Biomedical subjects

H Muroi

Publications and source records attributed to H Muroi.

9 recordsLinked to original sources

PubMed1996

Mode of antibacterial action of totarol, a diterpene from Podocarpus nagi.

The antimicrobial mechanism of totarol was studied using Pseudomonas aeruginosa IFO 3080. This diterpene inhibited oxygen consumption and respiratory-driven proton translocation in whole cells, and oxidation of NADH in membrane preparation. NADH-cytochrome c reductase was inhibited by totarol while cytochrome c oxidase was not. NADH-DPIP reductase and NADH-CoQ reductase were also inhibited. The site of respiratory inhibition of totarol was thought to be near CoQ in the bacterial electron transport chain.

Abietanes↗

PubMed1996

Antibacterial activity of anacardic acid and totarol, alone and in combination with methicillin, against methicillin-resistant Staphylococcus aureus.

The inhibitory and bactericidal activities of anacardic acid and totarol, alone and in combination with methicillin, were investigated against methicillin-resistant Staphylococcus aureus (MRSA). The growth of two MRSA strains was inhibited by 6 x 25 microg ml-1 of anacardic acid and 0 x 78 microg ml-1 of totarol. The time-kill curve study showed that these two compounds were bactericidal against MRSA. Anacardic acid killed MRSA cells more rapidly than totarol, and no viable cells were detected after being exposed to 6 x 25 microg ml-1 of anacardic acid for 6 h. Anacardic acid showed bactericidal activity against MRSA at any stage of growth, and also even when cell division was inhibited by chloramphenicol. In the combination studies, the minimal inhibitory concentration (MIC) of methicillin was lowered from 800 to 1 x 56 microg ml-1 for MRSA ATCC 33591, and from 800 to 6 x 25 microg ml-1 for MRSA ATCC 33592, by combining with 1/2 x MIC of anacardic acid. The time-kill curves demonstrated synergistic bactericidal activities for these combinations.

Abietanes↗

PubMed1995

Structural functions of antimicrobial long-chain alcohols and phenols.

Antimicrobial activity of a series of long-chain alcohols and common naturally occurring alcohols were tested against 15 selected microorganisms in order to gain new insights into their structural functions. The maximum activity seems to depend on the hydrophobic chain length from the hydrophilic hydroxyl group, and also the microorganisms being tested. The results obtained with the alcohols exhibit a generally applicable rule to many other compounds.

Alcohols↗

PubMed1994

Naturally occurring antiacne agents.

Antibacterial activity of various secondary metabolites from plants against Propionibacterium acnes was tested. In addition, the study of combinations of compounds to enhance the total activity against this follicular bacterium was investigated. A series of long-chain alcohols was studied in great detail to gain new insights into the role of the hydrophobic alkyl groups in the activity.

Acne Vulgaris↗

PubMed1994

Antimicrobial agents from Heterotheca inuloides.

By bioassay directed fractionation, four sesquiterpenoids 1-4 were isolated as antimicrobial agents from the dried flowers of Heterotheca inuloides, a Mexican medicinal plant locally known as "arnica". 7-Hydroxy-3,4-dihydrocadalin (3) and 7-hydroxycadalin (4) exhibited potent antibacterial activity against Gram-positive bacteria with minimum inhibitory concentrations (MICs) ranging from 6.25 to 12.5 micrograms/ml. Notably, 7-hydroxy-3,4-dihydrocadalin showed bactericidal activity against methicillin-resistant Staphylococcus aureus (MRSA) with a minimum bactericidal concentration (MBC) of 12.5 micrograms/ml.

Anti-Bacterial Agents↗

PubMed1993

Combination effects of antifungal nagilactones against Candida albicans and two other fungi with phenylpropanoids.

Antifungal activity of three nagilactones isolated from the root bark of Podocarpus nagi (Podocarpaceae), alone and in combination with a variety of phenylpropanoids, was investigated against three fungi, Candida albicans, Saccharomyces cerevisiae, and Pityrosporum ovale. Nagilactone E [2], the most abundant norditerpene dilactone, showed moderate to weak activity against these fungi. This activity was dramatically enhanced by several naturally occurring phenylpropanoids such as anethole [5] and isosafrole. For example, anethole enhanced the activity of nagilactone E as much as 128-fold for C. albicans, decreasing the MIC of this nagilactone from 800 to 6.25 micrograms/ml.

Amphotericin B↗

PubMed1992

Antibacterial activity of crinitol and its potentiation.

An acyclic diterpene alcohol, crinitol [1], was identified in a marine brown alga, Sargassum tortile, as the principal antibacterial agent against Gram-positive bacteria, among which Propionibacterium acnes was most sensitive and, Staphylococcus aureus was least. To enhance its activity, crinitol was combined with several antioxidants, which presumably retard oxidative destruction of this molecule which possesses two easily oxidizable allylic alcohol groups. Two synthetic antioxidants, BHA (butylated hydroxyanisole) and BHT (butylated hydroxytoluene), significantly enhanced the activity of crinitol, especially against Streptococcus mutans. Interestingly, crinitol also synergized BHT and BHA against this cariogenic bacterium.

Anti-Bacterial Agents↗

PubMed1992

Antibacterial activity of totarol and its potentiation.

Antimicrobial activity of six diterpenoids isolated from the bark of Podocarpus nagi (Podocarpaceae) has been tested against twelve selected microorganisms. Totarol [1], the most abundant compound among the six, exhibited potent bactericidal activity only against Gram-positive bacteria, among which Propionibacterium acnes was the most sensitive bacterium. Totarol also showed strong activity against four other Gram-positive bacteria tested: Streptococcus mutans, Bacillus subtilis, Brevibacterium ammoniagenes, and Staphylococcus aureus (both penicillin-resistant and penicillin-susceptible strains). The bactericidal activity of totarol was enhanced when it was tested in combination with several other natural products. Noticeably, the activity of totarol against Sta. aureus was increased eightfold when tested in combination with 1/2MIC of anacardic acid [9]. The synergistic activity of anacardic acid caused the minimum bactericidal concentration (MBC) of totarol to be lowered from 1.56 to 0.2 micrograms/ml.

Abietanes↗

PubMed1991

Determination of effector molecules in L-arabinose-induced bulge formation and lysis of Escherichia coli IFO 3545.

L-Ribulose 5-phosphate (L-Ru5P) was identified as the primary effector molecule of L-arabinose-induced bulge formation in Escherichia coli IFO 3545 observed in nutrient broth with 5% (w/v) sodium chloride. Hyperinduction of L-arabinose isomerase was due to exogenous sodium chloride and the resulting alteration in the balance of the L-arabinose-metabolizing enzymes resulted in accumulation of L-Ru5P. L-Ru5P induced the lysis of an L-arabinose-negative, L-Ru5P 4-epimerase-less mutant, ara-207, even when directly added to the medium but was not active against the wild-type strain. Some L-arabinose-utilizing (L-arabinose-resistant) revertants of ara-207 were still sensitive to L-Ru5P, indicating the involvement of another mutation in L-Ru5P-sensitivity other than genetic lack of L-Ru5P 4-epimerase. Among the various pentose phosphate esters tested, only L-Ru5P could induce lysis of ara-207. The lytic activity of L-Ru5P was attributed to its effect on bacterial sugar nucleotide metabolism which caused secondary accumulation of uridine 5'-diphosphate galactose (UDPGal), which provoked lysis induction.

Arabinose↗