Considering the relevance of natural products to the development of new drugs, this study focuses on the species Sida rhombifolia (L.), Malvaceae, widely used as a traditional remedy in several countries. The species is used to treat several diseases such as fevers, skin diseases, stomach pain, diarrhea, gum infection, conjunctivitis, urinary infections and inflammation. Many researchers around the word have investigated its pharmacological potential, and many uses have been confirmed. In spite of that, the phytochemical composition of its extracts is still poorly investigated. This research aims to make advances on the understanding of the constituents of S. rhombifolia identifying its alkaloidal compounds using ultra-high performance liquid chromatography coupled to mass spectrometry (UPLC-QTOF-MS/MS). By analyzing its alkaloidal fraction, it was possible to identify: 11-cryptolepine carboxylic acid (1), cryptolepine (2), quindoline (3), 11 methoxyquidoline (4), quindolinone (5), cryptolepinone (6), and 11-quindoline methyl ester (7). The alkaloids 1 and 7 are being reported for the first time from Sida genus. Based on the antimicrobial potential of cryptolepinone-type alkaloids, we prepared by semi-synthesis two cryptolepinone derivatives: 10-methylcryptolepinone (8) and the unreported compound 10-ethylcryptolepinone (9). Both derivatives were tested against fungal and bacterial strains and 10-methylcryptolepinone (8) showed strong activity against Cryptococcus neoformans, Candida albicans, Candida tropicalis, Aspergillus fumigatus and Aspergillus flavus.

Previous researches showed that fatty acids analysis might be a useful tool to support the taxonomic investigation. In this approach the fatty acids content of ten Malvoideae species was analyzed and its chemotaxonomic significance has been investigated. The aerial parts of the species were collected in the Northeast of Brazil and their fatty acid methyl esters were analyzed by gas chromatography with flame ionization detector. The chemometric analysis consisted of principal component analysis (PCA) and hierarchical clustering analysis (HCA) with the euclidean distance between the samples given by the Ward.D2 algorithm. This is the first report of fatty acids from Wissadula peripocifolia, Herissantia crispa, Bakeridesia pickelii, Sidastrum micranthum, Pavonia cancellata and Pavonia malacophylla. The results showed the predominance of palmitic (C16:0), oleic (C18:1) and linoleic (C18:2) acids in the studied species. By the PCA and HCA analysis, the fatty acid composition was able to distinguish the species Herissantia crispa and Pavonia malacophylla. Our findings showed a chemotaxonomic proximity among species from different genera reflecting the taxonomic and phylogenetic closeness previously demonstrated by molecular investigations on Malvoidae species. Furthermore, our results demonstrated that the fatty acid analysis may be an interesting tool to support the taxonomic investigations on Malvoideae species.

Helicteres genus, Malvaceae, has pantropical distribution, encompasses about 60 species, 31 of them found in Brazil. Species belonging to this genus are used for treatment of various diseases and aroused scientific interest in search for bioactive compounds present in these plants. In this context, this review aims to provide a complete and concise overview of scientific advances in phytochemical and pharmacological studies of these species and their use by folk medicine. The presented data were collected from scientific databases, ‘Web of Science’, ‘Scifinder’, ‘Pubmed’, ‘Sciencedirect’, and ‘Google Scholar’, using the keyword ‘Helicteres’. The species H. isora and H. angustifolia, found in Asia, are the most explored scientifically, whereas studies of species of this genus found in Americas are still rare, being possible to highlight studies carried out in Brazil with H. velutina and H. eichleri. About 149 compounds were isolated and characterized in the genus, being emphasized terpenoids, flavonoids and lignoids. These species have demonstrated various pharmacological properties in vitro and in vivo, incluinding insecticide, antidiabetic, antitumor and hepatoprotective activities. The presented data show the importance of studies carried out isolating bioactive compounds from this genus that may be used in several diseases’ treatment or/as prototypes to development of new drugs.

Abstract The species Waltheria viscosissima A.St.–Hil, Malvaceae, which is known as ‘malva-branca', is traditionally used in the Brazilian northeast for the treatment of coughs. This research looks towards reporting the isolation of phytoconstituents of W. viscosissima, as well as the quantification of its phenolics, total flavonoid content, and free radical scavenging potential, along with an evaluation of its larvicidal activity against Aedes aegypti larvae. Chromatographic techniques were used to isolate the compounds and a structural elucidation was performed by 1D and 2D NMR. The quantification of total phenolics and flavonoids and the DPPH˙ radical scavenging activity was determined through spectrophotometric methods. Consequently, the phytochemical investigation led to the identification of fourteen compounds from the aerial parts of the W. viscosissima: steroids, triterpenes, alkaloids, and eight flavonoids previously reported in the literature. The quantification of compounds showed that the aerial parts extract possessed high concentration of flavonoids, while the roots extract were rich in other phenolic compounds. At the DPPH˙ free radical scavenging assay, the roots extract presented EC50 = 77.32 ± 4.37 µg/ml and the aerial parts extracts showed EC50 = 118.10 ± 1.21 µg/ml. W. viscosissima roots extract showed the most potent larvicidal activity against Ae. aegypti (LC50 = 4.78 mg/ml), with the potential of being used in effective and economically viable preparations that can be catered for domestic use towards controlling the vector insect of severe diseases, such as dengue and Zika.