Apolar chromatography on Sephadex LH-20 combined with high-speed counter-current chromatography

Countercurrent chromatography isolation of green propolis biomarkers: Potential blockers of SARS-COV-2 RBD and ACE2 interaction

Propolis is a natural resinous mixture produced by honeybees with numerous biological activities. Considering the recently reported potential of propolis as an adjuvant in COVID-19 treatment, a methodology for the fractionation of the hexane extract of Brazilian green propolis (HEGP) was developed for the obtention of prenylated biomarkers by countercurrent chromatography. The inhibition of the interaction between the receptor binding domain (RBD) of spike and ACE2 receptor was evaluated by the Lumitᵀᴹ immunoassay. Fractionation of HEGP was performed by both normal (CCC1 and CCC2, with extended elution) and reversed (CCC3) phase elution-extrusion modes with the solvent system hexane-ethanol-water 4:3:1. The normal elution mode of CCC1 (471 mg HEGP in a 80 mL column volume, 1.6 mm id) was scaled-up (CCC5, 1211 mg HEGP in a 112 mL column volume, 2.1 mm id), leading to the isolation of 89.9 mg of artepillin C, 1; 52.7 mg of baccharin, 2; and 26.6 mg of chromene, with purities of 93 %, 83 % and 88 %, respectively, by HPLC-PDA. Among the isolated compounds, artepillin C, 1, and baccharin, 2, presented the best results in the Lumitᵀᴹ immunoassay, showing 67% and 51% inhibition, respectively, at the concentration of 10 μM. This technique proved to be of low operational cost and excellent reproducibility.

Advancements in Litchi chinensis Peel Processing: A Scientific Review of Drying, Extraction, and Isolation of Its Bioactive Compounds

This article systematically reviews the advancements in processing litchi peel (Litchi chinensis), emphasizing drying, extraction, purification methods, and the potential of bioactive compounds obtained from litchi peel. This work also highlights the impact of various drying techniques on phytochemical profiles, focusing on how methods such as hot air and freeze-drying affect the preservation of bioactive compounds. The study delves into extraction methods, detailing how different solvents and techniques influence the efficiency of extracting bioactive compounds from litchi peel. Furthermore, the purification and characterization of active compounds, showcasing the role of chromatographic techniques in isolating specific bioactive molecules, is discussed. Biological properties and mechanisms of action, such as antioxidant, antihyperglycemic, cardioprotective, hepatoprotective, anti-atherosclerotic, and anticancer activities, are reviewed, providing insight into the potential health benefits of litchi peel compounds. This review highlights the importance of optimizing and selecting accurate drying and extraction methods to maximize the therapeutic effects of litchi peel and its bioactive compounds. This review also reveals the broad pharmacological potential of the isolated compounds, underscoring the need for further research to discover their specific actions and health benefits.

Polyketides and a Dihydroquinolone Alkaloid from a Marine-Derived Strain of the Fungus Metarhizium marquandii

Three new natural products (1-3), including two butenolide derivatives (1 and 2) and one dihydroquinolone derivative (3), together with nine known natural products were isolated from a marine-derived strain of the fungus Metarhizium marquandii. The structures of the new compounds were unambiguously deduced by spectroscopic means including HRESIMS and 1D/2D NMR spectroscopy, ECD, VCD, OR measurements, and calculations. The absolute configuration of marqualide (1) was determined by a combination of modified Mosher's method with TDDFT-ECD calculations at different levels, which revealed the importance of intramolecular hydrogen bonding in determining the ECD features. The (3R,4R) absolute configuration of aflaquinolone I (3), determined by OR, ECD, and VCD calculations, was found to be opposite of the (3S,4S) absolute configuration of the related aflaquinolones A-G, suggesting that the fungus M. marquandii produces aflaquinolone I with a different configuration (chiral switching). The absolute configuration of the known natural product terrestric acid hydrate (4) was likewise determined for the first time in this study. TDDFT-ECD calculations allowed determination of the absolute configuration of its chirality center remote from the stereogenic unsaturated γ-lactone chromophore. ECD calculations aided by solvent models revealed the importance of intramolecular hydrogen bond networks in stabilizing conformers and determining relationships between ECD transitions and absolute configurations.

Altered membrane rigidity via enhanced endogenous cholesterol synthesis drives cancer cell resistance to destruxins

Destruxins, secondary metabolites of entomopathogenic fungi, exert a wide variety of interesting characteristics ranging from antiviral to anticancer effects. Although their mode of action was evaluated previously, the molecular mechanisms of resistance development are unknown. Hence, we have established destruxin-resistant sublines of HCT116 colon carcinoma cells by selection with the most prevalent derivatives, destruxin (dtx)A, dtxB and dtxE. Various cell biological and molecular techniques were applied to elucidate the regulatory mechanisms underlying these acquired and highly stable destruxin resistance phenotypes. Interestingly, well-known chemoresistance-mediating ABC efflux transporters were not the major players. Instead, in dtxA- and dtxB-resistant cells a hyper-activated mevalonate pathway was uncovered resulting in increased de-novo cholesterol synthesis rates and elevated levels of lanosterol, cholesterol as well as several oxysterol metabolites. Accordingly, inhibition of the mevalonate pathway at two different steps, using either statins or zoledronic acid, significantly reduced acquired but also intrinsic destruxin resistance. Vice versa, cholesterol supplementation protected destruxin-sensitive cells against their cytotoxic activity. Additionally, an increased cell membrane adhesiveness of dtxA-resistant as compared to parental cells was detected by atomic force microscopy. This was paralleled by a dramatically reduced ionophoric capacity of dtxA in resistant cells when cultured in absence but not in presence of statins. Summarizing, our results suggest a reduced ionophoric activity of destruxins due to cholesterol-mediated plasma membrane re-organization as molecular mechanism underlying acquired destruxin resistance in human colon cancer cells. Whether this mechanism might be valid also in other cell types and organisms exposed to destruxins e.g. as bio-insecticides needs to be evaluated.

Analytical Methods for Secondary Metabolite Detection

The entomopathogenic fungi Metarhizium brunneum, Beauveria bassiana, and B. brongniartii are widely applied as biological pest control agent in OECD countries. Consequently, their use has to be flanked by a risk management approach, which includes the need to monitor the fate of their relevant toxic metabolites. There are still data gaps claimed by regulatory authorities pending on their identification and quantification of relevant toxins or secondary metabolites. In this chapter, analytical methods are presented allowing the qualitative and quantitative analysis of the relevant toxic B. brongniartii metabolite oosporein and the three M. brunneum relevant destruxin (dtx) derivatives dtx A, dtx B, and dtx E.

Quantitative Assessment of Destruxins from Strawberry and Maize in the Lower Parts per Billion Range: Combination of a QuEChERS-Based Extraction Protocol with a Fast and Selective UHPLC-QTOF-MS Assay

The entomopathogenic fungus Metarhizium brunneum is widely applied as a biological pest control agent. Consequently, its use has to be accompanied by a risk management approach, which includes the need to monitor the fate of its bioactive metabolites in the environment, for example, in treated crops. A fast and selective UHPLC-QTOF-MS method was developed to monitor the presence of secreted destruxins in two model food plants for the application of this fungal biocontrol agent, namely, strawberry and maize. The liquid chromatography-mass spectrometric assay for destruxin trace analysis is combined with a novel QuEChERS-based extraction protocol. The whole assay was optimized for the application in these crops, and it allows quantitative analysis of the major M. brunneum metabolites destruxin A, 1, destruxin B, 2, and destruxin E, 3, down to the parts per billion range. In strawberry, limits of quantitation (LOQs) were found to be <2.0 ppb for all analytes; in maize LOQs were found to be <3.2 ppb for destruxin A and destruxin B. Destruxin E showed a distinctive loss of recovery in maize and was excluded from further quantitative analysis in this crop. For both crops assay linearities ranged from the LOQs to 100 ppb, interassay repeatabilities (RSD) were found to be better than 16.4%, and accuracies ranged from 83.5 to 105.3% (assessed at four spiking levels between 5 and 75 ppb).

Preparative isolation and purification of five steroid saponins from Dioscorea zingiberensis C.H.Wright by counter-current chromatography coupled with evaporative light scattering detector

A counter-current chromatography (CCC) method was successfully applied to separate and purify steroid saponins from the traditional Chinese medicine Dioscorea zingiberensis C.H.Wright for the first time. Ethyl acetate-n-butanol-methanol-water (4:1:2:4, v/v) was used as the two-phase solvent system, and evaporative light scattering detector (ELSD) was used as the detector in this method. The method separated in a single run the following five steroid saponins: 26-O-β-d-glucopyranosyl-(25R)-furost-5-en-3β, 22ζ, 26-triol-3-O-[β-d-glucopyranosyl-(1→3)-β-d-glucopyranol-(1→4)-α-l-rhamnopyranosyl-(1→2)]-β-d-glucopyranoside (Compound A); 26-O-β-d-glucopyranosyl-(25R)-furost-5-en-3β, 22ζ, 26-triol-3-O-[β-d-glucopyranosyl(1→3)-α-l-rhamnopyranosyl(1→2)]-β-d-glucopyranoside (Compound B); 26-O-β-d-glucopyranosyl-(25R)-furost-5-en-3β, 22ζ, 26-triol-3-O-[α-l-rhamnopyranosyl(1→4)]-β-d-glucopyranoside (Compound C); 26-O-β-d-glucopyranosyl-(25R)-furost-5, 20(22)-diene-3β, 26-diol-3-O-{α-l-rhamnopyranosyl-(1→4)-[β-d-glucopyranosyl-(1→3)-β-d-glucopyranosyl-(1→2)]}-β-d-glucopyranoside (Compound D); and 26-O-β-d-glucopyranosyl-(25R)-furost-5, 20(22)-diene-3β, 26-diol-3-O-[β-d-glucopyranosyl-(1→4)-α-l-rhamnopyranosyl(1→2)]-β-d-glucopyranoside (Compound E). Their structural identification of the five steroid saponins was performed by means of ESI-MS, and (13)C NMR.

Destruxins: fungal-derived cyclohexadepsipeptides with multifaceted anticancer and antiangiogenic activities

Destruxins (Dtx) are secondary metabolites of the entomopathogenic fungus Metarhizium anisopliae. Recently, Dtx came into focus of interest as anticancer therapeutics. However, data on human and especially on cancer cells are fragmentary. In order to successfully establish novel anticancer therapeutics, a broad knowledge on the cellular and molecular mechanisms underlying their activity is essential. Consequently, this study aimed to investigate the impact of the most common Dtx derivatives A, B and E on human cancer cell growth and survival with a focus on colon cancer cell models. Summarizing, the experimental data showed that (i) Dtx A and B exert potent antiproliferative activity in the micromolar and Dtx E in the nanomolar range in KB-3-1, A549, CaCo-2, and especially in HCT116 colon cancer cells, (ii) all three Dtx derivatives cause imbalance of cell cycle distribution, (iii) their cytostatic/cytotoxic effects are widely p53-independent but reduced by p21- and bax-deletion, respectively, (iv) cytotoxicity is based on intrinsic apoptosis induction and associated with phosphoinositide-3-kinase (PI3K)/Akt pathway inhibition, (v) anticancer activity of Dtx E but not Dtx A and B involves disturbance of the intracellular redox balance, (vi) Dtx inhibit the migration and tube formation of human endothelial cells indicating antiangiogenic potential, and (vii) all three Dtx derivatives possess ionophoric properties not differing in conductivity, ion selectivity and single channel kinetics. Thus, Dtx represent feasible, multifunctional anticancer drug candidates for preclinical development especially against colorectal cancer.

Route of infection and hematological effect of Metarhizium anisopliae (Metsch.) Sorokin on Dysdercus cingulatus (Fab.) adult

The primary objective of this work was to identify, under laboratory conditions, the route of infection and hemogram of Dysdercus cingulatus (Fab.) adults by Metarhizium anisopliae. The infection process in D. cingulatus by M. anisopliae involved the conidia adherence to the host cuticle and germination after 24 h post-infection, accompanied by falling of bristles. The subsequent step, within 24-48 h post-infection, comprised penetration of fungus through spiracles, root of bristles, hemolymph, and the three dorsal sacs. Subsequently, within 72-96 h post-infection, the fungus penetrated into trachea and sacs, then emerged on cuticular surface and was found to be maximum in hemolymph. A great decrease in hemocytes count was observed within 96 h from infection. The hemosomic index (HSI) decreased gradually as the incubation period increased. As far as we know, this is the first study to know the mechanism of action of M. anisopliae to D. cingulatus.

Development and applications of destruxins: a review

The insecticidal and phytotoxic activities of destruxins (dtxs) have been well studied. The cyclodepsipeptides, which are dtxs mainly isolated from the fungus Metarhizium anisopliae and other fungi, have been well characterized in vitro and in vivo. A succession of important function, such as antitumoral, antiviral, insecticidal, cytotoxic, immunosuppressant, phytotoxic, and antiproliferative effects have been observed. To date, 39 dtxs derivatives have been identified. Dtxs possess a variety of biological activities, including acting as virulence factors for specific insects, a V-ATPase inhibitor that provides a basis for the development of new drug to against osteoporosis, cancer, or biological control agents, etc. Here, we focus on some of the research progress made on understanding dtxs during the last decade, introduce some of the newly identified dtx members, especially from M. anisopliae, and give an overview of the applications of dtxs. Using the dtxs to learn about and moderate biological events has advanced significantly during the past year. We believe that several ongoing dtx application fields may benefit from the reviewed information herein.

On-line coupling of counter-current chromatography and macroporous resin chromatography for continuous isolation of arctiin from the fruit of Arctium lappa L

In this work, we have developed a novel hybrid two-dimensional counter-current chromatography and liquid chromatography (2D CCC x LC) system for the continuous purification of arctiin from crude extract of Arctium lappa. The first dimensional CCC column has been designed to fractionalize crude complex extract into pure arctiin effluent using a one-component organic/salt-containing system, and the second dimensional LC column has been packed with macroporous resin for on-line adsorption, desalination and desorption of arctiin which was effluent purified from the first CCC dimension. Thus, the crude arctiin mixture has been purified efficiently and conveniently by on-line CCC x LC in spite of the use of a salt-containing solvent system in CCC separation. As a result, high purity (more than 97%) of arctiin has been isolated by repeated injections both using the ethyl acetate-8% sodium chloride aqueous solution and butanol-1% sodium chloride aqueous solution. By contrast with the traditional CCC processes using multi-component organic/aqueous solvent systems, the present on-line CCC x LC process only used a one-component organic solvent and thus the solvent is easier to recover and regenerate. All of used solvents such as ethyl acetate, n-butanol and NaCl aqueous solution are low toxicity and environment-friendly. Moreover, the lower phase of salt-containing aqueous solution used as mobile phase, only contained minor organic solvent, which will save much organic solvent in continuous separation. In summary, our results indicated that the on-line hybrid 2D CCC x LC system using one-component organic/salt-containing aqueous solution is very promising and powerful tool for high-throughput purification of arctiin from fruits of A. lappa.

New antibacterial and cytotoxic activities of falcarindiol isolated in Crithmum maritimum L. leaf extract

Bioassay-guided fractionation of a chloroformic extract obtained from Crithmum maritimum leaves led to the chemical isolation of falcarindiol, a polyacetylene widely distributed within the Apiaceae family. Structure of this compound was confirmed by NMR and activity was tracked using a screening microplate bioassay. Falcarindiol strongly inhibited the growth of Micrococcus luteus and Bacillus cereus, with a minimum inhibitory concentration (MIC) value of 50 microg ml(-1). Moreover, this compound showed cytotoxicity against IEC-6 cells with an IC50 value of 20 microM after 48 h of exposition. These results suggest that Crithmum maritimum could be potentially used in food manufactures and cosmetology as preservative agents and biopesticides, or in medicine as new antibiotics, confirming the interest in studying halophytic species as sources of bioactive compounds.

Preparative isolation and purification of alkannin/shikonin derivatives from natural products by high-speed counter-current chromatography

Alkannin and shikonin (A/S) and their derivatives have been found in the roots of several Boraginaceous species and are also produced through plant tissue cultures. The chiral compounds A/S are potent pharmaceutical substances with a wide spectrum of biological and pharmacological activities like wound healing, antimicrobial, anti-inflammatory, anticancer and antioxidant activity. High-speed counter-current chromatography (HSCCC) was applied for the first time to the separation, preparative isolation and purification of A/S and their esters from extracts of Alkanna tinctoria roots, as well as commercial samples. The constituents of HSCCC fractions and their purity were determined by high-performance liquid chromatography-diode array detection-mass spectrometry (HPLC-DAD-MS), since DAD cannot detect oligomeric A/S derivatives that are present in most of the samples containing the respective monomeric derivatives. The purity of HSCCC fractions was compared with the one of fractions isolated by column chromatography (CC) using as stationary phases silica gel and Sephadex LH-20. As shown, the purity of monomeric alkannin/shikonin was greater by HSCCC than CC separation of commercial A/S samples.

Countercurrent separation of natural products

An assessment of the technology and method development in countercurrent chromatography (CCC) and centrifugal partition chromatography (CPC), collectively referred to as countercurrent separation (CS), is provided. More than six decades of CS theory and applications are critically reviewed and developed into a practical guide to CS for natural products research. The necessary theoretical foundation is given for better use of CS in the separation of biological molecules of any size, small to large, and from any matrix, simple to complex. The three operational fundamentals of CS--instrumentation, biphasic solvent systems, and theory--are covered in a prismatic fashion. The goal of this review is to provide the necessary background and references for an up-to-date perspective of CS and to point out its potential for the natural products scientist for applications in natural products chemistry, metabolome, and proteome research involving organisms from terrestrial and marine sources.