The venom of amphibians is a fascinating source of active substances. In view of their medical importance and aiming to explore the amazing Brazilian biodiversity, we conducted bioprospecting of antiproliferative activity in extracts of Rhinella marina and Rhaebo guttatus toads occurring in the Southern Amazon of Mato Grosso, Brazil. LC-MS and HPLC analysis of the venom extracts of R. marina revealed four bufadienolides (telocinobufagin, marinobufagin, bufalin and resibufogenin. R. guttatus venom extracts contained only marinobufagin. First, R. marina and R. guttatus venom extracts were evaluated for cytotoxicity against tumor cell lines by the MTT assay. All extracts revealed cytotoxicity, where R. marina extracts were comparable to doxorubicin (IC₅₀ values ranging from 0.01 to 0.23 μg/mL). Only extracts of R. guttatus toad venom caused membrane disruption of human erythrocytes. The extracts were investigated for selective activity by determining their effect on stimulated human peripheral blood mononuclear cells (PBMC) with the Alamar Blue™ assay. The extracts were up to 80-fold more selective against leukemia cells when compared to dividing leukocytes. Aiming to confirm these antiproliferative effects, BrdU incorporation into DNA was measured in HL-60 treated cells with R. marina venom extracts. These extracts decreased BrdU incorporation at both concentrations tested. In summary, nine extracts of R. marina and R. guttatus venom showed pronounced lethal and discriminating effects on tumor lines, especially those from R. marina, highlighting toad parotoid gland secretions as a promising source for novel lead anticancer chemicals.

The drug-resistance of malaria parasites is the main problem in the disease control. The huge Brazilian biodiversity promotes the search for new compounds, where the animal kingdom is proving to be a promising source of bioactive compounds. The main objective of this study was to evaluate the antiplasmodial and cytotoxic activity of the compounds obtained from the toad venoms of Brazilian Amazon. Toad venoms were collected from the secretion of Rhinella marina and Rhaebo guttatus in Mato Grosso State, Brazil. The powder was extracted at room temperature, yielding 2 extracts (RG and RM) and a substance (‘1’) identified as a bufadienolide, named telocinobufagin. Growth inhibition, intraerythrocytic development, and parasite morphology were evaluated in culture by microscopic observations of Giemsa-stained thin blood films. Cytotoxicity was determined against HepG2 and BGM cells by MTT and neutral red assays. The 2 extracts and the pure substance (‘1’) tested were active against chloroquine-resistant Plasmodium falciparum strain, demonstrating lower IC50 values. In cytotoxic tests, the 2 extracts and substance ‘1’ showed pronounced lethal effects on chloroquine-resistant P. faciparum strain and low cytotoxic effect, highlighting toad parotoid gland secretions as a promising source of novel lead antiplasmodial compounds.

Cutaneous secretions produced by amphibians of the family Bufonidae are rich sources of bioactive compounds that can be useful as new chemical templates for agrochemicals. In crop protection, the use of elicitors to induce responses offers the prospect of durable, broad-spectrum disease control using the plant’s own resistance. Therefore, we evaluated the potential of methanolic extracts of cutaneous secretions of two species of amphibians of the family Bufonidae found in the Amazon biome—Rhaebo guttatus (species 1) and Rhinella marina (species 2)—in the synthesis of phytoalexins in soybean cotyledons, bean hypocotyls, and sorghum mesocotyls. Additionally, changes in the enzyme activity of β-1,3-glucanase, peroxidase (POX), and polyphenol oxidase (PPO) and in the total protein content of soybean cotyledons were determined. In the soybean cultivar ‘TMG 132 RR’, our results indicated that the methanolic extract of R. guttatus cutaneous secretions suppressed glyceollin synthesis and β-1,3-glucanase activity and increased POX and PPO activities at higher concentrations and total protein content at a concentration of 0.2 mg/mL. On the other hand, the methanolic extract of R. marina cutaneous secretions induced glyceollin synthesis in the soybean cultivars ‘TMG 132 RR’ and ‘Monsoy 8372 IPRO’ at 0.1–0.2 mg/mL and 0.2 mg/mL, respectively. The methanolic extract of R. marina cutaneous secretions also increased the specific activity of POX and PPO in ‘Monsoy 8372 IPRO’ and ‘TMG 132 RR’, respectively, and decreased the activity of β-1,3-glucanases in ‘Monsoy 8372 IPRO’. At 0.3 mg/mL, it stimulated phaseolin synthesis. The extracts did not express bioactivity in the synthesis of deoxyanthocyanidins in sorghum mesocotyls. The study in soybean suggests that the bioactivity in defense responses is influenced by cultivar genotypes. Therefore, these results provide evidence that extracts of cutaneous secretions of these amphibians species may contribute to the bioactivity of defense metabolites in plants.

Species of the genus Cordia have shown biological activities, such as anti-inflammatory, analgesic, antioxidant, antiviral, and antifungal activities. The species Cordia glabrata (MART) A.DC. Has no information concerning its phytochemical profile and possible biological activities. Thus, this study aimed to evaluate this profile in ethanolic extracts of young, adult and senescent leaves, as well as their antioxidant, photoprotective, antimicrobial, and virucidal potentials. Phytochemical analysis was performed by TLC (thin-layer chromatography) and showed the presence of flavonoids, tannins, and terpenes. The evaluation by UPLC-MS/MS (Ultra performance liquid chromatography - tandem mass spectrometer) evidenced the presence of caffeic (3.89 mgL-1), p-cumaric (6.13 mgL-1), and ferulic (0.58 mgL-1) acids, whilst, in GC/MS (Gas chromatography–mass spectrometry) analysis there was a greater amount of palmitic (51.17%), stearic (20.34%), linoleic (9.62%), and miristic (8.16%) fatty acids. The DPPH (2,2-Diphenyl-1-picrylhydrazyl) and ABTS+ (2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) radicals were used to verify the potential antioxidant activity, observing a better activity for the leaf extract in the adult phenological stage: 54.63 ± 1.06 µgmL-1 (DPPH) and 44.21 ± 1.69 mM (ABTS). The potential photoprotective activity of the extracts was determined by spectrophotometry and the in vitro values of SPF (Sun Protection Factor) in young and adult leaves (5.47 and 5.41, respectively) showed values close to the minimum SPF of 6.0 required by ANVISA (Brazilian Health Regulatory Agency). It was not observed an antimicrobial activity for Staphylococcus aureus with a minimum inhibitory concentration of 2000 μgmL-1, however the anti-herpetic assay against the Herpes simplex virus type 2 (HSV-2) showed a potent virucidal activity at the tested concentrations with CV50 value <0.195 μgmL-1 and a Selectivity Index (SI = CC50 / CV50) greater than 448. The results obtained in this study suggest that extracts of leaves of C. glabrata in their adult phenological stage have potential antioxidant, photoprotective and virucidal activity, considering in vitro test results.

Debiasi et al.Comparison between maceration and ultrasound-assisted extraction of white bracts with spring flowers (Bougainvillea spectabilis Willd.

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Extracts of species from the Cordia genus have been reported with potential biological activities, such as antioxidant, antimicrobial, antiviral, and antiparasitic. The aim of this study was to develop microemulsions containing ethanolic extracts of C. glabrata leaves and to evaluate their stability and biological activities. The five developed microemulsions presented physicochemical stability and presented Newtonian behavior when submitted to rheological analysis. The diameter values of the globules ranged between 225.74 and 273.33 nm and the zeta potential of the formulations remained between -22.40 and -25.08. All phenolic acids of the extract, quantified by HPLC, showed consistency after being microemulsified. The EC50 values for the antioxidant activity by the DPPH scavenging method ranged between 38.13 and 45.54 µgmL-1, and between 34.46 and 39.60 mM for the ABTS+ scavenging method. The virucidal activity presented a CV50 <0.195 µgmL-1 and a selectivity index greater than 20. The photoprotection results ranged between 2.14 to 2.84. The study revealed stable microemulsions and potentiation of the antioxidant effect in the microemulsified extracts.

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