Specialized Metabolites of the Lichen Vulpicida pinastri Act as Photoprotective Agents.

The extreme resiliency of lichens to UV radiations makes them an interesting model to find new photoprotective agents acting as UV-blockers and antioxidant. In this research, using a new in vitro method designed to overcome the shortage of material associated to many studies dealing with natural products, we show that the three major compounds isolated from the lichen Vulpicida pinastri, vulpinic acid, pinastric acid and usnic acid, were UV blocker agents. Antioxidant assays evidenced superoxide anion scavenging activity. Combination of the most promising compounds against UVB and UVB radiations, usnic acid, vulpinic acid and pinastric acid, increased the photoprotective activity. At the same time, they were found not cytotoxic on keratinocyte cell lines and photostable in the UVA and UVB ranges. Thus, lichens represent an attractive source to find good candidate ingredients as photoprotective agents. Additionally, the uncommon scalemic usnic acid mixture in this Vulpicida species was proven through electronic circular dichroism calculation.

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.

Minor Pyranonaphthoquinones from the Apothecia of the Lichen Ophioparma ventosa.

Four new quinonoid naphthopyranones, ophioparmin (1), 4-methoxyhaemoventosins (2a and 2b), and 4-hydroxyhaemoventosin (3), together with anhydrofusarubin lactone (4) and haemoventosin (5) were isolated from the fruiting bodies of Ophioparma ventosa, a crustose lichen. Their structures were determined by spectroscopic analyses, and the absolute configurations of 1 and 2 were elucidated through experimental and calculated electronic circular dichroism analyses. Compounds 1, 2, and 5 exhibited moderate to strong antioxidant activities. The main pigment haemoventosin exhibited significant cytotoxicity toward a panel of nine cell lines.

Matrix-Free UV-Laser Desorption Ionization Mass Spectrometry as a Versatile Approach for Accelerating Dereplication Studies on Lichens.

The present study examined the suitability of laser desorption/ionization time-of-flight mass spectrometry (LDI-MS) for the rapid chemical fingerprinting of lichen extracts. Lichens are known to produce a wide array of secondary metabolites. Most of these compounds are unique to the symbiotic condition but some can be found in many species. Therefore, dereplication, that is, the rapid identification of known compounds within a complex mixture is crucial in the search for novel natural products. Over the past decade, significant advances were made in analytical techniques and profiling methods specifically adapted to crude lichen extracts, but LDI-MS has never been applied in this context. However, most classes of lichen metabolites have UV chromophores, which are quite similar to commercial matrix molecules used in matrix-assisted laser desorption ionization (MALDI). It is consequently postulated that these molecules could be directly detectable by matrix-free LDI-MS. The present study evaluated the versatility of this technique by investigating the LDI properties of a vast array of single lichen metabolites as well as lichen extracts of known chemical composition. Results from the LDI experiments were compared with those obtained by direct ESI-MS detection as well as LC-ESI-MS. It was shown that LDI ionization leads to strong molecular ion formation with little fragmentation, thus, facilitating straightforward spectra interpretation and representing a valuable alternative to time-consuming LC-MS analysis.

Analysis of the cyanolichen Lichina pygmaea metabolites using in situ DART-MS: from detection to thermochemistry of mycosporine serinol.

Direct Analysis in Real Time DART-HRMS is here first applied to the detection of molecules from a lichen, Lichina pygmaea. The aim was to propose an innovative method of in situ detection of lichen secondary metabolites using the possibilities of elemental composition determination available when a DART source is interfaced with a TOF analyzer. Three kinds of samples have been submitted to DART ionization, i.e. an intact thallus, a powder obtained from the crushed lichen and an aqueous extract. In situ analysis of crushed lichen, yields an extensive chemical profile, comparable to what is obtained from the aqueous extract, comprising both major polar metabolites described in literature along with some other signals that could correspond to potentially unknown metabolites. One of the detected secondary metabolites, mycosporine serinol, underwent a dehydration reaction prior to its transfer in the gas-phase by DART ionization. The consideration of the thermal transfers involved in the DART ionization process and the possibility to record time-dependent mass spectra through the use of the TOF analyzer allowed establishing Arrhenius plots of this water molecule loss to obtain associated thermodynamic quantities. The low values of corresponding activation enthalpy (Δr‡Hm° of the order of 25 kJ mol(-1)) enabled formulating some assumption regarding a possible role of such metabolites in the lichen.

Lichenic extracts and metabolites as UV filters.

Three lichen extracts and ten lichenic compounds have been screened for their photoprotective activities. The determination of their Sun Protection Factor (SPF) and Protection Factor-UVA (PF-UVA) values was done in vitro. Among them, a Lasallia pustulata extract and gyrophoric acid exhibited SPF values over 5, which is better than Homosalate (SPF≈4). Their photoprotective properties are only slightly modified after a 2-hours period of irradiation. Salazinic acid and L. pustulata presented characteristics of a UVA booster like the butyl-methoxydibenzoylmethane (Avobenzone) (PF-UVA≈2 vs. 2.8 for Avobenzone). Salazinic acid was a better anion superoxide scavenger than ascorbic acid and none of them exhibited a photosensitizing cytotoxicity by exposing them on HaCaT cells to UVA radiations (photo-irritancy factor PIF<5).

Novel chiral molecular tweezer from (+)-usnic acid.

A new chiral molecular tweezer was synthesized with (1R,2R)-1,2-diaminocyclohexane as spacer and two molecules of (+)-usnic acid as pincers. The ability of this molecular tweezer to bind 2,4,7-trinitrofluorenone was studied. A charge-transfer complex was formed in which TNF was sandwiched between the two usnic acid units with pi-pi-stacked aromatic interactions.