Hydroquinone Study

The hydroquinone metabolite purified from B. methylotrophicus MHC10 was evaluated for its antibacterial activity against a panel of several Gram-positive and Gram-negative bacterial pathogens. The zone of inhibition was used to evaluate the antagonistic activity of the metabolite. The standard antibiotics Ampicillin and Gentamycin were used as the positive control. Both antibiotics showed high antagonistic activity against all test pathogens. But in the case of P. aeruginosa, the hydroquinone treatment showed little high zone of inhibition than ampicillin

Lee et al., [85] studied the antimicrobial activities of the purified prodigiosin and cycloprodigiosin against B. subtilis KCTC 1914, E. coli KCTC 1924, Salmonella typhimurium KCTC 1926, S.

aureus SH1000 and two commonly used S. aureus susceptibility strains (ATCC 23723 and ATCC 29213). TBHQ exhibited an MIC and MBC of 8 and 8–16 mg/L, respectively, for all three strains. TBBQ had comparable activity, exhibiting an MIC and MBC of 4–8 mg/L and 8–16 mg/L, respectively. The MIC of 1, 4-benzoquinone (BQ) was also determined and found to be active against S. aureus up to a dose of 8 μg/mL, the same MIC found for 2,6-dimethoxy-1,4-benzoquinone (DMBQ) [212]. Interestingly, the MICs observed for DMBQ was higher than those obtained for BQ, except when tested against B. cereus. This was due to an interesting effect of the methoxy identity of 1, 4-benzoquinones. The MIC determination of methoxybenzoquinone (MBQ) against S. typhimurium was found to be significantly lower than that of DMBQ (512 and 32 μg/mL, respectively). The difference in the number of methoxy groups in the 1, 4-benzoquinones significantly affected their antibacterial activities against the Gram-negative bacteria S. typhimurium and E. coli. Furthermore, hydroquinone (HQ), a reduced form of BQ, had significantly lower antibacterial activity than

Daptomycin caused a reduction in cell viability of 3 log 10 CFU/mL after 6 h in PBS while tetracycline caused only bacteriostasis. TBHQ had no effect on bacterial viability for the first 120 min of the experiment, but killing was observed thereafter. The bacterial killing was initiated after the conversion of TBHQ into TBBQ and the extent of kill was increased with increasing TBBQ concentration, ultimately leading to a 4 log 10 drop in cell number after 6h. TBBQ was rapidly and extensively bactericidal, causing 5 log10 drop in cell number within 3 h. Kim et al., [212] determined the bactericidal effect of DMBQ by the time-kill curve experiment. The effect of DMBQ against S. typhimurium cells was bacteriostatic for the first 5 h of incubation after addition of the compound. The bactericidal effect DMBQ was observed against S. aureus after 12 h of incubation. Thus, doubling the MIC of DMBQ reduced the growth rate of S. aureus but did not have a siginificant effect on the final cell