprim/sulfamethoxazole (SxT), levofloxacin (LEVO), and chloramphenicol (C) in the presence or absence of 60 µM CCCP.

<p>Efflux pump activity was defined as present at least 4-fold decrease of MIC in the presence of CCCP. *, <i>p</i><0.05 (statistical analysis using the Mann-Whitney U test).</p

Antimicrobial susceptibilities of 66 <i>B. cepacia</i> complex isolates.

<p>Antimicrobial susceptibilities of 66 <i>B. cepacia</i> complex isolates.</p

Correlation between BCAL1672 mutants and antibiotic resistance in 25 efflux activity <i>B. cenocepacia</i> (genomovar IIIA) isolates.

a<p>. Sequence compared with <i>B. cenocepacia</i> HI2424 (GenBank accession number: CP000458.1).</p>b<p>. C = chloramphenicol, CAZ = ceftazidime, MEM = meropenem, LVX = levofloxacin, MI = minocycline, and SXT = Trimethoprim/sulfamethoxazole</p>c<p>. The variations in BCAL1672 that are related to RND-3 efflux pump activity are indicated in bold.</p