Solving the puzzle of 2-hydroxypropyl β-cyclodextrin: Detailed assignment of the substituent distribution by NMR spectroscopy

2-Hydroxypropyl-β-cyclodextrin (HPBCD) is one of the most important cyclodextrin derivatives, finding extensive applications in the pharmaceutical sector. Beyond its role as an excipient, HPBCD achieved orphan drug status in 2015 for Niemann-Pick type C disease treatment, prompting research into its therapeutic potential for various disorders. However, the acceptance of HPBCD as an active pharmaceutical ingredient may be impeded by its complex nature. Indeed, HPBCD is not a single entity with a well-defined structure, instead, it is a complex mixture of isomers varying in substituent positions and the degree of hydroxypropylation, posing several challenges for unambiguous characterization. Pharmacopoeias' methods only address the average hydroxypropylation extent, lacking a rapid approach to characterize the substituent positions on the CD scaffold. Recognizing that the distribution of substituents significantly influences the complexation ability and overall activity of the derivative, primarily by altering cavity dimensions, we present a straightforward and non-destructive method based on liquid state NMR spectroscopy to analyze the positions of the hydroxypropyl sidechains. This method relies on a single set of routine experiments to establish quantitative assignment and it provides a simple yet effective tool to disclose the substitution pattern of this complex material, utilizing easily accessible (400 MHz NMR) instrumentation.

Diterpenes Isolated from Three Different Plectranthus Sensu Lato Species and Their Antiproliferative Activities against Gynecological and Glioblastoma Cancer Cells

Fourteen diterpenes were isolated from methanol extracts of the aerial parts ofColeus comosus,Coleus forsteri "Marginatus", and Plectranthus ciliatus. The compounds belong to the abietane (1-4, 9-11, and 13), ent-clerodane (5-8), and ent-kaurane (14, 15) classes. Three new compounds were isolated from C. comosus, including 3-O-acetylornatin G (2), 3,12-di-O-acetylornatin G (3), ornatin B methyl ester (5), and ornatin F (4), for which we proposed a revised structure. The structures of the compounds were determined by comprehensive spectroscopic data analysis. The isolated diterpenes were examined in silico for their physicochemical and early ADME properties. Their antiproliferative effects were determined in vitro using human breast (MDA-MB-231 and MCF-7), cervical (HeLa), and glioblastoma (U-87 MG) cancer cell lines. The royleanone- and hydroquinone-type abietane diterpenes (9-13)exhibited the most potent antiproliferative activity against all cancer cell lines tested, particularly against glioblastoma cells, with IC50 values ranging from 1.1 to 15.6 μM.

Cyclodextrin-Enabled Enantioselective Complexation Study of Cathinone Analogs

The characteristic alkaloid component of the leaves of the catnip shrub (Catha edulis) is cathinone, and its synthetic analogs form a major group of recreational drugs. Cathinone derivatives are chiral compounds. In the literature, several chiral methods using cyclodextrins (CDs) have been achieved so far for diverse sets of analogs; however, a comprehensive investigation of the stability of their CD complexes has not been performed yet. To characterize the enantioselective complex formation, a systematic experimental design was developed in which a total number of 40 neutral, positively, and negatively charged CD derivatives were screened by affinity capillary electrophoresis and compared according to their cavity size, substituent type, and location. The functional groups responsible for the favorable interactions were identified in the case of para-substituted cathinone analog mephedrone, flephedrone, and 4-methylethcathinone (4-MEC) and in the case of 3,4-methylendioxy derivative butylone and methylenedioxypyrovalerone (MDPV). The succinylated-β-CD and subetadex exhibited the highest complex stabilities among the studied drugs. The complex stoichiometry was determined using the Job's plot method, and the complex structures were further studied using ROESY NMR measurements. The results of our enantioselective complex formation study can facilitate chiral method development and may lead to evaluate potential CD-based antidotes for cathinone analogs.

Anticholinesterase and Antityrosinase Secondary Metabolites from the Fungus Xylobolus subpileatus

Xylobolus subpileatus is a widely distributed crust fungus reported from all continents except Antarctica, although considered a rare species in several European countries. Profound mycochemical analysis of the methanol extract of X. subpileatus resulted in the isolation of seven compounds (1-7). Among them, (3β,22E)-3-methoxy-ergosta-4,6,814,22-tetraene (1) is a new natural product, while the NMR assignment of its already known epimer (2) has been revised. In addition to a benzohydrofuran derivative fomannoxin (3), four ergostane-type triterpenes 4-7 were identified. The structure elucidation of the isolated metabolites was performed by one- and two-dimensional NMR and MS analysis. Compounds 2-7 as well as the chloroform, n-hexane, and methanol extracts of X. subpileatus were evaluated for their tyrosinase, acetylcholinesterase, and butyrylcholinesterase inhibitory properties. Among the examined compounds, only fomannoxin (3) displayed the antityrosinase property with 51% of inhibition, and the fungal steroids proved to be inactive. Regarding the potential acetylcholinesterase (AChE) inhibitory activity of the fungal extracts and metabolites, it was demonstrated that the chloroform extract and compounds 3-4 exerted noteworthy inhibitory activity, with 83.86 and 32.99%, respectively. The butyrylcholinesterase (BChE) inhibitory assay revealed that methanol and chloroform extracts, as well as compounds 3 and 4, exerted notable activity, while the rest of the compounds proved to be only weak enzyme inhibitors. Our study represents the first report on the chemical profile of basidiome of the wild-growing X. subpileatus, offering a thorough study on the isolation and structure determination of the most characteristic biologically active constituents of this species.

Mixed β-γ-Cyclodextrin Branched Polymer with Multiple Photo-Chemotherapeutic Cargos

The achievement of biocompatible platforms for multimodal therapies is one of the major challenges in the burgeoning field of nanomedicine. Here, we report on a mixed β- and γ-cyclodextrin-based branched polymeric material (βγCD-NOPD) covalently integrating a nitric oxide (NO) photodonor (NOPD) within its macromolecular scaffold, and its supramolecular ensemble with a singlet oxygen (1O2) photosensitizer (PS) Zn(II) phthalocyanine (ZnPc) and the chemodrug Lenvatinib (LVB). This polymer is highly water-soluble and generates NO under visible blue light stimuli with an efficiency of more than 1 order of magnitude higher than that of the single NOPD. The PS, which in an aqueous solution is aggregated and non-photoresponsive, can be entangled in the polymeric network as a photoresponsive monomeric species. In addition, the poorly water-soluble LVB can be co-encapsulated within the polymeric host, which increases the drug solubility by more than 30-fold compared to the free drug and more than 2-fold compared with a similar branched polymer containing only βCD units. The supramolecular nanoensemble, ca. 15 nm in diameter, retains well the photochemical properties of both the NOPD and PS, which can operate in parallel under light stimuli of different energies. Irradiation with blue and red light results in the photogeneration of NO and 1O2 associated with red fluorescence emission, without inducing any photodegradation of LVB. This result is not trivial and is due to the absence of significant, mutual interactions between the NOPD, the PS and LVB both in the ground and excited states, despite these components are confined in the same host. The proposed polymeric nanoplatform may represent a potential trimodal nanomedicine for biomedical research studies, since it combines the double photodynamic action of NO and 1O2, two species that do not suffer multidrug resistance, with the therapeutic activity of a conventional chemodrug.

Characterization of alkaloid profile of Hyoscyamus reticulatus L. and Atropa belladonna subsp. caucasica (Kreyer) Avet by LC-MS and NMR

The alkaloid profile of Hyoscyamus reticulatus L. and Atropa belladonna subsp. caucasica (Kreyer) Avet have not been characterized yet. UHPLC-PDA-Q-TOF-MS/MS and LC-DAD-QqQ-MS/MS methods were used herein to characterize the metabolite profiles of these plants. Flash chromatography in combination with preparative- and semi preparative HPLC were utilized for the isolation of the compounds of interest. The structure of the isolated compounds was proposed based on their MS/MS fragmentation and NMR characteristics. As a total of 19 tropane derivatives, two tyramine derivatives (N-cis- and N-trans- feruloyl tyramine), a lignanamide (grossamide), an alkylamide (pellitorine) were identified in the root and herb extracts of H. reticulatus. Moreover, rutin and caffeoylquinic acids were found in the leaves and fruits, while kaempferol-3-O-glucoside-7-O-rhamnoside and quercetin-3-O-glucoside-rhamnoside-rhamnoside were exclusively characteristic for the leaves of H. reticulatus. The root and herb extracts of A. caucasica contained 16 tropane alkaloid derivatives along with methyl tropate and two tyramine derivatives.

Polyporenic Acids from the Mushroom Buglossoporus quercinus Possess Chemosensitizing and Efflux Pump Inhibitory Activities on Colo 320 Adenocarcinoma Cells

Polyporenic acids N-R (1-5), five novel 24-methylene lanostane triterpenes along with seven known polyporenic acids (6-12), were identified from the fruiting bodies of Buglossoporus quercinus. The isolation of compounds 1-12 was performed by a combination of multistep flash chromatography and reversed-phase high-performance liquid chromatography (HPLC). The structure determination was carried out by extensive spectroscopic analysis, including 1D and 2D nuclear magnetic resonance (NMR) and high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) experiments. The isolated fungal metabolites were investigated for their antiproliferative activity in vitro by 3-(4,5-dimethylthiazol2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay on the resistant Colo 320 human colon adenocarcinoma cell line expressing P-glycoprotein (ABCB1). The lanostane triterpenes exerted moderate antiproliferative activity with IC50 values in the range of 20.7-106.2 μM. A P-glycoprotein efflux pump modulatory test on resistant Colo 320 cells highlighted that fungal metabolites 3, 5, 8, and 10-12 have the ability to inhibit the efflux pump activity of cancer cells. Moreover, the drug interactions of triterpenes with doxorubicin were studied by the checkerboard method. Compounds 3-4, and 7-12 interacted in a synergistic manner, while an outstanding potency was detected for compound 9, which was defined as strong synergism (CI = 0.276). The current study reveals that B. quercinus is a remarkable source of fungal steroids with considerable chemosensitizing activity on cancer cells.

A cyclodextrin polymer as supramolecular matrix for scalable green photooxygenation of hydrophobic substrates in homogeneous phase

In the quest for new therapies targeting hypoxia, aromatic endoperoxides have intriguing potential as oxygen releasing agents (ORAs) able to free O2 in tissues upon suitable trigger. Four aromatic substrates were synthesized and the formation of their corresponding endoperoxides was optimized in organic solvent upon selective irradiation of Methylene Blue, a low-cost photocatalyst, producing the reactive singlet oxygen species. Complexation of the hydrophobic substrates within a hydrophilic cyclodextrin (CyD) polymer allowed their photooxygenation in homogeneous aqueous environment using the same optimized protocol upon dissolution in water of the three readily accessible reagents. Notably, reaction rates were comparable in buffered D2O and organic solvent and, for the first time, the photooxygenation of highly hydrophobic substrates was achieved for millimolar solutions in non-deuterated water. Quantitative conversion of the substrates, straightforward isolation of the endoperoxides and recovery of the polymeric matrix were achieved. Cycloreversion of one ORA to the original aromatic substrate was observed upon thermolysis. These results hold great potential for the launch of CyD polymers both as reaction vessels for green, homogeneous photocatalysis and as carrier for the delivery of ORAs in tissues.

Analysis of 3-nitropropionic acid in Fabaceae plants by HPLC-MS/MS

INTRODUCTION

3-Nitropropionic acid (3-NPA) is a toxic compound that can accumulate in esterified form in the Fabaceae family. In the Lotae tribe, many species have been identified as 3-NPA producers (e.g., Securigera varia), while some of the genetically close Lotae plants were formerly reported as 3-NPA-free (e.g., Lotus corniculatus and Anthyllis vulneraria). These plants are used as forage and have a tradition in ethnomedicine, also, the extracts of A. vulneraria are used in cosmetics.

OBJECTIVES

Our aim was to investigate the 3-NPA content of these selected Fabaceae species and to develop a validated quantitative method to evaluate 3-NPA concentrations in extracts of different herbal parts and cosmetic products.

MATERIALS AND METHODS

A UHPLC-ESI-Orbitrap-MS/MS method was applied for detection and identification of 3-NPA derivatives in the form of glucose esters. For the quantitative analysis, an optimized sample processing method was developed. The free 3-NPA content was determined using HPLC-ESI-MS/MS.

RESULTS

3-NPA esters could be detected in all three species, but their quantity showed a high variation. S. varia contained 0.5-1.0 g/100 g of 3-NPA, while in L. corniculatus samples only trace quantities were detectable, below the LOQ (25 ng/ml). Most of the A. vulneraria samples showed similarly low concentrations, but one sample had 3-NPA levels comparable to S. varia. 3-NPA could not be detected in the tested cosmetics containing A. vulneraria extracts.

CONCLUSIONS

Using highly sensitive analytical methods, new 3-NPA-containing species were identified. The developed validated quantitative method is suitable for the determination of 3-NPA concentrations in herbal samples.

High-performance thin-layer chromatography - antibacterial assay first reveals bioactive clerodane diterpenes in giant goldenrod (Solidago gigantea Ait.)

The present work introduces a high-performance thin-layer chromatography (HPTLC)-direct bioautography method using the Gram-positive plant pathogenic bacterium, Rhodococcus fascians. The screening and isolation procedure comprised of a non-targeted high-performance thin-layer chromatography-effect-directed analysis (HPTLC-EDA) against Bacillus subtilis, B. subtilis subsp. spizizenii, R. fascians, and Aliivibrio fischeri, a targeted HPTLC-mass spectrometry (MS), and bioassay-guided column chromatographic (preparative flash and semi-preparative HPLC) fractionation and purification. The developed new separation methods enabled the discovery of four bioactive cis-clerodane diterpenes, solidagoic acid H (1), solidagoic acid E (2), solidagoic acid I (3), and solidagoic acid F (4), in the n-hexane extract of giant goldenrod (Solidago gigantea Ait.) leaf for the first time. These compounds were identified by 1D and 2D nuclear magnetic resonance (NMR) spectroscopy. The initially used HPTLC method (chloroform - ethyl acetate - methanol 15:3:2, V/V/V) was changed (to n-hexane - isopropyl acetate - methanol - acetic acid 29:20:1:1, V/V/V/V) to achieve the separation of the closely related isomer pairs (1-2 and 3-4). Compounds 1 and 3 exhibited moderate antibacterial activity against the Gram-positive B. subtilis subsp. spizizenii and R. fascians bacterial strains in microdilution assays with half-maximal inhibitory concentration (IC₅₀) values in the range of 32.3-64.4 µg/mL. The mass spectrometric fragmentation of the isolated compounds was interpreted and their previously published NMR assignments lacking certain resonances were completed.

Az Ephedrae herba helye a nyugati orvoslásban

Összefoglaló. A Magyar és az Európai Hypertonia Társaság legújabb ajánlásában a gyógyszer okozta szekunder hypertoniák gyakoribb okai között szerepel az Ephedra – csikófark (kínai nevén Mahuang) fajok drogjának (Ephedrae herba) felhasználása is. Összefoglaló közleményünk célja az Ephedra nemzetségbe tartozó, a gyógyászatban is felhasznált, a VIII. Magyar Gyógyszerkönyvben és a Kínai Gyógyszerkönyvben szereplő hivatalos fajoknak a részletes bemutatása. Betekintést nyújtunk történetükbe, továbbá leírjuk a bennük található vegyületek farmakológiai tulajdonságait és azok hatásait. Ismertetjük előnyeiket, mellékhatásaikat és lehetséges gyógyszerkölcsönhatásaikat. Ezenkívül feltárjuk fogyasztó- és testsúlycsökkentő szerként való használatukat, étrend-kiegészítőként történő alkalmazásuk betiltásának okát, valamint tárgyaljuk a doppinglistán való szereplésük magyarázatát is. Ezzel párhuzamosan kitérünk az Ephedra fajok orvosi gyakorlatban betöltött szerepére is: rendeltetésszerű használatuk során a fitoterápiában – főleg kombinációban alkalmazva – számos jótékony hatás érhető el, de fontos hangsúlyozni óvatos használatukat és felismerni lehetséges mellékhatásaikat. Orv Hetil. 2022; 163(9): 343–349.

Summary. The Hungarian and the European Society of Hypertension guidelines mention Ephedrae herba, the drug of Ephedra species (in Chinese “Mahuang”) as one of the causes of secondary hypertension. The aim of our summary is to characterize the Ephedra species used in medicine (based on the VIII. Hungarian and the Chinese Pharmacopoeia), describe their history and their components alongside with possible pharmacological effects, benefits, side-effects, and interactions with other drugs. We demonstrate the herb’s history from being a popular weight-loss product to being prohibited as a dietary supplement and citing it in the World Anti-Doping Agency’s list. At the same time, we explain the role of the Ephedra species in the everyday medical practice. It is important to know their benefits in detail as used in combination with other herbs in phytotherapy, and recognize their possible side effects. Orv Hetil. 2022; 163(9): 343–349.

Isolation and quantification of diarylheptanoids from European hornbeam (Carpinus betulus L.) and HPLC-ESI-MS/MS characterization of its antioxidative phenolics

Detailed polyphenol profiling of European hornbeam (Carpinus betulus L.) bark, leaf, male and female catkin extracts was performed by high-performance liquid chromatography-diode array detection coupled to tandem mass spectrometry (HPLC-DAD-MS/MS). A total of 194 compounds were characterized and tentatively identified. Gallo- and ellagitannins dominated in the methanol extracts, while flavonol glycosides and methoxylated flavones prevailed in the ethyl acetate samples. In the quest for diarylheptanoids, twelve compounds were isolated by the combination of subsequent reversed-phase flash chromatographic and high-performance liquid chromatographic methods. The structural elucidation of the isolated components was performed by ultrahigh-performance liquid chromatography-Orbitrap mass spectrometry (UHPLC-Orbitrap-MS) as well as 1D and 2D nuclear magnetic resonance (NMR) spectroscopy. Six known cyclic diarylheptanoids, together with a new compound were described in Carpinus betulus for the first time. The occurrence of a linear diarylheptanoid and a lignan has also been unprecedented in the genus Carpinus. Moreover, three known flavonol glycosides were isolated. Based on the identification of characteristic fragment ions, a new mass spectrometric fragmentation pathway for meta,meta-cyclophane-type diarylheptanoids was proposed. Quantities of the four major cyclic diarylheptanoids in European hornbeam were determined by a validated UHPLC-DAD method for the first time. The antioxidant properties of the extracts and the isolated compounds were assessed by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. Contribution of the individual constituents to the total radical scavenging activity of the samples was evaluated by an off-line DPPH-HPLC-DAD method. This allowed the identification of gallo- and ellagitannin derivatives as the constituents being primarily responsible for the antioxidant capacity of the extracts.

Antimicrobial, Antioxidant and Antiproliferative Secondary Metabolites from Inonotus nidus-pici

Inonotus nidus-pici is a sterile conk which produces macrofungus, a neglected Central-Eastern European relative of the prized Inonotus obliquus, also known as chaga. Investigation of the methanol extract of the poroid fungus I. nidus-pici resulted in the isolation of citropremide (1), 3,4-dihydroxybenzalacetone (2) , lanosterol (3), ergost-6,8,22-trien-3β-ol (4), and ergosterol peroxide (5). The structures of fungal compounds were determined on the basis of one- and two-dimensional NMR and MS spectroscopic analysis. Compounds 1–2 and 4–5 were evaluated for their antioxidant and antimicrobial properties against several bacterial and fungal strains. 3,4-dihydroxybenzalacetone (2) and ergost-6,8,22-trien-3β-ol (4) demonstrated moderate antimicrobial activity, while the former possessed notable antioxidant activity in DPPH assay. The antiproliferative examinations performed on three human cancer (MES-SA, MES-SA/Dx5, A431) cell lines demonstrated that compounds 4 and 5 have notable cytotoxic activity with IC values in micromolar range. The current study represents the first report on the chemical profile of I. nidus-pici, providing a comprehensive study on the isolation and structure determination of bioactive secondary metabolites of this macrofungus.

Single Isomer N-Heterocyclic Cyclodextrin Derivatives as Chiral Selectors in Capillary Electrophoresis

In order to better understand the chiral recognition mechanisms of positively charged cyclodextrin (CD) derivatives, the synthesis, the pKa determination by 1H nuclear magnetic resonance (NMR)-pH titration and a comparative chiral capillary electrophoretic (CE) study were performed with two series of mono-substituted cationic single isomer CDs. The first series of selectors were mono-(6-N-pyrrolidine-6-deoxy)-β-CD (PYR-β-CD), mono-(6-N-piperidine-6-deoxy)-β-CD (PIP-β-CD), mono-(6-N-morpholine-6-deoxy)-β-CD (MO-β-CD) and mono-(6-N-piperazine-6-deoxy)-β-CD (PIPA-β-CD), carrying a pH-adjustable moiety at the narrower rim of the cavity, while the second set represented by their quaternarized, permanently cationic counterparts: mono-(6-N-(N-methyl-pyrrolidine)-6-deoxy)-β-CD (MePYR-β-CD), mono-(6-N-(N-methyl-piperidine)-6-deoxy)-β-CD (MePIP-β-CD), mono-(6-N-(N-methyl-morpholine)-6-deoxy)-β-CD (MeMO-β-CD) and mono-(6-N-(4,4-N,N-dimethyl-piperazine)-β-CD (diMePIPA-β-CD). Based on pH-dependent and selector concentration-dependent comparative studies of these single isomer N-heterocyclic CDs presented herein, it can be concluded that all CDs could successfully be applied as chiral selectors for the enantiodiscrimination of several negatively charged and zwitterionic model racemates. The substituent-dependent enantiomer migration order reversal of dansylated-valine using PIP-β-CD contrary to PYP-β-CD, MO-β-CD and PIPA-β-CD was also studied by 1H- and 2D ROESY NMR experiments.

Quantitative determination of isoflavonoids in Ononis species by UPLC-UV-DAD

INTRODUCTION

The root of the Ononis species has been used internally and externally in ethnomedicine for centuries and contains biologically valuable isoflavonoid compounds. Therefore, it is important to obtain quantitative information about the isoflavonoid profile of these plants.

OBJECTIVES

In this article we aimed to develop an optimised sample preparation protocol alongside a validated method for the quantitative measurement of isoflavones, isoflavanones and pterocarpans in the form of glucosides and aglycones, in order to compare the specialised metabolites of Ononis spinosa L. and O. arvensis L.

MATERIAL AND METHODS

Quantitative determination was carried out by the means of ultra-performance liquid chromatography coupled with ultraviolet diode-array detection (UPLC-UV-DAD).

RESULTS

An optimised sample preparation method was developed to transform malonyl glucosides to their glucosidic forms. Chromatographic methods were created for the baseline separation of isoflavones, isoflavanones and pterocarpans alongside with their glucosides. Altogether 12 compounds were evaluated quantitatively in samples of O. spinosa and O. arvensis.

CONCLUSION

As a result, no characteristic change could be observed between the two species regarding their isoflavonoid pattern.

Enantioseparation of solriamfetol and its major impurity phenylalaninol by capillary electrophoresis using sulfated gamma cyclodextrin

R-solriamfetol is a recently approved drug used for the treatment of excessive sleepiness associated with narcolepsy and sleep apnea. Herein, a capillary electrophoretic method was developed, enabling the simultaneous analysis of the API and its S-enantiomer in addition to the enantiomers of its major impurity phenylalaninol. Twenty-nine different cyclodextrins (CDs), including native, neutral, and charged ones were screened as potential chiral selectors, and the best results were obtained with sulfated CDs. Randomly sulfated-β-CD exhibited outstanding enantioresolution, the peaks of phenylalaninol enantiomers inserted between the two peaks of solriamfetol enantiomers, while sulfated-γ-CD (S-γ-CD) showed remarkable resolution values in a much shorter analysis time with the optimal enantiomer migration order. Among the single isomer sulfated CD derivatives, substituent dependent enantiomer migration order reversal could also be observed in the case of heptakis(6-O-sulfo)-β-CD (HS-β-CD) or heptakis(2,3-O-dimethyl-6-O-sulfo)-β-CD (HDMS-β-CD) with R-,S-solriamfetol, and heptakis(2,3-O-diacetyl-6-O-sulfo)-β-CD (HDAS-β-CD) resulting S-,R-solriamfetol migration order. The sulfated-γ-CD system was chosen for method optimization applying orthogonal experimental design. The optimized method (45 mM Tris-acetate buffer, pH 4.5, 4 mM S-γ-CD, 21°C, +19.5 kV) was capable for the baseline separation of solriamfetol and phenylalaninol enantiomers within 7 min. The optimized method was validated according to the ICH guidelines and successfully applied for the analysis of pharmaceutical preparation (Sunosi^® 75 mg tablet), thus it may serve as a routine procedure for the laboratories of regulatory authorities as well as in Pharmacopoeias.

Sulfobutylether-beta-cyclodextrin-enabled antiviral remdesivir: Characterization of electrospun- and lyophilized formulations

Veklury™ by Gilead Sciences, Inc., containing antiviral drug, remdesivir (REM) has received emergency authorization in the USA and in Europe for COVID-19 therapy. Here, for the first time, we describe details of the non-covalent, host-guest type interaction between REM and the solubilizing excipient, sulfobutylether-beta-cyclodextrin (SBECD) that results in significant solubility enhancement. Complete amorphousness of the cyclodextrin-enabled REM formulation was demonstrated by X-ray diffraction, thermal analysis, Raman chemical mapping and electron microscopy/energy dispersive spectroscopy. The use of solubilizing carbohydrate resulted in a 300-fold improvement of the aqueous solubility of REM, and enhanced dissolution rate of the drug enabling the preparation of stable infusion solutions for therapy. 2D ROESY NMR spectroscopy provided information on the nature of REM-excipient interaction and indicated the presence of inclusion phenomenon and the electrostatic attraction between anionic SBECD and nitrogen-containing REM in aqueous solution.

Structural characterization of fondaparinux interaction with per-6-amino-beta-cyclodextrin: An NMR and MS study

The highly anionic synthetic pentasaccharide fondaparinux (FDPX) - representing the antithrombin binding sequence of heparin - is in clinical use as a potent anticoagulant. Contrary to the unfractionated heparin, FDPX lacks potent antidote completely reversing its anticoagulant activity, therefore it is of great importance to identify new structures exhibiting strong intermolecular interactions towards FDPX. The polycationic heptakis(6-amino-6-deoxy)-beta-cyclodextrin (NH₂-β-CD) can serve as an excellent model compound to mimic these interactions between the oppositely charged oligosaccharides. Herein, extensive NMR spectroscopic and nano-electrospray ionization mass spectrometric (nESI-MS) studies were conducted to understand the molecular-level interactions in the FDPX - NH₂-β-CD systems. NMR experiments were performed at pD 7.4 and 2.0. Job's method of continuous variation and ¹H NMR titration experiments suggested the formation of FDPX∙NH₂-β-CD complex at pD 7.4, while the presence of multiple complexes was assumed at pD 2.0. Stability constants were determined by separate ¹H NMR titrations, yielding log β₁₁=3.65 ± 0.02 at pD 7.4, while log β₁₁ ≥ 4.9 value suggested a high-affinity system at pD 2.0. 2D NOESY NMR studies indicated spatial proximities between the anomeric resonance α-l-iduronic acid residue and the cyclodextrin's methylene unit in the proximity of the cationic amino function. Acidic degradation of FDPX was investigated by NMR and MS for the first time in detail confirming that desulfation occurs involving one to two sulfate moieties. The desulfation of FDPX was inhibited by the cationic cyclodextrin in the case of equimolar ratio at pD 2.0. This is the first report on the stabilizing effect of cyclodextrin complexation on heparin degradation.

Bioactive clerodane diterpenes of giant goldenrod (Solidago gigantea Ait.) root extract

Giant goldenrod (Solidago gigantea Ait.) root extract was screened for bioactive compounds by high-performance thin-layer chromatography (HPTLC), coupled with effect-directed analysis including antibacterial (Bacillus subtilis F1276, B. subtilis subsp. spizizenii, Aliivibrio fischeri and Xanthomonas euvesicatoria), antifungal (Fusarium avenaceum) and enzyme inhibition (acetyl- and butyrylcholinesterases, α- and β-glucosidases and α-amylase) assays. Compounds of six multipotent zones (Sg1-Sg6) were characterized by HPTLC-heated electrospray ionization-high-resolution mass spectrometry (HRMS) and HPTLC-Direct Analysis in Real Time-HRMS. Apart from zone Sg3, containing three compounds, a single characteristic compound was detectable in each bioactive zone. The bioassay-guided isolation using preparative-scale flash chromatography and high-performance liquid chromatography provided eight compounds that were identified by NMR spectroscopy as clerodane diterpenes. All isolates possessed inhibiting activity against at least one of the tested microorganisms.

Qualitative and Quantitative Phytochemical Analysis of Ononis Hairy Root Cultures

Hairy root cultures are genetically and biochemically stable, and they regularly possess the same or better biosynthetic capabilities for specialized (secondary) metabolite production compared to the intact plant. Ononis species are well-known herbal remedies in ethnopharmacology and rich sources of isoflavonoids. Besides isoflavones, less prevalent isoflavones and pterocarpans with valuable biological effects can be found in Ononis species as well. As these plants are only collected but not cultivated, biotechnological methods could play a role in the larger-scale extraction of Ononis isoflavonoids. Regarding this information, we aimed to establish Ononis spinosa and Ononis arvensis hairy root cultures (HRCs) and analyze the isoflavonoid profile of hairy root cultures qualitatively and quantitatively, in order to define their capacity to produce biologically valuable isoflavonoids. During the qualitative description, beside isoflavonoids, two new phenolic lactones, namely, bulatlactone 2″-O-β-D-glucoside and ononilactone, were isolated, and their structures were characterized for the first time. Altogether, 29 compounds were identified by the means of UPLC-Orbitrap-MS/MS. Based on UHPLC-UV-DAD measurements, the isoflavonoid spectrum of the Ononis HRCs differed markedly from wild-grown samples, as they produce a limited range of the scaffolds. The most abundant compounds in the HRCs were medicarpin glucoside and sativanone glucoside. The overall isoflavonoid production of the cultures was comparable to wild-grown O. arvensis and approximately twice as high as in wild-grown O. spinosa samples. As the overall content of wild-grown samples include more isoflavonoid derivatives, the HRCs contain structurally less divergent isoflavonoids but in higher quantity.

Variability of Bioactive Glucosinolates, Isothiocyanates and Enzyme Patterns in Horseradish Hairy Root Cultures Initiated from Different Organs

Horseradish hairy root cultures are suitable plant tissue organs to study the glucosinolate-myrosinase-isothiocyanate system and also to produce the biologically active isothiocyanates and horseradish peroxidase, widely used in molecular biology. Fifty hairy root clones were isolated after Agrobacterium rhizogenes infection of surface sterilized Armoracia rusticana petioles and leaf blades, from which 21 were viable after antibiotic treatment. Biomass properties (e.g. dry weight %, daily growth index), glucosinolate content (analyzed by liquid chromatography-electronspray ionization-mass spectrometry (LC-ESI-MS/MS)), isothiocyanate and nitrile content (analyzed by gas chromatography-mass spectrometry (GC-MS)), myrosinase (on-gel detection) and horseradish peroxidase enzyme patterns (on-gel detection and spectrophotometry), and morphological features were examined with multi-variable statistical analysis. In addition to the several positive and negative correlations, the most outstanding phenomenon was many parameters of the hairy root clones showed dependence on the organ of origin. Among others, the daily growth index, sinigrin, glucobrassicin, 3-phenylpropionitrile, indole-3-acetonitrile and horseradish peroxidase values showed significantly higher levels in horseradish hairy root cultures initiated from leaf blades.

Isolation and structural elucidation of a novel brunnein-type antioxidant β-carboline alkaloid from Cyclocybe cylindracea

Effect-directed isolation of free radical scavengers from the methanol extract of the freeze-dried fruiting bodies of the cultivated basidiomycetous mushroom, black poplar (Cyclocybe cylindracea), yielded a β-carboline alkaloid. Its structure was determined based on ESI-TOF-MS/MS, NMR and circular dichroism spectra by comparison with published data. The compound, identified as the C1-S diastereomer of brunnein B, exhibited explicit radical scavenging activity (EC₅₀ = 119.1 ± 1.2 μg/mL). The quantity of the active component was determined with HPLC-MS in the fruiting body (36.2 ± 2.8 ng/g DW, dry weight) and its different tissues such as peel (94.7 ± 1.9 ng/g DW), inner cap (90.5 ± 1.3 ng/g DW), gills (71.5 ± 0.6 ng/g DW), and stipe (162.2 ± 1.7 ng/g DW). It is a β-carboline alkaloid that was not reported previously.

Synthesis of the chiral selector heptakis(6-O-methyl)-β-cyclodextrin by phase-transfer catalysis and hydrazine-mediated transfer-hydrogenation

The exhaustive primary-side alkylation of cyclodextrins has never been achieved directly. The undesired and simultaneous derivatization of the secondary hydroxyl moieties generates intricate isomeric mixtures that are challenging to purify, analyse and characterize. The aim of this study was to develop a chromatography-free and up-scalable strategy towards the preparation of per-6-O-methylated cyclodextrin and to test the compound as potential chiral selector. The target molecule was prepared according to a five-step synthesis by using methyltriphenylphosphonium bromide as catalyst under heterogeneous conditions. The removal of benzyl moieties, used as temporary secondary-side protecting groups, was attained by applying hydrazine-carbonate in the presence of Pd/C. All the intermediates were obtained in high yields, thoroughly characterized and their purity was assessed by ad-hoc developed HPLC methods. The per-6-O-methylated β-cyclodextrin showed promising chiral recognition ability as background electrolyte additive in cyclodextrin-modified capillary electrophoresis using the recreational drug methylene-dioxypyrovalerone as model compound. Additionally, a model for the inclusion geometry between the single isomer host and the selected drug was developed based on the extensive 2D NMR analysis. The versatility of the proposed synthetic strategy opens the way to the industrial production of homogeneously primary-alkylated cyclodextrins and to their wide application in chiral separation of various drugs.

Identification of Triterpenes and β-sitosterol in the Bark of Plane Tree Extracts

Plane tree is planted as ornamental tree in urban areas. This tree naturally sheds its bark during the spring; however, the shed bark is commonly regarded as a waste material without any significant application.On the other hand, the bark of plane tree may be an important source of industrially relevant compounds, most notably betulinic acid. In our study a Supercritical Fluid Ultra Performance Convergence Chromatography (UPC2) system coupled with Evaporative Light Scattering Detector (ELSD), along with conventional HPLC, GC-MS and NMR were successfully utilized to analyze triterpenes in the extracts from the bark of plane tree. We show that not only betulinic acid, but other important triterpenes: betulin, betulinic aldehyde and β-sitosterol are also present in the extract of the plane tree bark. Among these the main compound is betulinic acid, with up to an order of magnitude larger concentration than the other constituents. The applied extraction method has a significant role on the concentration of the different compounds in the extracts. Most notably, neat scCO2 is not suitable to extract the polar betulinic acid, however betulin and betulinic aldehyde can be extracted selectively.

Homo- and hetero-difunctionalized β-cyclodextrins: Short direct synthesis in gram scale and analysis of regiochemistry

The regioselective difunctionalization of cyclodextrins (CDs) leading to derivatives amenable to further transformations is a daunting task due to challenging purification and unambiguous characterization of the obtained regioisomers with similar physicochemical properties. The primary-side homo-difunctionalization of β-CD can lead to three regioisomers, while the hetero-difunctionalization can generate three pairs of pseudoenantiomers. Previously, approaches with several synthetic steps, expensive reagents, high purification demands and low yields of the products have been employed. Herein we present direct, short and efficient primary-side difunctionalization strategies featuring reproducibility, ease of product purification, scalability of the reactions and versatility of the substituents introduced. Specifically, the prepared ditosylated β-CDs were separated using preparative reversed-phase column chromatography and their structures were elucidated by NMR experiments. Azidation led to the corresponding pure diazido regioisomers. Direct monotosylation of 6-monoazido-β-CD or monoazidation of the single regioisomers 6^A,6^X-ditosyl-β-CDs afforded hetero-difunctionalized 6^A-monoazido-6^X-tosyl-β-CDs in significant yields. Overall, the single regioisomers, 6^A,6^X-ditosyl-, 6^A,6^X-diazido- and 6^A-monoazido-6^X-monotosyl-β-CD were prepared in one or two steps and purified in multigram scale thus opening the way towards further selective and orthogonal functionalizations of β-CD hosts.

Flow-chemistry enabled efficient synthesis of β-peptides: backbone topology vs. helix formation

Enantiodiscriminative helix formation was observed for β-peptide H14 helices when enantiomers of bridged bicyclic residues were introduced.

Isoflavonoids with inhibiting effects on human hyaluronidase-1 and norneolignan clitorienolactone B from Ononis spinosa L. root extract

Human hyaluronidase-1 (Hyal-1) is one of the main enzymes in the homeostasis of hyaluronic acid (HA), the main polysaccharide of extracellular matrix. Development of specific Hyal-1 inhibitors might be a promising target for improved wound healing, tissue regeneration, and looking at renal function for diuresis. By using surface-displayed Hyal-1 on Escherichia coli F470 cells, HA as substrate and stains-all method for quantification of undegraded HA, the respective enzyme activity can be determined easily. Based on the traditional use of extracts from the roots from Ononis spinosa L. (Restharrow root) as a weak diuretic to achieve flushing of the urinary tract and as an adjuvant in minor urinary complaints the herbal material was selected for bioactivity guided fractionation for compounds with Hyal-1 inhibition activity. Hot water and hydroalcoholic extracts showed moderate inhibiting effects (IC₅₀ 1.36 resp. 0.73 mg/mL) while dichloromethane extract exerted an IC₅₀ of 190 μg/mL. Bioassay guided fractionation of the dichloromethane extract yielded four isoflavonoids with anti Hyal-1 activity: onogenin 1, sativanone 2, medicarpin 3 and calycosin-D 4 with inhibition rates of 25.4, 61.2, 22.4 and 23.0%, respectively at test concentration level of 250 μM. The norneolignan clitorienolactone B 5, the first time described for the genus Ononis, was inactive. The IC₅₀ of sativanone, the most active compound was determined with 1501 μM, which was better than that of the positive control glycyrrhizinic acid (177 μM). Thus, a possible explanation for diuretic properties of Ononis spinosa L. root extract may be postulated from the results so far obtained.

Chemodiversity of Cirsium fruits: Antiproliferative lignans, neolignans and sesquineolignans as chemotaxonomic markers

While analyzing the fruit composition of nine European Cirsium species representing three sections (i.e., Cephalonoplos, Chamaeleon and Eriolepis), four lignans, three neolignans and three sesquineolignans were determined and used as chemotaxonomic markers. Among them, desmethyl balanophonin and desmethyl picrasmalignan were determined for the first time in the plant kingdom, as the main metabolites of the Chamaeleon section. Prebalanophonin and prepicrasmalignan, identified so far exclusively in C. eriophorum, were also confirmed in C. boujartii and C. vulgare, highlighting the chemotaxonomic significance of these compounds in the Eriolepis section. The antiproliferative assay of the compounds isolated from their optimum sources, confirmed a dose-dependent inhibitory effect of the structures bearing the 4',7-epoxy moiety (balanophonin, picrasmalignan, desmethyl balanophonin, desmethyl picrasmalignan) against SW480 colon cancer cells, while those bearing the 4',7-dihydroxy motif (prebalanophonin, prepicrasmalignan) were inactive.

Three newly identified lipophilic flavonoids in Tanacetum parthenium supercritical fluid extract penetrating the Blood-Brain Barrier

Feverfew (Tanacetum parthenium L.) as a perennial herb has been known for centuries due to its medicinal properties. The main sesquiterpene lactone, parthenolide is considered to be responsible for the migraine prophylactic effect, however the pharmacological benefits of the lipophilic flavonoid components can not be neglected. Supercritical fluid extraction (7% ethanol, 22MPa, 64°C) was carried out on the leaves of Tanacetum parthenium L. from which the presence of methylated flavonoids beside parthenolide and other sesquiterpene lactones were indicated by preliminary LC-MS analyses. Specific Parallel Artificial Membrane Permeability Assay (PAMPA) was applied to identify the components capable to cross the Blood-Brain Barrier (BBB). Three lipophilic flavonoids were detected on the acceptor side, that were isolated (Prep-HPLC) and identified as sudachitin, aceronin and nevadensin (LC-MS/MS, NMR). These flavonoids were also characterized individually by PAMPA-BBB model. The presence of sudachitin and nevadensin was proven in the Asteraceae family, but neither of the three flavonoids were reported in Tanacetum parthenium L.

Layer chromatography-bioassays directed screening and identification of antibacterial compounds from Scotch thistle

The antibacterial profiling of Onopordum acanthium L. leaf extract and subsequent targeted identification of active compounds is demonstrated. Thin-layer chromatography (TLC) and off-line overpressured layer chromatography (OPLC) coupled with direct bioautography were utilized for investigation of the extract against eight bacterial strains including two plant and three human pathogens and a soil, a marine and a probiotic human gut bacteria. Antibacterial fractions obtaining infusion-transfusion OPLC were transferred to HPLC-MS/MS analysis that resulted in the characterization of three active compounds and two of them were identified as, linoleic and linolenic acid. OPLC method was adopted to preparative-scale flash chromatography for the isolation of the third active compound, which was identified after a further semi-preparative HPLC purification as the germacranolide sesquiterpene lactone onopordopicrin. Pure onopordopicrin exhibited antibacterial activity that was specified as minimal inhibitory concentration in the liquid phase as well.

Characterization of diarylheptanoids: An emerging class of bioactive natural products

Diarylheptanoids are a class of secondary plant metabolites with a wide variety of bioactivity. Research on their phytochemistry and phytoanalysis is rapidly growing and the number of identified structures bearing the aryl-C₇-aryl skeleton is at present approaching 500. Historically, the yellow pigment curcumin has been characterized as the first diarylheptanoid and the extensive research on naturally occurring analogues is still ongoing. In this review, studies dealing with the characterization of linear and cyclic derivatives are discussed from the phytoanalytical point of view. Isolation, fractionation and purification strategies from natural sources along with their chromatographic behavior and structural characteristics are discussed. The role of various techniques used for the extraction (such as Soxhlet extraction, sonication, maceration/percolation, microwave-assisted extraction, supercritical carbon dioxide extraction); isolation (liquid-liquid extraction, column chromatographic techniques, preparative thin-layer and high-performance liquid chromatography, centrifugal partition chromatography, counter-current chromatography); separation (thin-layer chromatography, high-performance liquid chromatography, gas chromatography, capillary electrophoresis) and structural characterization (UV/Vis spectroscopy, infrared spectroscopy, X-ray crystallography, mass spectrometry, nuclear magnetic resonance spectroscopy and circular dichroism spectroscopy) are critically reviewed.

Optimized conversion of antiproliferative lignans pinoresinol and epipinoresinol: Their simultaneous isolation and identification by centrifugal partition chromatography and high performance liquid chromatography

High amount of the valuable lignan pinoresinol (PR) was determined in Carduus nutans fruit (7.8mg/g) for the first time. A preparative separation method using two consecutive, identical steps of centrifugal partition chromatography (CPC) was developed in order (i) to isolate PR and (ii) to subsequently isolate PR and its 7' epimer epipinoresinol (EPR) simultaneously after an optimized acid treatment which resulted in PR epimerization forming equal amounts of PR and EPR, from C. nutans fruit. As optimal conditions, a two-phase solvent system consisting of methyl tert-butyl ether:acetone:water (4:3:3, v/v/v) for CPC separation, and an acid treatment performed at 50°C for 30min for the epimerization were applied. Thus, 33.7mg and 32.8mg PR and EPR, in as high as 93.7% and 92.3% purity, were isolated from 10.0gC. nutans fruit, representing 86.4% and 84.1% efficiency, respectively. Conversion characteristic of PR and EPR in acidic medium, determined as a function of time and temperature of acid treatment provides their unambiguous identification by on-line high performance liquid chromatography (HPLC). Antiproliferative assay of isolated PR and EPR in two different types of colon cancer cell lines (HCT116 and SW480) confirmed that both epimers caused a more significant decrease of viability in HCT116 cells than in SW480 cells, suggesting their similar mechanism of antiproliferative action.

Novel β-cyclodextrin-eosin conjugates

Eosin B (EoB) and eosin Y (EoY), two xanthene dye derivatives with photosensitizing ability were prepared in high purity through an improved synthetic route. The dyes were grafted to a 6-monoamino-β-cyclodextrin scaffold under mild reaction conditions through a stable amide linkage using the coupling agent 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride. The molecular conjugates, well soluble in aqueous medium, were extensively characterized by 1D and 2D NMR spectroscopy and mass spectrometry. Preliminary spectroscopic investigations showed that the β-cyclodextrin–EoY conjugate retains both the fluorescence properties and the capability to photogenerate singlet oxygen of the unbound chromophore. In contrast, the corresponding β-cyclodextrin–EoB conjugate did not show either relevant emission or photosensitizing activity probably due to aggregation in aqueous medium, which precludes any response to light excitation.

Enzyme-hydrolyzed Fruit of Jurinea mollis: A Rich Source of (-)-(8R,8′R)-Arctigenin

In Jurinea mollis fruit, the dibenzylbutyrolactone-type lignan glycoside arctiin and its aglycone arctigenin were determined for the first time using a combination of optimized enzymatic treatment and complementary spectrometric (HPLC-MS, GC-MS) and spectroscopic (CD and NMR) methods. Analysis of separated fruit parts, i.e., the fruit wall and embryo, demonstrated the specific accumulation of arctiin, since it was exclusively found in the embryo. Arctiin in the embryo samples (71.5 mg/g) was found to be quantitatively converted into arctigenin (50.7 mg/g) by endogenous enzymatic hydrolysis, resulting in one of the highest arctigenin-containing plant tissues reported to date and allowing the selective isolation of arctigenin by our recently reported three-step isolation method. The absolute configuration of the isolated arctigenin was determined to be (-)-(8 R,8′ R). Conformational analysis of arctigenin was also performed, resulting in three major low energy conformations.

Enzyme-hydrolyzed Fruit of Jurinea mollis: a Rich Source of (-)-(8R,8'R)-Arctigenin

In Jurinea mollis fruit, the dibenzylbutyrolactone-type lignan glycoside arctiin and its aglycone arctigenin were determined for the first time using a combination of optimized enzymatic treatment and complementary spectrometric (HPLC-MS, GC-MS) and spectroscopic (CD and NMR) methods. Analysis of separated fruit parts, i.e., the fruit wall and embryo, demonstrated the specific accumulation of arctiin, since it was exclusively found in the embryo. Arctiin in the embryo samples (71.5 mg/g) was found to be quantitatively converted into arctigenin (50.7 mg/g) by endogenous enzymatic hydrolysis, resulting in one of the highest arctigenin-containing plant tissues reported to date and allowing the selective isolation of arctigenin by our recently reported three-step isolation method. The absolute configuration of the isolated arctigenin was determined to be (-)-(8R,8'R). Conformational analysis of arctigenin was also performed, resulting in three major low energy conformations.