Metabolic response induced by abiotic elicitors in Anacardium othonianum seedlings.

Applying elicitors in plants growing under natural conditions change the metabolic content of volatile compounds extracted from their tissues. Here, we have investigated how abiotic elicitors influence the volatile composition of the ethyl acetate extract of Anacardium othonianum seedlings propagated in vitro and ex-vitro cultures. Abiotic factors such as salicylic acid, silver nitrate, light quality, and cultivation mode affected the composition of volatile compounds in ethyl acetate extract of A. othonianum leaves seedlings. GC/MS analysis demonstrated that α-tocopherol was the main metabolite in cultures added with chemical elicitors, reaching 22.48 ± 4.06% in the case of 30 µM salicylic acid. Higher concentrations of salicylic acid decreased the amount of α-tocopherol. The addition of AgNO3 had a linear effect on α-tocopherol. Thus, the production of this metabolite indicates that salicylic acid and AgNO3 elicitors positively affect α-tocopherol production at specific concentrations helping to understand how plant culture can be better manipulated.

Phenolic Compound Biotransformation by Trametes versicolor ATCC 200801 and Molecular Docking Studies.

The filamentous fungus Trametes versicolor is a rich source of laccase (Tvlac). Laccases catalyze reactions that convert substituted phenol substrates into diverse derivatives through aromatic oxidation. We investigated methyl p-coumarate, methyl ferulate, and methyl caffeate biotransformation by Trametes versicolor ATCC 200801. Despite substrate similarity, the biotransformation reactions varied widely. Only methyl p-coumarate was converted into three derivatives. We isolated and identified the chemical structures of such derivatives by NMR and IR analysis. Hydroxylation, methylation, and hydrolysis were the main reactions resulting from the studied biotransformation. We also analyzed the interactions between Tvlac (PDB ID: 1GYC) and the three phenolic substrates by molecular docking simulations. The substituents in the phenol ring influenced substrate conformation and orientation in the Tvlac site. The biotransformation reaction selectivity correlated with the different binding energies to the Tvlac site. Our results demonstrated that docking studies successfully predict the biotransformation of cinnamic acid analogs by T. versicolor.

Essential oils from Piper aduncum inflorescences and leaves: chemical composition and antifungal activity against Sclerotinia sclerotiorum.

Even though essential oils from Piper aduncum (Piperaceae) have different biological activities, little is known about their application to agricultural areas. White mold is a plant disease caused by the phytopathogen Sclerotinia sclerotiorum, which needs to be controlled by alternative measures. This study aimed at evaluating the effect of essential oils from P. aduncum leaves (PL-EO) and inflorescences (PI-EO) on the mycelial growth of S. sclerotiorum. Essential oils from P. aduncum were obtained by hydrodistillation by a Clevenger-type apparatus while their chemical composition was analyzed by GC-MS and GC-FID. Piperitone (23.4 %), myristicin (12.4 %), terpinen-4-ol (12.3 %), ß-caryophyllene (7.2 %), α-humulene (6.9 %), germacrene-D (6.9 %) and dillapiol (6.3 %) were the main constituents found in oils from P. aduncum. The in vitro antifungal activity showed that PI-EO dose above 30 µL inhibited mycelial growth in 100 %, whereas PL-EO at 50 µL inhibited it in 98.74 %. This is the first report of the chemical composition of PI-EO and results suggest that the essential oils under evaluation have high potential to control the phytopathogenic fungus S. sclerotiorum.

Differentiation between 3,4- and 4,15-Epoxyeudesmanolides by Electrospray Ionization Tandem Mass Spectrometry.

We investigated the fragmentation of the eudesmanolide-type sesquiterpene lactones 1α-(4-hydroxymethacryloyloxy)-3α,4α-epoxy-8α-hydroxyeudesm-11(13)-6α,12-olide (1) and 1α-(2,3-epoxyangeloyloxy)-4α,15-epoxy-8α-hydroxyeudesm-11(13)-6α,12-olide (2) by electrospray ionization tandem mass spectrometry (ESI-MS/MS). The elimination of the different ester substituent at C(1) directly from protonated 1 and 2 (A) led to the formation of two regioisomer product ions B (A - RCO2H). Further fragmentation of B resulted from consecutive eliminations of H2O and CO molecules. However, we identified four product ions that allowed for the differentiation between 3,4- and 4,15-epoxyeudesmanolides. The formation of these diagnostic ions was associated with the C(3)-O bond of compound 1, which propitiates the participation of the lone pair of the oxygen epoxide in the formation of B through a Grob-Wharton-type fragmentation, then resulting in an alternative fragmentation pathway. These data can be useful for the fast differentiation between epoxyeudesmanolide regioisomers directly from Dimerostemma extracts by liquid chromatography-tandem mass spectrometry (LC-MS/MS), as an alternative to NMR, or even for quantitation studies of these compounds using multiple reaction monitoring (MRM) scan.

Antifungal activity of plant-derived essential oils on Candida tropicalis planktonic and biofilms cells.

Dental prosthesis supports Candida species growth and may predispose the oral cavity to lesions. C. tropicalis has emerged as a colonizer of prosthesis and has shown resistance to clinically used antifungal agents, which has increased the search for new antifungals. This work describes the effectiveness of fifteen essential oils (EOs) against C. tropicalis The EOs were obtained by hydrodistillation and were chemically characterized by gas chromatography-mass spectrometry. The antifungal activities of the EOs were evaluated by the microdilution method and showed that Pelargonium graveolens (Geraniaceae) (PG-EO) was the most effective oil. Geraniol and linalool were the major constituents of PG-EO. The 2,3-Bis-(2-Methoxy-4-Nitro-5-Sulfophenyl)-2H-Tetrazolium-5-Carboxanilide (XTT) assay showed that all the clinical C. tropicalis strains formed viable biofilms. Scanning electron microscopy examination of the biofilms revealed a complex architecture with basal layer of yeast cells and an upper layer of filamentous cells. Treatments with PG-EO, linalool, and geraniol significantly reduced the number of viable biofilm cells and inhibited biofilm formation after exposure for 48 h. PG-EO, geraniol, and linalool were not toxic to normal human lung fibroblasts (GM07492A) at the concentrations they were active against C. tropicalis Together, our results indicated that C. tropicalis is susceptible to treatment with PG-EO, geraniol, and linalool, which could become options to prevent or treat this infection.

Antimicrobial Activity of the Essential Oil of Plectranthus neochilus against Cariogenic Bacteria.

This work used the broth microdilution method to investigate the antimicrobial activity of the essential oil obtained from the leaves of Plectranthus neochilus (PN-EO) against a representative panel of oral pathogens. We assessed the antimicrobial activity of this oil in terms of the minimum inhibitory concentration (MIC). PN-EO displayed moderate activity against Enterococcus faecalis (MIC = 250 µg/mL) and Streptococcus salivarus (MIC = 250 µg/mL), significant activity against Streptococcus sobrinus (MIC = 62.5 µg/mL), Streptococcus sanguinis (MIC = 62.5 µg/mL), Streptococcus mitis (MIC = 31.25 µg/mL), and Lactobacillus casei (MIC = 31.25 µg/mL), and interesting activity against Streptococcus mutans (MIC = 3.9 µg/mL). GC-FID and GC-MS helped to identify thirty-one compounds in PN-EO; α-pinene (1, 14.1%), ß-pinene (2, 7.1%), trans-caryophyllene (3, 29.8%), and caryophyllene oxide (4, 12.8%) were the major chemical constituents of this essential oil. When tested alone, compounds 1, 2, 3, and 4 were inactive (MIC > 4000 µg/mL) against all the microorganisms. These results suggested that the essential oil extracted from the leaves of Plectranthus neochilus displays promising activity against most of the evaluated cariogenic bacteria, especially S. mutans.