Antibacterial activity of sugar maple autumn-shed leaf extract: Identification of the active compound

Ethanolic crude extract prepared from autumn-shed leaves of sugar maple (Acer saccharum Marsh.) was recently shown to have antibacterial activity against Pseudomonas cichorii and Xanthomonas campestris pv. vitians, two bacteria causing diseases in lettuce production. In this study, antibacterial activity of sugar maple autumn-shed leaves (SMASL) extract was further investigated. SMASL ethanolic crude extract was fractionated using HPLC system and geraniin was identified as the antibacterial compound by UPLC/Q-Tof-MS system. Geraniin, an ellagitannin, was then purified from SMASL crude extract using a glass chromatographic C18-reversed phase silica gel column (purification Step 1) and a semi-preparative HPLC system equipped with 5 μm XTerra Prep MS C18 column (purification Step 2). Minimal inhibitory concentrations (MICs) and minimal bactericidal concentrations (MBCs) of purified geraniin (purity of 96%) against P. cichorii and X. campestris pv. vitians were determined. X. campestris pv. vitians (MIC of 0.024 mg ml⁻¹ and MBC of 3.125 mg ml⁻¹) was more sensitive to geraniin than P. cichorii (MIC of 0.781 mg ml⁻¹ and MBC of 6.25 mg ml⁻¹). In the present study, geraniin is reported for the first time as the main antibacterial compound present in SMASL.     

Systematics and health effects of chemically distinct tannins in medicinal plants

The research began with an investigation of tannins from traditional medicinal plants and resulted in isolation and structure determination of hundreds of ellagitannins and dehydroellagitannins, as well as their oligomers and oxidized derivatives with various structures specific to each plant species. These polyphenols have been classified according to the stage of oxidative structural transformation and oligomerization, into types I-IV and I+ to IV+, etc. Parallels were found between their oxidative transformations and plant evolution. They were also classified by the linkage units between the monomers, into DOG, GOD, GOG and DOGOD types (D=Diphenoyl, G=Galloyl, O=Oxygen), etc. Besides their fundamental activities, e.g., reduction and anti-peroxidation properties, remarkable biological and pharmacological activities of various potencies have also been found, including, amongst others, inhibition of lipid-peroxidation, mutagenicity of carcinogens and tumor promotion, host-mediated antitumor effects specific to particular tannin structures, antiviral activity and potentiation of antibacterial activity.     

Bergenin derivatives from Mallotus japonicus

Three new bergenin derivatives were isolated from the bark of Mallotus japonicus and determined to be 11-O-galloylbergenin, 4-O-galloylbergenin and 11-O-galloyldemethylbergenin. The ¹³C resonances of bergenin were fully assigned.     

Astringent tannins of the leaves of Geranium species

Fifty per cent methanolic extracts of the leaves of 70 species (including some subspecies, varieties and one hybrid) of Geratiium have been analysed for proanthoeyanidins, total galloyl esters, hexahydroxydiphenoylglucose and astringency. Proanthoeyanidins are present in most species (prodelphinidin in four) but only rarely in considerable quantities and then not readily extracted. A reaction with potassium iodate characteristic of geraniin (a derivative of dihexahydroxydiphenoylglucose) is given by most species. The very considerable differences in astringency between species cannot at present be accounted for in terms of chemical differences, but a systematic review suggests that geographical location, chromosome number and annual or biennial habit are involved in the amount ofiannin present in particular species.     

The distribution of geraniin and mallotusinic acid in the order geraniales

The distribution of geraniin and mallotusinic acid in Geraniaceae, Euphorbiaceae and other families in the Geraniales were investigated by HPLC. Geraniin composes the main part of the tannin in all of the investigated species of Geranium, but not in species of Pelargonium. The species of Geraniaceae lack mallotusinic acid. Geraniin was also detected in most of the species in the subfamily Euphorbioideae of Euphorbiaceae, although the amount was generally smaller than in Geranium, except for some woody species. Several species of Euphorbioideae contained mallotusinic acid. Characteristic of the subfamily Phyllanthoideae is the absence of mallotusinic acid and poor distribution of geraniin. Geraniin and mallotusinic acid were not detected in most of the species of other families in the Geraniales, except in Erythroxylum coca. Hyperin was found to be the main flavonol glycoside in most species of Geranium.