Cytotoxic,antimicrobial activities,AChE and BChE inhibitory effects of compounds from Tanacetum chiliophyllum (Fisch. & Mey.) Schultz Bip. var. oligocephalum (D.C.) Sosn. and T. chiliophyllum (Fisch. & Mey.) Schultz Bip. var. monocephalum Grierson

Tanacetum L. species traditionally used for insecticidal purposes as well as in folk medicine for their antitumor, antimicrobial, antifungal activities. In our previous study a novel sesquiterpene lactone and triterpene lactone together with 12 known flavonoids, coumarin and a triterpene were isolated from T. chiliophyllum var. oligocephalum and T. chiliophyllum var. monocephalum extracts which have insecticidal and antimicrobial activity. In this study, cytotoxic, antimicrobial activities and acetylcholinesterase (AChE), butyrylcholinesterase (BChE) inhibitory effects of pure compounds isolated from these plants were investigated. The tested compounds showed AChE and BChE inhibition which ranged between 7.20–80.37% and 9.19%–76.99% respectively. The highest AChE and BChE inhibition was observed for ulubelenolide which afforded 80.37% and 76.99% inhibition respectively. The cytotoxic effect of the compounds ranged between 22.34–49.77 μg/mL IC₅₀ values. Highest cytotoxic activity was observed against MCF-7 and HEK 293 cell line by 5–hydroxy-3′,4′,7-trimethoxy flavone and 5-hydroxy-3′,4′,6,7-tetramethoxyflavone that produced 25.80 ± 0.17 and 22.34 ± 0.70 IC₅₀ values respectively. Compounds eupatilin, cirsilineol, 5–hydroxy-3′,4′,7-trimethoxy flavone and ulubelenolide showed significant antimicrobial effect on C. albicans with 7.8 μg/mL MIC. The new compound ulubelenolide afforded high AChE and BChE inhibition as well as high antifungal activity. In our opinion activity of this substance should be evaluated further against other fungal species.     

Structure based design of novel 6,5 heterobicyclic mitogen-activated protein kinase kinase (MEK) inhibitors leading to the discovery of imidazo[1,5-a] pyrazine G-479

Use of the tools of SBDD including crystallography led to the discovery of novel and potent 6,5 heterobicyclic MEKi’s [J. Med. Chem. 2012, 55, 4594]. The core change from a 5,6 heterobicycle to a 6,5 heterobicycle was driven by the desire for increased structural diversity and aided by the co-crystal structure of G-925 [J. Med. Chem. 2012, 55, 4594]. The key design feature was the shift of the attachment of the five-membered heterocyclic ring towards the B ring while maintaining the key hydroxamate and anilino pharamcophoric elements in a remarkably similar position as in G-925. From modelling, changing the connection point of the five membered ring heterocycle placed the H-bond accepting nitrogen within a good distance and angle to the Ser212 [J. Med. Chem. 2012, 55, 4594]. The resulting novel 6,5 benzoisothiazole MEKi G-155 exhibited improved potency versus aza-benzofurans G-925 and G-963 but was a potent inhibitor of cytochrome P450’s 2C9 and 2C19. Lowering the log D by switching to the more polar imidazo[1,5-a] pyridine core significantly diminished 2C9/2C19 inhibition while retaining potency. The imidazo[1,5-a] pyridine G-868 exhibited increased potency versus the starting point for this work (aza-benzofuran G-925) leading to deprioritization of the azabenzofurans. The 6,5-imidazo[1,5-a] pyridine scaffold was further diversified by incorporating a nitrogen at the 7 position to give the imidazo[1,5-a] pyrazine scaffold. The introduction of the C7 nitrogen was driven by the desire to improve metabolic stability by blocking metabolism at the C7 and C8 positions (particularly the HLM stability). It was found that improving on G-868 (later renamed GDC-0623) required combining C7 nitrogen with a diol hydroxamate to give G-479. G-479 with polarity distributed throughout the molecule was improved over G-868 in many aspects.     

H<Superscript>+</Superscript> translocation by weak acid uncouplers is independent of H<Superscript>+</Superscript> electrochemical gradient

According to the common view, weak acid uncouplers increase proton conductance of biological (and phospholipid bilayer) membranes, thus effecting H⁺ fluxes driven by their electrochemical gradients. Under certain conditions, however, uncouplers can induce unexpected effects opposite to the dissipation of H⁺ gradients. Results are presented here demonstrating CCCP-induced proton influx into Saccharomyces cerevisiae cytosol driven by the electrochemical potentials of CCCP and its CCCP^? anions, independent of electrochemical H⁺-gradient. Another view of week acid uncouplers’ action is proposed that is logically consistent with these observations.     

New insights into the chemical biodiversity of Minthostachys mollis in Argentina

Variations in the chemical composition of the essential oils of Minthostachys mollis Griseb. (Lamiaceae) collected in their natural habitat in Argentina were determined using GC-FID-MS analysis. Seventy five samples collected out of 40 wild plant populations in the Central and Northwestern Argentina during four years sampling, were analyzed. Principal Component Analysis was made on the chemical data showing that samples from Córdoba and San Luis belonged to the typical menthone – pulegone chemotype in accordance with previous reports; meanwhile samples from Tucumán, Salta and Catamarca showed the presence of different compositions, some previously unreported, mainly those detected in Tucumán province. In addition, cluster analysis was applied using Euclidean distance to measure the dissimilarity in the relative composition of samples from Tucumán, Salta and Catamarca, using Ward's method as the agglomeration technique. Five groups were retained with less than 10% of information loss: i) dihydrocarvone-carvone, ii) pulegone with absence of menthone, iii) carvacryl acetate-carvacrol, iv) limonene and v) linalool.It is worth mentioning that the compositions of the different chemotypes remained constant throughout the four years of collection and despite the highly diverse pattern of compositions revealed in this search, the typical chemotype was not found present northwards Córdoba and San Luis provinces. This is the first report of a deep study on natural populations of peperina throughout the whole distribution area in Argentina with consecutive sampling repetitions of the same populations during several years.     

BioEssays 10/2020

Frequent independent origins of environmental sex determination (ESD) are assumed within amniotes. However, the phylogenetic distribution of sex-determining modes suggests that ESD is likely very ancient and may be homologous across ESD groups. Sex chromosomes are demonstrated to be old and stable in endothermic (mammals and birds) and many ectothermic (non-avian reptiles) lineages, but they are mostly non-homologous between individual amniote lineages. The phylogenetic pattern may be explained by ancestral ESD with multiple transitions to later evolutionary stable genotypic sex determination. It is pointed out here that amniote ESD shares several key aspects with sequential hermaphroditism of fishes such as a lack of sex differences in genomes, biased population sex ratios, and potentially also molecular mechanism related to general stress responses. Here, it is speculated that ESD evolves via a heterochronic shift of the sensitive period of sex change from the adult to the embryonic stage in a hermaphroditic amniote ancestor. Also see the video abstract here https://youtu.be/q2mjtlCefu4 .