Marko Z. Mladenović

Toxic essential oils. Part III: Identification and biological activity of new allylmethoxyphenyl esters from a Chamomile species (Anthemis segetalis Ten.)

To determine the exact structure of previously tentatively identified minor essential-oil constituents of a Chamomile species (Antemis segetalis Ten. (Asteraceae)), we have synthesized a small combinatorial library of 54 regioisomeric allylmethoxyphenyl pentanoates and 2-pentenoates (49 completely new compounds). GC-MS in combination with 1D- and 2D-NMR analyses of the library compounds provided unambiguous data that led to a straightforward identification of the mentioned A. segetalis constituents as eugenyl angelate, 2-methylbutanoate and 3-methylbutanoate (0.21, 0.22, and 0.13 mg/100 g of fresh plant material, respectively). To assess the safety and potential beneficial pharmacological uses of these naturally occurring esters and several other library compounds (these were tested to provide relevant data for a SAR (structure-activity relationship) analysis), we have studied the effect of these compounds in several models of toxicity (acute toxicity against Artemia salina, cytotoxicity against two cell lines (fibroblast and melanoma)), as well as their acetylcholinesterase inhibitory and antibacterial activities. Anthemis segetalis constituents showed low to moderate activity in all tests. The obtained results suggest that the intake of these compounds in naturally available amounts, on their own, would probably not represent a risk to human health but the possible adverse interactions with the plant matrix should not be neglected.

Platismatia glaucia and Pseudevernia furfuracea lichens as sources of antioxidant, antimicrobial and antibiofilm agents

The antioxidative, antimicrobial and antibiofilm potentials of acetone, ethyl acetate and methanol extracts of lichen species Platismatia glauca and Pseudevernia furfuracea were evaluated. The phytochemical analysis by GC, GC/MS and NMR revealed caperatic acid, atraric acid, atranorin and chloroatranorin as the predominant compounds in Platismatia glauca. Atraric acid, olivetoric acid, atranorin and chloroatranorin were the major constituents in Pseudevernia furfuracea. The strong antioxidant capacities of the Platismatia glauca and Pseudevernia furfuracea extracts were assessed by their total phenolic and flavonoid contents and DPPH scavenging activities. The methanol extracts of both species exhibited the strongest antioxidant activities with the highest IC50 value for Pseudevernia furfuracea (95.33 µg/mL). The lichen extracts demonstrated important antibacterial activities against 11 bacterial strains with detectable MIC values from 0.08 mg/mL to 2.5 mg/mL for Platismatia glauca and from 0.005 mg/mL to 2.5 mg/mL for Pseudevernia furfuracea. While the antibacterial activities of Pseudevernia furfuracea were solvent–independent, the acetone and ethyl acetate extracts of Platismatia glauca showed higher antibacterial activities compared to its methanol extract. The methanol extracts of both species demonstrated significant antifungal activities against 9 fungal strains with detectable MIC values from 0.04 mg/mL to 2.5 mg/mL. The best antifungal activities were determined against Candida species in Pseudevernia furfuracea extracts with remarkable MIC values which were lower than the MIC values of the positive contol fluconazole. The acetone and ethyl acetate extracts of Platismatia glauca showed better antibiofilm activities on Staphylococcus aureus and Proteus mirabilis with BIC value at 0.63 mg/mL then its methanol extract. On the other hand, the methanol extract of Pseudevernia furfuracea was more potent with BIC value at 1.25 mg/mL on Staphylococcus aureus and 0.63 mg/mL on Proteus mirabilis compared to other types of extracts. Our study indicates a possible use of lichens Platismatia glauca and Pseudevernia furfuracea as natural antioxidants and preservatives in food, pharmaceutical and cosmetic industry.

Toxic essential oils. Part IV: The essential oil of Achillea falcata L. as a source of biologically/pharmacologically active trans-sabinyl esters

Herein we report on the comprehensive chemical analysis of the essential oils obtained from above- and underground parts of a previously unreported chemotype of Achillea falcata L. (Asteraceae) and, for the first time, on the biological/toxicological profile of its dominant/newly discovered volatile metabolites. Detailed spectral analyses, in combination with chemical synthesis and theoretical study, of selected constituents, enabled the identification of trans-sabinol and its esters - the formate, tiglate (new compounds), acetate, butanoate, isobutanoate, 2-methylbutanoate and 3-methylbutanoate - in both aerial and underground parts of A. falcata. Evaluation of acute toxicity in Artemia salina model, in vitro and in silico (molecular docking) evaluation of acetylcholinesterase inhibitory activity and in vivo (mice) evaluation of antinociceptive activity (hot plate, tail immersion and acetylcholine-induced abdominal writhing tests) of trans-sabinol and its esters suggested that they may interact with different targets in crustacean/mammalian organisms. Alongside moderate acute toxicity (LD50 (48 h) = 0.03-0.26 mmol/L), the tested compounds exert influence on both the peripheral and central nervous systems (in the hot plate test, trans-sabinyl tiglate, at 50 mg/kg, produced a 140% baseline increase 15 min after the treatment) and to moderately inhibit acetylcholinesterase (at the concentration of 20 µg/mL, these compounds caused a reduction of acetylcholinesterase activity up to 40%).

Chemotypification of Astrantia major L. (Apiaceae): Essential-Oil and Lignan Profiles of Fruits

The fruit essential oils of two populations of Astrantia major L. (Apiaceae, subfamily Saniculoideae) were analyzed in detail by GC and GC/MS analyses. Seventy‐six constituents identified accounted for 92.7–94.0% of the oils. The two oils differed significantly: the wild‐growing population from Serbia contained zingiberene (47.9%), β‐bisabolene (9.7%), and β‐sesquiphellandrene (7.9%), while the one from Poland (botanical gardens) was sesquiterpene‐poor with the major contributors oleic acid (38.6%), nonacosane (15.4%), and linoleic acid (5.1%). Motivated by the unresolved taxonomical relations between the Saniculoideae and Apioideae subfamilies, we performed multivariate statistical analyses on the compositional data of these A. major samples, and additional 14 Saniculoideae and 31 Apioideae taxa. This allowed us to assess the chemotaxonomical usefulness of such chemical data in differentiating taxa from these two Apiaceae subfamilies and to corroborate the existence of at least two A. major chemotypes. Diethyl ether extracts of the two samples of A. major fruits yielded seven diaryltetrahydrofurofurano lignans. Except for eudesmin that has been found for the first time in a Saniculoideae taxon, all other lignans (magnolin, epimagnolins A and B, epieudesmin, yangambin, and epiyangambin) are new for the entire plant family Apiaceae. The lignan profiles also supported the existence of two separate A. major chemotypes.

α-Tocopherol Reduces Morphological Changes and Oxidative Stress during Gentamicin-Induced Acute Renal Failure

We studied the effect of α-tocopherol on gentamicin-induced morphological and functional changes in the kidneys of Wistar rats. Special attention was paid to the ability of α-tocopherol administered in combination with gentamicin to correct ultrastructural changes in the glomerular basal membrane and tubules. Combined treatment with α-tocopherol (100 mg/kg) and gentamicin (100 mg/kg) led to correction of histopathological and biochemical changes and oxidative injury to the kidneys induced by this antibiotic.