Recent acquisitions on oxyprenylated secondary metabolites as anti-inflammatory agents

The anti-inflammatory activity of flavonoids and alkaloids from Sophora flavescens alleviates psoriasiform lesions: Prenylation and methoxylation beneficially enhance bioactivity and skin targeting

The herb Sophora flavescens displays anti-inflammatory activity and can provide a source of antipsoriatic medications. We aimed to evaluate whether S. flavescens extracts and compounds can relieve psoriasiform inflammation. The ability of flavonoids (maackiain, sophoraflavanone G, leachianone A) and alkaloids (matrine, oxymatrine) isolated from S. flavescens to inhibit production of cytokine/chemokines was examined in keratinocytes and macrophages. Physicochemical properties and skin absorption were determined by in silico molecular modeling and the in vitro permeation test (IVPT) to establish the structure-permeation relationship (SPR). The ethyl acetate extract exhibited higher inhibition of interleukin (IL)-6, IL-8, and CXCL1 production in tumor necrosis factor-α-stimulated keratinocytes compared to the ethanol and water extracts. The flavonoids demonstrated higher cytokine/chemokine inhibition than alkaloids, with the prenylated flavanones (sophoraflavanone G, leachianone A) led to the highest suppression. Flavonoids exerted anti-inflammatory effects via the extracellular signal-regulated kinase, p38, activator protein-1, and nuclear factor-κB signaling pathways. In the IVPT, prenylation of the flavanone skeleton significantly promoted skin absorption from 0.01 to 0.22 nmol/mg (sophoraflavanone G vs. eriodictyol). Further methoxylation of a prenylated flavanone (leachianone A) elevated skin absorption to 2.65 nmol/mg. Topical leachianone A reduced the epidermal thickness in IMQ-treated mice by 47%, and inhibited cutaneous scaling and cytokine/chemokine overexpression at comparable levels to a commercial betamethasone product. Thus, prenylation and methoxylation of S. flavescens flavanones may enable the design of novel antipsoriatic agents.

Protection of Mitochondrial Potential and Activity by Oxyprenylated Phenylpropanoids

A series of five naturally occurring oxyprenylated phenylpropanoids, namely, the coumarins auraptene (7-geranyloxycoumarin) 1 and 7-isopentenyloxycoumarin 2, and the coumaric acid and ferulic acid derivatives, 4'-isopentenyloxycoumaric acid 3, boropinic acid 4, and 4'-geranyloxyferulic acid 5 were tested for their effects on mitochondrial functionality using the organophosphate pesticides glyphosate and chlorpyrifos, and resveratrol, as the reference. While not showing an appreciable in vitro antioxidant activity, and virtually no or a little effect on the viability of non-cancer cell lines BEAS-2B and SHSY-5Y, all phytochemicals exhibited a marked protective effect on mitochondrial potential and activity, with values that were comparable to resveratrol. Auraptene 1 and 7-isopentenyloxycoumarin 2 were seen to be the most effective secondary metabolite to this concern, in particular in being able to completely abolish the decrease of mitochondrial potential induced by increasing concentration of both glyphosate and chlorpyrifos. All the compounds tested also exhibited a protective effect on mitochondrial activity. The potency displayed will shed more light on the molecular basis of the beneficial effects of auraptene, 7-isopentenyloxycoumarin, and structurally related oxyprenylated phenylpropanoids reported to date in the literature.

Oxyprenylated Secondary Metabolites as Modulators of Lipid and Sugar Metabolism

O-Prenylcoumarins (3,3-dimethylallyl, geranyl-, farnesyl- and related biosynthetic derivatives) represent a class of rarely occurring natural compounds. The most part of these secondary metabolites have been obtained from plant species belonging to the Rutaceae, Apiaceae, andFabaceae families, and from fungi, and bacteria. In the last two decades prenyloxycoumarinshave been found to possess a great potential in terms of pharmacological activities. The aim of this comprehensive review is to make a survey of the in so far reported literature citations about these valuable phytochemicals and structurally related compounds about their modulatory properties of lipid and sugar metabolism. Literature data have been acquired from the main Internet database. Several oxyprenylated secondary metabolites have been surveyed. Among these prenyloxycoumarins represented the main group exerting displayed valuable effects as modulators of lipid and sugar metabolism. The title phytochemicals have been found in common edible and fruits vegetables already known to have beneficial effects to this concern, thus enforcing the nutraceutical role of these food plants. All compounds outlined in the present review article have a great potential for the next future for the prevention and management of acute and chronic metabolic disorders.

7-Isopentenyloxycoumarin: What Is New across the Last Decade

7-Isopentenyloxycoumarin is among the most widespread naturally occurring prenyloxy umbelliferone derivatives. This secondary metabolite of mixed biosynthetic origin has been typically isolated from plants belonging to several genera of the Rutaceae and Apiaceae families, comprising widely used medicinal plants and in general plants with beneficial effects on human welfare, as well as edible fruits and vegetables. Although known for quite a long time (more than 50 years), only in the last two decades has this natural compound been revealed to exert powerful and promising pharmacological properties, such as active cancer chemopreventive, antibacterial, antiprotozoal, antifungal, anti-inflammatory, neuroprotective, and antioxidant properties, among the activities best outlined in the recent literature. The aim of this comprehensive miniature review article is to detail the novel natural sources and the effects described during the last decade for 7-isopentenyloxycoumarin and what has been reported on the mechanisms of action underlying the observed biological activities of this oxyprenylated secondary metabolite. In view of the herein described data, suggestions on how to address future research on the abovementioned natural product and structurally related derivatives in the best ways according to the authors will be also provided.

Ameliorative effects of the traditional Chinese medicine formula Qing-Mai-Yin on arteriosclerosis obliterans in a rabbit model

CONTEXT

Qing-Mai-Yin (QMY) is a clinically used herbal formula for treating arteriosclerosis obliterans (ASO).

OBJECTIVE

To evaluate the chemical constituents and effects of QMY on ASO rabbit model.

MATERIALS AND METHODS

Forty-eight New Zealand rabbits were divided into six groups (n = 8): normal (normal rabbits treated with 0.5% CMC-Na), vehicle (ASO rabbits treated with 0.5% CMC-Na), positive (simvastatin, 1.53 mg/kg), and QMY treatment (300, 600, and 1200 mg/kg). ASO rabbit model was prepared by high fatty feeding, roundly shortening artery, and bovine serum albumin immune injury. QMY (300, 600 and 1200 mg/kg) was orally administered for 8 weeks. The effects and possible mechanisms of QMY on ASO rabbits were evaluated by pathological examination, biochemical assays, and immunohistochemical assays. The compositions of QMY were analysed using HPLC-Q-TOF-MS/MS analysis.

RESULTS

Compared to the vehicle rabbit, QMY treatment suppressed plaque formation and intima thickness in aorta, and decreased intima thickness, whereas increased lumen area of femoral artery. Additionally, QMY treatment decreased TC, TG and LDL, decreased CRP and ET, and increased NO and 6-K-PGF1α in serum. Furthermore, the potential mechanisms studied revealed that QMY treatment could suppress expression of TNF-α, IL-6, ICAM-1 and NF-κB in endothelial tissues, and increase IκB. In addition, HPLC analysis showed QMY had abundant anthraquinones, stilbenes, and flavonoids.

CONCLUSION

QMY has ameliorative effects on ASO rabbit, and the potential mechanisms are correlated to reducing inflammation and down-regulating NF-κB. Our study provides a scientific basis for the future application and investigation of QMY.

Genomic and Metabolomic Analysis of Antarctic Bacteria Revealed Culture and Elicitation Conditions for the Production of Antimicrobial Compounds

Concern about finding new antibiotics against drug-resistant pathogens is increasing every year. Antarctic bacteria have been proposed as an unexplored source of bioactive metabolites; however, most biosynthetic gene clusters (BGCs) producing secondary metabolites remain silent under common culture conditions. Our work aimed to characterize elicitation conditions for the production of antibacterial secondary metabolites from 34 Antarctic bacterial strains based on MS/MS metabolomics and genome mining approaches. Bacterial strains were cultivated under different nutrient and elicitation conditions, including the addition of lipopolysaccharide (LPS), sodium nitroprusside (SNP), and coculture. Metabolomes were obtained by HPLC-QTOF-MS/MS and analyzed through molecular networking. Antibacterial activity was determined, and seven strains were selected for genome sequencing and analysis. Biosynthesis pathways were activated by all the elicitation treatments, which varies among strains and dependents of culture media. Increased antibacterial activity was observed for a few strains and addition of LPS was related with inhibition of Gram-negative pathogens. Antibiotic BGCs were found for all selected strains and the expressions of putative actinomycin, carotenoids, and bacillibactin were characterized by comparison of genomic and metabolomic data. This work established the use of promising new elicitors for bioprospection of Antarctic bacteria and highlights the importance of new "-omics" comparative approaches for drug discovery.

Investigation of the cytotoxicity of bioinspired coumarin analogues towards human breast cancer cells

Abstract

Coumarins possess a wide array of therapeutic capabilities, but often with unclear mechanism of action. We tested a small library of 18 coumarin derivatives against human invasive breast ductal carcinoma cells with the capacity of each compound to inhibit cell proliferation scored, and the most potent coumarin analogues selected for further studies. Interestingly, the presence of two prenyloxy groups (5,7-diprenyloxy-4-methyl-coumarin, 4g) or the presence of octyloxy substituent (coumarin 4d) was found to increase the potency of compounds in breast cancer cells, but not against healthy human fibroblasts. The activity of potent compounds on breast cancer cells cultured more similarly to the conditions of the tumour microenvironment was also investigated, and increased toxicity was observed. Results suggest that tested coumarin derivatives could potentially reduce the growth of tumour mass. Moreover, their use as (combination) therapy in cancer treatment might have the potential of causing limited side effects.

Graphic abstract

Electronic supplementary material

The online version of this article (10.1007/s11030-020-10082-6) contains supplementary material, which is available to authorized users.

A novel and efficient subcritical butane extraction method and UHPLC analysis of oxyprenylated phenylpropanoids from grapefruits peels

Biologically active prenyoxyphenylpropanoids are well known to be biosynthesized by Citrus species, for which they have been found most abundantly in fruit peels. Although several extraction methodologies have been described, the development of novel and alternative extraction processes is a field of research of current interest. In this preliminary communication, we studied the performance of the subcritical butane promoted extraction of selected oxyprenylated phenylpropanoids from grapefruit peels under a counter-current mode using a handmade extraction apparatus coupled to UHPLC analysis. The application of such a method yielded 7-isopentenyloxycoumarin, auraptene, and boropinic acid in quantities higher than those recorded for other extraction methodologies like the ultrasound- and microwave-assisted macerations (0.234, 1.035, and 0.211 mg/g of dry extract respectively). The use of subcritical butane as the extraction solvent for oxyprenylated phenylpropanoids is reported herein for the first time and can be easily adopted for several other food matrices.

Novel 3-aryl-5-substituted-coumarin analogues: Synthesis and bioactivity profile

Eighteen 3-aryl-5-substituted-coumarins-six 5-acetyloxy-derivatives, six 5-hydroxy-derivatives, and six 5-geranyloxy-derivatives-were synthesized, structurally characterized and their antioxidant activity, lipoxygenase inhibitory ability, as well as their cytotoxic activity against human neuroblastoma SK-N-SH and HeLa adenocarcinoma cell lines were evaluated. The 5-acetyloxy-compounds 3a-3f were found to be the best cytotoxic agents among all the compounds studied. The bromo-substituted coumarins 3a and 3b were remarkably active against HeLa cell line showing IC₅₀ 1.8 and 6.1 μM, respectively. Coumarin 5e possessing a geranyloxy-chain on position 5 of the coumarin scaffold presented dual bioactivity, while 5-geranyloxy-coumarin 5f was the most competent soybean lipoxygenase inhibitor of this series (IC₅₀ 10 μM). As shown by in silico docking studies, the studied molecules present allosteric interactions with soybean lipoxygenases.

UHPLC-UV/Vis Quantitative Analysis of Hydroxylated and O-prenylated Coumarins in Pomegranate Seed Extracts

A simple and rapid analytical UHPLC methodology with spectrophotometric (UV/Vis) detection, coupled with different extraction procedures, has been perfected to investigate the presence of biologically active O-prenylated umbelliferone derivatives, such as auraptene and umbelliprenin, in pomegranate (Punica granatum L.) seed extracts. Absolute ethanol was the most efficient extraction solvent in terms of yields, after a short ultrasound-assisted. The highest concentration values recorded under these experimental conditions were 1.99 μg/g of dry extract and 6.53 μg/g for auraptene and umbelliprenin, respectively. The parent metabolite umbelliferone was also detected (0.67 μg/g). The extraction and UHPLC analytical methodology set up in the present study proved to be an efficient, powerful, and versatile technique for the simultaneous qualitative analysis and quantification of oxyprenylated coumarins in pomegranate seed extracts. The characterization of such secondary metabolites in the mentioned phytopreparation represents, to the best of our knowledge, the first example in the literature.

HPLC Analysis and Skin Whitening Effects of Umbelliprenin-containing Extracts of Anethum Graveolens, Pimpinella Anisum, and Ferulago Campestris

Umbelliprenin has recently been shown to have great potential as a skin whitening agent. Wishing to investigate the same effect in plant species known to biosynthesize this coumarin, three plants belonging to the Apiaceae family, namely Anethum graveolens L. (dill), Pimpinella anisum L. (anise), and Ferulago campestris (Besser) Grecescu (field ferula) were screened by HPLC analysis for their respective content of umbelliprenin in extracts obtained with different solvent mixtures and by maceration and ultrasound-assisted processes. EtOH was shown to be the best solvent, providing umbelliprenin yields ranging from 1.7% to 14.4% (with respect to the total amount of extract obtained). Extracts with the highest content of this farnesyloxycoumarin were then assayed as modulators of melanogenesis in cultured murine Melan A cells employing the same umbelliprenin obtained by chemical synthesis as the reference. A parallelism between the content of the coumarin and the recorded depigmenting effect (60% for the EtOH extract of F. campestris as the best value) was revealed for all plants extracts when applied at a dose of 100 μg/mL. Our results demonstrate that the same potential of umbelliprenin can be ascribed also to umbelliprenin-enriched plant extracts which reinforces enforce the widespread use of phyto-preparations for cosmetic purposes (e.g., A. graveolens).

Diploquinones A and B, Two New Phytotoxic Tetrasubstituted 1,4-Naphthoquinones from Diplodia mutila, a Causal Agent of Grapevine Trunk Disease

Two new phytotoxic tetrasubstituted 1,4-naphthoquinones, named diploquinones A and B, were isolated together with vanillic acid from Diplodia mutila (DAR78993), a grapevine pathogen involved in Botryosphaeria dieback in Australia. Diploquinones A and B were characterized as 6,7-dihydroxy-2-methoxy-5-methylnaphthalene-1,4-dione and 3,5,7-trihydroxy-2-methoxynaphthalene-1,4-dione using spectroscopic methods (essentially 1D and 2D ¹H and ¹³C NMR and HR ESIMS). The already known vanillic acid was isolated for the first time as fungal phytotoxin and as metabolite of D. mutila. The three compounds were assayed on detached grapevine leaves ( Vitis vinifera cv. Shiraz) at concentrations of 10^-3 M and 2.5 × 10^-3 M. Vanillic acid showed the highest phytotoxic effect on grapevine leaves irrespective of the tested concentration, while diploquinones A and B showed varying degrees of toxicity.