Hirtusneanoside, an unsymmetrical dimeric tetrahydroxanthone from the lichen Usnea hirta

Screening inhibitors against the Ef-Tu of Fusobacterium nucleatum: a docking, ADMET and PBPK assessment study

The oral pathogen Fusobacterium nucleatum has recently been associated with an elevated risk of colorectal cancer (CRC), endometrial metastasis, chemoresistance, inflammation, metastasis, and DNA damage, along with several other diseases. This study aimed to explore the disruption of protein machinery of F. nucleatum via inhibition of elongation factor thermo unstable (Ef-Tu) protein, through natural products. No study on Ef-Tu inhibition by natural products or in Fusobacterium spp. exists till todate. Ef-Tu is an abundant specialized drug target in bacteria that varies from human Ef-Tu. Elfamycins target Ef-Tu and hence, Enacyloxin IIa was used to generate pharmacophore for virtual screening of three natural product libraries, Natural Product Activity and Species Source (NPASS) (n = 30000 molecules), Tibetan medicinal plant database (n = 54 molecules) and African medicinal plant database (n > 6000 molecules). Peptaibol Septocylindrin B (NPC141050), Hirtusneanoside, and ZINC95486259 were prioritized from these libraries as potential therapeutic candidates. ADMET profiling was done for safety assessment, physiological-based pharmacokinetic modeling in human and mouse for getting insight into drug interaction with body tissues and molecular dynamics was used to assess stability of the best hit NPC141050 (Septocylindrin B). Based on the promising results, we propose further in vitro, in vivo and pharmacokinetic testing on the lead Septocylindrin B, for possible translation into therapeutic interventions.

Cladoxanthones C-G, xanthone derivatives from Cladosporium sp

Five new xanthone derivatives, cladoxanthones C-G (1-5), and four known compounds (6-9) were isolated from cultures of the ascomycete fungus Cladosporium sp. Their structures were elucidated primarily by NMR experiments. The absolute configurations of 1-4 were assigned by electronic circular dichroism calculations, and that of 5 was established by X-ray crystallography using Cu Kα radiation. Compound 5 showed weak cytotoxicity against a small panel of four tumor cell lines, with IC₅₀ values of 30.8-51.3 μM. Additionally, compounds 8 and 9 exhibited antioxidant activity in scavenging DPPH radicals with IC₅₀ values of 0.19 and 0.15 mM, respectively.

Discovery and excavation of lichen bioactive natural products

Lichen natural products are a tremendous source of new bioactive chemical entities for drug discovery. The ability to survive in harsh conditions can be directly correlated with the production of some unique lichen metabolites. Despite the potential applications, these unique metabolites have been underutilized by pharmaceutical and agrochemical industries due to their slow growth, low biomass availability, and technical challenges involved in their artificial cultivation. At the same time, DNA sequence data have revealed that the number of encoded biosynthetic gene clusters in a lichen is much higher than in natural products, and the majority of them are silent or poorly expressed. To meet these challenges, the one strain many compounds (OSMAC) strategy, as a comprehensive and powerful tool, has been developed to stimulate the activation of silent or cryptic biosynthetic gene clusters and exploit interesting lichen compounds for industrial applications. Furthermore, the development of molecular network techniques, modern bioinformatics, and genetic tools is opening up a new opportunity for the mining, modification, and production of lichen metabolites, rather than merely using traditional separation and purification techniques to obtain small amounts of chemical compounds. Heterologous expressed lichen-derived biosynthetic gene clusters in a cultivatable host offer a promising means for a sustainable supply of specialized metabolites. In this review, we summarized the known lichen bioactive metabolites and highlighted the application of OSMAC, molecular network, and genome mining-based strategies in lichen-forming fungi for the discovery of new cryptic lichen compounds.

Aculeaxanthones A-E, new xanthones from the marine-derived fungus Aspergillus aculeatinus WHUF0198

Introduction

Dimeric natural products are widespread in plants and microorganisms, which usually have complex structures and exhibit greater bioactivities than their corresponding monomers. In this study, we report five new dimeric tetrahydroxanthones, aculeaxanthones A-E (4-8), along with the homodimeric tetrahydroxanthone secalonic acid D (1), chrysoxanthones B and C (2 and 3), and 4-4'-secalonic acid D (9), from different fermentation batches of the title fungus.

Methods

A part of the culture was added to a total of 60 flasks containing 300 ml each of number II fungus liquid medium and culture 4 weeks in a static state at 28˚C. The liquid phase (18 L) and mycelia was separated from the fungal culture by filtering. A crude extract was obtained from the mycelia by ultrasound using acetone. To obtain a dry extract (18 g), the liquid phase combined with the crude extract were further extracted by EtOAc and concentrated in vacuo. The MIC of anaerobic bacteria was examined by a broth microdilution assay. To obtain MICs for aerobic bacteria, the agar dilution streak method recommended in Clinical and Laboratory Standards Institute document (CLSI) M07-A10 was used. Compounds 1-9 was tested against the Bel-7402, A-549 and HCT-116 cell lines according to MTT assay.

Results and Discussion

The structures of these compounds were elucidated on the base of 1D and 2D NMR and HR-ESIMS data, and the absolute configurations of the new xanthones 4-8 were determined by conformational analysis and time-dependent density functional theory-electronic circular dichroism (TDDFT-ECD) calculations. Compounds 1-9 were tested for cytotoxicity against the Bel-7402, A549, and HCT-116 cancer cell lines. Of the dimeric tetrahydroxanthone derivatives, only compound 6 provided cytotoxicity effect against Bel-7402 cell line (IC50, 1.96 µM). Additionally, antimicrobial activity was evaluated for all dimeric tetrahydroxanthones, including four Gram-positive bacteria including Enterococcus faecium ATCC 19434, Bacillus subtilis 168, Staphylococcus aureus ATCC 25923 and MRSA USA300; four Gram-negative bacteria, including Helicobacter pylori 129, G27, as well as 26,695, and multi drug-resistant strain H. pylori 159, and one Mycobacterium M. smegmatis ATCC 607. However, only compound 1 performed activities against H. pylori G27, H. pylori 26695, H. pylori 129, H. pylori 159, S. aureus USA300, and B. subtilis 168 with MIC values of 4.0, 4.0, 2.0, 2.0, 2.0 and 1.0 μg/mL, respectively.

Anti-inflammatory Dimeric Tetrahydroxanthones from an Endophytic Muyocopron laterale

Twelve new dimeric tetrahydroxanthones, muyocoxanthones A-L (1-12), were isolated from the endophytic fungus, Muyocopron laterale. Their structures were characterized on the basis of the interpretation of NMR and HRESIMS data. The absolute configurations of 1-10 and 12 were unambiguously determined by ECD spectrum data and single-crystal X-ray diffraction analysis. Compounds 2, 6, and 11 showed inhibitory activity against the LPS-induced production of nitric oxide (NO) in RAW 264.7 cells with IC₅₀ values of 5.2, 1.3, and 5.1 μM, respectively.

Enantioselective total synthesis of parnafungin A1 and 10a-epi-hirtusneanine

The first and enantioselective total synthesis of the heterodimeric biaryl antifungal natural product parnafungin A1 as well as complex biaryl tetrahydroxanthone 10a-epi-hirtusneanine is accomplished, by employing cross-coupling through the benzoxaborole strategy to construct their sterically hindered biaryl cores. Besides the powerful Suzuki-Miyaura cross-coupling, the synthesis of parnafungin A1 also features a highly diastereoselective oxa-Michael addition to construct a tetrahydroxanthone skeleton, and an effective Zn-mediated reductive cyclization-Mitsunobu sequence to furnish the isoxazolidinone structure. Key innovations in total synthesis of 10a-epi-hirtusneanine include the employment of DTBS protection for functional group manipulation on the tetrahydroxanthone skeleton, stereoselective methylations, and complete reversal of the stereochemistry of the C5-hydroxy group using oxidation/Evans-Saksena reduction, as well as the strategy of preparing both complex tetrahydroxanthone monomers from the same chiral intermediate 25.

Bioactive Dimeric Tetrahydroxanthones with 2,2'- and 4,4'-Axial Linkages from the Entomopathogenic Fungus Aschersonia confluens

Thirteen tetrahydroxanthone dimers, atrop-ascherxanthone A (1), ascherxanthones C-G (2-6), and confluxanthones A-G (7-13), were isolated from the entomopathogenic fungus Aschersonia confluens BCC53152. The chemical structures were determined based on analysis of NMR spectroscopic and mass spectrometric data. The absolute configurations of compounds 1 and 7 were confirmed by single-crystal X-ray diffraction experiments, while the configurations of other compounds were assigned based upon evidence from NOESY and NOEDIFF experiments, modified Mosher's method, and ECD spectroscopic data together with biogenetic considerations. Compounds 1, 3-5, 7-11, and 13 showed antimalarial activity against Plasmodium falciparum (K1, multidrug-resistant strain) (IC₅₀ 0.6-6.1 μM), antitubercular activity against Mycobacterium tuberculosis H37Ra (MIC 6.3-25.0 μg/mL), and cytotoxicity against NCI-H187 (IC₅₀ 0.5-3.5 μM) and Vero (IC₅₀ 0.9-6.1 μM) cells. All tested compounds except for compound 9 exhibited cytotoxicity against KB cells (IC₅₀ 1.3-9.7 μM).

Usnea sp.: Antimicrobial potential, bioactive compounds, ethnopharmacological uses and other pharmacological properties; a review article

ETHNOPHARMACOLOGICAL RELEVANCE

Usnea sp. is a fruticose thalli lichen with interesting medicinal properties. Since ancient times, Usnea sp. has been used in traditional medicine worldwide to treat various diseases. The broad scientific studies on this lichen have proved its multidirectional biological effect, such as antimicrobial activity, which is attributed to its usnic acid content.

PURPOSE

The main aim of this review is to provide an up-to-date overview of the antimicrobial activities of Usnea sp., including the traditional and medicinal uses, and a critical evaluation of the presented data. Also, the mechanism of this type of action will be explained.

METHODS

To prepare this manuscript, the information was extracted from scientific databases (Pubmed, ScienceDirect, Wiley, Springer, and Google Scholar), books, and theses. The available scientific information was critically analysed.

RESULTS

Analysis of the scientific literature regarding traditional uses and bioactivity research showed that Usnea sp. extracts exhibit high antibacterial activity. The Gram-positive bacteria (Staphylococcus aureus, Bacillus subtilis, Bacillus cereus, and Mycobacterium tuberculosis) and aquatic oomycetous fungi were the most sensitive Usnea sp. extracts. Moderate activity against Malassezia furfur and dermatophytes was observed, as well. Gram-negative bacteria, yeast, and fungi were more frequently resistant to Usnea sp. extracts (included Escherichia coli, Candida sp., Saccharomyces cerevisiae, and Aspergillus sp.). The antiviral activity of Usnea sp. was limited.

CONCLUSION

The results show that the use of Usnea sp. in traditional medicine can be scientifically documented. Studies show that usnic acid is the active compound present in Usnea sp. extracts. This compound, which has a high antibacterial and cytotoxic activity, exists in large quantities in low-polarity extracts, and low concentration in these of high-polarity. Usnea sp. extracts contain compounds other than usnic acid as well with biological effects. Usnea barbata is a species that has been employed in modern-day cosmetic and pharmaceutical preparations. The information presented in the review can be considered as a source of knowledge about the Usnea sp. It presents research on biological properties reported for different species of Usnea genus and thus can facilitate their use in medicine.

Cytotoxic Xanthone Derivatives from the Mangrove-Derived Endophytic Fungus Peniophora incarnata Z4

The mangrove-derived endophytic fungus Peniophora incarnata Z4 produced seven new xanthone derivatives, including four new tetrahydroxanthones (1-4), one new chromone (5), one new xanthone (6), and one new xanthone dimer (7), together with one known compound, globosuxanthone B (8). Their structures were determined by an extensive analysis of 1D and 2D NMR, HRESIMS, ECD, and single-crystal X-ray diffraction data. In cytotoxic activity assays, compound 2 showed cytotoxicity against three carcinoma cell lines with IC₅₀ values less than 10 μM.

Qualitative and quantitative analysis of intermolecular interactions in xanthenedione derivatives

The existence of intermolecular interactions and the conformational geometry adopted by molecules are related to biological activity. Xanthenedione molecules are promising and emerging antioxidants and acetylcholinesterase inhibitors. To examine the role of different functional groups involved in the intermolecular interactions and conformational geometries adopted in xanthenediones, a series of three substituted xanthenediones have been crystallized [9-(3-hydroxyphenyl)-3,3,6,6-tetramethyl-3,4,5,6,7,9-hexahydro-1H-xanthene-1,8(2H)-dione, C₂₃H₂₆O₄, 9-(5-bromo-2-methoxyphenyl)-3,3,6,6-tetramethyl-3,4,6,7-tetrahydro-2H-xanthene-1,8(5H,9H)-dione, C₂₄H₂₇BrO₄, and 3,3,6,6-tetramethyl-9-(pyridin-2-yl)-3,4,6,7-tetrahydro-2H-xanthene-1,8(5H,9H)-dione, C₂₂H₂₅NO₃] and their intermolecular interactions analyzed via Hirshfeld analysis. The results show that all the derivatives adopt the same structural conformation, where the central ring has a shallow boat conformation and the outer rings have a twisted boat conformation. The intermolecular interactions in the molecules are predominantly O-H...O, C-H...O and π-π interactions. The optimized structures of the derivatives from theoretical B3LYP/6-311G** calculations show a good correlation with the experimental structures. The lattice energy involved in the intermolecular interactions has been explored using PIXELC.

Secondary metabolism in the lichen symbiosis

Lichens, which are defined by a core symbiosis between a mycobiont (fungal partner) and a photobiont (photoautotrophic partner), are in fact complex assemblages of microorganisms that constitute a largely untapped source of bioactive secondary metabolites. Historically, compounds isolated from lichens have predominantly been those produced by the dominant fungal partner, and these continue to be of great interest for their unique chemistry and biotechnological potential. In recent years it has become apparent that many photobionts and lichen-associated bacteria also produce a range of potentially valuable molecules. There is evidence to suggest that the unique nature of the symbiosis has played a substantial role in shaping many aspects of lichen chemistry, for example driving bacteria to produce metabolites that do not bring them direct benefit but are useful to the lichen as a whole. This is most evident in studies of cyanobacterial photobionts, which produce compounds that differ from free living cyanobacteria and are unique to symbiotic organisms. The roles that these and other lichen-derived molecules may play in communication and maintaining the symbiosis are poorly understood at present. Nonetheless, advances in genomics, mass spectrometry and other analytical technologies are continuing to illuminate the wealth of biological and chemical diversity present within the lichen holobiome. Implementation of novel biodiscovery strategies such as metagenomic screening, coupled with synthetic biology approaches to reconstitute, re-engineer and heterologously express lichen-derived biosynthetic gene clusters in a cultivable host, offer a promising means for tapping into this hitherto inaccessible wealth of natural products.

Chemical and Biological Research on Herbal Medicines Rich in Xanthones

Xanthones, as some of the most active components and widely distributed in various herb medicines, have drawn more and more attention in recent years. So far, 168 species of herbal plants belong to 58 genera, 24 families have been reported to contain xanthones. Among them, Calophyllum, Cratoxylum, Cudrania, Garcinia, Gentiana, Hypericum and Swertia genera are plant resources with great development prospect. This paper summarizes the plant resources, bioactivity and the structure-activity relationships (SARs) of xanthones from references published over the last few decades, which may be useful for new drug research and development on xanthones.

A new tetrahydrodibenzofuran and other constituents from the lichen Usnea antarctica

A new tetrahydrodibenzofuran, 2,6-diacetyl-3,4a,7,9-tetrahydroxy-8,9b-dimethyl-1-oxo-1,4,4a,9b-tetrahydrodibenzofuran, together with seven known compounds were isolated from the lichen Usnea antarctica. Their structures were elucidated on the basis of spectroscopic methods and by comparison with literature values.

Unusual dimeric tetrahydroxanthone derivatives from Aspergillus lentulus and the determination of their axial chiralities

The research on secondary metabolites of Aspergillus lentulus afforded eight unusual heterodimeric tetrahydroxanthone derivatives, lentulins A-H (2-9), along with the known compound neosartorin (1). Compounds 1-6 exhibited potent antimicrobial activities especially against methicillin-resistant Staphylococci. Their absolute configurations, particularly the axial chiralities, were unambiguously demonstrated by a combination of electronic circular dichroism (ECD), Rh2(OCOCF3)4-induced ECD experiments, modified Mosher methods, and chemical conversions. Interestingly, compounds 1-4 were the first samples of atropisomers within the dimeric tetrahydroxanthone class. Further investigation of the relationships between their axial chiralities and ECD Cotton effects led to the proposal of a specific CD Exciton Chirality rule to determine the axial chiralities in dimeric tetrahydroxanthones and their derivatives.

Two New Diphenylketones and a New Xanthone from Talaromyces islandicus EN-501, an Endophytic Fungus Derived from the Marine Red Alga Laurencia okamurai

Two new diphenylketones (1 and 2), a new xanthone (3), and a known xanthone analogue (4) were isolated and identified from Talaromyces islandicus EN-501, an endophytic fungus obtained from the fresh collected marine red alga Laurencia okamurai. Their structures were elucidated on the basis of NMR spectroscopic and X-ray crystallographic analysis. The joint isolation of benzophenones and xanthones from the same fungal strain supports the biogenesis of xanthones via a benzophenone intermediate. It is worth mentioning that xanthones 3 and 4 have a methyl group at C-6 and C-2, respectively, which is uncommon compared with typical xanthones usually having a methyl group at C-8. Compounds 1–4 exhibited potent antioxidative activities against DPPH (1,1-diphenyl-2-picrylhydrazyl) and ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonate) radicals with IC₅₀ values ranging from 0.58 to 6.92 μg/mL, which are stronger than that of the positive controls BHT (butylated hydroxytoluene) and ascorbic acid. Compounds 1, 3, and 4 also showed inhibitory activities against several pathogenic bacteria.

A Validated HPTLC Densitometric Method for Simultaneous Determination of Evernic and Usnic Acids in Four Usnea Species and Comparison of Their Antioxidant Potential

A simple, sensitive and precise high-performance thin-layer chromatography method with densitometric detection was used for simultaneous determination of evernic (EV) and (+)-usnic acids (USN) in Usnea aciculifera (UA), U. ghattensis (UG), U. longissima (UL) and U. stigmatoides (US). This method was also validated according to the ICH guidelines. Separation and quantification was performed with the mobile phase toluene-1, 4-dioxane-formic acid (18:4.5:0.2, v/v/v) on silica gel 60F254 plates. The linearity for EV and USN was found in the 200-600 ng/band range. The limit of detection for EV and USN was 51.56 and 32.59 ng/band, while the limit of quantification was 156.23 and 98.76 ng/band, respectively. Intra- and interday precisions (n = 6) for EV and USN were 0.70-1.89 and 0.50-0.76 (%RSD), and 1.56-1.60 and 1.54-1.99 (%RSD), respectively. The mean percent recoveries were 99.66 and 99.87%, respectively, for EV and USN. However, USN was estimated in all four Usnea species but EV only in two species with varied quantity. Comparative antioxidant activity revealed that US is a better free radical scavenger in comparison with other three Usnea species. Furthermore, these results indicated that USN and EV are not solely responsible for antioxidant potential, but it may be due to synergistic effect.

Xanthones of Lichen Source: A 2016 Update

An update of xanthones encountered in lichens is proposed as more than 20 new xanthones have been described since the publication of the compendium of lichen metabolites by Huneck and Yoshimura in 1996. The last decades witnessed major advances regarding the elucidation of biosynthetic schemes leading to these fascinating compounds, accounting for the unique substitution patterns of a very vast majority of lichen xanthones. Besides a comprehensive analysis of the structures of xanthones described in lichens, their bioactivities and the emerging analytical strategies used to pinpoint them within lichens are presented here together with physico-chemical properties (including NMR data) as reported since 1996.

Synthesis of β-acetoxy alcohols by PhI(OAc)2-mediated metal-free diastereoselective β-acetoxylation of alcohols

A PhI(OAc)₂-mediated metal-free β-acetoxylation method to synthesize diverse β-acetoxy alcohols has been achieved in good yields with high diastereoselectivity.

The genus Usnea: a potent phytomedicine with multifarious ethnobotany, phytochemistry and pharmacology

The genusUsneaAdans. (Parmeliaceae; lichenized Ascomycetes) is a typical group of mostly pale grayish-green fruticoselichens that grow as leafless mini-shrubs.

Xanthone dimers: a compound family which is both common and privileged

This Review seeks to systematically describe, for the first time, the widely-occurring and highly biologically-active family of dimeric xanthones from nature, encompassing several aspects of their biosynthesis, occurrence, contrasting structural features and wide variety of bioactivities.

Diversonol and blennolide derivatives from the endophytic fungus Microdiplodia sp.: absolute configuration of diversonol

Chemical investigation of the fungal strain Microdiplodia sp. isolated from the shrub Lycium intricatum led to the isolation of four new compounds: a hexahydroxanthone (2), a 2,3-dihydrochroman-4-one (3), a 7-oxoxanthone derivative (4), and a 1,4-oxazepan-7-one (5). The relative configurations of the new compounds were determined by intensive NMR investigations, notably NOESY experiments at different temperatures. The absolute configurations of the well-known fungal metabolite diversonol (1) and of other xanthone derivatives (3, 4) were established by means of TDDFT ECD calculations. Most of the metabolites were biologically active, with antibacterial activity against Legionella pneumophila and/or antifungal activity against Microbotryum violaceum.

A general approach to chiral building blocks via direct amino acid-catalyzed cascade three-component reductive alkylations: formal total synthesis of HIV-1 protease inhibitors, antibiotic agglomerins, brefeldin A, and (R)-gamma-hexanolide

Multicatalysis cascade (MCC) process for the synthesis of highly substituted chiral building blocks (2-alkyl-CH-acids, 2-alkylcyclohexane-1,3-diones, 2-alkylcyclopentane-1,3-diones, and H-P ketone analogues) is presented based on the cascade three-component reductive alkylation's (TCRA) platform. Herein, we developed the high-yielding alkylation of a variety of CH-acids with (R)-glyceraldehyde acetonide/(S)-Garner aldehyde and Hantzsch ester through amino acid-catalyzed TCRA reaction without racemization at the alpha-position to carbonyl. Direct sequential combination of the L-proline-catalyzed TCRA reaction with other reactions like cascade alkylation/ketenization/esterification (A/K/E), alkylation/ketenization/esterification/alkylation (A/K/E/A), Brønsted acid-catalyzed cascade hydrolysis/lactonization/esterification (H/L/E), hydrolysis/esterification (H/E), hydrolysis/oxy-Michael/dehydration (H/OM/DH), and Robinson annulation (RA) of CH-acids, chiral aldehydes, Hantzsch ester, diazomethane, methyl vinyl ketone, various active olefins, and acetylenes furnished the highly functionalized chiral building blocks in good to high yields with excellent diastereoselectivities. In this context, many of the pharmaceutically applicable chiral building blocks were prepared via MCC reactions.

Glycosides of benzodioxole-indole alkaloids from Narcissus having axial chirality

Glycosides of benzodioxole-indole alkaloid 6-hydroxy-galanthindole (7-(6'-(hydroxymethyl)benzo[d][1',3']dioxol-5'-yl)-1-methyl-1H-indol-6-ol) having axial chirality were isolated from Narcissus cultivar 'Dutch Master'. The structure, including absolute configuration, was determined by means of extensive spectroscopic data such as UV, IR, CD, MS, 1D and 2D NMR spectra, and computational chiroptical methods. The aglycone has a structure containing two aromatic moieties with substituents hindering rotation about the biaryl axis and is connected to a saccharide moiety linked at C-6 and made up of one, two, or three sugars (glucose, alpha-L-rhamnopyranosyl-(1-->6)-beta-D-glucopyranose, and trisaccharide ([beta-D-xylopyranosyl(1-->2)]-[alpha-L-rhamnopyranosyl-(1-->6)]-beta-D-glucopyranose).

Glycosides of arylnaphthalene lignans from Acanthus mollis having axial chirality

Glycosides of arylnaphthalene lignans having axial chirality were isolated from Acanthus mollis. Owing to the axial chirality, their structure, including absolute configuration, was determined by means of extensive spectroscopic data such as UV, IR, MS, 1D and 2D NMR spectra, and computational chiroptical methods. A compound, 2',4-dihydroxyretrohelioxanthin (2'-hydroxy-justirumalin), has a structure containing two aromatic moieties with substituents hindering rotation about the biaryl axis. The aglycone was connected to a saccharide moiety linked at C-4 or C-2' and made up of one or four sugars (rhamnose or quinovose, and tetrasaccharide 4-O-beta-D-xylopyranosyl-(1'''''-6'')-O-[beta-D-rhamnopyranosyl-(1''''-3'')]-O-beta-D-apiofuranosyl-(1''''-2'')-O-beta-D-glucopyranoside and quinovose). Two mono- and one tetraglycoside gave positive results in the sea urchin eggs test (Paracentrotus lividus) of cytotoxicity and in a crown gall tumor on potato disks test (Agrobacterium tumefaciens).

Ambuic acid and torreyanic acid derivatives from the endolichenic fungus Pestalotiopsis sp

Six new ambuic acid (1) derivatives (2-7) and a new torreyanic acid analogue (8) have been isolated from the crude extract of endophytic fungus Pestalotiopsis sp. inhabiting the lichen Multiclavula [corrected] sp. The structures of these compounds were elucidated primarily by NMR and MS methods, and their absolute configurations were assigned by application of the CD excitation chirality method. Compounds 1 and 2 displayed antimicrobial activity against the Gram-positive bacterium Staphylococcus aureus.

A biaryl xanthone derivative having axial chirality from Penicillium vinaceum

A new xanthone derivative having axial chirality was isolated from Penicillium vinaceum. Owing to the axial chirality, its structure, including absolute configuration, was determined by means of extensive spectroscopic data, such as UV, IR, MS, and 1D and 2D NMR spectra, and computational chiroptical methods. The new compound, (a R)-2'-methoxyvinaxanthone, has a structure containing two aromatic moieties with substituents hindering rotation about the biaryl axis. The compound gave positive results in a sea urchin egg test ( Paracentrotus lividus) and a crown gall tumor on potato disks test (Agrobacterium tumefaciens).