The evaluation of four nano-formulations loaded-Elsinochrome A on characteristics and in vitro cytotoxicity effect

Elsinochrome A (EA) is a naturally occurring photosensitizer with potential applications in photodynamic therapy (PDT) for various malignancies. Despite its promising therapeutic properties, the poor solubility of EA hampers its effective utilization in clinical settings. To circumvent this limitation, we engineered four distinct nano-formulations: PLGA/EA nanoparticles (NPs), CMC-PLGA/EA NPs, mPEG-PCL/EA nanomicelles (NMs), and LHP-CHOL/EA nanoliposomes (NLs), all designed to enhance the solubility of EA. A comparative evaluation of these formulations, based on metrics such as particle size, Zeta potential, drug loading efficiency, and encapsulation efficiency, identified PLGA/EA NPs and mPEG-PCL/EA NMs as the most efficacious candidates. Subsequent in vitro investigations into the drug release kinetics under varying pH conditions and the impact on cell viability and apoptosis in A549 and MCF-7 cell lines were conducted. Remarkably, the maximum drug release for PLGA/EA NPs and mPEG-PCL/EA NMs was recorded at 62.5% and 70.8% in an acidic environment (pH 5.7), respectively. Upon exposure to 460 nm light, PLGA/EA NPs induced a significant reduction in A549 cell viability to 13.8% and an apoptosis rate of 93.8%, whereas mPEG-PCL/EA NMs elicited a decrease in MCF-7 cell viability to 12.8% and an apoptosis rate of 73.0%.

Advances and perspectives on perylenequinone biosynthesis

Under illumination, the fungal secondary metabolites, perylenequinones (PQs) react with molecular oxygen to generate reactive oxygen species (ROS), which, in excess can damage cellular macromolecules and trigger apoptosis. Based on this property, PQs have been widely used as photosensitizers and applied in pharmaceuticals, which has stimulated research into the discovery of new PQs and the elucidation of their biosynthetic pathways. The PQs-associated literature covering from April 1967 to September 2022 is reviewed in three sections: (1) the sources, structural diversity, and biological activities of microbial PQs; (2) elucidation of PQ biosynthetic pathways, associated genes, and mechanisms of regulation; and (3) advances in pathway engineering and future potential strategies to modify cellular metabolism and improve PQ production.

Photodynamic therapy for cancer: Role of natural products

Photodynamic therapy (PDT) is a promising modality for the treatment of cancer. PDT involves administering a photosensitizing dye, i.e. photosensitizer, that selectively accumulates in tumors, and shining a light source on the lesion with a wavelength matching the absorption spectrum of the photosensitizer, that exerts a cytotoxic effect after excitation. The reactive oxygen species produced during PDT are responsible for the oxidation of biomolecules, which in turn cause cell death and the necrosis of malignant tissue. PDT is a multi-factorial process that generally involves apoptotic death of the tumor cells, degeneration of the tumor vasculature, stimulation of anti-tumor immune response, and induction of inflammatory reactions in the illuminated lesion. Numerous compounds with photosensitizing activity have been introduced commercially. Although many papers have been published with regard to PDT in the last decade, there has been relatively little focus on natural medicinal plant extracts and compounds derived therefrom. Herbal plants and their extracts are natural substances, and in comparison with synthetic chemicals are considered "green". This review focuses on the different mechanisms of PDT and discusses the role of various plant extracts and natural compounds either alone or in combination for carrying out PDT on different types of cancers.

Elsinopirins A-D, Decalin Polyketides from the Ascomycete Elsinoё pyri

In course of our screening for new secondary metabolites from ecological niche specialized, phytopathogenic fungi, the plant pathogen Elsinoё pyri, strain 2203C, was found to produce four novel compounds (1-4), which were named elsinopirins A-D, in addition to the known metabolite elsinochrome A (5). After isolation by preparative high-performance liquid chromatography (HPLC), their structures, including relative stereochemistry, were elucidated by 1D and 2D nuclear magnetic resonance (NMR) and mass spectrometry (MS) data. Finally, absolute stereochemistry was assigned by chemical shifts of Mosher's esters (α-methoxy-α-trifluoromethylphenylacetic acid; MTPA) derivatives of elsinopirin B (2). The compounds were found to be devoid of significant antibacterial, antifungal, and cytotoxic activities.

Fourier transform ion cyclotron resonance mass spectrometric analysis of the green fraction of soil humic acids

RATIONALE

The green fraction of soil humic acids (HAs), designated Pg, contains 4,9-dihydroxyperylene-3,10-quinone (DHPQ) as a chromophore. Although various naturally occurring DHPQ derivatives are known to occur and Pg-like absorption is observed in the UV-visible spectra of HAs from various types of soils worldwide, the chemical structure of Pg is still unknown.

METHODS

For a better understanding of the chemical composition of Pg, the pre-isolated (crude Pg) and purified Pg (G2) samples and three soil HAs with different degrees of humification were analyzed using negative-mode electrospray ionization coupled with Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS) at 12 Tesla. The Pg samples were characterized using H/C-O/C ratios and based on the type and magnitude of the molecular formulae having DHPQ or related compounds as a potential structure.

RESULTS

The H/C-O/C diagram indicated that most of the lipids, proteins, other aliphatics, and lignin-like components were removed, while condensed aromatic components were concentrated during the purification process of crude Pg to G2 using Sephadex G-50. More than 27 molecular formulae resembling DHPQ, DHPQ substituted with varying numbers of carboxyl and/or hydroxyl groups, and phenyl-DHPQ derivatives were identified in both Pg samples. The peak magnitudes of these formulae in G2 (accounting for 40% of the total assigned magnitude) were greater than that in the crude Pg (21%). Most of the 27 molecular formulae were also detected in the three soil HAs, suggesting a common existence of Pg-related compounds in various soil HAs.

CONCLUSIONS

The important molecular formulae of Pg components were estimated utilizing FTICRMS. Copyright © 2013 John Wiley & Sons, Ltd.

Development of an HPLC method to analyze and prepare elsinochrome C and hypocrellin A in the submerged fermentation broth of Shiria sp. SUPER-H168

A rapid and sensitive analytical method based on reverse-phase high-performance liquid chromatography was first developed to simultaneously determine elsinochrome C (EC) and hypocrellin A (HA) in the submerged fermentation. The mobile phase consisted of acetonitrile-water 60:40 (v/v) with a flow-rate of 1 mL/min. The calibration curves were as follows: y = 37,625x + 249,775 for EC, y = 30,813x + 556,409 for HA and linear at the investigated concentration. The correlation coefficients (R(2) ) were 0.9989 and 0.9998 respectively for EC and HA. The limits of detection and quantification were 175 and 585 µg/L for EC and 205 and 610 µg/L for HA. The precisions of concentration and retention times were less than 2.5 and 0.3%. The recovery of the method was greater than 95.0%. The methodology was applied to analyze simultaneously EC and HA concentrations in a submerged fermentation, and was adequate for analysis of biosynthesis of perylenequinones. The method was also amplified to separate and purify EC and HA using a semi-preparative C(18) column. In addition, elsinochrome C was first identified in the submerged fermentation broth of Shiraia sp. SUPER-H168.

Transcriptional regulation of elsinochrome phytotoxin biosynthesis by an EfSTE12 activator in the citrus scab pathogen Elsinoë fawcettii

Elsinochrome (ESC), produced by the citrus pathogen Elsinoë fawcettii, is a nonhost-selective, light-dependent, polyketide-derived phytotoxin and plays a crucial role for full virulence. The biosynthesis of ESC is regulated by a wide array of environmental stimuli and is primarily governed by the pathway-specific TSF1 transcription regulator whose coding gene is clustered with the EfPKS1 gene encoding a polyketide synthase and other biosynthetic genes in the genome. In this report, an EfSTE12 gene, encoding a polypeptide resembling the yeast STE12 transcription factor, was cloned and characterized to play a role, independent of TSF1, for ESC production in E. fawcettii. The loss-of-function mutant, specifically disrupted at the EfSTE12 locus, displays reduced ESC accumulation, elevated activities for pectinase and proteolytic enzymes but unaltered in conidiation and fungal pathogenicity. Impairment of the EfSTE12 gene decreased the abundance of the EfPKS1 but not the TSF1 gene transcript. In contrast, expression of the EfSTE12 gene appears normal in the EfPKS1 or TSF1 disruptants. The results indicate that EfSTE12 is functioning for ESC biosynthesis by directly activating the biosynthetic genes without regulating the pathway-specific TSF1 regulator. The defective phenotypes were fully reverted when a functional copy of EfSTE12 was re-introduced into the disrupted mutant. A hypothetical model underlying intertwined regulatory pathways via TSF1, EfSTE12, and other potent transcriptional activators led to the ESC biosynthesis and conidiation is described.

Design, synthesis, and investigation of protein kinase C inhibitors: total syntheses of (+)-calphostin D, (+)-phleichrome, cercosporin, and new photoactive perylenequinones

The total syntheses of the PKC inhibitors (+)-calphostin D, (+)-phleichrome, cercosporin, and 10 novel perylenequinones are detailed. The highly convergent and flexible strategy developed employed an enantioselective oxidative biaryl coupling and a double cuprate epoxide opening, allowing the selective syntheses of all the possible stereoisomers in pure form. In addition, this strategy permitted rapid access to a broad range of analogues, including those not accessible from the natural products. These compounds provided a powerful means for evaluation of the perylenequinone structural features necessary to PKC activity. Simpler analogues were discovered with superior PKC inhibitory properties and superior photopotentiation in cancer cell lines relative to the more complex natural products.

Cellular toxicity of elsinochrome phytotoxins produced by the pathogenic fungus, Elsinoë fawcettii causing citrus scab

Elsinochromes are the red/orange pigments produced by many Elsinoë fungal species and are structurally similar to the phytotoxin, cercosporin. Here, pigments were extracted from cultures of a citrus pathogen, Elsinoë fawcettii and tested for cellular toxicity. On irradiation with light, elsinochromes rapidly killed suspension cultured citrus and tobacco cells. The toxicity was decreased by adding the singlet oxygen ((1)O(2)) quenchers (bixin (carotenoid carboxylic acid), DABCO (1, 4-diazabicyco octane), ascorbate or reduced glutathione). Application of elsinochromes onto rough lemon leaves resulted in necrotic lesions, whereas lesion development was inhibited by the addition of bixin, DABCO or ascorbate, but not a-tocopherol. Incubation of rough lemon leaf discs with elsinochromes in the light induced a steady increase of electrolyte leakage. Compared with two photosensitizing compounds, hematoporphyrin and cercosporin, the accumulation of (1)O(2) induced by elsinochromes after irradiation was indicated by successful detection of the cholesterol oxidation product, 5a-hydroperoxide. Addition of a potent quencher, beta-carotene prevented 5alpha-hydroperoxide production. Elsinochromes generated superoxide ions (O(2)(*-)), whereas accumulation of O(2)(*-)was blocked by addition of the superoxide dismutase, a scavenger of O(2)(*-), but not the (1)O(2)-quencher, DABCO. Our study indicated that elsinochromes are functioning as photosensitizing compounds that produce (1)O(2)and O(2)(*-), and exert toxicity to plant cells.

Hypocrellins and their use in photosensitization

Hypocrellins A and B are pigments which are isolated from parasitic fungi Hypocrella bambuase (B. et Br) sacc. and Shiraia bambusicola P. Heen found in the People's Republic of China (P.R.C.) and Sri Lanka respectively. These agents, which belong to the general class of perylene quinonoid pigments, have a long history of traditional medicinal agents especially in the P.R.C. Recently their marked photosensitizing properties have been established and exploratory studies initiated. This effort has led to the realization of the potential of the hypocrellins for the photodynamic therapy of tumors. The review summarizes the chemical and photophysical properties of the hypocrellins and their derivatives as well as studies on photosensitization to date at the molecular, cellular and in vivo levels, and their prospects as PDT agents.