Hélcio Silva dos Santos

Casbane diterpene as a promising natural antimicrobial agent against biofilm-associated infections

Croton nepetaefolius is a native plant from northeastern Brazil that belongs to the Euphorbiaceae family. The biological action of this plant has been extensively explored, being the secondary metabolites responsible for its properties alkaloids, diterpenes, and triterpenes. This study aimed to evaluate the ability of casbane diterpene (CD), isolated from the ethanolic extract of C. nepetaefolius, to inhibit microbial growth and biofilm formation of several clinical relevant species (bacteria and yeasts). It was found that CD possessed biocidal and biostatic activity against the majority of the species screened, with minimal active concentrations ranging between 125 and 500 µg/mL. In addition, it was observed that biofilm formation was inhibited even when the planktonic growth was not significantly affected. In conclusion, CD showed potential to be a natural tool for the treatment of diseases caused by different infectious microorganisms.

Antimicrobial and antibiofilm action of Casbane Diterpene from Croton nepetaefolius against oral bacteria.

OBJECTIVE The antibacterial activity of Casbane Diterpene (CD) was evaluated in vitro against Streptococcus oralis, S. mutans, S. salivarius, S. sobrinus, S. mitis and S. sanguinis. The viability of planktonic cells was analysed by susceptibility tests (MIC and MBC) and antibiofilm action was assayed. METHODS The minimal inhibitory and bactericidal concentrations (MIC and MBC) of oral Streptococcus were evaluated through microdilution tests. To assay antibiofilm activity, biofilms were generated on 96-wells polystyrene plates under the presence of CD and quantified by a crystal violet technique and colonies forming units counting. RESULTS The CD isolated from Croton nepetaefolius showed antimicrobial effect on planktonic forms and biofilms of oral pathogens, with MIC values of 62.5 μg/mL against Streptococcus oralis and values between 125 and 500 μg/mL against S. mutans, S. salivarius, S. sobrinus, S. mitis and S. sanguinis. CD showed an inhibitory effect on S. mutans biofilm formation at 250 μg/mL, and a decrease on viable cell of 94.28% compared to the normal biofilm growth. CONCLUSIONS The compound CD can be considered as a promising molecule for the treatment against oral pathogens responsible for dental biofilm.

Amyrin esters induce cell death by apoptosis in HL-60 leukemia cells

Four derivatives of an α,β-amyrin mixture were synthesized by acylation with appropriate anhydrides. The structures of the compounds were confirmed by means of IR and (1)H and (13)C NMR. The compounds were screened for cytotoxic activity using four human tumor cell lines (HL-60, MDAMB-435, SF-295 and HCT-8) and normal peripheral blood mononuclear cells (PBMC). 3-O-Carboxymaleinate of α,β-amyrin (3a/3b) were found to be the only active compounds of the series (high cytotoxicity), showing IC(50) values ranging from 1.8 to 3μM. In PBMC, 3a/3b were not toxic, suggesting selectivity for tumor cells. To better understand the mechanism of action involved in the cytotoxicity of 3a/3b, HL-60 cells treated with 3a/3b were examined for morphological changes, DNA fragmentation, cell cycle perturbation, externalization of phosphatidylserine and activation of caspases 3/7, with doxorubicin serving as the positive control. The results indicate that the cytotoxicity of 3a/3b involves the induction of cell death by apoptosis.

Cytotoxic Diterpenoids from Croton argyrophylloides

Two new diterpenes, 1 and 2, together with the known ent-15-oxo-kaur-16-en-18-oic acid (3), were isolated from the bark of Croton argyrophylloides. The structural characterization of 1 and 2 was determined on the basis of spectroscopic data interpretation. The cytotoxicity of each compound was evaluated against HL-60 (leukemia), MDAMB-435 (melanoma), SF-295 (glioblastoma), and HCT-8 (colon carcinoma) human tumor cell lines and against human peripheral blood mononuclear cells. The hemolytic potential in mouse erythrocytes was also tested for 1-3.

Diterpenos casbanos e acetofenonas de Croton nepetaefolius (Euphorbiaceae)

Croton nepetaefolius is an aromatic plant native to the northeast of Brazil where it is extensively used in folk medicine as a sedative, orexigen and antispasmodic agent. The present work deals with the chromatographic analysis of the ethanolic extract of Croton nepetaefolius stalk. It allowed the isolation and characterization of two diterpenoids named 1,4-dihydroxy-2E,6E,12E-trien-5-one-casbane and 4-hydroxy-2E,6E,12E-5-one-casbane, two acetophenones named 2-hydroxy-4,6-dimethoxyacetophenone and 2-hydroxy-3,4,6-trimethoxyacetophenone and the steroids 3-O-b-D-glucopiranosylsitosterol and a mixture of b-sitosterol and stigmasterol. Structural elucidation was done on the basis of spectral data, mainly high field NMR and EIMS.

Quinones from plants of northeastern Brazil: structural diversity, chemical transformations, NMR data and biological activities

The present review focus in quinones found in species of Brazilian northeastern Capraria biflora, Lippia sidoides, Lippia microphylla and Tabebuia serratifolia. The review cover ethnopharmacological aspects including photography of species, chemical structure feature, NMR datea and biological properties. Chemical transformations of lapachol to form enamine derivatives and biological activities are discussed.

Constituents of the Essential Oil of Lippia microphylla Cham. from Northeast Brazil

Abstract The essential oil from the fresh leaves of Lippia microphylla obtained by hydrodistillation was analyzed by GC/MS. Twelve compounds were identified representing 99.9% of the total components detected. The major constituents of the leaf oil were 1,8-cineole (36.0%), thymol (11.1%) and α-pinene (10.9%).

Obtenção de derivados da mistura triterpenoídica alfa- e beta-amirina

Using classic reactions such as esterification and oxidation, a series of derivatives was obtained from the a- and b-amyrin mixture, major compounds of the Protium heptaphyllum resin. The obtained compounds were characterized by spectroscopic data such as: IR, 1 H and 13C NMR and comparison with literature.

Antimicrobial Effect of the Triterpene 3β,6β,16β-Trihydroxylup-20(29)-ene on Planktonic Cells and Biofilms from Gram Positive and Gram Negative Bacteria

This study evaluated the antimicrobial effect of 3β,6β,16β-trihydroxylup-20(29)-ene (CLF1), a triterpene isolated from Combretum leprosum Mart., in inhibiting the planktonic growth and biofilms of Gram positive bacteria Streptococcus mutans and S. mitis. The antimicrobial activity was assessed by determining the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The antibiofilm potential was determined by quantifying total biomass and enumerating biofilm-entrapped viable bacteria. In addition, the acute toxicity of CLF1 on Artemia sp. nauplii was also determined. The results showed that CLF1 was able in inhibiting the growth of S. mutans and S. mitis with MIC and MBC of 7.8 μg/mL and 15.6 μg/mL, respectively. CLF1 was highly effective on biofilms of both bacteria. Only 7.8 μg/mL CLF1 was enough to inhibit by 97% and 90% biomass production of S. mutans and S. mitis, respectively. On the other hand, such effects were not evident on Gram negative Pseudomonas aeruginosa and Klebsiella oxytoca. The toxicity tests showed that the LC50 of CLF1 was 98.19 μg/mL. Therefore, CLF1 isolated from C. leprosum may constitute an important natural agent for the development of new therapies for caries and other infectious diseases caused by S. mutans and S. mitis.

Antispasmodic effects of a new kaurene diterpene isolated from Croton argyrophylloides on rat airway smooth muscle.

Objectives  The effects of rel‐(1S,4aS,7S,8aS)‐7‐(1‐vinyl)‐tetradecahydro‐1,4a‐dimethylphenanthrene‐7,8a‐carbolactone‐1‐carboxylic acid (TCCA), a new ent‐kaurene diterpene isolated from Croton argyrophylloides, on rat tracheal preparations were investigated.