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Aromatic and medicinal plants form a reservoir of active molecules; among them, Juglans regia is a plant of the Juglandaceae family, and it is used thanks to its medicinal properties. The present study was conducted to investigate the secondary metabolite content and biological activities of the infusion, methanolic extracts, and essential oil of the bark essential oil (EO) of Juglans regia harvested from North Tunisia, as well as its chemical composition. Essential oil, infusion, and methanolic extracts were prepared. Identification of essential oil composition was determined using GC-MS. Phenolic content, antioxidant, and antimicrobial activities were evaluated with the colorimetric method. The obtained data indicate that J. regia is very abundant in bioactive compounds. The infusion extract of J. regia bark has been found to contain elevated amounts of phenolic compounds. The infusion extract showed stronger antioxidants and radical scavenging action than methanol. The studied methanolic extract displayed antimicrobial activity against all ten tested microbial strains but with variable degrees according to the microbial strain. The infusion extract, instead, was inactive. The use of gas chromatography coupled with mass spectrometry (GC-MS) revealed the existence of 34 components in the bark (EO). The main compounds were: carvacrol (13.82%), isoeugenol (13.71%), β-caryophyllene (7.81%), 1,8-cineole (8.60%), and bornyl acetate (7.13%). Our results suggest that Juglans regia is a natural source of potent antioxidants and antimicrobials and may be useful as preventive agents in some diseases.

The lichen's special symbiotic structure enables it to produce bioactive substances. They have historically been recognized for their aesthetic and medicinal benefits. Furthermore, in recent years, they have performed in various fields, including perfumery, dyeing, and pharmacology due to their rich secondary metabolites. From our study, four compounds were isolated from organic extracts of Parmotrema hypoleucinum, Roccella phycopsis, and Xanthoria parietina and identified by spectroscopic investigation as atranorin, (+)-iso-usnic acid, methyl orsellinate, and parietin, respectively. The anti-inflammatory effects of lichens extracts, and pure compounds were evaluated on RAW 264.7 macrophages cells at different concentrations. At 25 μg/mL all treated samples did not show any effect on cell viability. Atranorin and (+)-iso-usnic acid showed an inhibitory effect on nitric oxide (NO) levels in lipopolysaccharide (LPS)-stimulated macrophages. Nitric oxide (NO) production was measured using Griess reagent, atranorin and (+)-iso-usnic acid showed a high anti-inflammatory potential (75.99 % and 57.27 % at 25 μg/mL). On the other hand, methyl orsellinate and the organic extracts of three lichens showed good anti-inflammatory activity ranging from 29.16 % at 25 μg/mL to 86.91 % at 100 μg/mL.

The effects of the lichenicolous fungus Heterocephalacria bachmannii on the antimicrobial potential of the lichen Cladonia foliacea demonstrated that the extracts investigated have antimicrobial potential against gram-positive and negative bacteria, and yeast, and inhibit the germination of fungal spores. Inhibition activity varied considerably depending on the extract, the bacterial species, and the absence or presence of H. bachmannii; unparasitised C. foliacea has a higher antimicrobial activity. Methanol and acetone extracts of C. foliacea alone have higher inhibition diameters than C. foliacea with H. bachmannii against Enterobacter cloacae; the methanol extract of C. foliacea showed the best inhibition (250 µg/ml). C. foliacea also has a high lysozyme potential against Streptococcus agalactiae and Staphylococcus aureus. Fungal hyphae of Alternaria alternata were more affected by the methanol extract from C. foliacea.

Lichens produce a myriad of bioactive compounds that can be exploited as reducing and capping agents in the green process of synthesizing nanoparticles. In this study, we exploit a simple, environmentally safe method for synthesizing silver nanoparticles (AgNPs), using aqueous extracts of three lichen species (Lobaria pulmonaria, Ramalina farinacea, and Evernia prunastri) for the first time. Characterization showed that the three lichen species selected could be perfectly suitable as reducing agents to produce AgNPs. First, ultraviolet-visible spectroscopy confirmed the presence of metallic silver with a maximum absorbance at 425 nm. Second, Fourier transform infrared spectroscopy analysis confirmed the chemical compounds involved in reduction. Third, the elemental composition of AgNPs was illustrated by energy dispersive X-ray spectroscopy. Finally, scanning electron microscopy images displayed the size and shape of biosynthesized particles. The prepared extracts containing AgNPs showed high contents of phenolic compounds and high antioxidant activities on three assays (DPPH, ferric reducing power, and chelating power). Moreover, since bacteria are developing resistance to many common antibiotics, AgNPs produced in an environmentally safe method are an interesting replacement. The antibacterial assessment revealed more effective activity against Gram-negative than Gram-positive bacteria and a bactericidal effect against all strains tested. In this study, we present a pioneering evaluation of acetylcholinesterase inhibition by lichen-based AgNPs. The three extracts exhibited strong enzyme inhibition, with IC50 values of 3.46 ± 0.09, 3.59 ± 0.02, and 4.34 ± 0.03 mg/mL for L. pulmonaria, R. farinacea, and E. prunastri, respectively. The green approach presented would encourage the nontoxic production of AgNPs, suggesting pharmaceutical applications.

The objective of the current study was to compare the mycochemical composition and biological activities of two extracts (aqueous extracts and ground materials prepared with the QUENCHER approach) of three wild Basidiomy-cetes, Agaricus vaporarius, Lactarius deliciosus, and Lycoperdon pyriforme, collected from a region located in the north of Tunisia. Mycochemical analysis in terms of total phenolic compounds, flavonoids, flavanols, proanthocyanidins, and tannin contents were determined. In addition, the antioxidant activities of the mushrooms were evaluated using three assays (2,2-di-phenyl-1-picrylhydrazyl free radical scavenging, ferric reducing antioxidant power assay, and metal chelating assay). Their antimicrobial activities were assessed against seven bacterial species. The obtained data revealed the presence of significant differences between secondary metabolites and the biological activities of the different tested extracts. Extracts of Basidiomy-cetes prepared with the QUENCHER approach had higher total phenolic content and antimicrobial activity against the evaluated strains. Antioxidant activity showed that the water extract had the greatest activity. The water extracts were analyzed with high-performance liquid chromatography, and the results showed that these three wild macromycetes contain a wide variety of antioxidant compounds in addition to many other bioactive compounds of nutritional and therapeutic interest.