Targeted isolation of photoactive pigments from mushrooms yielded a highly potent new photosensitizer: 7,7′-biphyscion

Revised taxon definition in European Cortinarius subgenus Dermocybe based on phylogeny, chemotaxonomy, and morphology

Cortinarius (Fr.) Fr. is one of the most species-rich genera in the Agaricales (Basidiomycota). Cortinarius subgen. Dermocybe (Fr.) Trog includes brightly coloured Cortinarii with anthraquinone pigments. The chemotaxonomic approach has always been as important as classical methods for species definition of Dermocybe and helped to improve overall species concepts. However, some species concepts within this group remain unclear. We therefore address this topic based on a combined phylogenetic, morphological, and pigment-chemical approach. For this, sequence data, HPLC-MS pigment profiles and spore sizes were included were included to obtain a better resolution of taxa. The study was based on 173 recent collections and 12 type specimens. A total of 117 rDNA ITS sequences were produced from the collections in this study, 102 sequences were retrieved from databases. We could detect and clearly delimit 19 Dermocybe species occurring in central European habitats, from which 16 are discussed in detail. Additionally, we grouped the detected anthraquinone pigments into four groups. This detailed analysis of dermocyboid Cortinarius species occurring in a restricted number of habitat types confirmed our hypothesis that species diversity is much higher than currently assumed. This high diversity is blurred by too wide and incorrect species concepts of several classical species like C. croceus and C. cinnamomeus. Molecular and chemotaxonomical studies carried out together with careful phenotypical analyses resulted in a good differentiation of species. A key is presented for these taxa to allow a better identification of Cortinarius subgenus Dermocybe spp. occurring in Central Europe mainly in the alpine range.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11557-024-01959-z.

Ruthenium-Based Photoactivated Chemotherapy

Ruthenium(II) polypyridyl complexes form a vast family of molecules characterized by their finely tuned photochemical and photophysical properties. Their ability to undergo excited-state deactivation via photosubstitution reactions makes them quite unique in inorganic photochemistry. As a consequence, they have been used, in general, for building dynamic molecular systems responsive to light but, more particularly, in the field of oncology, as prodrugs for a new cancer treatment modality called photoactivated chemotherapy (PACT). Indeed, the ability of a coordination bond to be selectively broken under visible light irradiation offers fascinating perspectives in oncology: it is possible to make poorly toxic agents in the dark that become activated toward cancer cell killing by simple visible light irradiation of the compound inside a tumor. In this Perspective, we review the most important concepts behind the PACT idea, the relationship between ruthenium compounds used for PACT and those used for a related phototherapeutic approach called photodynamic therapy (PDT), and we discuss important questions about real-life applications of PACT in the clinic. We conclude this Perspective with important challenges in the field and an outlook.

Fungal Anthraquinone Photoantimicrobials Challenge the Dogma of Cationic Photosensitizers

The photoantimicrobial potential of four mushroom species (i.e., Cortinarius cinnabarinus, C. holoxanthus, C. malicorius, and C. sanguineus) was explored by studying the minimal inhibitory concentrations (MIC) via a light-modified broth microdilution assay based on the recommended protocols of the European Committee on Antimicrobial Susceptibility Testing (EUCAST). The extracts were tested against Candida albicans, Escherichia coli, and Staphylococcus aureus under blue (λ = 428 and 478 nm, H = 30 J/cm2) and green light (λ = 528 nm, H = 30 J/cm2) irradiation. Three extracts showed significant photoantimicrobial effects at concentrations below 25 μg/mL. Targeted isolation of the major pigments from C. sanguineus led to the identification of two new potent photoantimicrobials, one of them (i.e., dermocybin) being active against S. aureus and C. albicans under green light irradiation [PhotoMIC530 = 39.5 μM (12.5 μg/mL) and 2.4 μM (0.75 μg/mL), respectively] and the other one (i.e., emodin) being in addition active against E. coli in a low micromolar range [PhotoMIC428 = 11.1 μM (3 μg/mL)]. Intriguingly, dermocybin was not (photo)cytotoxic against the three tested cell lines, adding an additional level of selectivity. Since both photoantimicrobials are not charged, this discovery shifts the paradigm of cationic photosensitizers.

Highlighting the Phototherapeutical Potential of Fungal Pigments in Various Fruiting Body Extracts with Informed Feature-Based Molecular Networking

Fungal pigments are characterized by a diverse set of chemical backbones, some of which present photosensitizer-like structures. From the genus Cortinarius, for example, several biologically active photosensitizers have been identified leading to the hypothesis that photoactivity might be a more general phenomenon in the kingdom Fungi. This paper aims at testing the hypothesis. Forty-eight fruiting body-forming species producing pigments from all four major biosynthetic pathways (i.e., shikimate-chorismate, acetate-malonate, mevalonate, and nitrogen heterocycles) were selected and submitted to a workflow combining in vitro chemical and biological experiments with state-of-the-art metabolomics. Fungal extracts were profiled by high-resolution mass spectrometry and subsequently explored by spectral organization through feature-based molecular networking (FBMN), including advanced metabolite dereplication techniques. Additionally, the photochemical properties (i.e., light-dependent production of singlet oxygen), the phenolic content, and the (photo)cytotoxic activity of the extracts were studied. Different levels of photoactivity were found in species from all four metabolic groups, indicating that light-dependent effects are common among fungal pigments. In particular, extracts containing pigments from the acetate-malonate pathway, e.g., extracts from Bulgaria inquinans, Daldinia concentrica, and Cortinarius spp., were not only efficient producers of singlet oxygen but also exhibited photocytotoxicity against three different cancer cell lines. This study explores the distribution of photobiological traits in fruiting body forming fungi and highlights new sources for phototherapeutics.

Photochemical defense as trait of fungi from Cortinarius subgenus Dermocybe

The photobiological activity of ten colorful species belonging to subgenus Dermocybe of the basidiomycete genus Cortinarius was investigated. Extracts of all species produced singlet oxygen and are thus photoactive. Pigment analysis was performed and showed similarities of the anthraquinone pigments across the species in dependency to their respective pigmentation types. Detailed content analysis of the pigments in the whole agaricoid fruiting body compared to the three different tissue types (pileus, stipe, and lamellae) revealed that the pigments emodin, dermocybin, and dermorubin, as well as their respective glycosides, are enhanced in the gills. In an independent experiment, the gills were shown to be the most photoactive tissues of the fruiting body. Photobiological experiments with invertebrates (i.e., glassworm Chaoborus crystallinus) proved a phototoxic effect of the methanolic extract of the red blood webcap (Cortinarius sanguineus var. aurantiovaginatus). This work adds further evidence to a common photobiological trait in Cortinarius subgenus Dermocybe and underpins the possibility of a photochemical defense mechanism in fungi.

Development of Biotechnological Photosensitizers for Photodynamic Therapy: Cancer Research and Treatment-From Benchtop to Clinical Practice

Photodynamic therapy (PDT) is a noninvasive therapeutic approach that has been applied in studies for the treatment of various diseases. In this context, PDT has been suggested as a new therapy or adjuvant therapy to traditional cancer therapy. The mode of action of PDT consists of the generation of singlet oxygen (¹O₂) and reactive oxygen species (ROS) through the administration of a compound called photosensitizer (PS), a light source, and molecular oxygen (³O₂). This combination generates controlled photochemical reactions (photodynamic mechanisms) that produce ROS, such as singlet oxygen (¹O₂), which can induce apoptosis and/or cell death induced by necrosis, degeneration of the tumor vasculature, stimulation of the antitumor immune response, and induction of inflammatory reactions in the illuminated region. However, the traditional compounds used in PDT limit its application. In this context, compounds of biotechnological origin with photosensitizing activity in association with nanotechnology are being used in PDT, aiming at its application in several types of cancer but with less toxicity toward neighboring tissues and better absorption of light for more aggressive types of cancer. In this review, we present studies involving innovatively developed PS that aimed to improve the efficiency of PDT in cancer treatment. Specifically, we focused on the clinical translation and application of PS of natural origin on cancer.