T-cell immunity to SARS-CoV-2: what if the known best is not the optimal course for the long run? Adapting to evolving targets.

Humanity did surprisingly well so far, considering how unprepared it was to respond to the coronavirus disease 2019 (COVID-19) threat. By blending old and ingenious new technology in the context of the accumulated knowledge on other human coronaviruses, several vaccine candidates were produced and tested in clinical trials in record time. Today, five vaccines account for the bulk of the more than 13 billion doses administered worldwide. The ability to elicit biding and neutralizing antibodies most often against the spike protein is a major component of the protection conferred by immunization but alone it is not enough to limit virus transmission. Thus, the surge in numbers of infected individuals by newer variants of concern (VOCs) was not accompanied by a proportional increase in severe disease and death rate. This is likely due to antiviral T-cell responses, whose evasion is more difficult to achieve. The present review helps navigating the very large literature on T cell immunity induced by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and vaccination. We examine the successes and shortcomings of the vaccinal protection in the light of the emergence of VOCs with breakthrough potential. SARS-CoV-2 and human beings will likely coexist for a long while: it will be necessary to update existing vaccines to improve T-cell responses and attain better protection against COVID-19.

Immune Response Resetting as a Novel Strategy to Overcome SARS-CoV-2-Induced Cytokine Storm.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes coronavirus disease 2019 (COVID-19), which rapidly became a pandemic of global proportions. Sepsis is commonly present with high lethality in the severe forms of the disease. The virus-induced cytokine storm puts the immune system in overdrive at the expense of the pathogen-specific immune response and is likely to underlie the most advanced COVID-19 clinical features, including sepsis-related multiple organ dysfunction as well as the pathophysiological changes found in the lungs. We review the major therapeutic strategies that have been considered for sepsis and might be amenable to repurposing for COVID-19. We also discuss two different immunization strategies that have the potential to confer antiviral heterologous protection: innate-induced trained immunity and adaptive-induced immune response resetting.

TP53 p.Arg337His geographic distribution correlates with adrenocortical tumor occurrence.

BACKGROUND: The p.Arg337His mutation of the TP53 is the most frequent germline missense variant associated with cancer described so far in this gene. It is mainly found in the South and Southeastern regions of Brazil, where it has been associated with a high incidence of pediatric adrenocortical (ACT) and choroid plexus tumors. The frequency and geographic distribution of this mutation is largely unknown, except for the Parana State, where a mean prevalence of 0.27% was reported. In the present study, we developed a high-throughput method for p.Arg337His genotyping, what allowed us to determine the frequency and geographic distribution of this mutation in a cohort from the most populous state in Brazil. METHODS: Consecutive samples from 31,612 newborns from São Paulo State were screened for p.Arg337His. The allelic discrimination was done by real-time polymerase chain reaction (PCR) and the presence of haplotype A3 in carriers was examined by using allele-specific oligonucleotide PCR, followed by nested-PCR to detect the SNP rs9894946. RESULTS: We found 67 (0.21%) samples positive for this mutation. The highest p.Arg337His frequencies were found in the cities close to the boundary between São Paulo and Minas Gerais State. No association could be found between p.Arg337His and gender, ethnicity, premature birth or twinning. Remarkably, a trend was found between the geographic distribution of p.Arg337His carriers and occurrence of ACT. CONCLUSION: We presented for the first time the p.Arg337His frequency among individuals unselected for any disease from a subset of the São Paulo State, the most populous in Brazil. The allele discrimination assay we presented here has proven to be a reliable and efficient method for high-throughput genotyping. ACT was found to be a good sentinel cancer to suppose p.Arg337His presence in our region.

Immune Response Resetting in Ongoing Sepsis.

Cure of severe infections, sepsis, and septic shock with antimicrobial drugs is a challenge because morbidity and mortality in these conditions are essentially caused by improper immune response. We have tested the hypothesis that repeated reactivation of established memory to pathogens may reset unfavorable immune responses. We have chosen for this purpose a highly stringent mouse model of polymicrobial sepsis by cecum ligation and puncture. Five weeks after priming with a diverse Ag pool, high-grade sepsis was induced in C57BL/6j mice that was lethal in 24 h if left untreated. Antimicrobial drug (imipenem) alone rescued 9.7% of the animals from death, but >5-fold higher cure rate could be achieved by combining imipenem and two rechallenges with the Ag pool (p < 0.0001). Antigenic stimulation fine-tuned the immune response in sepsis by contracting the total CD3+ T cell compartment in the spleen and disengaging the hyperactivation state in the memory T subsets, most notably CD8+ T cells, while preserving the recovery of naive subsets. Quantitative proteomics/lipidomics analyses revealed that the combined treatment reverted the molecular signature of sepsis for cytokine storm, and deregulated inflammatory reaction and proapoptotic environment, as well as the lysophosphatidylcholine/phosphatidylcholine ratio. Our results showed the feasibility of resetting uncontrolled hyperinflammatory reactions into ordered hypoinflammatory responses by memory reactivation, thereby reducing morbidity and mortality in antibiotic-treated sepsis. This beneficial effect was not dependent on the generation of a pathogen-driven immune response itself but rather on the reactivation of memory to a diverse Ag pool that modulates the ongoing response.

Further drimane sesquiterpenes from Drimys brasiliensis stem barks with cytotoxic potential.

Drimys brasiliensis Miers (Winteraceae) is used in folk medicine for the treatment of cancer. Its anti-tumor activity has been demonstrated in vitro models using extracts and isolated compounds. This study investigates the cytotoxic effects of stem bark extracts of D. brasiliensis as well as isolated compounds that may be responsible for the activitys and evaluates them in leukemia cells. The stem bark extract were subjected to column chromatography, and the structures of compounds were elucidated based on spectroscopic methods by using NMR and infrared spectroscopy and GC/MS. The cytotoxicity of the isolated compounds was evaluated in chronic myeloid (K562) and acute B lymphoblastic (Nalm6) leukemia cells using tetrazolium assay (MTT). Two new compounds were isolated 1ß-O-p-methoxy-E-cinnamoyl-5α-keto-11α-enol-albicanol (1a) and the isomer 1ß-O-p-methoxy-E-cinnamoyl-5α-keto-11ß-enol-albicanol (1b) and 1ß-O-p-methoxy-E-cinnamoyl-isodrimeninol (2). The known compounds polygonal acid (3a) and the isomer isopolygonal acid (3b), fuegin (4a) and the isomer epifuegin (4b), the mixture drimanial (5) and 1ß-O-(p-methoxy-E-cinnamoyl)-6α-hydroxypolygodial (6) were also isolated. The drimanes (1-4) and drimanial (5), 1ß-(p-coumaroyloxy)-polygodial (7), 1ß-(p-methoxycinnamoyl)-polygodial (8), and polygodial (9) isolated previously were assessed in tumor cells. The IC50 values were between 3.56 and 128.91 µM. 1-ß-(p-cumaroiloxi)-polygodial showed the best result with IC50 8.18 and 3.56 µM by K562 and Nalm6, respectively. The chloroform extract of the stem bark of D. brasiliensis is a great source of drimane sesquiterpenes. Our experimental data suggest that drimanes are responsible for cytotoxicity activity demonstrated by this species, especially those with the aldehyde group linked to carbons C-11 and C-12.

Characterization and evaluation of the cytotoxic potential of the essential oil of Chenopodium ambrosioides

Abstract The essential oil of Chenopodium ambrosioides L., Amaranthaceae, was obtained by steam distillation in a Clevenger apparatus and characterization was performed using chromatographic and spectroscopic assays (GC-FID, GC/MS, 1H NMR). Two major compounds were identified: p-cymene (42.32%) and ascaridole (49.77%). The ethanolic extract and hydrolate were fractionated by liquid–liquid partitioning and the compounds were characterized by GC/MS. The essential oil, ethanol extract and fractions by partitioning with dicloromethane, ethyl acetate and butanol were tested in tumor cell lines (K562, NALM6, B15, and RAJI). Significant cytotoxic activity was found for essential oil (IC50 = 1.0 µg/ml) for RAJI cells and fraction dicloromethane (IC50 = 34.0 µg/ml) and ethanol extract (IC50 = 47.0 µg/ml) for K562 cells. The activity of the essential oil of C. ambrosioides is probably related to the large amount of ascaridol, since the other major compound, p-cymene, is recognized as a potent anti-inflammatory and has low cytotoxic activity.

SB225002 Induces Cell Death and Cell Cycle Arrest in Acute Lymphoblastic Leukemia Cells through the Activation of GLIPR1.

Acute Lymphoblastic Leukemia (ALL) is the most frequent childhood malignancy. In the effort to find new anti-leukemic agents, we evaluated the small drug SB225002 (N-(2-hydroxy-4-nitrophenyl)-N'-(2-bromophenyl)urea). Although initially described as a selective antagonist of CXCR2, later studies have identified other cellular targets for SB225002, with potential medicinal use in cancer. We found that SB225002 has a significant pro-apoptotic effect against both B- and T-ALL cell lines. Cell cycle analysis demonstrated that treatment with SB225002 induces G2-M cell cycle arrest. Transcriptional profiling revealed that SB225002-mediated apoptosis triggered a transcriptional program typical of tubulin binding agents. Network analysis revealed the activation of genes linked to the JUN and p53 pathways and inhibition of genes linked to the TNF pathway. Early cellular effects activated by SB225002 included the up-regulation of GLIPR1, a p53-target gene shown to have pro-apoptotic activities in prostate and bladder cancer. Silencing of GLIPR1 in B- and T-ALL cell lines resulted in increased resistance to SB225002. Although SB225002 promoted ROS increase in ALL cells, antioxidant N-Acetyl Cysteine pre-treatment only modestly attenuated cell death, implying that the pro-apoptotic effects of SB225002 are not exclusively mediated by ROS. Moreover, GLIPR1 silencing resulted in increased ROS levels both in untreated and SB225002-treated cells. In conclusion, SB225002 induces cell cycle arrest and apoptosis in different B- and T-ALL cell lines. Inhibition of tubulin function with concurrent activation of the p53 pathway, in particular, its downstream target GLIPR1, seems to underlie the anti-leukemic effect of SB225002.

Novel capsaicin analogues as potential anticancer agents: synthesis, biological evaluation, and in silico approach.

A novel class of benzo[d][1,3]dioxol-5-ylmethyl alkyl/aryl amide and ester analogues of capsaicin were designed, synthesized, and evaluated for their cytotoxic activity against human and murine cancer cell lines (B16F10, SK-MEL-28, NCI-H1299, NCI-H460, SK-BR-3, and MDA-MB-231) and human lung fibroblasts (MRC-5). Three compounds (5f, 6c, and 6e) selectively inhibited the growth of aggressive cancer cells in the micromolar (µM) range. Furthermore, an exploratory data analysis pointed at the topological and electronic molecular properties as responsible for the discrimination process regarding the set of investigated compounds. The findings suggest that the applied designing strategy, besides providing more potent analogues, indicates the aryl amides and esters as well as the alkyl esters as interesting scaffolds to design and develop novel anticancer agents.

Seasonal influence and cytotoxicity of extracts, fractions and major compounds from Allamanda schottii

The aim of this research was to evaluate the fractions obtained from the leaf, stem and roots of Allamanda schottii Pohl, Apocynaceae, responsible for the cytotoxicity, using several cell lines. Cytotoxicity was correlated with the season the part of the plant, and the major compounds were assessed. The ethanol extracts of leaves, stems and roots obtained at different seasons were evaluated in the human erythromyeloblastoid leukemia cell line (K562). Subsequently the ethanol extracts and dichloromethane fractions collected in winter were evaluated in mouse fibroblast cell line (Mus musculus) (L929), cervix adenocarcinoma (HeLa), human pre-B leukemia (Nalm6), as well as K562 cell line. The compounds plumericin, plumieride and ursolic acid isolated from ethanol extracts of the stems were evaluated in the same cell lines, as well as on breast adenocarcinoma cell line (MCF-7), and Mus musculus skin melanoma cell line (B16F10). The chromatographic profiles of the dichloromethane fractions were obtained by high performance liquid chromatography. The results revealed that the season during which A. schottii was collected, and the part of the plant analyzed, influence the cytotoxicity on the K562 cells tested. On the other hand the dichloromethane fractions, mainly from the stems and roots, are responsible for the cytoxicity on the cells tested. These results may be associated with the seasonal variation of plumericin in these parts of the plant. This information is in accordance with the HPLC analysis. The results clearly show the potential for the phytotherapeutic use of this species, and suggest that the cytotoxic activity observed may be due to the presence of plumericin, or to minor compounds not yet identified. The seasonal influence on the production of secondary metabolites was verified.

Antifungal and cytotoxic 2-acylcyclohexane-1,3-diones from Peperomia alata and P. trineura.

Bioactivity-guided fractionation of the separate CH2Cl2 extracts from the aerial parts of Peperomia alata and P. trineura yielded seven polyketides: alatanone A [3-hydroxy-2-(5'-phenylpent-4'E-enoyl)cyclohex-2-en-1-one, 1a] and alatanone B [3-hydroxy-2-(3'-phenyl-6'-methylenedioxypropanoyl)cyclohex-2-en-1-one, 2a] from P. alata and trineurone A [3-hydroxy-2-(11'-phenylundec-10'E-enoyl)cyclohex-2-en-1-one, 1b], trineurone B [3-hydroxy-2-(15'-phenyl-18'-methylenedioxypentadecanoyl)cyclohex-2-en-1-one, 2b], trineurone C [3-hydroxy-2-(17'-phenyl-20'-methylenedioxyheptadecanoyl)cyclohex-2-en-1-one, 2c], trineurone D [3-hydroxy-2-(hexadec-10'Z-enoyl)cyclohex-2-en-1-one, 3a], and trineurone E [(6R)-(+)-3,6-dihydroxy-2-(hexadec-10'Z-enoyl)cyclohex-2-en-1-one, 3b] from P. trineura. The isolated compounds were evaluated for antifungal activity against Cladosporium cladosporioides and C. sphaeospermum and for cytotoxicity against the K562 and Nalm-6 leukemia cell lines.

Cytotoxic non-aromatic B-ring flavanones from Piper carniconnectivum C. DC.

The EtOAc extract from the leaves of Piper carniconnectivum C. DC. was subjected to chromatographic separation to afford two non-aromatic B-ring flavanone compounds: 5-hydroxy-2-(1'-hydroxy-4'-oxo-cyclohex-2'-en-1'-yl)-6,7-dimethoxy-2,3-dihydro-4H-chromen-4-one (1) and 5-hydroxy-2-(1',2'-dihydroxy-4'-oxo-cyclohexyl)-6,7-dimethoxy-2,3-dihydro-4H-chromen-4-one (2). The absolute configuration of (+)-1 was unambiguously determined as 2S,1'R by electronic circular dichroism (ECD) spectroscopy and comparison to simulated spectra that were calculated using time-dependent density functional theory (TDDFT). This methodology allowed the assignment of the absolute configuration of (+)-2 also as 2S,1'R, except for the stereogenic center at C-2', which was assigned as R because of the evidence drawn from high resolution NMR experiments. The cytotoxic activity of both compounds and 3 (hydrogenated B-ring derivative of 1) was evaluated on twelve human leukemia cell lines, and the IC50 values (<10 µM) indicated the activity of 1 against seven cell lines.

Cytotoxic, antitumour and antimetastatic activity of two new polyacetylenes isolated from Vernonia scorpioides (Lam.) Pers.

Vernonia scorpioides (Lam.) Pers., popularly known as Enxuga, Erva-de-São Simão and Piracá, has been used in folk medicine for its anti-inflammatory, wound healing and antimicrobial properties. Two polyacetylenes, 5-octa-2,4,6-triynyl-furan-2(5H)-one (1) and 8'-hydroxy 3-4 dihydrovernoniyne (2), were isolated from the dichloromethane extract fraction of V. scorpioides. In this study, polyacetylene 1 demonstrated a more potent cytotoxic activity than 2 in the tumour cell lines examined, and cytotoxicity was found to be comparable to a commercial drug (p > 0.05) in melanoma cells. No significant cytotoxic effect was observed in normal cell lines. Furthermore, polyacetylene 1 induced an in vitro increase in caspase-3 activity in B16F10 cells. When polyacetylene 1 was administered intraperitoneally (i.p.) in mice, a reduction in solid tumour volume and metastasis was observed in mice injected with B16F10 cells. An increase in locomotor activity was also observed in mice with solid tumours, and an inhibition of mechanical hypersensitivity was observed in a mouse model of metastasis. Notably, no significant morphological change was observed in several organs harvested from the treated mice. In conclusion, in vitro and in vivo anticancer activity of polyacetylene 1 was consistently observed and involved the induction of apoptosis by the activation of caspase-3. The anticancer activity demonstrated by polyacetylene 1, together with the absence of preliminary toxicological effects, represents a new and interesting option for the management of neoplastic disease.

Phenotypic and functional characterization of NK cells in human immune response against the dimorphic fungus Paracoccidioides brasiliensis.

Besides their role in fighting viral infection and tumor resistance, recent studies have shown that NK cells also participate in the immune response against other infectious diseases. The aim of this study was to characterize the possible role of NK cells in the immune response against Paracoccidioides brasiliensis. Purified NK cells from paracoccidioidomycosis patients and healthy individuals were incubated with P. brasiliensis yeast cells or P. brasiliensis-infected monocytes, with or without the addition of recombinant IL-15. We found that NK cells from paracoccidioidomycosis patients exhibit a lower cytotoxic response compared with healthy individuals. NK cells are able directly to recognize and kill P. brasiliensis yeast cells, and this activity seems to be granule-dependent but perforin-independent, whereas the cytotoxicity against P. brasiliensis-infected monocytes is perforin-dependent. These results indicate that NK cells participate actively in the immune response against the P. brasiliensis infection either by directly destroying yeast cells or by recognizing and killing infected cells. Granulysin is the possible mediator of the cytotoxic effect, as the reduced cytotoxic activity against the yeast cells detected in patients with paracoccidioidomycosis is accompanied by a significantly lower frequency of CD56(+)granulysin(+) cells compared with that in healthy controls. Furthermore, we show that NK cells released granulysin in cultures after being stimulated by P. brasiliensis, and this molecule is able to kill the yeast cells in a dose-dependent manner. Another important finding is that stimulated NK cells are able to produce proinflammatory cytokines (IFN-γ and TNF-α) supporting their immunomodulatory role in the infection.

Comparison of effects of the ethanolic extracts of brazilian propolis on human leukemic cells as assessed with the MTT assay.

Propolis is a resinous product collected by honey bees. It was also reported that propolis has a wide variety of biological actions, including antimicrobial activity and antioxidant, anti-inflammatory, and suppressive effects of dioxin toxicity activities. The aim of this study was to compare the in vitro cytotoxic activities of green propolis (G12) and red propolis (G13) in human leukemia cells. These cells were incubated with different concentrations of propolis and 48 hours after the IC(50) was calculated for each cell. The results showed that the red propolis has cytotoxic effect in vitro higher than green propolis. Red propolis was showed to be cytostatic in K562 cells and caused the same amount of apoptosis as its control Gleevec. In conclusion, these results showed that red propolis is more cytotoxic than the green propolis in a variety of human cell lines of leukemia. Red propolis may contain drugs capable of inhibiting cancer cell growth. Therefore, further isolation of respective chemical ingredients from the red propolis (G13) for identification of the activities is necessary.

PTEN posttranslational inactivation and hyperactivation of the PI3K/Akt pathway sustain primary T cell leukemia viability.

Mutations in the phosphatase and tensin homolog (PTEN) gene leading to PTEN protein deletion and subsequent activation of the PI3K/Akt signaling pathway are common in cancer. Here we show that PTEN inactivation in human T cell acute lymphoblastic leukemia (T-ALL) cells is not always synonymous with PTEN gene lesions and diminished protein expression. Samples taken from patients with T-ALL at the time of diagnosis very frequently showed constitutive hyperactivation of the PI3K/Akt pathway. In contrast to immortalized cell lines, most primary T-ALL cells did not harbor PTEN gene alterations, displayed normal PTEN mRNA levels, and expressed higher PTEN protein levels than normal T cell precursors. However, PTEN overexpression was associated with decreased PTEN lipid phosphatase activity, resulting from casein kinase 2 (CK2) overexpression and hyperactivation. In addition, T-ALL cells had constitutively high levels of ROS, which can also downmodulate PTEN activity. Accordingly, both CK2 inhibitors and ROS scavengers restored PTEN activity and impaired PI3K/Akt signaling in T-ALL cells. Strikingly, inhibition of PI3K and/or CK2 promoted T-ALL cell death without affecting normal T cell precursors. Overall, our data indicate that T-ALL cells inactivate PTEN mostly in a nondeletional, posttranslational manner. Pharmacological manipulation of these mechanisms may open new avenues for T-ALL treatment.

Comparative study of eosinophil chemotaxis, adhesion, and degranulation in vitro in ulcerative colitis and Crohn's disease.

BACKGROUND: Eosinophils have been identified in tissues from patients with Crohn's disease (CD) and ulcerative colitis (UC) but whether they contribute to IBD pathogenesis is unknown. This study aimed to investigate the functional activity and morphological aspects of peripheral-blood eosinophils from IBD patients compared to those from healthy volunteers (HVs). METHODS: Eosinophils from HVs and CD and UC patients were purified using a Percoll gradient and then a immunomagnetic cell separator. Functional activity in inactivated and previously activated cells was investigated by measuring adhesion to fibronectin and chemotaxis to fMLP, and degranulation was measured by release of eosinophil peroxidase (EPO). Cell morphology was investigated using electron microscopy. RESULTS: Eosinophil adhesion to human fibronectin in both inactivated and PAF-stimulated and PMA-stimulated eosinophils was markedly higher in patients with CD than in either patients with UC or HVs. Similarly, the chemotactic response was markedly higher in eosinophils isolated from CD patients than in those isolated from UC patients or HVs. Baseline EPO release was higher in eosinophils isolated from UC patients than in those isolated from HVs or CD patients. Stimulation with fMLP or PMA did not further increase EPO release in cells from UC or CD patients. Comparable expression of MAC- 1 and VLA-4 adhesion molecules was observed on the surfaces of eosinophils from all groups, and an greater number of granules was noted in the eosinophils from UC patients than in those from CD patients. CONCLUSIONS: Our results indicate that peripheral-blood eosinophils are potentially primed and activated in IBD patients. Whether the differences in the morphology and functional responses of eosinophil from UC and CD patients reflect differences in disease phenotype remains to be elucidated.

Prognostic significance of WT1 gene expression in pediatric acute myeloid leukemia.

BACKGROUND: The Wilms Tumor gene (WT1) encodes a transcription factor involved in kidney development and malignancy. WT1 expression in a subpopulation of early CD34+ cells has suggested its involvement in hematopoiesis. WT1 is aberrantly expressed in leukemias. High expression of WT1 at diagnosis has been associated with unfavorable prognosis in adult acute myeloid leukemia (AML). The prognostic relevance of WT1 expression in pediatric AML was evaluated in only one study, including 47 patients, which showed that very low levels of WT1 at presentation were associated with an excellent outcome. To test the validity of these findings we measured levels of WT1 in 41 newly diagnosed pediatric AML of the non-M3 FAB subtype. PROCEDURE: Patients were treated according to an AML-BFM 83-based protocol in a single institution. Mononucleated cells obtained from presentation BM aspirates were cryopreserved and later thawed and used for total RNA extraction and cDNA synthesis. The quantitative assessment of WT1 transcripts was made by real-time PCR (RQ-PCR). WT1 transcripts values were normalized with respect to the number of ABL transcripts. RESULTS: WT1 levels were significantly higher in patients bearing favorable chromosome abnormalities, t(8;21) and inv(16) (P = 0.002). Higher levels of WT1 expression were unexpectedly associated with a higher probability of overall survival by Cox regression analysis (P = 0.002). Multivariate regression analysis could not discriminate between the effects of WT1 and cytogenetics on survival. CONCLUSIONS: Higher WT1 expression was associated with favorable cytogenetics subtypes and accordingly with better outcome in children with AML in this study.

Evaluation of the anti-proliferative effect the extracts of Allamanda blanchetti and A. schottii on the growth of leukemic and endothelial cells.

PURPOSE: To investigate the anti-proliferative effect of A. blanchetti and A. schottii extracts. METHODS: The anti-proliferative effect of A. blanchetti and A. schottii ethanolic extracts on K562 leukemic cells as well as on BMEC and HUVEC were evaluated. Phytochemical analysis to identify the possible active components was carried out. RESULTS: The root extract of A. schottii was the most active of them. At 80 microg/mL, the root extracts showed a cytostatic effect on K562, whereas at 400 microg/mL, there was a strong cytotoxic effect. Similar cytostatic and cytotoxic effects were seen in the endothelial cells, but at lower doses. The effect of A. schottii root extract on endothelial cells was seen at concentrations ten times lower (8 microg/mL) than the effect of the A. blanchetti root extract (80 microg/mL). Phytochemical investigation of different fractions and parts of the plant led to the isolation of several known compounds, some of which are described for the first time in the genus Allamanda, and with previous evidence of anticancer and antitumoral properties. CONCLUSIONS: Our results suggest that both plants studied exhibit cytostatic and cytotoxic activity, but the most active compounds are located in the roots.