Screening the dermatological potential of Plectranthus species components: antioxidant and inhibitory capacities over elastase,collagenase and tyrosinase

A series of Plectranthus spp. plant extracts (aqueous, acetonic, methanolic and ethyl acetic) obtained from eight different species, and previously isolated compounds (ranging from polyphenols, diterpenes and triterpenes), were assayed for in vitro inhibition of the skin-related enzymes tyrosinase, collagenase and elastase, and for studying their antioxidant properties. The ethyl acetic extracts of P. grandidentatus and P. ecklonii registered the highest antioxidant activity, whereas acetonic, methanolic and ethyl acetic extracts of P. ecklonii, P. grandidentatus, P. madagascariensis and P. saccatus concerning the enzymatic inhibition assays revealed high anti-tyrosinase and anti-collagenase activities. From the isolated compounds tested, abietane diterpenes and triterpenes were highly active against tyrosinase and elastase activity. Overall, the experimental results showed the powerful antioxidant and inhibitory action on skin-related enzymes tyrosinase, collagenase and elastase of Plectranthus spp. extracts and/or isolated compounds, supporting their further research as bioactive metabolites against skin sagging and hyperpigmentation in cosmetic and pharmaceutical formulations.     

GMP synthase is essential for viability and infectivity of Trypanosoma brucei despite a redundant purine salvage pathway

The causative agent of human African trypanosomiasis, Trypanosoma brucei, lacks de novo purine biosynthesis and depends on purine salvage from the host. The purine salvage pathway is redundant and contains two routes to guanosine‐5′‐monophosphate (GMP) formation: conversion from xanthosine‐5′‐monophosphate (XMP) by GMP synthase (GMPS) or direct salvage of guanine by hypoxanthine‐guanine phosphoribosyltransferase (HGPRT). We show recombinant T. brucei GMPS efficiently catalyzes GMP formation. Genetic knockout of GMPS in bloodstream parasites led to depletion of guanine nucleotide pools and was lethal. Growth of gmps null cells was only rescued by supraphysiological guanine concentrations (100 μM) or by expression of an extrachromosomal copy of GMPS. Hypoxanthine was a competitive inhibitor of guanine rescue, consistent with a common uptake/metabolic conversion mechanism. In mice, gmps null parasites were unable to establish an infection demonstrating that GMPS is essential for virulence and that plasma guanine is insufficient to support parasite purine requirements. These data validate GMPS as a potential therapeutic target for treatment of human African trypanosomiasis. The ability to strategically inhibit key metabolic enzymes in the purine pathway unexpectedly bypasses its functional redundancy by exploiting both the nature of pathway flux and the limited nutrient environment of the parasite's extracellular niche.     

Abietanes from Plectranthus grandidentatus and P. hereroensis against methicillin- and vancomycin-resistant bacteria

The antimicrobial activity of 10 natural abietanes isolated from Plectranthus grandidentatus and P. hereroensis acetonic extract was evaluated against methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus faecalis (VRE). The results revealed that the most active diterpenes were coleon U (1), 7alpha-acetoxy-6beta-hydroxyroyleanone (2) and horminone (3). Minimum inhibitory concentration (MIC) values ranging 0.98-15.63 microg/ml were obtained for MRSA clinical strains, and MIC values of 15.63 and 31.25 microg/ml were obtained for VRE clinical strains. Some structure-activity relationships are emphasized.     

Two new diterpenoids from Plectranthus species

Two new diterpenoids, ent-7α-acetoxy-15-beyeren-18-oic acid and (13S,15S)-6β,7α,12α,19-tetrahydroxy-13β,16-cyclo-8-abietene-11,14-dione, have been isolated from Plectranthus saccatus and Plectranthus porcatus, respectively, and their structures were established by 1D and 2D NMR spectroscopic studies. The new diterpenes showed no activity against Gram-negative bacteria and Candida albicans (yeast strain). Among Gram-positive bacteria, the lower MIC value was 62.50 μg/ml for the abietane derivative against Staphylococcus aureus ATCC 6538.     

Seasonal changes in some photosynthetic properties of Ceratonia siliqua (carob tree) leaves under natural conditions

Rates of photosynthesis and leaf conductance of the leaves of carob trees ( Ceratonia siliqua L.) growing in natural conditions were measured during the course of the seasons to define the effects of the main climatic factors limiting growth in the region: temperature during the winter and water in the summer. The highest photosynthetic rates were measured in spring and autumn and could reach 25 μmol m₋₂ s₋₁ with optimal temperature and available water. Due to lower temperatures (4 to 6°C in the night) these values were frequently around 15 μmol m₋₂ s₋₁ during winter, but the strongest depression was due to prolonged drought in summer. However a reduction in photosynthesis rate down to 5 μmol m₋₂ s₋₁ occurred only after depletion of all the available water in the soil layer up to a depth of 50 cm. In the end of the summer, leaf conductance and water potential were in the order of 20 mmol m₋₂ s₋₁ and −3 MPa respectively. Compared to other trees that make up the Mediterranean sclerophyll forest, the photosynthetic activity of carob is high, and the tree tolerates a considerable depletion of soil water.     

Multidimensional Single-Cell Analysis of BCR Signaling Reveals Proximal Activation Defect As a Hallmark of Chronic Lymphocytic Leukemia B Cells

Purpose

Chronic Lymphocytic Leukemia (CLL) is defined by a perturbed B-cell receptor-mediated signaling machinery. We aimed to model differential signaling behavior between B cells from CLL and healthy individuals to pinpoint modes of dysregulation.

Experimental Design

We developed an experimental methodology combining immunophenotyping, multiplexed phosphospecific flow cytometry, and multifactorial statistical modeling. Utilizing patterns of signaling network covariance, we modeled BCR signaling in 67 CLL patients using Partial Least Squares Regression (PLSR). Results from multidimensional modeling were validated using an independent test cohort of 38 patients.

Results

We identified a dynamic and variable imbalance between proximal (pSYK, pBTK) and distal (pPLCγ2, pBLNK, ppERK) phosphoresponses. PLSR identified the relationship between upstream tyrosine kinase SYK and its target, PLCγ2, as maximally predictive and sufficient to distinguish CLL from healthy samples, pointing to this juncture in the signaling pathway as a hallmark of CLL B cells. Specific BCR pathway signaling signatures that correlate with the disease and its degree of aggressiveness were identified. Heterogeneity in the PLSR response variable within the B cell population is both a characteristic mark of healthy samples and predictive of disease aggressiveness.

Conclusion

Single-cell multidimensional analysis of BCR signaling permitted focused analysis of the variability and heterogeneity of signaling behavior from patient-to-patient, and from cell-to-cell. Disruption of the pSYK/pPLCγ2 relationship is uncovered as a robust hallmark of CLL B cell signaling behavior. Together, these observations implicate novel elements of the BCR signal transduction as potential therapeutic targets.     

Approaches for the Isolation of Arabidopsis adh1 Regulatory Mutants Using Allyl Alcohol Selection

Allyl alcohol, a suicide substrate for the alcohol dehydrogenase enzyme (EC.1.1.1.1), has been frequently used as a negative selection method for the isolation of alcohol dehydrogenase mutants in plants, animals and microorganisms. This approach led to the isolation of mutants that mapped to the ADH gene itself. We attempted to use allyl alcohol selection for the isolation of adh1 regulatory mutants in Arabidopsis. First we selected at plantlet level on ADH1–GUS transgenic plants. This enabled us to use GUS staining to discriminate between structural and regulatory mutants. Allyl alcohol selection of 50000 EMS-treated seeds did not yield any potential mutants. Secondly we selected EMS and -ray-treated seeds of a transgenic line transformed with an additional copy of the ADH1 gene including its own promoter. Fifteen allyl alcohol-resistant plants were selected from the mutagenized seed. Genetic analysis of three putative mutants (adr8, adr10, and adr15) indicated that the ADH1-null phenotype was due to monogenic trans-recessive mutations. But treatment with the demethylating agent 5-azacytidine and analysis of methylation levels of the ADH1 gene indicated that these mutant candidates have increased levels of methylation in the promoter and coding region of ADH1. These results suggest that the allyl alcohol resistance of adr8, adr10, and adr15 is due to silencing of ADH1 rather than to a mutation of a regulatory locus.     

Antimycobacterial Metabolites from Plectranthus: Royleanone Derivatives against Mycobacterium tuberculosis Strains

The antimycobacterial activities of eight diterpenes, 1 – 8 , isolated previously from Plectranthus and eleven esters, 9 – 19 , of 7α‐acetoxy‐6β,12‐dihydroxyabieta‐8,12‐diene‐11,14‐dione ( 5 ) were evaluated against the MTB strains H₃₇Rv and MDR. Only diterpenoids with a quinone framework revealed anti‐MTB activity. Abietane 5 and its 6,12‐dibenzoyl, 12‐methoxybenzoyl, 12‐chlorobenzoyl, and 12‐nitrobenzoyl esters, 9, 11, 12 , and 13 , respectively, showed potent activities against the MDR strain with MIC values between 3.12 and 0.39 μg/ml. Cytotoxic activities towards 3T3 and Vero cells were also evaluated. Compound 11 , with the best selectivity index, may be a suitable lead for further chemical modifications. The complete structural elucidation of the new esters, 9 – 14, 16, 18 , and 19 , as well as the NMR data of known derivatives 15 and 17 are reported.