Alexandre Gomes da Silva

Potential of medicinal plants from the Brazilian semi-arid region (Caatinga) against Staphylococcus epidermidis planktonic and biofilm lifestyles

ETHNOPHARMACOLOGICAL RELEVANCE Medicinal plants from the Caatinga, a Brazilian xeric shrubland, are used in folk medicine to treat infections. These ethnopharmacological data can contribute to obtaining new antimicrobial/antibiofilm extracts and natural product prototypes for the development of new drugs. The aim of this study was to investigate the antibiofilm and antibacterial activities of 45 aqueous extracts from 24 Caatinga plant species. MATERIALS AND METHODS The effect of aqueous extracts on planktonic cells and on biofilm formation by Staphylococcus epidermidis was studied by the OD(600) absorbance and by the crystal violet assay, respectively. Scanning electron microscopy (SEM) was used to generate comparative images of extract-treated and untreated biofilms. Chromatographic analyses were performed to characterize the active extracts. RESULTS The in vitro screening, at 0.4 mg/mL and 4.0mg/mL, showed 20 plants effective in preventing biofilm formation and 13 plants able to inhibit planktonic bacterial growth. SEM images demonstrated distinct profiles of bacterial adhesion, matrix production and cell morphology according to different treatments and surfaces. The phytochemical analysis of the selected active extracts indicates the polyphenols, coumarins, steroids and terpenes as possible active compounds. CONCLUSION This study describes the first antibiofilm and antibacterial screening of Caatinga plants against S. epidermidis. The evaluation presented in this study confirms several ethnopharmacological reports and can be utilized to identify new antibiofilm and antibacterial products against S. epidermidis from traditional Brazilian medicine.

(E)-Caryophyllene and α-Humulene: Aedes aegypti Oviposition Deterrents Elucidated by Gas Chromatography-Electrophysiological Assay of Commiphora leptophloeos Leaf Oil.

Aedes aegypti is responsible for the transmission of dengue, a disease that infects millions of people each year. Although essential oils are well recognized as sources of compounds with repellent and larvicidal activities against the dengue mosquito, much less is known about their oviposition deterrent effects. Commiphora leptophloeos, a tree native to South America, has important pharmacological properties, but the chemical profile and applicability of its essential oil in controlling the spread of the dengue mosquito have not been investigated. The aim of this study was to determine the composition of C. leptophloeos leaf oil and to evaluate its larvicidal and oviposition deterrent effects against A. aegypti. Fifty-five components of the essential oil were detected by gas chromatography (GC)—mass spectrometry, with α-phellandrene (26.3%), (E)-caryophyllene (18.0%) and β-phellandrene (12.9%) identified as the major constituents. Bioassays showed that the oil exhibited strong oviposition deterrent effects against A. aegypti at concentrations between 25 and 100 ppm, and possessed good larvicidal activity (LC50 = 99.4 ppm). Analysis of the oil by GC coupled with electroantennographic detection established that seven constituents could trigger antennal depolarization in A. aegypti gravid females. Two of these components, namely (E)-caryophyllene and α-humulene, were present in substantial proportions in the oil, and oviposition deterrence assays confirmed that both were significantly active at concentrations equivalent to those present in the oil. It is concluded that these sesquiterpenes are responsible, at least in part, for the deterrent effect of the oil. The oviposition deterrent activity of the leaf oil of C. leptophloeos is one of the most potent reported so far, suggesting that it could represent an interesting alternative to synthetic insecticides. The results of this study highlight the importance of integrating chemical and electrophysiological methods for screening natural compounds for their potential in combating vectors of insect-borne diseases.

Structure and rheological properties of a xyloglucan extracted from Hymenaea courbaril var. courbaril seeds

Hymenaea courbaril var courbaril seed xyloglucan was efficiently extracted with 0.1M NaCl, followed by ethanol precipitation (yield=72±5% w/w). Its amorphous structure was identified by the pattern of X-ray diffraction. The monosaccharide composition was determined by GC/MS analysis of the alditol acetates and showed the occurrence of glucose:xylose:galactose:arabinose (40:34:20:6). One-(1D) and two-dimensional-(2D) NMR spectra confirmed a central backbone composed by 4-linked β-glucose units partially branched at position 6 with non-reducing terminal units of α-xylose or β-galactose-(1→2)-α-xylose disaccharides. The xyloglucan solution was evaluated by dynamic light scattering and presents a polydisperse and practically neutral profile, and at 0.5 and 1.0% (w/v) the solutions behave as a viscoelastic fluid. The polysaccharide did not show significant antibacterial or hemolytic activities. Overall our results indicate that xyloglucan from H. courbaril is a promising polysaccharide for food and pharmaceutical industries.

Purification, characterization and antibacterial potential of a lectin isolated from Apuleia leiocarpa seeds

Apuleia leiocarpa is a tree found in Caatinga that has great value in the timber industry. Lectins are carbohydrate-binding proteins with several biotechnological applications. This study shows the isolation, characterization, and antibacterial activity of A. leiocarpa seed lectin (ApulSL). The lectin was chromatographically isolated from a crude extract (in 150 mM NaCl) by using a chitin column. ApulSL adsorbed to the matrix and was eluted using 1.0 M acetic acid. Native ApulSL was characterized as a 55.8-kDa acidic protein. SDS-PAGE showed three polypeptide bands, whereas two-dimensional electrophoresis revealed four spots. The peptides detected by MALDI TOF/TOF did not show sufficient homology (<30%) with the database proteins. Circular dichroism spectroscopy suggested a disordered conformational structure, and fluorescence spectrum showed the presence of tyrosine residues in the hydrophobic core. The hemagglutinating activity of ApulSL was present even after heating to 100 °C, was Mn(2+)-dependent, and inhibited by N-acetylglucosamine, D(-)-arabinose, and azocasein. ApulSL demonstrated bacteriostatic and bactericide effects on gram-positive and gram-negative species, being more effective against three varieties of Xanthomonas campestris (MIC ranging from 11.2 to 22.5 μg/mL and MBC of 22.5 μg/mL). The results of this study reinforce the importance of biochemical prospecting of Caatinga by revealing the antibacterial potential of ApulSL.

Antimicrobial Activity and Phytochemical Screening of Buchenavia tetraphylla (Aubl.) R. A. Howard (Combretaceae: Combretoideae)

This study evaluated the antimicrobial and hemolytic activities and phytochemical constituents of hydroalcoholic extract and its fractions from Buchenavia tetraphylla leaves. Cyclohexane (BTCF), ethyl acetate (BTEF), and n-butanol-soluble (BTSBF) and non-soluble (BTNBF) fractions were obtained from a liquid-liquid partition of hydroalcoholic extract (BTHE) from B. tetraphylla leaves. The hemolytic activity of active fractions was checked. The BTHE inhibited the growth of Micrococcus luteus (MIC: 0.10 mg/mL), Pseudomonas aeruginosa (MIC: 0.20 mg/mL), Mycobacterium smegmatis (MIC: 0.39 mg/mL), Proteus vulgaris, and Staphylococcus aureus (MIC: 0.78 mg/mL for both). The more active fractions were BTCF and BTBSF. BTCF showed better potential to inhibit M. luteus (0.10 mg/mL), P. aeruginosa (0.20 mg/mL), S. enteritidis (0.39 mg/mL), and S. aureus (1.56 mg/mL). BTBSF showed the best results for M. luteus (0.10 mg/mL), M. smegmatis, B. subtilis (0.39 mg/mL for both), and P. vulgaris (0.10 mg/mL). The HC50 were greater than observed MIC: 20.30, 4.70 and 2.53 mg/mL, respectively, to BTBF, BTHE and BTCF, which. The phytochemical analysis detected the presence of flavanoids, triterpene, carbohydrate, and tannin. Our work showed for the first time the broad-spread antimicrobial activity of B. tetraphylla, which has nonhemolytic action, creating a new perspective on the interesting association of traditional and scientific knowledge.

Anti-infective effects of Brazilian Caatinga plants against pathogenic bacterial biofilm formation

Abstract Context: The local communities living in the Brazilian Caatinga biome have a significant body of traditional knowledge on a considerable number of medicinal plants used to heal several maladies. Objective: Based on ethnopharmacological data, this study screened 23 aqueous plant extracts against two well-known models of biofilm-forming bacteria: Staphylococcus epidermidis and Pseudomonas aeruginosa. Materials and methods: Crystal violet assay and scanning electron microscopy (SEM) were used to evaluate the effect of extracts on biofilm formation and measurements of the absorbance at 600 nm to assess bacterial growth. Selected extracts were investigated regarding the cytotoxicity by MTT assay using mammal cells and the qualitative phytochemical fingerprint by thin layer chromatography. Results: Harpochilus neesianus Mart. ex Nees. (Acanthaceae) leaves, Apuleia leiocarpa Vogel J. F. Macbr. (Fabaceae), and Poincianella microphylla Mart. ex G. Don L. P. Queiroz (Fabaceae) fruits showed non-biocidal antibiofilm action against S. epidermidis with activities of 69, 52, and 63%, respectively. SEM confirmed that biofilm structure was strongly prevented and that extracts promoted overproduction of the matrix and/or bacterial morphology modification. Poincianella microphylla demonstrated toxicity at 4.0 mg/mL and 2.0 mg/mL, A. leiocarpa presented toxicity only at 4.0 mg/mL, whereas H. neesianus presented the absence of toxicity against Vero cell line. Preliminary phytochemical analysis revealed the presence of flavonoids, terpenoids, steroids, amines, and polyphenols. Discussion and conclusions: This work provides a scientific basis which may justify the ethnopharmacological use of the plants herein studied, indicating extracts that possess limited mammal cytotoxicity in vitro and a high potential as a source of antibiofilm drugs prototypes.

Validity and relative ability of 4 balance tests to identify fall status of older adults with type 2 diabetes

Background and Purpose: The Berg Balance Scale (BBS), the Balance Evaluation Systems Test (BESTest), the Mini-BESTest, and the Brief-BESTest are useful tests to assess balance; however, their clinimetric properties have not been studied well in older adults with type 2 diabetes (T2D). This study compared the validity and relative ability of the BBS, BESTest, Mini-BESTest, and Brief-BESTest to identify fall status in older adults with T2D. Methods: This study involved a cross-sectional design. Sixty-six older adults with T2D (75 ± 7.6 years) were included and asked to report the number of falls during the previous 12 months and to complete the Activities-specific Balance Confidence scale. The BBS and the BESTest were administered, and the Mini-BESTest and Brief-BESTest scores were computed based on the BESTest performance. Receiver operating characteristics were used to assess the ability of each balance test to differentiate between participants with and without a history of falls. Results: The 4 balance tests were able to identify fall status (areas under the curve = 0.74-0.76), with similar sensitivity (60%-67%) and specificity (71%-76%). Conclusions: The 4 balance tests were able to differentiate between older adults with T2D with and without a history of falls. As the BBS and the BESTest require longer application time, the Brief-BESTest may be an appropriate choice to use in clinical practice to detect fall risk.

Chemical Composition and Larvicidal Activity of the Essential Oil from Leaves of Eugenia brejoensis Mazine (Myrtaceae)

Abstract The essential oil obtained by hydrodistillation of leaves of Eugenia brejoensiscollected in the Caatinga domain in northeastern Brazil was analyzed by gas chromatography-mass spectrometry. The forty-one compounds identified in the leaf oil accounted for 89.3 % of detected components and comprised mainly sesquiterpenes (62.7 %) and oxygenated sesquiterpenes (26.6 %). The principal constituents of the oil were δ-cadinene (22.6 %), β-caryophyllene (14.4 %), α-muurolol (9.34 %), α-cadinol (8.49 %) and bicyclogermacrene (7.93 %). The larvicidal activity of the leaf oil against the yellow fever mosquito Aedes aegypti was assessed as moderate and an LC50 value of 214.7 ppm was established in bioassays with fourth instar larvae. This paper constitutes the first report of the composition and larvicidal activity of the essential oil from leaves of E. brejoensis.

The chemical composition and trypanocidal activity of volatile oils from Brazilian Caatinga plants

Essential/volatile oils (EOs) from plants used in the traditional medicine are known as a rich source of chemically diverse compounds with relevant biological activities. In this work we analysed the chemical composition and the in vitro effects of EOs from leaves of Eugenia brejoensis (EBEO), Hyptis pectinata (HPEO), Hypenia salzmannii (HSEO), Lippia macrophylla (LMEO) and seeds of Syagrus coronata (SCEO) on Trypanosoma cruzi, the etiological agent of Chagas disease. The EOs were extracted through hydrodistillation and its chemical composition analysed by GC/MS. The trypanocidal activity against epi- and trypomastigotes was evaluated by optical microscopy and the cytotoxicity to mammalian cells by MTT. The effects of EOs on parasite infection in macrophages were estimated by determining the survival index and the percentage of infection inhibition. The cytotoxicity against mammalian cells was compared to those of parasite by determining the Selectivity Index (SI). Overall, 114 compounds were identified: The main constituents of EOS were: δ-cadinene (15.88%), trans-caryophyllene (9.77%) e α-Muurolol (9.42%) for EBEO; trans-caryophyllene (15.24%), bicyclogermacrene (7.33%) e cis-calamenene (7.15%) for HFEO; trans-caryophyllene (30.91%), caryophyllene oxide (13.19%) and spathulenol (5.68%) for HPEO; Xanthoxylin (17.20%) trans-caryophyllene (14.34%) and methyl-eugenol (5.60%) for HSEO; Thymol (49.81%), carvacrol (31.6%) and σ-cimene (10.27%) for LMEO and octanoic acid (38.83%) dodecanoic acid (38.45%) and decanoic acid (20.51%) for SCEO. All the tested oils showed an inhibitory effect on the growth and survival of all forms of T. cruzi and moderate cytotoxicity towards the mammalian cells (100 < CC50 < 500 μg/mL). The EO of E. brejoensis was the most effective against the parasite presenting higher Selectivity Index for trypo- (SI = 14.45) and amastigote forms (SI = 20.11). Except for SCEO, which was the most cytotoxic for both parasite and mammalian cells, all the oils demonstrated to be more selective for the parasite than the reference drug benznidazole. Taken together our results point the essential oils from Caatinga plants, especially Eugenia brejoensis, as promissory agents for the development of new drugs against Chagas disease.

Effects of Caatinga Plant Extracts in Planktonic Growth and Biofilm Formation in Ralstonia solanacearum

This study describes the first antibiofilm and antibacterial screening for plants from Caatinga against Ralstonia solanacearum, a causal agent of bacterial wilt that presents serious difficulties in control. There were prepared 22 aqueous extracts of plants collected in the Vale do Catimbau—PE, Brazil. The potential antibacterial activity was evaluated by absorbance in OD600 and the antibiofilm activity through the crystal violet method, both of them performed in microplate against isolates of R. solanacearum biofilm formers. The results of the screening showed that Jacaranda rugosa presented antimicrobial activity higher than 90%, while Harpochilus neesianus and Myroxylon peruiferum presented antibiofilm activity higher than 50% for all tested isolates. However, Croton heliotropiifolius showed both the activities, being thus very promising for application in the control of this phytopathogen. The search for viable alternatives to the development of new bioactive compounds safe for the environment, humans, and animals from an adverse and scarce environment such as the Caatinga and encouraged us to find plants that produce effective metabolites against phytopathogenic microorganisms. This in vitro screening is important to guide the development of new products in addition to guide research studies of bioactive compounds.