Jorge Bórquez

Lichens are mutualistic symbiosis between a fungus (mycobiont) and an alga or cyanobacteria (photobiont), forming metabolically versatile holobionts capable of producing diverse secondary metabolites that facilitate their survival in extreme environments. Chrysothrix species, commonly known as “gold dust lichens,” are characterized by their vivid yellow thalli and their production of pulvinic acid derivatives, although their bioactive potential remains poorly explored. In this study, using organic chemistry techniques, we characterized the methanolic extract of Chrysothrix sp.—collected from the Paposo Fog Oasis in northern Chile, a unique coastal ecosystem sustained by persistent fog (“camanchacas”) within the Atacama Desert—and identified calycin as its major secondary metabolite through chromatographic purification and single-crystal X-ray diffraction. Antibacterial assays revealed that both the crude methanolic extract and purified calycin exhibited selective inhibitory activity against multidrug-resistant Gram-positive ESKAPE-E pathogens. Minimum Inhibitory Concentrations (MICs) ranged from 125 to 500 μg/mL, with the strongest effects observed against Enterococcus faecium (MDR, VRE) and Staphylococcus aureus (MDR, MRSA). No meaningful activity was detected against Gram-negative bacteria, consistent with the known permeability barrier conferred by the outer membrane. This work provides the first evidence of antibacterial activity for calycin isolated from Chrysothrix sp., highlighting the relevance of pulvinic acid derivatives as promising scaffolds for antimicrobial development. These findings highlight the potential of lichen-derived agents and alternative sources of antibacterial agents to address the global challenge of antimicrobial resistance.

Gypothamnium pinifolium Phil. (Asteraceae) is a small shrub that grows in the Paposo Valley of the II Antofagasta Region of Chile. This initial study is of the high-resolution phenolic fingerprinting, antioxidant activity, the relaxation effects in rat aorta, the inhibitory enzyme potential, plus the antiproliferative activity of the ethyl acetate and n-hexane extract from G. pinifolium and its two major isolated secondary metabolites (one coumarin: 2-nor-1,2-secolycoserone, and one diterpene: ent-labda-8,13-E-diene-15-ol). The study involves using ultra-high-performance liquid chromatography todiode array detection coupled with Q-Orbitrap mass spectrometry analysis (UHPLC-PDA-Orbi-trap-MS), in which various compounds were identified, including specific coumarins. The n-hexane extract showed total phenolic and flavonoid contents of 517.4 ± 12.5 mg GAE/100 g extract and 72.3 ± 3.7 mg QE/100 g extract, respectively. In addition, the antioxidant activity of the n-hexane extract was assessed using in-vitro assays such as bleaching of DPPH and ABTS (IC₅₀: 14.3 ± 0.52 and 2.51 ± 0.43 µg extract/mL, respectively), FRAP (347.12 ± 1.15 μmol Trolox equivalent/g extract), and ORAC (287.3 ± 1.54 μmol Trolox equivalents/g extract). Furthermore, the inhibition against cholinesterases (acetylcholinesterase (AChE) 4.58 ± 0.04 µg/mL, butyrylcholinesterase (BChE) IC₅₀: 23.44 ± 0.03 µg/mL) and tyrosinase (IC₅₀: 9.25 ± 0.15 µg/mL) enzymes of the n-hexane extract, and main compounds (IC₅₀: 1.21 ± 0.03 µg/mL, 11.23 ± 0.02 µg/mL, 3.23 ± 0.12 µg/mL, and 103.43 ± 16.86 µg/mL, correspondingly for the most active coumarin 1) were measured. The antiproliferative potential of the extracts and the two principal compounds against several solid human cancer cells was investigated. All of them showed good activity against cancer cells. Label-free live-cell imaging studies on HeLa cells exposed to the isolated coumarin and the diterpene enabled the observation of cell death and several apoptotic hallmarks. Our results indicate that G. pinifolium Phil. is a valuable source of secondary metabolites with potential activity against noncommunicable diseases.

Ovidia pillopillo (Lloime) is an endemic species of the Valdivian Forest of Chile. Little is known on the chemistry and biological activity of this plant. In this study, the phenolic profile, antioxidant capacities and enzyme inhibition capacities (against tyrosinase and cholinesterase) of the plant were investigated for the first time. The phenolic profile of the plant was obtained by UHPLC-MS fingerprinting with high resolution, which showed the presence of several flavonoids and coumarins. The antioxidant potential was measured by FRAP and ORAC (45.56 ± 1.32; 25.33 ± 1.2 μmol Trolox equivalents/g dry plant, respectively) plus ABTS and DPPH methods (IC₅₀ = 9.95 ± 0.05 and 6.65 ± 0.5 μg/mL, respectively). Moreover, the flavonoid and phenolic contents were determined (57.33 ± 0.82 and 38.42 ± 1.32, μg of Trolox and quercetin equivalents/100 g dry weight, respectively). The ethanolic extract showed cholinesterase (IC₅₀ = 1.94 ± 0.07 and 2.73 ± 0.05 μg/mL, for AChE and BuChE, respectively) and tyrosinase (4.92 ± 0.05 μg/mL) enzyme inhibition activities. Based on these in vitro studies, in silico simulations were performed, which determined that the major compounds as ligands likely docked in the receptors of the enzymes. These results suggest that Ovidia pillopillo produce interesting special coumarins and flavonoids, which are potential candidates for the exploration and preparation of new medicines.

Tuberculosis causes more than 1.2 million deaths each year. Worldwide, it is the first cause of death by a single infectious agent. The emergence of drug-resistant strains has limited pharmacological treatment of the disease and today, new drugs are urgently needed. Semi-synthetic mulinanes have previously shown important activity against multidrug-resistant (MDR) Mycobacterium tuberculosis. In this investigation, a new set of semi-synthetic mulinanes were synthetized, characterized, and evaluated for their in vitro activity against three drug-resistant clinical isolates of M. tuberculosis: MDR, pre-extensively Drug-Resistant (pre-XDR), and extensively Drug-Resistant (XDR), and against the drug-susceptible laboratory reference strain H37Rv. Derivative 1a showed the best anti-TB activity (minimum inhibitory concentration [MIC] = 5.4 µM) against the susceptible strain and was twice as potent (MIC = 2.7 µM) on the MDR, pre-XDR, and XDR strains and also possessed a bactericidal effect. Derivative 1a was also tested for its anti-TB activity in mice infected with the MDR strain. In this case, 1a produced a significant reduction of pulmonary bacilli loads, six times lower than the control, when tested at 0.2536 mg/Kg. In addition, 1a demonstrated an adjuvant effect by shortening second-line chemotherapy. Finally, the selectivity index of >15.64 shown by 1a when tested on Vero cells makes this derivative an important candidate for future studies in the development of novel antitubercular agents.

The implementation of corrosion engineering control methods and techniques is crucial to extend the life of urban and industrial infrastructure assets and industrial equipment affected by natural corrosion. Then, the search of stable and environmentally friendly corrosion inhibitors is an important pending task. Here, we provide experimental evidence on the corrosion inhibitory activity of aqueous extracts of Skytanthus acutus Meyen leaf, a native plant from the Atacama Desert in northern Chile. Skytanthus extracts as a powder should be prepared at 55 °C to avoid thermal decomposition and loss of corrosion inhibitory activity. Corrosion of carbon steel AISI1020 immersed in 0.5 M NaCl was evaluated in the presence of different doses of Skytanthus extract by complementary and simultaneous linear polarization, electrochemical impedance spectroscopy, and weight-loss technique under high hydrodynamic conditions. Mixed Potential Theory was applied to confirm the electrochemical activity of the extract inhibitory capabilities. The Skytanthus extracts reached a 90% corrosion inhibitory efficiency when tested at 100 to 1200 ppm in a time span of 48 h, through an electrochemical interaction between the extract inhibitor component and the carbon steel surface. The corrosion inhibition activity observed in Skytanthus dry extracts involves a protective film formation by a mechanism that includes an iron dissolution at the expense of either oxygen reduction and/or hydrogen evolution, followed by a ferrous-ferric iron cycling, the formation of an iron complex and adsorption to the metal surface, and, finally, desorption or degradation of the protecting film. The water-soluble plant extract was subjected to HPLC-MS analyses that rendered 14 major signals, with quinic acid, protocatechuic acid, chlorogenic acid isomers, vanillic acid hexoside, and patuletin 3-methoxy-7-glucoside as the most abundant components. Then, we propose that a phenolic derivative is responsible for the corrosion inhibitory activity found in Skytanthus extracts.

Haloarchaea are extreme halophilic microorganisms belonging to the domain Archaea, phylum Euryarchaeota, and are producers of interesting antioxidant carotenoid compounds. In this study, four new strains of Haloarcula sp., isolated from saline lakes of the Atacama Desert, are reported and studied by high-resolution mass spectrometry (UHPLC-Q-Orbitrap-MS/MS) for the first time. In addition, determination of the carotenoid pigment profile from the new strains of Haloarcula sp., plus two strains of Halorubrum tebenquichense, and their antioxidant activity by means of several methods is reported. The effect of biomass on cellular viability in skin cell lines was also evaluated by MTT assay. The cholinesterase inhibition capacity of six haloarchaea (Haloarcula sp. ALT-23; Haloarcula sp. TeSe-41; Haloarcula sp. TeSe-51; Haloarcula sp. Te Se-89 and Halorubrum tebenquichense strains TeSe-85 and Te Se-86) is also reported for the first time. AChE inhibition IC₅₀ was 2.96 ± 0.08 μg/mL and BuChE inhibition IC₅₀ was 2.39 ± 0.09 μg/mL for the most active strain, Halorubrum tebenquichense Te Se-85, respectively, which is more active in BuCHe than that of the standard galantamine. Docking calculation showed that carotenoids can exert their inhibitory activity fitting into the enzyme pocket by their halves, in the presence of cholinesterase dimers.