Antifungal activity of the amyrin derivatives and in vitro inhibition of Candida albicans adhesion to human epithelial cells

AIMS: The antifungal activity of amyrin pentacyclic triterpene and 15 synthetic derivatives was evaluated against Candida species. Additionally, inhibition of adhesion of Candida albicans to human epithelial cells in vitro was determined. METHODS AND RESULTS: Esterification of alpha- and beta-amyrin with a variety of acyl chlorides produced a series of analogue derivatives. These substances were synthesized to evaluate the antifungal properties against Candida species. Among the 15 derivatives, alpha- and beta-amyrin formiate (2) and alpha- and beta-amyrin acetate (3) were the most active, inhibiting all the Candida species tested in concentrations that ranged from 30 to 250 microg ml(-1). alpha- and beta-amyrin formiate inhibited the adhesion ability of C. albicans to buccal epithelial cells (BEC) in 65.3%. CONCLUSIONS: alpha- and beta-amyrin formiate and alpha- and beta-amyrin acetate derivatives exhibited potential antifungal activity against Candida spp. and amyrin formiate showed inhibition of the adhesion ability of C. albicans to buccal epithelial cells. SIGNIFICANCE AND IMPACT OF THE STUDY: This study demonstrated that two derivatives of amyrin pentacyclic triterpene exhibited significant antifungal activity against Candida species. Additionally, alpha- and beta-amyrin formiate was as effective as fluconazole in inhibiting the adhesion of C. albicans to buccal epithelial cells.     

Impact of climatic and hydrological disturbances on blackwater floodplain forests in Central Amazonia

Extreme climatic events and anthropic disturbances affect the hydrological regime of Amazonian rivers and connected floodplain forests. This study aims to investigate the impacts of the Balbina hydroelectric power plant on the floodplain forests of the Uatumã River, in the Central Amazon. For this, tree age and diameter increment from the most abundant tree species of three different topographic levels were obtained and analyzed in the affected area downstream of the Balbina dam (Uatumã River) and compared to an undisturbed site (Abacate River, affluent) considering age structure and mean diameter increments between the topographic levels and the two systems. The occurrence of old trees is much lower at the disturbed site compared to the undisturbed system. Especially at the middle topography of the Uatumã site, we observed tree species with high mean diameter increment indicating a strong disturbance. We suggest that the disturbances may be associated with extreme hydro‐climatic events, such as extreme droughts that occurred during the El Niño years 1925/26 and 1982/83 and that these events may increase vulnerability of igapó floodplains to wildfires. Abstract in Portuguese is available with online material.     

Resistance inducers applied alone or in association with fungicide for the management of leaf rust and brown eye spot of coffee under field conditions

The use of resistance inducers is a promising development in the management of plant diseases, owing to their ability to control a broad spectrum of pathogens and improve the efficacy of fungicides. This study evaluates different sources of phosphonates (potassium, manganese, copper), a formulation prepared from the by‐products of the coffee industry (Greenforce CuCa), as well as the effects of their application, alone or in association with fungicide, in the management of two important coffee fungal diseases in Brazil: leaf rust and brown eye spot, caused by Hemileia vastatrix and Cercospora coffeicola, respectively. The effect of these products on defoliation, productivity and chemical composition of coffee beans (content of trigonelline, chlorogenic acid, caffeine and total soluble solids) was evaluated. Among all the alternative products tested individually, potassium phosphonate (P₂O₅—33.6% + K₂O—29%) stood out, particularly for rust control, which was similar to the results of fungicide treatments. Treatments with fungicide, Greenforce CuCa and cuprous oxide, individually, caused less plant defoliation. Regarding the chemical composition of the coffee beans, the manganese phosphonate treatment showed the highest values for trigonelline, chlorogenic acid, caffeine and total soluble solid content. The results of this study show that resistance inducers can be useful in disease management, may come to eventually replace traditional fungicides and can also contribute to the beverage quality.     

Production of omega-3 polyunsaturated fatty acids through hydrolysis of fish oil by Candida rugosa lipase immobilized and stabilized on different supports

This paper describes the fish oil hydrolysis performed to obtain Omega-3 fatty acids using Candida rugosa lipase (CRL) immobilized and stabilized on different supports. The enzyme was successfully immobilized, presenting higher thermal stability than the free enzyme. Besides, the cationic derivatives were more stable than the others derivatives and free enzyme in methanol, propanol and cyclohexane. Reactions of fish oil hydrolysis were carried out in organic aqueous medium using 10?U of biocatalyst per gram of oil, at 37?°C. After 96?h, the CRL immobilized on cyanogen bromide agarose rendered the lower fish oil hydrolysis, producing 218?μM of Omega-3, which was 1.1-fold more than the hydrolysis catalyzed by free enzyme, while the ionic derivatives rendered the highest fish oil hydrolysis producing 582 and 577?μM of Omega-3 using the carboxymethyl and sulfopropyl derivatives, respectively. The carboxymethyl and the sulfopropyl derivatives resulted in a 2.9-fold increase in the hydrolysis of fish oil, making these derivatives attractive for industrial applications.     

The Role of Polygalacturonase (PG) in the Ripening of Apple Fruits

Polygalacturonase (PG) activity and changes in respiratory intensity of apple fruits were investigated. The respiratory rate was decreased to a preclimacteric minimum from 30 Aug. to 20 Sept., Then increased to a climacteric peak (20–30 Sept.) and again drop down gradually with approaching the senescence stage. The PG activity was undetectable in a developing fruit until the onset climacteric phase. It rose rapidly after harvest, and reaching its highest level on 27 Oct. Just a month after the climacteric peak. The PG activity fell gradually. The amount of the fractions of pectic acid in fruits changed with the modifications of PG activity. With the ripening of fruits, the content of alcohol-soluble small molecules of pectic acids was increased from 12 to 13 5 mg/100 g of tissue, while the amount of alcohol- insoluble large molecules of pectic acids reduced from 530 to 280/100 g of tissue. PG activity would indicate the destruction of cell walls and the separation of cells. The onset of softening of fruits occurred 20 days after the rise of PG activity. It is supposed that the process of softening is directly controlled by PG activity.     

Headcase Promotes Cell Survival and Niche Maintenance in the Drosophila Testis

At the apical tip of the Drosophila testis, germline and somatic stem cells surround a cluster of somatic cells called the hub. Hub cells produce a self-renewal factor, Unpaired (Upd), that activates the JAK-STAT pathway in adjacent stem cells to regulate stem cell behavior. Therefore, apical hub cells are a critical component of the stem cell niche in the testis. In the course of a screen to identify factors involved in regulating hub maintenance, we identified headcase (hdc). Hub cells depleted for hdc undergo programmed cell death, suggesting that anti-apoptotic pathways play an important role in maintenance of the niche. Using hdc as paradigm, we describe here the first comprehensive analysis on the effects of a progressive niche reduction on the testis stem cell pool. Surprisingly, single hub cells remain capable of supporting numerous stem cells, indicating that although the size and number of niche support cells influence stem cell maintenance, the testis stem cell niche appears to be remarkably robust in the its ability to support stem cells after severe damage.     

Phosphites of manganese and zinc potentiate the resistance of common bean against infection by Xanthomonas axonopodis pv. phaseoli

Common bacterial blight (CBB), caused by Xanthomonas axonopodis pv. phaseoli var. fuscans (Xapf), negatively impact common bean production globally. Considering the potential of phosphites to protect plants against different diseases, this study investigated the potential of using manganese (Mn) and zinc (Zn) phosphites in common bean for CBB control. Plants were inoculated with Xapf 48 hr after being sprayed with water (control) and solutions (7.5 ml/L) of Mn and Zn phosphites. The area under common bacterial blight progress curve (AUCBBPC) was significantly lower by 34% and 59% for Mn and Zn phosphite treatments in comparison with the control treatment. The AUCBBPC was significantly reduced by 38% for Zn phosphite-sprayed plants compared to Mn phosphite treatment. Phosphite-sprayed plants displayed higher values for area under the curves of net CO₂ assimilation rate, stomatal conductance to water vapour, transpiration rate and internal-to-ambient CO₂ concentration ratio than non-sprayed plants. This indicates the effect of Mn and Zn phosphites in attenuating the photochemical dysfunctions caused by Xapf infection. Moreover, plants sprayed with Mn phosphite displayed higher values for area under the curves of efficiency in capturing the excitation energy of open reaction centres of PSII and electron transport rate than those non-sprayed indicating their capacity to preserve the capture and the use of the collected energy more efficiently. Lower AUCBBPC for Zn phosphite-sprayed plants resulted in higher concentrations of total chlorophylls. The Zn phosphite-sprayed plants showed higher values for area under the curves of β-1,3-glucanase, phenylalanine ammonia-lyase, polyphenoloxidase, ascorbate peroxidase and superoxide dismutase activities. The Zn phosphite spray primed the plants to enhance their defence response and antioxidant capacity to reduce Xapf-triggered oxidative stress with the preservation of the photosynthetic apparatus more efficiently.