Antibacterial compounds from the mushroom Ganoderma colossum from Nigeria.

Three colossolactones (colossolactone E, colossolactone B and 23-hydroxycolossolactone E) were isolated and characterized from an n-hexane:dichloromethane (2:7) extract of Ganoderma colossum using chromatographic techniques. The antimicrobial activity of the three compounds was then tested against Gram-positive and Gram-negative bacteria. The activity was evaluated by the thin-layer chromatography agar overlay method. The results showed that colossolactone E and 23-hydroxycolossolactone E were active against Bacillus subtilis and Pseudomonas syringae. Colossolactone B was not active against the bacteria. Their structures were elucidated by spectroscopic methods. Potency of the compounds against bacteria tested supports the use of this mushroom in therapeutic medicine.

Antimicrobial activity of some Ganoderma species from Nigeria.

The crude n-hexane:diethyl ether, chloroform:acetone and methanol extracts of four species of Ganoderma (Ganoderma colossum (Fr.) C. F. Baker, G. resinaceum Boud., G. lucidum (cf.) (Curtis) P. Karst. and G. boninense (cf.) Pat.), from Nigeria, were tested for antimicrobial activity. The three solvent extracts of all the species of Ganoderma were active against Pseudomonas syringae and Bacillus subtilis, whereas none of the extracts were active against Cladosporium herbarum. Preliminary thin layer chromatography chemical tests on these extracts of Ganoderma showed that they contained compounds that stained blue-violet and blue or green when sprayed with anisaldehyde-sulphuric acid or Dragendorff, respectively. The profile of compounds in the extracts showed some variation among the four species.

Phylogeny of Veronica--a combination of molecular and chemical evidence.

A molecular phylogenetic tree of the genus Veronica, based on sequences of the ITS region of nuclear ribosomal DNA, provided a framework to test the use of iridoid chemical data in the classification of the genus. The distribution of ten iridoid glucosides, determined in 27 species of Veronica, supported the molecular results. The nine clades of the molecular tree appeared to correlate with a specific pattern of catalpol esters and chromosome base numbers. Some relationships within Veronica, previously suggested on the basis of morphological and karyological characters, were supported by our data. Neither the molecular, nor the chemical features were in favour of the classical circumscription and classification of the genus.

Acacetin glycosides as taxonomic markers in Calamintha and Micromeria.

A new acetylated flavone glycoside, acacetin 7-O-[6""-O-acetylglucosyl(1""-->2")]rhamnosyl(1"'-->6")glucoside, has been isolated from the leaves of Calamintha glandulosa together with the known compound acacetin 7-O-rhamnosyl(1"'-->6")glucoside. The occurrence of these flavonoids in the closely related genera Satureja, Micromeria, Acinos and Clinopodium indicates that their distribution may be of taxonomic significance.

In vitro studies on the immunomodulatory effects of extracts of Osbeckia aspera.

Ayruvedic medical practitioners in Sri Lanka use aqueous extracts of the mature leaves of Osbeckia aspera to treat liver disease. The extract has been shown to have hepatoprotective effects in vitro and in vivo, and to have inhibitory effects on the complement system and on in vitro phagocytosis by polymorphonuclear cells. The aim of this study was to investigate the effect of an aqueous extract of Osbeckia on lymphocyte proliferation stimulated by mitogens and antigen. In control peripheral blood mononuclear cells (PBMC), high concentrations of the Osbeckia extract were inhibitory to proliferation stimulated by phytohaemagglutinin (PHA) and tuberculin purified protein derivative (PPD). On stimulation by phorbol myristate acetate and ionomycin (PMA+I) the extract showed stimulation of proliferation at low concentrations (<10 microg/ml) with inhibition at higher concentrations. A similar inhibitory pattern on mitogen/antigen stimulation was seen with PBMC from patients with chronic hepatitis C virus (HCV) infection. These results suggest that the inhibitory agent(s) in the aqueous extract of Osbeckia may have an effect on antigen-presenting cell function. The combined hepatoprotective and immunosuppressive effects of the extract are more likely to be beneficial in acute hepatitis rather than chronic hepatitis viral infection.

Acylated flavone C-glycosides from Cucumis sativus.

Leaves of Cucumis sativus plants treated with silicon and infected with Sphaerotheca fuliginea yielded five new acylated flavone C-glycosides identified as isovitexin 2"-O-(6"'-(E)-p-coumaroyl)glucoside (6), isovitexin 2"-O-(6"'-(E)-p-coumaroyl)glucoside-4'-O-glucoside (7), isovitexin 2"-O-(6"'-(E)-feruloyl)glucoside-4'-O-glucoside (11), isoscoparin 2"-O-(6"'-(E)-p-coumaroyl)glucoside (9), and isoscoparin 2"-O-(6"'-(E)-feruloyl)glucoside-4'-O-glucoside (12). The known flavone-glycosides isovitexin (1), saponarin (2), saponarin 4'-O-glucoside (3), vicenin-2 (4), apigenin 7-O-(6"-O-p-coumaroylglucoside) (5), isovitexin 2"-O-(6"'-(E)-feruloyl)glucoside (8) and isoscoparin 2"-O-(6"'-(E)-feruloyl)glucoside (10), were also identified in this plant material.

Distribution of 8-oxygenated leaf-surface flavones in the genus Ocimum.

Nine species of Ocimum (Lamiaceae) were surveyed for leaf-surface flavonoids by means of HPLC with diode array detection and atmospheric pressure chemical ionisation (APCI) mass spectrometry. The analysis revealed the presence of 23 different flavones, most of which were identified by comparing their UV and mass spectra with those of standards. Almost all taxa investigated contained flavones methoxylated in the 6- and 8-positions, such as nevadensin, xanthomicrol and gardenin B. The same taxa also produced flavones methoxylated in the 6-position but hydroxylated in the 8-position, including isothymusin (5,8,4'-trihydroxy-6,7-dimethoxyflavone), pedunculin (5,8-dihydroxy-6,7,4'-trimethoxyflavone) and a new flavone, 5,7,8-trihydroxy-6,4'-dimethoxyflavone, which was given the trivial name pilosin. This compound was isolated from O. americanum var. pilosum and also detected as a minor constituent in O. x citriodorum leaf extracts. Its molecular structure was elucidated by means of NMR spectroscopy. 8-Oxygenated flavones were absent only from O. lamiifolium. APCI mass spectrometry of the flavonoids revealed that the product ions formed by collision induced dissociation of the protonated molecule provided structural information about the substitution pattern of the A-ring. The chemotaxonomic and biogenetic implications of the results are discussed.

Plant--fungal interactions: the search for phytoalexins and other antifungal compounds from higher plants.

A brief review is given of some biological, chemical and chemotaxonomic aspects of phytoalexin research. Emphasis is placed on the search for antifungal compounds in the plant families Leguminosae and Rosaceae, and in rice, Oryza sativa. The possible role of phytoalexins in the resistance of rice plants against the fungus Pyricularia oryzae (= Magnaporthe grisea) is discussed, and the future prospects of phytoalexin research are outlined.

A distinctive flavonoid chemistry for the anomalous genus Biebersteinia.

Leaf surface extracts of Biebersteinia orphanidis have yielded a complex mixture of five flavones with the unusual 5,7-dihydroxy-6,8-dimethoxy A ring substitution pattern. They are acerosin, hymenoxin, nevadensin, sudachitin and 5,7,4'-trihydroxy-6,8-dimethoxyflavone. Also present at the leaf surface are gardenin B, luteolin, apigenin, acacetin and the coumarin umbelliferone. The internal leaf flavonoids include the 7-glucosides of apigenin, luteolin and tricetin, together with the 7-rutinosides of apigenin and luteolin. This profile differs from those of B. heterostemon and B. odora. It appears that B. orphanidis is as highly distinctive in its flavonoid pattern as it is phytogeographically. The data also confirm the conclusion of other studies, including rbcL and atpB gene sequence analysis, that Biebersteinia is completely unrelated to the Geraniaceae, where it was once placed.

Phenolic compounds of Chromolaena odorata protect cultured skin cells from oxidative damage: implication for cutaneous wound healing.

Extracts from the leaves of Chromolaena odorata have been shown to be beneficial for treatment of wounds. The crude ethanol extract of the plant had been demonstrated to be a powerful antioxidant to protect fibroblasts and keratinocytes in vitro. In this study, the most active compounds were fractionated and identified from the crude extract using liquid chromatography coupled with UV spectroscopy and mass spectrometry. The antioxidant effects of purified fractions on cultured fibroblasts and keratinocytes were investigated using colorimetric and lactate hydrogenase release assay. The results showed that the phenolic acids present (protocatechuic, p-hydroxybenzoic, p-coumaric, ferulic and vanillic acids) and complex mixtures of lipophilic flavonoid aglycones (flavanones, flavonols, flavones and chalcones) were major and powerful antioxidants to protect cultured skin cells against oxidative damage. In conclusion, the extract from C odorata contains a mixture of powerful antioxidant compounds that may be one of potential mechanism contributing to enhanced wound healing.

An 8-hydroxylated external flavone and its 8-O-glucoside from Becium grandiflorum.

The major vacuolar flavonoid of a greenhouse-grown plant of Becium grandiflorum has been identified as the 8-O-glucoside of isothymusin (5,8,4'-trihydroxy-6,7-dimethoxyflavone), while the major external flavonoids in the diethyl ether surface wash of the same plant are found to be isothymusin and cirsimaritin (5,4'-dihydroxy-7,8-dimethoxyflavone). Although isothymusin is already known as a conversion product of thymusin (5,6,4'-trihydroxy-6,7-dimethoxyflavone) formed by means of the Wessely-Moser rearrangement, this is the first report of isothymusin as a plant constituent, both as aglycone and glycoside. The biogenetic and chemotaxonomic implications of the occurrence of these flavonoids in B.grandiflorum are briefly discussed.

Complexes of iron with phenolic compounds from soybean nodules and other legume tissues: prooxidant and antioxidant properties.

The low-molecular-mass fraction of the soybean nodule cytosol contains Fe capable of catalyzing free radical production through Fenton chemistry. A large portion of the pool of catalytic Fe, measured as bleomycin-detectable Fe, was characterized as complexes of Fe with phenolic compounds of three classes: phenolic acids, cinnamic acids, and flavonoids. Many of these compounds, along with other phenolics present in legume tissues, were used for a systematic structure-activity relationship study. All phenolics tested were able to chelate Fe, as judged from their inhibitory effect on site-specific deoxyribose degradation (minus EDTA assay). However, only those having catechol, pyrogallol, or 3-hydroxy-4-carbonyl groupings were potent chelators and reductants of Fe3+ at pH 5.5. The same phenolics promoted oxidative damage to DNA (bleomycin assay) and to deoxyribose (plus EDTA assay), but inhibited linolenic acid peroxidation by chelating and reducing Fe3+ and by neutralizing lipid radicals. Also, phenolics having a pyrogallol nucleus attenuated the free radical-mediated inactivation of glutamine synthetase, which was used as a model system, by chelating Fe2+. It is reasoned that under the microaerobic (10-20 nM O2) and acidic (pH 5.5-6.4) conditions prevailing in nodules, phenolics are likely to act primarily as antioxidants, decreasing oxidative damage to biomolecules.

Infraspecific taxonomy and essential oil chemotypes in sweet basil, Ocimum basilicum.

Essential oil compositions of fresh and freeze-dried leaves were determined for 16 accessions of Ocimum basilicum belonging to different varieties to see whether they could be used as infraspecific taxonomic characters. One accession of O. x citriodorum was also studied. Some 30 monoterpenoids, sesquiterpenoids and phenylpropanoids were identified, the major components (more than 20% of the total essential oil composition in one or more accessions) being geranial and neral in O. x citriodorum, and linalool, methyl chavicol, eugenol, methyl eugenol and geraniol in O. basilicum. Based on a combination of the latter compounds, five major essential oil profiles could be distinguished in the accessions studied for O. basilicum. These profiles were largely the same for fresh and freeze-dried material of the same plant, although in the dried leaves, methyl chavicol and eugenol concentrations had generally declined in comparison to those of linalool. There appeared to be little correlation between essential oil patterns and varietal classification within O. basilicum. In view of the chemical heterogeneity of O. basilicum and its use as an essential oil-producing crop, culinary herb, medicinal plant and insect-controlling agent, in all of which chemicals play an important role, the infraspecific classification of this taxon should take chemical characters into consideration. A system for the classification of essential oil chemotypes in O. basilicum is proposed.