A crude MeOH extract of Syzygium aromaticum (clove) exhibited preferential growth-inhibitory activity against Gram-negative anaerobic periodontal oral pathogens, including Porphyromonas gingivalis and Prevotella intermedia. By means of bioassay-directed chromatographic fractionation, eight active compounds were isolated from this extract and were identified as 5,7-dihydroxy-2-methylchromone 8-C-beta-D-glucopyranoside, biflorin, kaempferol, rhamnocitrin, myricetin, gallic acid, ellagic acid, and oleanolic acid, based on spectroscopic evidence. The antibacterial activity of these pure compounds was determined against Streptococcus mutans, Actinomyces viscosus, P. gingivalis, and P. intermedia. The flavones, kaempferol and myricetin, demonstrated potent growth-inhibitory activity against the periodontal pathogens P. gingivalis and P. intermedia.

Compounds from Syzygium aromaticum possessing growth inhibitory activity against oral pathogens

A newly described plant-derived flavonoid, hypolaetin-8-glucoside, which has anti-inflammatory and gastroprotective actions in-vivo, and its corresponding aglycone, hypolaetin, have been compared with 14 other flavonoids for inhibition of eicosanoid generation via the 5-lipoxygenase and cyclo-oxygenase pathways in elicited rat peritoneal leukocytes stimulated with calcium ionophore. Comparable results for the inhibitory profiles of the compounds were obtained using either radioimmunoassay of released eicosanoids or radio-TLC of metabolites formed from labelled arachidonate, but there were differences in absolute potency of the inhibitors. Hypolaetin-8-glucoside was a weak but selective inhibitor of 5-lipoxygenase (IC50 56 microM vs 5-lipoxygenase; greater than 1000 microM vs cyclo-oxygenase), whereas the aglycone hypolaetin was a more potent and selective 5-lipoxygenase inhibitor (IC50 4.5 microM vs 70 microM). Results with three other glycoside/aglycone pairs confirmed that addition of sugar residues greatly reduces inhibitory potency whilst retaining selectivity against 5-lipoxygenase. Analysis of 12 aglycone flavonoids showed that inhibitory potency and selectivity against 5-lipoxygenase is conferred by the presence of 3'4'-vicinal diol (catechol) in ring B as part of a 3,4-dihydroxycinnamoyl structure as proposed by others and by incorporation of additional hydroxyl substituents. In contrast, "cross-over" of inhibitory selectivity is observed in compounds containing few hydroxyl substituents (with none in ring B) which are selective against cyclo-oxygenase. These results are discussed in relation to possible mechanisms of hypolaetin-8-glucoside's protective actions and the concept that these inhibitory effects of flavonoids cannot be ascribed to a unitary free radical scavenging action.

Selectivity of neutrophil 5-lipoxygenase and cyclo-oxygenase inhibition by an anti-inflammatory flavonoid glycoside and related aglycone flavonoids.

Antitumor effects of Scutellariae radix and its components baicalein, baicalin, and wogonin on bladder cancer cell lines.

Antibacterial activity and mode of action of plant flavonoids against Proteus vulgaris and Staphylococcus aureus

Flavonoid baicalin inhibits hiv-1 infection at the level of viral entry

Ogon, an important Chinese crude drug (the dried roots of SCUTELLARIA BAICALENSIS G EORGI), is listed in ancient Chinese herbals and is used in the treatment of a number of diseases. Ether extract of this crude drug showed a relatively marked antibacterial activity against Gram-positive bacteria. Fractionation of the extract accompanied by the bioassay led to the isolation of active principles. The structure of one of these was elucidated as 2( S), 2′, 5, 6′, 7-tetrahydroxyflavanone.

K. Namba

Papers

Studies on Scutellariae radix. Part II: The antibacterial substance.