Are Ionic Liquids Better Extracting Agents Than Toxic Volatile Organic Solvents? A Combination of Ionic Liquids, Microwave and LC/MS/MS, Applied to the Lichen Stereocaulon glareosum

Microwave-Assisted Extraction of Secondary Metabolites Using Ethyl Lactate Green Solvent from Ambrosia arborescens: LC/ESI-MS/MS and Antioxidant Activity

Alternative solvents are being tested as green solvents to replace the traditional organic solvents used in both academy and industry. Some of these are already available, such as ethyl lactate, cyrene, limonene, glycerol, and others. This alternative explores eco-friendly processes for extracting secondary metabolites from nature, thus increasing the number of unconventional extraction methods with lower environmental impact over conventional methods. In this context, the Peruvian Ambrosia arborescens was our model while exploring a microwave-assisted extraction (MAE) approach over maceration. The objective of this study was to perform a phytochemical study including UHPLC-ESI-MS/MS and the antioxidant activity of Ambrosia arborescens, using sustainable strategies by mixing both microwaves and ethyl lactate as a green solvent. The results showed that ethyl lactate/MAE (15.07%) achieved a higher extraction yield than methanol/maceration (12.6%). In the case of the isolation of psilostachyin, it was similar to ethyl lactate (0.44%) when compared to methanol (0.40%). Regarding UHPLC-ESI-MS/MS studies, the results were similar. Twenty-eight compounds were identified in the ethyl lactate/MAE and methanol/maceration extracts, except for the tentative identification of two additional amino acids (peaks 4 and 6) in the MeOH extract. In relation to the antioxidant assay, the activity of the ethyl lactate extract was a little higher than the methanol extract in terms of ORAC (715.38 ± 3.2) and DPPH (263.04 ± 2.8). This study on A. arborescens demonstrated that the unconventional techniques, such as MAE related to ethyl lactate, could replace maceration/MeOH for the extraction and isolation of metabolites from diverse sources. This finding showed the potential of unconventional methods with green solvents to provide eco-friendly methods based on green chemistry.

Green ultrasound-assisted extraction of lichen substances from Hypotrachyna cirrhata. Ethyl lactate, a better extracting agent than methanol toxic organic solvent?

For the first time, we report a green extraction of lichen substances assisted by high power ultrasounds from Hypotrachyna cirrhata using ethyl lactate. This sustainable alternative was comparable, both in isolation and detection of lichen substances, to methanol. In the metabolomic analysis, a total of 77 lichen substances were detected comprising depsides, depsidones, dibenzofurans, organic acids, and lipids. Although the UHPLC/ESI/MS profiles were similar, the antioxidant activity was higher for the ethyl lactate extract. Ethyl lactate can replace toxic organic solvents, such as methanol, in order to provide more sustainable green chemistry methods.

A sustainable application for the extraction of lichen metabolites from Usnea cornuta: nontargeted metabolomics and antioxidant activity

In this study, isolation and purification of lichen substances from Usnea cornuta were performed using conventional solvents, green solvents and green technologies. In addition, several lichen compounds were tentatively identified by UHPLC/ESI/MS/MS and usnic acid, diffractaic and galbinic acids were quantified as well. Limonene, ethyl lactate and methanol, were compared regarding their extraction properties and antioxidant capacities, determined by DPPH, ORAC, and FRAP assays. In the ethyl lactate, methanol and limonene extracts, 28 compounds in all, were detected for the first time by high resolution UHPLC-MS/MS fingerprinting. Untargeted metabolomics tentatively identified 14 compounds from the methanolic extract, 4 from limonene extract, and 20 metabolites from ethyl lactate extract. The green extract of ethyl lactate showed a similar antioxidant capacity to toxic methanol extract, except at ORAC assay where it was higher. Therefore, ethyl lactate can replace methanol, to provide more sustainable green chemistry methods.

Two New Fumarprotocetraric Acid Lactones Identified and Characterized by UHPLC-PDA/ESI/ORBITRAP/MS/MS from the Antarctic Lichen Cladonia metacorallifera

Lichens are symbiotic organisms between algae and fungi, which are makers of secondary compounds named as lichen substances. Hyphenated techniques have significantly helped natural product chemistry, especially UHPLC/ESI/MS/MS in the identification, separation, and tentative characterization of secondary metabolites from natural sources. Twenty-five compounds were detected from the Antarctic lichen Cladonia metacorallifera for the first time using UHPLC-PDA/ESI/Orbitrap/MS/MS. Compounds 5 and 7 are reported as new compounds, based on their MS/MS fragmentation routes, and considered as fumarprotocetraric acid derivatives. Besides, ten known phenolic identified as orsellinic acid, ethyl 4-carboxyorsellinate, psoromic acid isomer, succinprotocetraric acid, siphulellic acid, connorstictic acid, cryptostictic acid, lecanoric acid, lobaric acid and gyrophoric acid are noticed for the first time in the Cladonia genus.

Efficiency and selectivity of ionic liquids in microwave-assisted extraction of major lichen phenolic compounds: a scalable process with recycling of ionic liquids

INTRODUCTION

Pseudevernia furfuracea, a lichen used classically for cosmetic applications, contains interesting metabolites possessing antimicrobial and anti-inflammatory or antioxidant properties.

OBJECTIVES

Ionic liquid combined to microwave-assisted extraction (IL-MAE) was successfully applied for metabolites extraction from Pseudevernia furfuracea.

MATERIALS AND METHODS

Three imidazolium and pyridinium-based ionic liquids (ILs): 1,3-dimethylimidazolium methylsulphate [C₁ C₁ Im][MeSO₄ ], 1-ethyl-3-methylimidazolium ethylsulphate [C₂ C₁ Im][EtSO₄ ], and N-ethylpyridinium ethylsulphate [C₂ Py][EtSO₄ ] were assessed for this process. The efficiency of the extraction method was evaluated using thin-layer chromatography (TLC) coupled to a Camag® spectrophotodensitometer and using high-performance liquid chromatography (HPLC) analysis.

RESULTS

ILs under MAE showed extraction time efficiency (15 min vs. 24 h for conventional heating) and high selectivity in extracting the targeted metabolites: atranorin (AT), methyl-β-orcinol carboxylate (MOC), fumarprotocetraric acid (Fum. Ac.), and physodic acid (Phys. Ac.) despite the increased degradation of AT under MAE. We showed a tunable selectivity of ILs towards extracting metabolites by changing anion or cation due to the modification of the interaction between the IL and the metabolites. While [C₂ Py][EtSO₄ ] was the most efficient IL and could extract all the targeted metabolites, [C₂ C₁ Im][EtSO₄ ] was the most selective. It fully extracted AT and partially Fum. Ac. Moreover, the lichen prepared by mixing procedure provided AT and Fum. Ac. more than the milled one. A 100 times scale-up extraction was successfully performed on mixed samples with full IL recycling after back extraction.

CONCLUSION

IL-MAE is reliable for lichen metabolites extraction. The method is reproducible, scalable, with possible IL recycling, opening the door for potential industrial applications.

Rethinking the Applications of Ionic Liquids and Deep Eutectic Solvents in Innovative Nano-Sorbents

With the development of green chemistry and nano materials, new alternatives to traditional volatile solvents are one of many important hotspots in the field of nano materials. Ionic liquids (ILs) and deep eutectic solvents (DESs) as excellent alternative solvents are being applied in the innovation of nano-sorbents, including nanoparticles, nanogels, and nanofluid. ILs and DESs are often used as carriers/modifiers/dispersers of nano-sorbents to enhance the adsorption capacity and selectivity in the extraction procedure. Various extraction technologies, such as solid-phase extraction, solid-phase microextraction, micro-solid phase extraction, hollow fiber liquid phase microextraction, and magnetic solid-phase extraction, have also been promoted by them to achieve rapid development. This paper focused on the latest development of nano-sorbents based on ILs and DESs. The problems and bottlenecks encountered were analyzed in order to provide meaningful and valuable references for the related research and thus promote further development and application of alternative solvents-assisted nano-sorbents.

Correlating Bromelain's activity with its structure and active-site dynamics and the medium's physical properties in a hydrated deep eutectic solvent

Deep eutectic solvents (DESs) are emerging as new media of choice for biocatalysis due to their environmentally friendly nature, fine-tunability, and potential biocompatibility. This work deciphers the behaviour of bromelain in a ternary DES composed of acetamide, urea, and sorbitol at mole fractions of 0.5, 0.3, and 0.2, respectively (0.5Ac/0.3Ur/0.2Sor), with various degrees of hydration. Bromelain is an essential industrial proteolytic enzyme, and the chosen DES is non-ionic and liquid at room temperature. This provides us with a unique opportunity to contemplate protein behaviour in a non-ionic DES for the very first time. Our results infer that at a low DES concentration (up to 30% V/V DES), bromelain adopts a more compact structural conformation, whereas at higher DES concentrations, it becomes somewhat elongated. The microsecond conformational fluctuation time around the active site of bromelain gradually increases with increasing DES concentration, especially beyond 30% V/V. Interestingly, bromelain retains most of its enzymatic activity in the DES, and at some concentrations, the activity is even higher compared with its native state. Furthermore, we correlate the activity of bromelain with its structure, its active-site dynamics, and the physical properties of the medium. Our results demonstrate that the compact structural conformation and flexibility of the active site of bromelain favour its proteolytic activity. Similarly, a medium with increased polarity and decreased viscosity is favourable for its activity. The presented physical insights into how enzymatic activity depends on the protein structure and dynamics and the physical properties of the medium might provide useful guidelines for the rational design of DESs as biocatalytic media.

Mass Spectrometry: A Rosetta Stone to Learn How Fungi Interact and Talk

Fungi are a highly diverse group of heterotrophic organisms that play an important role in diverse ecological interactions, many of which are chemically mediated. Fungi have a very versatile metabolism, which allows them to synthesize a large number of still little-known chemical compounds, such as soluble compounds that are secreted into the medium and volatile compounds that are chemical mediators over short and long distances. Mass spectrometry (MS) is currently playing a dominant role in mycological studies, mainly due to its inherent sensitivity and rapid identification capabilities of different metabolites. Furthermore, MS has also been used as a reliable and accurate tool for fungi identification (i.e., biotyping). Here, we introduce the readers about fungal specialized metabolites, their role in ecological interactions and provide an overview on the MS-based techniques used in fungal studies. We particularly present the importance of sampling techniques, strategies to reduce false-positive identification and new MS-based analytical strategies that can be used in mycological studies, further expanding the use of MS in broader applications. Therefore, we foresee a bright future for mass spectrometry-based research in the field of mycology.