Plant constituents biologically active to insects. VI. Antifeedants for larvae of the yellow butterfly, Eurema hecabe mandarina, in Osmunda japonica. (2)

The traditional utilization, biological activity and chemical composition of edible fern species

ETHNOPHARMACOLOGICAL RELEVANCE

Ferns form an important part of the human diet. Young fern fiddleheads are mostly consumed as vegetables, while the rhizomes are often extracted for starch. These edible ferns are also often employed in traditional medicine, where all parts of the plant are used, mostly to prepare extracts. These extracts are applied either externally as lotions and baths or internally as potions, decoctions and teas. Ailments traditionally treated with ferns include coughs, colds, fevers, pain, burns and wounds, asthma, rheumatism, diarrhoea, or skin diseases (eczema, rashes, itching, leprosy).

AIM OF THE REVIEW

This review aims to compile the worldwide knowledge on the traditional medicinal uses of edible fern species correlating to reported biological activities and isolated bioactive compounds.

MATERIALS AND METHODS

The articles and books published on edible fern species were searched through the online databases Web of Science, Pubmed and Google Scholar, with critical evaluation of the hits. The time period up to the end of 2022 was included.

RESULTS

First, the edible fern species were identified based on the literature data. A total of 90 fern species were identified that are eaten around the world and are also used in traditional medicine. Ailments treated are often associated with inflammation or bacterial infection. However, only the most common and well-known fern species, were investigated for their biological activity. The most studied species are Blechnum orientale L., Cibotium barometz (L.) J. Sm., Diplazium esculentum (Retz.) Sw., Marsilea minuta L., Osmunda japonica Thunb., Polypodium vulgare L., and Stenochlaena palustris (Burm.) Bedd. Most of the fern extracts have been studied for their antioxidant, anti-inflammatory and antimicrobial activities. Not surprisingly, antioxidant capacity has been the most studied, with results reported for 28 edible fern species. Ferns have been found to be very rich sources of flavonoids, polyphenols, polyunsaturated fatty acids, carotenoids, terpenoids and steroids and most of these compounds are remarkable free radical scavengers responsible for the outstanding antioxidant capacity of fern extracts. As far as clinical trials are concerned, extracts from only three edible fern species have been evaluated.

CONCLUSIONS

The extracts of edible fern species exert antioxidant anti-inflammatory and related biological activities, which is consistent with their traditional medicinal use in the treatment of wounds, burns, colds, coughs, skin diseases and intestinal diseases. However, studies to prove pharmacological activities are scarce, and require chemical-biological standardization. Furthermore, correct botanical classification needs to be included in publications to simplify data acquisition. Finally, more in-depth phytochemical studies, allowing the linking of traditional use to pharmacological relevance are needed to be done in a standardized way.

A Simple and Rapid High-Performance Liquid Chromatography-Photodiode Array Method for Quantitation of Triacetin Contents From 30 Batches Produced in China

In our present study, the standard chemicals of triacetin were purified by reverse-phase and normal-phase semi-preparative high-performance liquid chromatography (HPLC), and 1H NMR and 13C NMR were employed to determine the purity and structure of triacetin. Moreover, a simple and rapid HPLC-photodiode array (PDA) method was developed to determine the contents of triacetin in 30 batches from different suppliers. The chromatographic separation was performed on a Phenomenex Gemini-NX C18 column (250 × 4.6 mm, 5 μm) using a gradient elution system of water and acetonitrile (contained 0.1% of formic acid) solution with a flow rate of 1.0 mL/min at 30°C at 210 nm. Sample preparation method is rapid and energy efficient, and the obtained sample have a good purity. Validation shows good specificity, linearity (R2 = 0.9995), precision, stability, repeatability (% RSD < 2.80) and the average recovery (99.72%) of triacetin. The content of triacetin in most samples is concentrated in 94-97%. This developed approach is simple, rapid, accurate and can be used to quickly determine the purity and the content of triacetin in plasticizers and filter plugs.

Preparation of Curdlan sulphate - Chitosan nanoparticles as a drug carrier to target Mycobacterium smegmatis infected macrophages

In this study, curdlan sulphate - chitosan nanoparticles were prepared through polyelectrolyte complexing at a mass ratio of 2:1 respectively. The curdlan was produced by fermentation with Agrobacterium sp. ATCC 31750, which was then sulphated to form the polyanionic polymer. A first-line tuberculosis drug, Rifampicin and a phytochemical, DdPinitol, were encapsulated into Curdlan Sulphate (CS) - Chitosan Nanoparticles (C) (CSC NPs) of size 205.41 ± 7.24 nm. The drug release kinetics followed a Weibull model with initial burst release (48 % Rifampicin and 27 % d-Pinitol within 6 h), followed by a sustained release. The prepared CSC: d-PIN + RIF NPs was cytocompatible and entered the M.smegmatis infected macrophages through multiple endocytic pathways including clathrin, caveolae and macropinocytosis. They showed superior bactericidal activity (2.4-2.7 fold) within 4 h when compared to free drug Rifampicin (1.6 fold). The drug encapsulated CSC: RIF suppressed the pro-inflammatory gene (TNF-α by 3.66 ± 0.19 fold) and CSC: d-PIN + RIF increased expression of the anti-inflammatory gene (IL-10 by 13.09 ± 0.47 fold). Expression of TGF- β1 gene also increased when treated with CSC: d-PIN + RIF (13.00 ± 0.19 fold) which provided the immunomodulatory activity of the encapsulated CSC NPs. Thus, curdlan sulphate - chitosan polyelectrolyte complex can be a potential nanocarrier matrix for intracellular delivery of multiple drugs.

Polyketide Derivatives in the Resistance of Gerbera hybrida to Powdery Mildew

Powdery mildew is a common disease affecting the commercial production of gerbera flowers (Gerbera hybrida, Asteraceae). Some varieties show a certain degree of resistance to it. Our objective was to identify biomarkers of resistance to powdery mildew using an ¹H nuclear magnetic resonance spectroscopy and chemometrics approach in a complex, fully factorial experiment to suggest a target for selection and breeding. Resistant varieties were found to differ from those that were susceptible in the metabolites of the polyketide pathway, such as gerberin, parasorboside, and gerberinside. A new compound probably involved in resistance, 5-hydroxyhexanoic acid 3-O-β-D-glucoside, was described for the first time. A decision tree model was built to distinguish resistant varieties, with an accuracy of 57.7%, sensitivity of 72%, and specificity of 44.44% in an independent test. Our results suggest the mechanism of resistance to powdery mildew in gerbera and provide a potential tool for resistance screening in breeding programs.

Inhibitory activity of traditional plants against Mycobacterium smegmatis and their action on Filamenting temperature sensitive mutant Z (FtsZ)-A cell division protein

The study was designed to assess whether plant extracts / phytochemical (D-Pinitol) synergistically combine with antituberculosis drugs and act on Mycobacterium smegmatis (M. smegmatis) as well as assess their mode of action on Mycobacterium tuberculosis (M.tb) Filamenting temperature sensitive mutant Z (FtsZ) protein. Resazurin microtitre plate assay (Checker board) was performed to analyze the activity of plant extracts against M. smegmatis. Synergistic behaviour of plant extracts / D-Pinitol with Isoniazid (INH) and Rifampicin (RIF) were determined by time–kill and checker board assays. Elongation of M. smegmatis cells due to this treatment was determined by light microscopy. The effect of Hexane methanol extract (HXM) plant extracts on cell viability was determined using PI/SYTO9 dual dye reporter Live/Dead assay. Action of HXM plant extracts / D-Pinitol on inhibition of FtsZ protein was done using Guanosine triphosphatase (GTPase) light scattering assay and quantitative Polymerase Chain Reaction (qPCR). The Hexane-methanolic plant extract of Acacia nilotica, Aegle marmelos and Glycyrrhiza glabra showed antimycobacterial activity at 1.56 ± 0.03, 1.32 ± 0.02 and 1.25 ± 0.03 mg/mL respectively and that of INH and RIF were 4.00 ± 0.06 μg/mL and 2.00 ± 0.04 μg/mL respectively. These plant extracts and major phytochemical exudate D-Pinitol was found to act synergistically with antimycobacterial drugs INH and RIF with an FIC index ~ 0.20. Time-Kill kinetics studies indicate that, these plant extracts were bacteriostatic in nature. D-Pinitol in conjunction with INH and RIF exhibited a 2 Log reduction in the growth of viable cells compared to untreated. Attempt to elucidate their mode of action through phenotypic analysis indicated that these plant extracts and D-Pinitol was found to interfere in cell division there by leading to an abnormal elongated cellular morphology. HXM extracts and D-Pinitol synergistically combined with the first line tuberculosis drugs, INH and RIF, to act on M. smegmatis. The increase in the length of M. smegmatis cells on treatment with D-Pinitol and HXM extract of the plants indicated that they hinder the cell division mechanism thereby leading to a filamentous phenotype, and finally leading to cell death. In addition, the integrity of the bacterial cell membrane is also altered causing cell death. Further gene expression analysis showed that these plant extracts and D-Pinitol hampers with function of FtsZ protein which was confirmed through in vitro inhibition of FtsZ–GTPase enzymatic activity.

Metabolomics of endemic six Astragalus species by combined NMR and GC-MS analysis

INTRODUCTION

Astragalus anthylloides, A. dipsaceus, A. karamasicus, A. lycius, A. sigmoideus and A. xylobasis var. angustus are an endemic and generally grow in the Irano-Turanian phytogeographic region of Turkey. Astragalus species contain saponins, polysaccharides, and phenolics, while the toxic compounds include imidazoline alkaloids, nitro toxins, and selenium derivatives.

OBJECTIVES

To apply a combined metabolomic fingerprinting approach by nuclear magnetic resonance (NMR) and gas chromatography-mass spectrometry (GC-MS) of endemic six Astragalus species extract.

METHODOLOGY

The whole plant collected in Turkey of six endemic Astragalus subsp. were dried and then extracted with hexane, chloroform, ethylacetate, n-butanol and methanol solvents, respectively. The hexane extracts were analyzed by GC-MS. Carbon-13 (¹³ C)-NMR analyzes of all extracts were performed. In both analyses, a biomarker was obtained.

RESULTS

The hexane extracts were determined as palmitic acid, arachidic acid, behenic acid, and linolenic acid as the main components. As a result of ¹³ C-NMR analyzes, in hexane, chloroform, and ethylacetate the extracts detected were palmitic acid, arachidic acid, behenic acid, and linolenic acid. d-Pinitol was obtained using ¹³ C-NMR analyzes with n-butanol and methanol extracts.

CONCLUSION

This study demonstrated that d-pinitol is a biomarker for the endemic six Astragalus subsp.

An Oviposition Stimulant for a Magnoliaceae-Feeding Swallowtail Butterfly, Graphium doson, from its Primary Host Plant, Michelia compressa

Chemical examination of plant constituents responsible for oviposition by a Magnoliaceae-feeding butterfly, Graphium doson, was conducted using its major host plant, Michelia compressa. A methanol extract prepared from young leaves of the plant elicited a strong oviposition response from females. The methanolic extract was then separated by solvent partition into three fractions: CHCl₃, i-BuOH, and aqueous fractions. Active substance(s) resided in both i-BuOH- and water-soluble fractions. Bioassay-guided further fractionation of the water-soluble substances by means of various chromatographic techniques led to the isolation of an oviposition stimulant. The stimulant was identified as D-(+)-pinitol on the basis of ¹³C NMR spectra and physicochemical properties. D-(+)-Pinitol singly exhibited a moderate oviposition-stimulatory activity at a dose of 150 μg/cm². This compound was present also in another host plant, Magnolia grandiflora, in a sufficient amount to induce oviposition behavior of G. doson females. Certain cyclitols including D-(+)-pinitol have been reported to be involved in stimulation of oviposition by some Aristolochiaceae- and Rutaceae-feeding papilionid butterflies. A possible pathway of phytochemical-mediated host shifts in the Papilionidae, in which certain cyclitols could enact important mediators, is discussed in relation to the evolution of cyclitol biosynthesis in plants.

Sarocladione, a unique 5,10:8,9-diseco-steroid from the deep-sea-derived fungusSarocladium kiliense

Sarocladione was isolated from the deep-sea-derived fungusSarocladium kilienseas the first example of a 5,10:8,9-diseco-steroid.

Two-dimensional NMR analysis of Angiopteris evecta rhizome and improved extraction method for angiopteroside

INTRODUCTION

The rhizome of Angiopteris evecta is of academic interest in Kalimantan, Indonesia, from an ethnobotanical perspective. Angiopteroside is a substance of pharmaceutical importance that is found in the rhizome of A. evecta.

OBJECTIVE

The aims of this research are to improve the extraction method for angiopteroside from the rhizome, compared to that in a previous report, and to determine the yield of angiopteroside from the rhizome of A. evecta, as well as to obtain precise data for extractives from the rhizome of A. evecta by using two-dimensional NMR spectroscopy and liquid chromatography-mass spectrometry (LC-MS).

METHODOLOGY

We investigated the chemical constituents of the whole rhizome by means of two-dimensional NMR (heteronuclear single quantum coherence or HSQC) spectroscopy, neutral sugar analysis using the alditol acetate method, and lignin analysis using alkaline nitrobenzene oxidation and Klason lignin methods. LC-MS revealed the purity of the angiopteroside. Antimicrobial assays were also performed for the purified angiopteroside by using a broth microdilution method.

RESULTS

Angiopteroside was isolated by Soxhlet extraction with aqueous acetone followed by preparative thin-layer chromatography (eluent: 20% methanol/dichloromethane). LC-MS revealed that angiopteroside can be found in the rhizome of A. evecta in 9.9% yield, which is an extremely high yield for a plant extractive.

CONCLUSION

HSQC analysis is a powerful tool for surveying compounds in plant materials, such as the whole rhizome of A. evecta. Soxhlet extraction with aqueous acetone is an effective method for extracting glycosides from plant materials.

Bioactivity-Guided Isolation of Antimicrobial and Antioxidant Metabolites from the Mushroom Tapinella atrotomentosa

Bioassay-guided fractionation of the chloroform extract of Tapinella atrotomentosa led to the isolation of four secondary metabolites 1⁻4. Two of the compounds are lactones—osmundalactone (1) and 5-hydroxy-hex-2-en-4-olide (2)—while 3 and 4 were identified as terphenyl quinones, spiromentins C and B, respectively. The structures of the compounds were established on the basis of NMR and MS spectroscopic analysis. The isolated fungal metabolites were evaluated for their antibacterial activities against several Gram-positive and negative bacteria. In addition, their synergistic effect with cefuroxime against methicillin-resistant Staphylococcus aureus (MRSA) was also evaluated. Compounds 1⁻3 proved to possess significant antibacterial activity against multiresistant Acinetobacter baumannii and extended-spectrum β-lactamase (ESBL)-producing Escherichia coli. The investigation of the antioxidant effect of the isolated compounds in DPPH and ORAC assays revealed that spiromentins C (3) and B (4) have remarkable antioxidant activity.

Integrin Inhibitors in Prostate Cancer

Prostate cancer (PCa) is the most frequently diagnosed cancer and the third highest cause of cancer-related deaths in men in the U.S. The development of chemotherapeutic agents that can bind PCa tumor cells with high specificity is critical in order to increase treatment effectiveness. Integrin receptors and their corresponding ligands have different expression patterns in PCa cells. They have been identified as promising targets to inhibit pathways involved in PCa progression. Currently, several compounds have proven to target specific integrins and their subunits in PCa cells. In this article, we review the role of integrins inhibitors in PCa and their potential as therapeutic targets for PCa treatments. We have discussed the following: natural compounds, monoclonal antibodies, statins, campothecins analog, aptamers, d-aminoacid, and snake venom. Recent studies have shown that their mechanisms of action result in decrease cell migration, cell invasion, cell proliferation, and metastasis of PCa cells.

Siliquapyranone: A Tannic Acid Tetrahydropyran-2-one Isolated from the Leaves of Carob (Ceratonia siliqua) by Pressurised Hot Water Extraction

Studies of the phytochemistry of carob (Ceratonia siliqua) leaf material are extremely limited. This report features the second natural product isolation study of carob leaves and the first such investigation of C. siliqua grown in Australia. Investigation of leaf material from seven carob cultivars using pressurised hot water extraction (PHWE) revealed the presence of high levels of myricitrin, d-pinitol, and sucrose in addition to the previously unreported natural product siliquapyranone {(2R,3R,4S,5R,6R)-5-hydroxy-6-(hydroxymethyl)-2-(((2S,4S)-2-methyl-6-oxotetrahydro-2H-pyran-4-yl)oxy)tetrahydro-2H-pyran-3,4-diyl bis(3,4,5-trihydroxybenzoate)}. Siliquapyranone represents a biosynthetic fusion of conventional 2,3-gallate esters on a β-glucose tannin with a hydroxytetrahydro-2H-pyran-2-one-related non-tannin tetrahydropyran-2-one, parasorboside. Preliminary biological testing indicates that siliquapyranone exhibits weak activity against both tumour and normal cell lines. This suggests that, like most tannins and parasorboside, siliquapyranone may act as an antifeedant.

Oral microbe-host interactions: influence of β-glucans on gene expression of inflammatory cytokines and metabolome profile

Background

The aim of this study was to evaluate the effects of β-glucan on the expression of inflammatory mediators and metabolomic profile of oral cells [keratinocytes (OBA-9) and fibroblasts (HGF-1) in a dual-chamber model] infected by Aggregatibacter actinomycetemcomitans. The periodontopathogen was applied and allowed to cross the top layer of cells (OBA-9) to reach the bottom layer of cells (HGF-1) and induce the synthesis of immune factors and cytokines in the host cells. β-glucan (10 μg/mL or 20 μg/mL) were added, and the transcriptional factors and metabolites produced were quantified in the remaining cell layers and supernatant.

Results

The relative expression of interleukin (IL)-1-α and IL-18 genes in HGF-1 decreased with 10 μg/mL or 20 μg/mL of β-glucan, where as the expression of PTGS-2 decreased only with 10 μg/mL. The expression of IL-1-α increased with 20 μg/mL and that of IL-18 increased with 10 μg/mL in OBA-9; the expression of BCL 2, EP 300, and PTGS-2 decreased with the higher dose of β-glucan. The production of the metabolite 4-aminobutyric acid presented lower concentrations under 20 μg/mL, whereas the concentrations of 2-deoxytetronic acid NIST and oxalic acid decreased at both concentrations used. Acetophenone, benzoic acid, and pinitol presented reduced concentrations only when treated with 10 μg/mL of β-glucan.

Conclusions

Treatment with β-glucans positively modulated the immune response and production of metabolites.

Anti-inflammatory effect of D-pinitol isolated from the leaves of Colutea cilicica Boiss et Bal. on K562 cells

Aim:

D-pinitol, a natural compound has shown various biological and pharmacological effects. Last studies are focused on the determination of its further pharmacological activities including mainly biological activity. Therefore, isolation of D-pinitol from the leaves of

Materials and methods:

Isolation of D-pinitol was performed by column chromatography. Chemical structure of the compound was confirmed by spectroscopic methods including

Results:

Stimulation of cells with D-pinitol (0–80 μM) was observed for 24, 48 and 72 h. It is determined that D-pinitol inhibited protein expression of Cox-2 in K562 cells. We observed that Poly (ADP-ribose) polymerase (PARP) protein expression did not change, but Cox-2 protein expression reduced with non-cytotoxic concentrations of D-pinitol.

Conclusion:

It is concluded that D-pinitol did not affect cell proliferation and apoptosis in K562 cells however reduced the inflammation, significantly. These results show that D-pinitol may be anti-inflammatory agent for the treatment of K562 cells.

D-pinitol inhibits prostate cancer metastasis through inhibition of αVβ3 integrin by modulating FAK, c-Src and NF-κB pathways

Prostate cancer is the most commonly diagnosed malignancy in men and shows a predilection for metastasis to the bone. D-pinitol, a 3-methoxy analogue of d-chiro-inositol, was identified as an active principle in soy foods and legumes, and it has been proven to induce tumor apoptosis and metastasis of cancer cells. In this study, we investigated the anti-metastasis effects of D-pinitol in human prostate cancer cells. We found that D-pinitol reduced the migration and the invasion of prostate cancer cells (PC3 and DU145) at noncytotoxic concentrations. Integrins are the major adhesive molecules in mammalian cells and have been associated with the metastasis of cancer cells. Treatment of prostate cancer cells with D-pinitol reduced mRNA and cell surface expression of αvβ3 integrin. In addition, D-pinitol exerted its inhibitory effects by reducing focal adhesion kinase (FAK) phosphorylation, c-Src kinase activity and NF-κB activation. Thus, D-pinitol may be a novel anti-metastasis agent for the treatment of prostate cancer metastasis.

D-pinitol inhibits RANKL-induced osteoclastogenesis

Numerous studies have indicated that inflammatory cytokines play a major role in osteoclastogenesis, leading to the bone resorption that is frequently associated with osteoporosis. D-pinitol, a 3-methoxy analogue of D-chiroinositol, was identified as an active principle in soy foods and legumes. Here we found that D-pinitol markedly inhibited the receptor activator of nuclear factor kappa B ligand (RANKL)-induced osteoclastic differentiation from bone marrow stromal cells and RAW264.7 macrophage cells. In addition, D-pinitol also reduced RANKL-induced p38 and JNK phosphorylation. Furthermore, RANKL-mediated increase of IKK, IκBα, and p65 phosphorylation and NF-κB-luciferase activity was inhibited by D-pinitol. However, D-pinitol did not affect the proliferation and differentiation of osteoblasts. In addition, D-pinitol also prevented the bone loss induced by ovariectomy in vivo. Our data suggest that D-pinitol inhibits osteoclastogenesis from bone marrow stromal cells and macrophage cells via attenuated RANKL-induced p38, JNK, and NF-κB activation, which in turn protect bone loss from ovariectomy.

Polyketide derivatives active against Botrytis cinerea in Gerbera hybrida

A previously isolated cDNA molecule from Gerbera hybrida (Asteraceae) codes for a new chalcone synthase-like polyketide synthase, 2-pyrone synthase (2PS). 2PS is able to synthesise 4-hydroxy-6-methyl-2-pyrone (triacetolactone), a putative precursor for gerberin and parasorboside, two abundant glucosides in gerbera. In this study, we show that gerbera plants transformed with the gene for 2PS in an antisense orientation and unable to synthesise gerberin and parasorboside are susceptible to Botrytis cinerea infection. In addition to the preformed glucosides, the transgenic plants also lack several compounds that are induced in control plants when infected with the mould. Some of these induced substances are effective in inhibiting fungal growth both in vitro and in vivo. Two of the phytoalexins were identified as the aglycones of gerberin and trans-parasorboside. The third phytoalexin is a rare coumarin, 4-hydroxy-5-methylcoumarin; however, it is typical of many plants of the sunflower family Asteraceae. The coumarin cannot be structurally derived from either gerberin or parasorboside, but may be derived from a related polyketide intermediate.

Lactones from Angiopteris caudatiformis

Angiopterlactones A (1) and B (2), two unique lactones, and three known lactones, osmundalactone (3), osmundalin (4), and 3,5-dihydroxy-gamma-caprolactone (5), have been isolated from the rhizome of Angiopteris caudatiformis. The structures of 1 and 2 were determined by NMR and MS methods, and the structure of 2 was confirmed by X-ray crystallography. The absolute configurations of 1 and 2 were assigned by application of the CD excitation chirality method and the modified Mosher's method. Compound 1 was slightly cytotoxic against HeLa cells, with an IC(50) value of 68.8 microM, and compounds 3 and 4 showed moderate insect antifeeding activity against Plutella xylostella and Heliothis virescens.

Caffeoyl arbutin and related compounds from the buds of Vaccinium dunalianum

Dunalianosides A-I (1-9), esters of arbutin and related phenolic glucosides, were isolated from the buds of Vaccinium dunalianum Wight (Ericaceae) together with 20 known compounds, and their structures were established on the basis of 1- and 2D NMR spectroscopic evidence. Dunalianosides F-H were dimers of p-hydroxyphenyl 6-O-trans-caffeoyl-beta-D-glucopyranoside (10). The latter was obtained in extraordinary high yield (22% of dry weight), and dunalianoside I (9) was found to be a conjugate of arbutin with an iridoid glucoside.

Mining plant diversity: Gerbera as a model system for plant developmental and biosynthetic research

Gerbera hybrida is a member of the large sunflower family (Asteraceae). Typical of Asteraceae, Gerbera bears different types of flowers in its inflorescence. The showy marginal flowers comprise elongate, ligulate corollas that are female, whereas the central and inconspicuous disc flowers are complete, with both male and female organs. As such, Gerbera offers great potential for comparative developmental research within a single genotype. Moreover, different Gerbera varieties show an impressive spectrum of color patterns, directly displaying responses to developmental cues at all important morphological levels (flower type, flower organ and within organs). Further, Gerbera harbors an arsenal of Asteraceae-type secondary metabolites, not present in other model plants. With powerful reverse genetics methods, a large collection of EST sequences and a new cDNA microarray, Gerbera has become a model plant of the sunflower family.

Mild and efficient method for the cleavage of benzylidene acetals by using erbium (iii) triflate

Er(OTf)3 is proposed as new efficient Lewis acid catalyst in a mild deprotection protocol of benzylidene derivatives. In a modified procedure, where acetic anhydride is used as the reaction solvent, the simultaneous cleavage of the benzylidene acetal and the peracetylation of the substrates is obtained in quantitative yields and very short reaction times.

Chemical constituents from the Hydrangea chinensis

Two quinazolone alkaloids, (+)-febrifugine (1) and isofebrifugine (2), along with three coumarin derivatives, 6-hydroxy coumarin (3), skimmin (5), and umbelliferone-7-O-alpha-L-rhamnopyranosyl(1-->4)-beta-D-glucopyranoside (6), were isolated from the roots of Hydrangea chinensis. Compound 6 is a new compound. In addition, umbelliferone (4), linoleic acid (7), two steroidal glycosides (8, 9), three furfural derivatives (10-12), and butyl-beta-D-fructofuranoside (13) were isolated from the leaves of the same plant. The structures of all isolates were elucidated by spectral methods.

Application of centrifugal force to the extraction and separation of parasorboside and gerberin from Gerbera hybrida

A method for the separation of parasorboside and gerberin from the ornamental plant Gerbera hybrida (Asteraceae) has been developed. The two closely related glucosides were extracted using an Extrachrom instrument, a prototype multi-functional separation tool equipped with an extraction chamber. The rotation planar extraction procedure was compared with that of a medium pressure solid-liquid extraction system. The resulting extracts were pre-purified using rotation planar chromatography and the results compared with those obtained using medium pressure liquid chromatography with silica gel as the stationary phase and a mobile phase of methanol:ethyl acetate:tetrahydrofuran at selectivity point Ps = 111 with 1% formic acid as modifier. The title compounds were isolated from the purified extracts by TLC and their structures confirmed by 1H- and 13C-NMR spectroscopy.

New glycosides from the Japanese fern Hymenophyllum barbatum

Thirteen glycosides and methyl (3R,5R)-5-hydroxy-(beta-D-glucopyranosyloxy)-hexanoate were newly isolated from the Japanese fern Hymenophyllum barbatum, although our previous work revealed the isolation of hemiterpene glycosides, hymenosides A-J, from the same species. The structures of the newly isolated glycosides were elucidated by extensive two-dimensional (2D) NMR and/or chemical evidence. The structures of those aglycones were divided into four types, 2-methyl-but-2-ene-1,4-diol, 2-hydroxymethyl-but-2-ene-1,4-diol, 2-methylene-butane-1,3,4-triol, and 3-hydroxy-5-hexanolide. The sugar moieties, which were acylated by phenylacetic acid derivatives, were also established by chemical and spectroscopic methods. Eight glucosides of the isolated compounds in the present investigation had a bitter or weakly pungent taste. It is clear that a phenylacetyl group attached to glucose or allose as an ester is necessary for the bitter taste.

New bitter-tasting hemiterpene glycosides from the Japanese fern Hymenophyllum barbatum

Hymenosides G--J were newly isolated from the Japanese fern Hymenophyllum barbatum, in addition to hymenosides A--F. The structures of hymenosides were elucidated by extensive two-dimensional nuclear magnetic resonance and/or chemical evidence. The structures of those aglycones were divided into three types, 1,4-dihydroxy-2-hydroxymethyl-but-2-ene, 1,4-dihydroxy-2-methyl-but-2-ene, and 3-hydroxy-5-hexanolide. The sugar moieties were also established by chemical and spectroscopic methods, which were acylated by phenylacetic acid derivatives. These glycosides had a bitter or weakly pungent taste.

Flavone C-glycosides from Scleranthus uncinatus

Two flavone C-glycosides, 5,7,4'-trihydroxy-3'-methoxyflavone-8-C-beta-D-xylopyranoside-2"-O-glucoside, 5,7-dihydroxy-3'-methoxy-4'-acetoxyflavone-8-C-beta-D- xylopyranoside-2"-O-glucoside and one known maltol beta-D-glucopyranoside were isolated for the first time from the Scleranthus uncinatus and their structures deduced by high field 1D and 2D 400 MHz NMR and (+) FAB-MS spectra.

Structural control of polyketide formation in plant-specific polyketide synthases

BACKGROUND

Polyketide synthases (PKSs) generate molecular diversity by utilizing different starter molecules and by controlling the final length of the polyketide. Although exploitation of this mechanistic variability has produced novel polyketides, the structural foundation of this versatility is unclear. Plant-specific PKSs are essential for the biosynthesis of anti-microbial phytoalexins, anthocyanin floral pigments, and inducers of Rhizobium nodulation genes. 2-Pyrone synthase (2-PS) and chalcone synthase (CHS) are plant-specific PKSs that share 74% amino acid sequence identity. 2-PS forms the triketide methylpyrone from an acetyl-CoA starter molecule and two malonyl-CoAs. CHS uses a p-coumaroyl-CoA starter molecule and three malonyl-CoAs to produce the tetraketide chalcone. Our goal was to elucidate the molecular basis of starter molecule selectivity and control of polyketide length in this class of PKS.

RESULTS

The 2.05 A resolution crystal structure of 2-PS complexed with the reaction intermediate acetoacetyl-CoA was determined by molecular replacement. 2-PS and CHS share a common three-dimensional fold, a set of conserved catalytic residues, and similar CoA binding sites. However, the active site cavity of 2-PS is smaller than the cavity in CHS. Of the 28 residues lining the 2-PS initiation/elongation cavity, four positions vary in CHS. Point mutations at three of these positions in CHS (T197L, G256L, and S338I) altered product formation. Combining these mutations in a CHS triple mutant (T197L/G256L/S338I) yielded an enzyme that was functionally identical to 2-PS.

CONCLUSIONS

Structural and functional characterization of 2-PS together with generation of a CHS mutant with an initiation/elongation cavity analogous to 2-PS demonstrates that cavity volume influences the choice of starter molecule and controls the final length of the polyketide. These results provide a structural basis for control of polyketide length in other PKSs, and suggest strategies for further increasing the scope of polyketide biosynthetic diversity.

The glycosidic precursor of (Z)-5-ethylidene-2(5H)-furanone in Halocarpus biformis juvenile foliage

A new glycosidic lactone, (5R,6R)-5-(1-hydroxyethyl)-2(5H)-furanone beta-D-glucopyranoside, has been identified as the principal precursor of (Z)-5-ethylidene-2(5H)-furanone in juvenile foliage of the New Zealand tree Halocarpus biformis. Three related lactone glycosides were isolated in smaller amounts, together with the known phenolic glycosides pyroside, arbutin and picein. The principal lactone glycoside underwent facile elimination of glucose, in neutral or basic conditions, to yield (Z)-5-ethylidene-2(5H)-furanone and its E-isomer. This lactone glycoside was also detected in foliage of H. bidwillii and H. kirkii.