tetracycline and baicalein

To explore whether intestinal microflora plays a role in anti-pruritic activity of baicalin, a main constituent of the rhizome of Scutellaria baicalensis (SB).. Baicalin was anaerobically incubated with human fecal microflora, and its metabolites, baicalein and oroxylin A, were isolated. The inhibitory effect of baicalin and its metabolites was accessed in histamine- or compound 48/80-induced scratching behavior in mice.. Baicalin was metabolized to baicalein and oroxylin A, with metabolic activities of 40.2+/-26.2 and 1.2+/-1.1 nmol.h(-1).mg(-1) wet weight of human fecal microflora, respectively. Baicalin (20, 50 mg/kg) showed more potent inhibitory effect on histamine-induced scratching behavior when orally administered than intraperitoneally. In contrast, baicalein and oroxylin A had more potent inhibitory effect when the intraperitoneally administered. The anti-scratching behavior activity of oral baicalin and its metabolites was in proportion to their inhibition on histamine-induced increase of vascular permeability with oroxylin A more potent than baicalein and baicalin. In Magnus test using guinea pig ileum, oroxylin A is more potent than baicalein and baicalin in inhibition of histamine-induced contraction. The anti-scratching behavioral effect of oral baicalin was significantly reduced when oral antibiotics were simultaneously administered, whereas the effect of baicalein and oroxylin A were not affected.. Oral baicalin may be metabolized by intestinal microflora into baicalein and oroxylin A, which ameliorate pruritic reactions through anti-histamine action.

Topics: Animals; Anti-Bacterial Agents; Antipruritics; Feces; Flavanones; Flavonoids; Guinea Pigs; Histamine; Histamine Antagonists; Intestines; Male; Mice; Mice, Inbred BALB C; Mice, Inbred ICR; Phytotherapy; Pruritus; Scutellaria baicalensis; Streptomycin; Tetracycline

During the screening of compounds that potentiate the effect of antimicrobial agents against methicillin-resistant Staphylococcus aureus(MRSA), we found that an extract of thyme (Thymus vulgaris L) leaves greatly reduced the minimum inhibitory concentration (MIC) of tetracycline against MRSA. We isolated the effective compound and identified it as baicalein (5, 6, 7-trihydroxyflavone). One of the clinically isolated MRSA strains possessed tetK, a gene encoding active efflux pump for tetracycline. We examined the effect of baicalein on the efflux of tetracycline, using Escherichia coli KAM32/pTZ1252 carrying the tetK. The E. coli KAM32/pTZ1252 showed 8 to 16 times higher MIC than E. coli KAM32. We observed strong inhibition of transport of tetracycline by baicalein with membrane vesicles prepared from E. coli KAM32/pTZ1252. Baicalein also showed synergy with tetracycline in a MRSA strain that doesn't possess tetK, or with beta-lactams. Thus, mechanisms of the synergies seem to be versatile.

Topics: Anti-Bacterial Agents; beta-Lactams; Biological Transport, Active; Drug Synergism; Escherichia coli; Flavanones; Methicillin Resistance; Microbial Sensitivity Tests; Molecular Structure; Staphylococcus aureus; Tetracycline; Tetracycline Resistance