Minor Pyranonaphthoquinones from the Apothecia of the Lichen Ophioparma ventosa

A Review of the Chemistry and Biological Activities of Natural Colorants, Dyes, and Pigments: Challenges, and Opportunities for Food, Cosmetics, and Pharmaceutical Application

Natural pigments are important sources for the screening of bioactive lead compounds. This article reviewed the chemistry and therapeutic potentials of over 570 colored molecules from plants, fungi, bacteria, insects, algae, and marine sources. Moreover, related biological activities, advanced extraction, and identification approaches were reviewed. A variety of biological activities, including cytotoxicity against cancer cells, antioxidant, anti-inflammatory, wound healing, anti-microbial, antiviral, and anti-protozoal activities, have been reported for different pigments. Considering their structural backbone, they were classified as naphthoquinones, carotenoids, flavonoids, xanthones, anthocyanins, benzotropolones, alkaloids, terpenoids, isoprenoids, and non-isoprenoids. Alkaloid pigments were mostly isolated from bacteria and marine sources, while flavonoids were mostly found in plants and mushrooms. Colored quinones and xanthones were mostly extracted from plants and fungi, while colored polyketides and terpenoids are often found in marine sources and fungi. Carotenoids are mostly distributed among bacteria, followed by fungi and plants. The pigments isolated from insects have different structures, but among them, carotenoids and quinone/xanthone are the most important. Considering good manufacturing practices, the current permitted natural colorants are: Carotenoids (canthaxanthin, β-carotene, β-apo-8'-carotenal, annatto, astaxanthin) and their sources, lycopene, anthocyanins, betanin, chlorophyllins, spirulina extract, carmine and cochineal extract, henna, riboflavin, pyrogallol, logwood extract, guaiazulene, turmeric, and soy leghemoglobin.

Ultrastructural, Energy-Dispersive X-ray Spectroscopy, Chemical Study and LC-DAD-QToF Chemical Characterization of Cetraria islandica (L.) Ach

The lichen Cetraria islandica (L.) Ach. has been used in traditional and modern medicines for its many biological properties such as immunological, immunomodulating, antioxidant, antimicrobial, and anti-inflammatory activities. This species is gaining popularity in the market, with interest from many industries for selling as medicines, dietary supplements, and daily herbal drinks. This study profiled the morpho-anatomical features by light, fluorescence, and scanning electron microscopy; conducted an elemental analysis using energy-dispersive X-ray spectroscopy; and phytochemical analysis was performed using high-resolution mass spectrometry combined with a liquid chromatography system (LC-DAD-QToF) of C. islandica. In total, 37 compounds were identified and characterized based on comparisons with the literature data, retention times, and their mass fragmentation mechanism/s. The identified compounds were classified under five different classes, i.e., depsidones, depsides, dibenzofurans, aliphatic acids, and others that contain simple organic acids in majority. Two major compounds (fumaroprotocetraric acid and cetraric acid) were identified in the aqueous ethanolic and ethanolic extracts of C. islandica lichen. This detailed morpho-anatomical, EDS spectroscopy, and the developed LC-DAD-QToF approach for C. islandica will be important for correct species identification and can serve as a useful tool for taxonomical validation and chemical characterization. Additionally, chemical study of the extract of C. islandica led to isolation and structural elucidation of nine compounds, namely cetraric acid (1), 9'-(O-methyl)protocetraric acid (2), usnic acid (3), ergosterol peroxide (4), oleic acid (5), palmitic acid (6), stearic acid (7), sucrose (8), and arabinitol (9).

Phylogenetic Studies and Metabolite Analysis of Sticta Species from Colombia and Chile by Ultra-High Performance Liquid Chromatography-High Resolution-Q-Orbitrap-Mass Spectrometry

Eleven species of lichens of the genus Sticta, ten of which were collected in Colombia (S. pseudosylvatica S. luteocyphellata S. cf. andina S. cf. hypoglabra, S. cordillerana, S. cf. gyalocarpa S. leucoblepharis, S. parahumboldtii S. impressula, S. ocaniensis) and one collected in Chile (S. lineariloba), were analyzed for the first time using hyphenated liquid chromatography with high-resolution mass spectrometry. In the metabolomic analysis, a total of 189 peaks were tentatively detected; the analyses were divided in five (5) groups of compounds comprising lipids, small phenolic compounds, saturated acids, terpenes, and typical phenolic lichen compounds such as depsides, depsidones and anthraquinones. The metabolome profiles of these eleven species are important since some compounds were identified as chemical markers for the fast identification of Sticta lichens for the first time. Finally, the usefulness of chemical compounds in comparison to traditional morphological traits to the study of ancestor–descendant relationships in the genus was assessed. Chemical and morphological consensus trees were not consistent with each other and recovered different relationships between taxa.

Natural Product Investigation in Lichens: Extraction and HPLC Analysis of Secondary Compounds in Mycobiont Cultures

Chromatography techniques facilitate separation, purification, and identification of secondary compounds (natural products) in lichens and their mycobiont cultures. In particular, high-performance liquid chromatography (HPLC) plays a vital role in the identification of lichen substances because of its high sensitivity, speed, and reliability with the minimal sample. Therefore, we describe the extraction and HPLC protocol for the investigation of secondary compounds with a special focus on lichen mycobiont cultures.

A Review of Anti-Cancer and Related Properties of Lichen-Extracts and Metabolites

BACKGROUND

Lichens are a composite consortium of fungus and alga. The symbiotic organisms are naturally equipped with distinct characteristics as compared to constituting organisms separately. Lichens due to their peculiar anatomy and physiology, are the reservoir of more than 600 unique secondary metabolites, also known as 'lichen substances'. Since ancient times, many ethnic groups from various parts of the world had knowledge about the applications of lichens as major provenance of food/fodder, medicine, dyes, spices, perfumes, etc. Lichen substances have shown impressive antioxidant, antimicrobial, antiviral, antitumor, and anti-inflammatory activities under experimental conditions. Usnic acid, a well-known metabolite, found in several species of lichens, possesses potent antioxidant and anti-inflammatory activities. It also has significant anti-proliferative potential as revealed through testing in different cancer cell lines. Atranorin, Lecanoric acid, Norstictic acid, Lobaric acid, Stictic acid, Ramalin, Gyrophoric acid, Salazinic acid, Protolichesterinic, and Fumarprotocetraric acid are some of the other purified lichen metabolites with potent anti-cancer activities.

OBJECTIVE

This study presents an overview of lichen derived extracts/compounds augmenting the anti-cancer (related) properties.

METHOD

The review comprehends different studies (in vivo and in vitro) backing up the possibility of lichen extracts and metabolites towards their use as antioxidant, anti-proliferative, anti-inflammatory and EMT-inhibiting agents.

RESULTS

The review focuses on anti-cancer and related properties of lichen extracts and metabolites that include their anti-oxidative, anti-inflammatory, anti-proliferative and pro-apoptotic, cancer stemness reduction, activities and, the potential of inhibition of cancer-associated Epithelial-mesenchymal transition (EMT) that is responsible for multiple drug-resistance and metastasis of cancer cells in a large proportion of cases.

CONCLUSION

Lichens can be the repertoire of a plethora of lichen metabolites with putative bioactive potential, which is needed to be explored in order to find out novel anti-cancer drugs.

A database of high-resolution MS/MS spectra for lichen metabolites

While analytical techniques in natural products research massively shifted to liquid chromatography-mass spectrometry, lichen chemistry remains reliant on limited analytical methods, Thin Layer Chromatography being the gold standard. To meet the modern standards of metabolomics within lichenochemistry, we announce the publication of an open access MS/MS library with 250 metabolites, coined LDB for Lichen DataBase, providing a comprehensive coverage of lichen chemodiversity. These were donated by the Berlin Garden and Botanical Museum from the collection of Siegfried Huneck to be analyzed by LC-MS/MS. Spectra at individual collision energies were submitted to MetaboLights (https://www.ebi.ac.uk/metabolights/MTBLS999) while merged spectra were uploaded to the GNPS platform (CCMSLIB00004751209 to CCMSLIB00004751517). Technical validation was achieved by dereplicating three lichen extracts using a Molecular Networking approach, revealing the detection of eleven unique molecules that would have been missed without LDB implementation to the GNPS. From a chemist's viewpoint, this database should help streamlining the isolation of formerly unreported metabolites. From a taxonomist perspective, the LDB offers a versatile tool for the chemical profiling of newly reported species.

Secondary metabolism in the lichen symbiosis

Lichens, which are defined by a core symbiosis between a mycobiont (fungal partner) and a photobiont (photoautotrophic partner), are in fact complex assemblages of microorganisms that constitute a largely untapped source of bioactive secondary metabolites. Historically, compounds isolated from lichens have predominantly been those produced by the dominant fungal partner, and these continue to be of great interest for their unique chemistry and biotechnological potential. In recent years it has become apparent that many photobionts and lichen-associated bacteria also produce a range of potentially valuable molecules. There is evidence to suggest that the unique nature of the symbiosis has played a substantial role in shaping many aspects of lichen chemistry, for example driving bacteria to produce metabolites that do not bring them direct benefit but are useful to the lichen as a whole. This is most evident in studies of cyanobacterial photobionts, which produce compounds that differ from free living cyanobacteria and are unique to symbiotic organisms. The roles that these and other lichen-derived molecules may play in communication and maintaining the symbiosis are poorly understood at present. Nonetheless, advances in genomics, mass spectrometry and other analytical technologies are continuing to illuminate the wealth of biological and chemical diversity present within the lichen holobiome. Implementation of novel biodiscovery strategies such as metagenomic screening, coupled with synthetic biology approaches to reconstitute, re-engineer and heterologously express lichen-derived biosynthetic gene clusters in a cultivable host, offer a promising means for tapping into this hitherto inaccessible wealth of natural products.

Spatial mapping of lichen specialized metabolites using LDI-MSI: chemical ecology issues for Ophioparma ventosa

Imaging mass spectrometry techniques have become a powerful strategy to assess the spatial distribution of metabolites in biological systems. Based on auto-ionisability of lichen metabolites using LDI-MS, we herein image the distribution of major secondary metabolites (specialized metabolites) from the lichen Ophioparma ventosa by LDI-MSI (Mass Spectrometry Imaging). Such technologies offer tremendous opportunities to discuss the role of natural products through spatial mapping, their distribution patterns being consistent with previous chemical ecology reports. A special attention was dedicated to miriquidic acid, an unexpected molecule we first reported in Ophioparma ventosa. The analytical strategy presented herein offers new perspectives to access the sharp distribution of lichen metabolites from regular razor blade-sectioned slices.

In situ DART-MS as a Versatile and Rapid Dereplication Tool in Lichenology: Chemical Fingerprinting of Ophioparma ventosa

INTRODUCTION

Lichens widely occur all over the world and are known to produce unique secondary metabolites with various biological activities.

OBJECTIVE

To develop high-throughput screening approaches requiring little to no sample preparation to alleviate the dereplication holdup and accelerate the discovery workflow of new structures from lichens.

METHODOLOGY

The extracellular distribution of lichen metabolites is incentive for in situ chemical profiling of lichens using the ambient mass spectrometry DART-MS. For this purpose, the chlorolichen Ophioparma ventosa, producing an array of lichen polyphenolics that encompass the main structural classes associated to lichen chemodiversity, represented a relevant model to assess the versatility of this platform. The feasibility of this approach was first established by analysing the pure compounds known from this species prior to being extended to different solid organs of the lichen.

RESULTS

All tested compounds could be detected in positive and negative ion modes, most often with prevalent protonated or deprotonated molecules. Only depsides underwent a significant in-source fragmentation in both ionisation modes, which should be regarded as an added value for their structural elucidation. In situ DART-MS analyses of Ophioparma ventosa provided an extensive chemical profile and noteworthy pinpointed miriquidic acid, an unusual lichen depside so far unknown within this species. At last, in situ DART-MS granted a first insight into the distribution of the metabolites within the lichen.

CONCLUSION

DART-MS represents a versatile tool to the wide field of lichenology, facilitating accelerated and sharp analyses of lichens and bypassing costly and tedious procedures of solvent extraction. Copyright © 2016 John Wiley & Sons, Ltd.

Chemotaxonomic discrimination of lichen species using an infrared chalcogenide fibre optic sensor: a useful tool for on-field biosourcing

Spectral analysis of lichen extracts obtained by MIR-FEWS permits to discriminate species and the identification of their major compounds. MIR-FEWS is a rapid, efficient and convenient tool for metabolic profiling.