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In this work it is described the synthesis, characterization and antimicrobial and toxicity evaluation of a series of analogs of piplartine, a piperamide found in Piper sp. The compounds structures were confirmed by infrared spectroscopy, 1H, 13C nuclear magnetic resonance, high resolution mass spectroscopy and were evaluated against strains of Candida spp., Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. Derivative 24 was almost four-fold more potent (IC50: 48.83 μM) and five-fold less toxic (SI > 3) than piplartine (IC50: 189.2 μM; SI: 0.21) against Candida krusei, as well as two-fold more potent than fluconazole (IC50: 104.48 μM). This compound was also active against Candida tropicalis at 97.67 μM. Benzoyl derivative 17 was three-fold more potent (IC50: 85.2 μM) and more than five-fold less toxic (CC50: 231.71 μM) than piplartine (IC50: 315.33 μM and CC50: 41.14 μM) against Staphylococcus aureus. Given these findings, we have found analogs of piplartine which can be assumed as prototypes for the optimization and the development of new antimicrobial (compounds 24 and 17) agents.

Background Great biodiversity is a highlight of Brazilian flora. In contrast, the therapeutic potentialities of most species used in folk medicine remain unknown. Several of these species are commonly used to treat cancer. In this study, we investigated the cytotoxic activity of 18 plants from 16 families that are found in the northeast region of Brazil. Methods The following species were studied: Byrsonima sericea DC. (Malpighiaceae), Cupania impressinervia Acev. Rodr. var. (revoluta) Radlk (Sapindaceae), Duranta repens Linn. (Verbenaceae), Helicostylis tomentosa (Poepp. & Endl) Rusby (Moraceae), Himatanthus bracteatus (A.DC.) Woodson (Apocynaceae), Ipomoea purga (Wender.) Hayne (Convolvulaceae), Ixora coccinea Linn. (Rubiaceae), Mabea piriri Aubl. (Euphorbiaceae), Miconia minutiflora (Melastomataceae), Momordica charantia L. (Cucurbitaceae), Ocotea glomerata (Nees) Mez (Lauraceae), Ocotea longifolia Kunth (Oreodaphne opifera Mart. Nees) (Lauraceae), Pavonia fruticosa (Mill.) Fawc. & Rendle (Malvaceae), Psychotria capitata Ruiz & Pav. (Rubiaceae), Schefflera morototoni (Aubl.) Maguire, Steyerm. & Frodin (Araliaceae), Solanum paludosum Moric. (Solanaceae), Xylopia frutescens Aubl. (Annonaceae) and Zanthoxylum rhoifolium Lam. (Rutaceae). Their dried leaves, stems, flowers or fruits were submitted to different solvent extractions, resulting in 55 extracts. After incubating for 72 h, the cytotoxicity of each extract was tested against tumor cell lines using the alamar blue assay. Results The B. sericea, D. repens, H. bracteatus, I. purga, I. coccinea, M. piriri, O. longifolia and P. capitata extracts demonstrated the most potent cytotoxic activity. The chloroform soluble fractions of D. repens flowers and the hexane extract of I. coccinea flowers led to the isolation of quercetin and a mixture of α- and β-amyrin, respectively, and quercetin showed moderate cytotoxic activity. Conclusion The B. sericea, D. repens, H. bracteatus, I. purga, I. coccinea, M. piriri, O. longifolia and P. capitata plants were identified as having potent cytotoxic effects. Further investigations are required to determine the mechanisms of cytotoxicity exhibited and their in vivo activities. This work reinforces the need to understand the therapeutics potentialities of Brazilian medicinal plants.