Nine isolates of Canine parvovirus (CPV) were obtained from Vietnamese dogs and cats. One canine isolate showed a unique antigenic property which indicates a novel antigenic variant of CPV-2b when examined with hemagglutination inhibition tests using our monoclonal antibodies, 21C3 and 19D7, which were recently developed. This isolate had an amino acid substitution of residue 426, Asp to Glu, and the same substitution has recently been found in CPV from Italian dogs. This study first showed that such substitution caused an antigenic difference demonstrable by monoclonal antibodies and that a similar evolution may have occurred in CPV in Vietnam.
Five carvotacetone derivatives, including two known ones, 3,5-diangeloyloxy-7-hydroxycarvotacetone (1) and 3-angeloyloxy-5-[2″,3″-epoxy-2″-methylbutanoyloxy]-7-hydroxycarvotacetone (2), along with three new compounds, 3-angeloyloxy-5-[3″-chloro-2″-hydroxy-2″-methylbutanoyloxy]-7-hydroxycarvotacetone (3), 5-angeloyloxy-7-hydroxy-3-tigloyloxycarvotacetone (4), and 3-angeloyloxy-5,7-dihydroxycarvotacetone (5), were isolated from the aerial parts of Sphaeranthus africanus collected in Vietnam. Bioassay-guided fractionation was monitored by the antiproliferative activity on CCRF-CEM human cancer cells. The structures of compounds 1-5 were determined on the basis of NMR spectroscopic and mass spectrometric data. Activities of compounds 1-5 were evaluated in vitro against the human cancer cell lines CCRF-CEM, MDA-MB-231, U-251, and HCT-116. All compounds exhibited significant antiproliferative activity against all four cancer cell lines. CCRF-CEM was most sensitive to the compounds, with IC values ranging from 0.6 to 1.5 μM. Compounds 3 and 4 possessed the highest activity, with IC values in the four cell lines ranging from 0.6 to 2.9 μM and 1.3 to 2.5 μM, respectively. These compounds also showed inhibitory activity toward the HEK-293 human embryonic kidney cells with IC values ranging from 2.5 to 5.5 μM. This is the first time that antiproliferative activity of S. africanus has been reported, and 1-5 are the most cytotoxic carvotacetone derivatives reported so far.
Carvotacetones (1–7) isolated from Sphaeranthus africanus were screened for their antimycobacterial and efflux pump (EP) inhibitory potential against the mycobacterial model strains Mycobacterium smegmatis mc2 155, Mycobacterium aurum ATCC 23366, and Mycobacterium bovis BCG ATCC 35734. The minimum inhibitory concentrations (MICs) of the carvotacetones were detected through high-throughput spot culture growth inhibition (HT-SPOTi) and microbroth dilution assays. In order to assess the potential of the compounds 1 and 6 to accumulate ethidium bromide (EtBr) in M. smegmatis and M. aurum, a microtiter plate-based fluorometric assay was used to determine efflux activity. Compounds 1 and 6 were analyzed for their modulating effects on the MIC of EtBr and the antibiotic rifampicin (RIF) against M. smegmatis. Carvotacetones 1 and 6 had potent antibacterial effects on M. aurum and M. bovis BCG (MIC ≤ 31.25 mg/L) and could successfully enhance EtBr activity against M. smegmatis. Compound 1 appeared as the most efficient agent for impairing the efflux mechanism in M. smegmatis. Both compounds 1 and 6 were highly effective against M. aurum and M. bovis BCG. In particular, compound 1 was identified as a valuable candidate for inhibiting mycobacterial efflux mechanisms and as a promising adjuvant in the therapy of tuberculosis or other non-tubercular mycobacterial infections.
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