Leaf surface flavonoids of Eriodictyon trichocalyx

Extraction of the leaf resin of Eriodictyon trichocalyx var. trichocalyx ether, yielded naringenin, eriodictyol, eriodictyol 3′-methyl ether, apigenin, 6-methoxy-apigenin, luteolin, 6-methoxyluteolin, chrysoeriol, luteolin 3′,7-dimethyl ether and isorhamnetin. The flavonoid profile agrees weil in most respects with the types of compounds exhibited by other Eriodictyon species, particularly with regard to the presence of 6-substituted flavones and a moderate level of O-methylation. Flavonoid variation in E. californicum is briefly discussed.     

Leaf resin flavonoids of Diplacus aurantiacus

Two previously unknown flavonoids, diplacone and diplacol, have been isolated from the leaf resin of Diplacus aurantiacus (Scrophulariaceae). Diplacone is 6-geranyl-eriodictyol, and diplacol is the corresponding dihydroflavonol. The resin is produced at high levels (up to 30% of leaf dry wt) and apparently composed primarily of these two compounds and their methyl ethers.     

External flavonoid aglycones of Viguiera series Viguiera (asteraceae: heliantheae)

Distribution of external flavonoid aglycones supports other data to suggest that Viguiera series Viguiera (series Dentatae Blake) is a mixed taxonomic grouping. Two species, V. dentata and V. potosina, lack external flavonoid aglycones, whereas the remaining species of the series all produce external flavonoid aglycones and appear to form a natural taxonomic group. The latter group, which consists of species from Baja California and nearby xeric areas, exhibits a diversity of flavonoid types, with different diploid species variously producing flavonols, simple flavones, 6-methoxyflavones, 6-hydroxy,7-methoxyflavones and a chalkone as major compounds. Polyploid species exhibit combinations of flavonoid types from possible diploid ancestors. Compounds of the 6-hydroxy,7-methoxyflavone type appear to characterize the group of species from Baja California and nearby areas within Viguiera.     

Exudate flavonoid aglycones of Veronica: Ecological and systematic implications

A survey on the distribution of surface flavonoid aglycones in 52 samples of 29 species of Veronica resulted in detection of eight flavone aglycones. Apigenin and luteolin were the most common constituents of the studied exudates, followed by the methylated derivatives apigenin 4′-methyl ether, apigenin 7,4′-dimethyl ether and luteolin 3′-methyl ether. Some intraspecific variations and the main ecological trends of flavonoid aglycone accumulation in Veronica were discussed. The observed exudate profiles appeared to be characteristic for some related groups within the genus, in agreement with the morphological, karyological, molecular and other chemical data.     

Two polymethoxylated flavonoids with antioxidant activities and a rearranged clerodane diterpenoid from the leaf exudates of Microglossa pyrifolia

Three novel compounds; two polymethoxylated flavonoids, 5,7,4′-trihydroxy-3,8,3′,5′-tetramethoxyflavone (1), 5,7,3′-trihydroxy-3,8,4′,5′-trimethoxyflavone (2), and a clerodane diterpenoid; 8-acetoxyisochiliolide lactone (3) were characterized from the leaf exudates of Microglossa pyrifolia. In addition, three known polymethoxylated flavonoids including; 5,7,4′-trihydroxy-3,8,3′-trimethoxyflavone (4), 5,3′4′-trihydroxy-3,7,8-trimethoxyflavone (5), 5,3′4′-trihydroxy-7-methoxyflavanone (6) and a clerodane diterpenoid; 7,8-epoxyisocholiolide lactone (7) were identified. Their structures were determined on the basis of spectroscopic evidence. All the compounds did not exhibit antiplasmodial and antimicrobial activities at 47.6 μg/mL and were not cytotoxic at 5 μg/mL. Compound 6 exhibited modest antileishmanial activity with IC₅₀ value of 13.13 μg/mL with 5 and 7 showing activities with IC₅₀ values of 31.13 and 38.00 μg/mL, respectively, therefore inactive. The flavonoids (quercetin derivatives, 4 and 5) showed similar antioxidant activities, using 2,2-diphenylpicrylhydrazyl (DPPH) assay, with IC₅₀ values of 6.2 ± 0.3 μg/mL for 4 (17.3 μM) and 5 (17.8 μM) respectively. These activities were comparable to that of the standard quercetin (IC₅₀ value of 6.0 ± 0.2 μg/mL (19.9 μM)), irrespective of methylation of the characteristic hydroxyl groups expected to be responsible for activity and additional substitution at C-8 in ring A of the flavonoid ring. These studies revealed that the presence of an hydroxyl group at C-4′ positions and oxygenation at C-3 in flavone skeleton, appears to be necessary for good antioxidant activities as encountered in compounds 1, 4 and 5. Substantial reduction in antioxidant activity was shown by methoxylation of the 4′-OH as observed in compound 2 with an IC₅₀ value of 8.79 ± 0.3 μg/mL (24.4 μM).     

Chemotaxonomic significance of flavonoids and phenolic acids in the Hieracium rohacsense group (Hieracium sect. Alpina; Lactuceae, Compositae)

Five apomictic taxa from the Hieracium rohacsense group were studied for their phenolic constituent composition. The following substances represent dominant compounds in the leaves: chlorogenic acid, 3,5-dicaffeoylquinic acid, luteolin 7-O-β- -glucopyranoside, luteolin 4′-O-β- -glucuronopyranoside and apigenin 4′-O-β- -glucuronopyranoside. Within the group only quantitative differences were found, luteolin 7-O-glucoside being the most important chemotaxonomic marker. Each taxon has its own specific quantitative pattern, invariable within the taxon. Based on these characteristic profiles, H. rohacsense can be distinguished from a closely related and still undescribed taxon from Mt. Pip Ivan. The proportion of luteolin 7-O-glucoside to apigenin 4′-O-glucuronoside also clearly separates the individuals of two morphologically close species—H. ratezaticum and H. pseudocaesium, which corresponds to a few slight but recognisable morphological and phenological characteristics. The ontogenetic stage of leaf development and seasonal variation are also important factors, which must be taken into consideration, as the quantity of the substances changes during leaf ontogeny and with season.     

宁夏枸杞不同品种叶的总黄酮含量及清除自由基能力分析

采用紫外分光光度法和DPPH法分别对宁夏枸杞不同品种叶的总黄酮含量及其清除自由基能力进行分析。结果表明:宁夏枸杞不同品种的叶总黄酮含量和清除自由基能力之间均存在显著性差异。其中宁杞菜1号叶的总黄酮含量极显著高于其它几个品种(^**P<0.01),并且其清除自由基能力也最强,与其它品种之间差异显著(^*P<0.05)。说明宁杞菜1号是开发枸杞茶的优良品种。     

Synthesis of part of the antigenic repeating-unit of streptococcus pneumoniae type II

Condensation of methyl 4-O-acetyl-3-O-(2,3,4-tri-O-acetyl-α- -rhamnopyranosyl)-α- -rhamnopyranoside with 2,3,4,6-tetra-O-benzyl-α- -glucopyranosyl chloride gave a mixture of methyl O-[2,3,4,6-tetra-O-benzyl-α- (4) and -β- -glucopyranosyl]-(1→2)-O-[(2,3,4-tri-O-acetyl-α- -rhamnopyranosyl)-(1→3)]-4-O-acetyl-α- -rhamnopyranoside (9) in 43:7 proportion in 63% yield. After chromatographic separation, removal of the benzyl and acetyl groups gave methyl O-α- -glucopyranosyl-(1→2)-[O-α- -rhamnopyranosyl-(1→3)]-α- -rhamnopyranoside and the β anomer. Removal of benzyl groups of 4 was followed by tritylation, acetylation, and detritylation of the α- -glucopyranosyl group, and finally condensation with benzyl (2,3,4-tri-O-benzyl- -glucopyranosyl chloride)uronate gave a mixture of two tetrasaccharides (15 and 16), containing the α- and β- -glucopyranosyluronic acid groups in the ratio 81:19, and an overall yield of 71%. After chromatographic separation, alkaline hydrolysis and hydrogenation of 15 gave methyl O-α- -glucopyranosyluronic acid-(1→6)-O-α- -glucopyranosyl-(1→2)-[O-α- -rhamnopyranosyl-(1→3)]-α- -rhamnopyranoside. The β- anomer was obtained by similar treatment of 16. 6-O-α- -glucopyranosyluronic acid-α,β- -glucopyranose was synthesized as a model compound.     

Inhibitory effects of Hymenaea and Copaifera leaf resins on the leaf fungus, Pestalotia subcuticularis

Leaf resins in the leguminous genera Hymenaea and Copaifera may play a role in restricting infection by the associated leaf fungus, Pestalotia. We tested this hypothesis by assessing growth of the geographically widespread Pestalotia subcuticularis presented with different compositions of resins. Leaf resins of Hymenaea and Copaifera are composed of the same suite of sesquiterpene hydrocarbons, but these vary quantitatively to form discrete compositional patterns among individuals and populations. Leaf resins may also contain sesquiterpene oxides; caryophyllene oxide, which may have been formed from the caryophyllene precursor common in these resins, inhibited fungal growth in vitro.     

Leaf productivity along a precipitation gradient in lowland Panama: patterns from leaf to ecosystem

Moisture availability has the potential to affect tropical forest productivity at scales ranging from leaf to ecosystem. We compared data for leaf photosynthetic, chemical and structural traits of canopy trees, litterfall production and seasonal availability of soil water at four sites across a precipitation gradient (1,800–3,500 mm year^–1) in lowland Panamanian forest to determine how productivity at leaf and ecosystem scales may be related. We found stronger seasonality in soil water potential at drier sites. Values were close to zero at all sites during the wet season and varied between a minimum of –2.5 MPa and –0.3 MPa at the driest and wettest sites, respectively, during the dry season. Leaf photosynthesis and nitrogen concentration decreased with increasing precipitation, whereas leaf thickness increased with increasing precipitation. Leaf toughness and fiber/N ratios increased with increasing precipitation indicating reduced nutritional content and palatability with precipitation. Seasonality of litter production and quality decreased with increasing precipitation, but the amount of litterfall produced was not substantially different among sites. It appears that in Neotropical forest, moisture availability is associated with leaf photosynthetic and defensive traits that influence litterfall timing and quality. Therefore, variation in leaf physiological traits has the potential to influence decomposition and nutrient cycling through effects on litter quality.     

Further studies of flavonoids in Saxifraga

The flavonoid composition of Saxifraga cernua, S. micranthidifolia, S. tolmiei, and S. tricuspidata has been determined. The major proportion of the profiles comprise a complex mixture of flavonol 3-O-glycosides, including mono-, di-, and triglycosides. Kaempferol, quercetin, isorhamnetin, and myricetin were observed although not all taxa had all aglycones. The monoglycoside fraction of S. tolmiei was unusual in that it consisted only of quercetin 3′-O-glucoside and myricetin 7-O-glucoside; both compounds are unusual for the family. Saxifraga tricuspidata exhibited an unusually complex array of monoglycosides which was comprised of glucosides, galactosides, xylosides, several isomeric arabinosides, and acylated derivatives of some of the arabinosides. The diversity of biosynthetic capacity observed for Saxifraga (present and earlier data) reflect the complexity described for the Saxifrageae.     

Studies on the leaf anatomy of Euphorbia: II. Venation patterns*

Leaf venation patterns of 150 species of Euphorbia are presented and their value as a diagnostic feature in the genus assessed. Based on the gross venation patterns, the species have been grouped into uni-, bi-, tri-veined and special categories. The majority of the species studied belonged to the tri-veined category, in which ornamentation of the veins and the course of traces in the lamina proved useful additional characters. Features such as the size of the areoles, the number of vein endings, and their further ramifications and composition in each areole varied in the same leaf or in different leaves of a given species. Furthermore, no direct correlation could be established between the areole size and the numbers of vein endings and tips per areole. Forty species possess a parenchymatous vein sheath. Globular chloroplasts showed up conspicuously in the sheath cells of a few species. Dilated tracheidal elements, localized on the venules or at the tips of vein endings, are characteristic of the xerophytic species. In some instances, correlation was apparent between plants grouped according to their venation patterns and their habit.     

Targeted gene disruption in Francisella tularensis by group II introns

Francisella tularensis is a highly infectious Gram-negative bacterium that is the causative agent of tularemia. Very little is known about the molecular mechanisms responsible for F. tularensis virulence, in part due to the paucity of genetic tools available for the study of F. tularensis. We have developed a gene knockout system for F. tularensis that utilizes retargeted mobile group II introns, or “targetrons”. These targetrons disrupt both single and duplicated target genes at high efficiency in three different F. tularensis subspecies. Here we describe in detail the targetron-based method for insertional mutagenesis of F. tularensis genes, which should facilitate a better understanding of F. tularensis pathogenesis. Group II introns can be adapted to inactivate genes in bacteria for which few genetic tools exist, thus providing a powerful tool to study the genetic basis of bacterial pathogenesis.     

Distribution of exudate flavonoids in the genus Plectranthus

Thirty-four species of the genus Plectranthus (including species of the former genera Coleus and Solenostemon, fam. Lamiaceae) were surveyed for exudate flavonoids to see whether the distribution of these compounds would support a recent classification of the genus based on molecular and morphological characters. In this classification two major groups had been identified, the Coleus and Plectranthus clades. Only about 40% of the species, predominantly from the Plectranthus clade, were found to produce exudate flavonoids, which were mainly flavones. Flavanones were restricted to five species of the Plectranthus clade, whereas flavonols were only found in two species of the Coleus clade, Plectranthus montanus Benth. (synonyms Plectranthus marrubioides Hochst. ex Benth. and Plectranthus cylindraceus Hochst. ex Benth.) and Plectranthus pseudomarrubioides R.H.Willemse. Four of these flavonols were isolated from P. montanus and identified by NMR spectroscopy as the 3,7-dimethyl ether and 3,7,4′-trimethyl ether of quercetin and the 3,6,7-trimethyl ether and 3,6,7,4′-tetramethyl ether of quercetagetin. The remaining flavonols and flavones were identified by HPLC–UV and LC–MS of crude extracts on the basis of their UV and mass spectra, retention times and comparison with standards. Most flavonols were 3-methyl ethers and many of the flavones and flavonols were oxygenated at the 6-position. The most common flavones, occurring in both clades, were cirsimaritin and salvigenin, which are methoxylated at the 6- and 7-positions. 6-Hydroxylated flavones such as scutellarein and ladanein were restricted to species of the Plectranthus clade.     

Saprotrophy of Conidiobolus and Basidiobolus in leaf litter

This study of the putative saprotrophs of Conidiobolus and Basidiobolus aids the understanding of their ecological roles in litter, and their relationship with the entomogenous fungi of the Entomophthorales. A total of 47 isolates (ten spp.) were screened for their ability to utilise pure compounds, arthropod cadavers, and plant leaf fragments as substrates. Isolates co-occurred in a larch plantation (Larix sp.) or were from adjacent habitats. Of the 21 isolates (nine spp.) tested on potential prime carbon sources, none could utilise common plant structural polymers. Conidiobolus adiaeretus, C. iuxtagenitus, and B. ranarum from litter and some soil isolates of C. heterosporus, C. pumilus, and C. firmipilleus could use starches and glycogen. In marked contrast, all could utilise animal chitin, gelatine, casein, N-acetyl glucosamine, and trehalose. The lipids tributyrin and sunflower oil also supported growth. Conidia on cadavers usually led to high levels of colonisation as was the case for 30 isolates (ten species). Collembola were more frequently and rapidly colonised than mites. Cadavers of many other arthropods were also internally colonised. The ability to utilise cadavers of diverse arthropods indicates that trophic competition between co-occurring test species may be minimal. Niche differentiation may depend more on non-trophic features of their life history. Negative correlation of performance with the presence of naturally occurring, non-test fungi suggests competition with (or antibiosis from) at least some of the other fungi. In washed or unwashed plant fragments of larch litter (F-layer) only occasional local growth and resting spore formation occurred. Extra nutrients did not facilitate colonisation. Alternative forms of repetitional conidia showed a strong association with plant fragments but not with cadavers.     

A survey of leaf flavonoids in the portulacaceae

A survey of 26 species in 12 genera of the Portulacaceae showed the presence of flavonoids in 24, and their absence in two, Hectorella caespitosa Hooker fil. and Lyallia kerguelensis Hooker fil. Of the 24 positive species, 16 are reported for the first time. In all 24 however, flavonols and flavones did not occur together suggesting that this dichotomy might be useful for classification at and below the generic level in the Portulacaceae, e.g. the genera Silvaea Philippi (syn. Philippiamara Kuntze), Ceraria Pearson & Stephens and Portulacaria Jacquin which were previously grouped together on palynological characteristics have now been shown to differ in their leaf flavonoids, subsidiary cells of the stomata and geographical location: Silvaea possesses flavones and is endemic to South America, while Ceraria and Portulacaria possess flavonols and are endemic to Africa. The dichotomy also occurs below the generic level. In Calandrinia H.B.K. and Portulaca L. the dichotomy amongst their species is supported by other new taxonomic characters from cytology, palynology, pubescence of surfaces, type of subsidiary cells surrounding the leaf stomata and seed morphology recently elucidated by the author.     

Choleretic effects of yarrow (Achillea millefolium s.l.) in the isolated perfused rat liver

Different species from the Achillea millefolium aggregate are used against gastrointestinal and hepato-biliary disorders in traditional European medicine. In this work, a fraction enriched in dicaffeoylquinic acids (DCCAs) and luteolin-7-O-β-d-glucuronide was investigated on its choleretic effect in the isolated perfused rat liver (IPRL) compared to cynarin (1,3-DCCA), the main choleretic compound of Cynara scolymus L. A fraction containing 3,4-, 3,5- and 4,5-DCCA and luteolin-7-O-β-d-glucuronide was prepared by solid phase extraction from a 20% methanolic extract of yarrow. A total amount of 48.8% DCCAs and 3.4% luteolin-7-O-β-d-glucuronide was determined by HPLC analysis with cynarin as internal standard. IPRL experiments revealed a dose-dependant increase in bile flow (23–44–47%) by the Achillea fraction. Choleresis was two- to three-fold higher than that of cynarin. The combined effect of DCCAs and luteolin-7-O-β-d-glucuronide stimulated bile flow more effectively than the single compound cynarin. Due to their polar structure, these compounds are quantitatively extracted into teas and tinctures; hence, they seem to be the choleretic active principles in the traditional application forms of yarrow.     

Distribution of flavonoids in the Myristicaceae

During the past two decades the study of the Myristicaceae species has increased, and many flavonoids of different types have been isolated. This review discusses the flavonoids presently known in the Myristicaceae.     

Distribution of artemisinin and bioactive flavonoids from Artemisia annua L. during plant growth

Artemisia annua L. (Qinghao, Asteraceae) is a promising and potent antimalarial herbal drug. Its activity has been ascribed to the content of artemisinin, a sesquiterpene lactone that is very effective against drug-resistant Plasmodium. Many studies have pointed out that the presence of polymethoxyflavonoids in the phytocomplex can enhance the bioavailability or the activity of artemisinin. In this study the production of both artemisinin and flavonoids by plants of an aromatic ecotype of A. annua L. was characterized in different aerial parts of the plants at different developmental stages. The qualitative profile of the investigated plant parts was similar; in addition to artemisinin, four flavonoids were identified: chrysoplenetin, casticin, eupatin and artemetin. The highest contents of both flavonoids and artemisinin were found at the full blooming stage. At this developmental stage, artemisinin was higher in leaves than in inflorescences, while the total flavonoid levels were similar in both plant organs.