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.

Halogenated compounds are valuable substrates for the field of organic synthesis and more specifically as reagents for coupling reactions. Environmental friendly procedures for regioselective iodination is the aim of this study, using four different methods previously described in the literature, that embrace green chemistry concepts, to obtain the 6- and 8-iodo-isomers of 3,7,3’,4’-tetramethoxy-quercetin. As traditional column chromatography does not resolve the mixture of isomers, the regioselectivity for iodination was quantified by use of HPLC. The use of a protic polar solvent improves selectivity for formation of the 8-iodo- isomers (tipically, I2, LiOH, MeOH, 3 h, 54% yield), while the use of a polar aprotic solvent or in the absence of a solvent favors formation of the 6-iodo- isomer (typically, I2, K2CO3, without solvent, 5 min, 60% yield). Twenty-one reaction procedures were investigated, five of which selectively gave the 6,8-diiodo-derivative. To the best of our knowledge, selective methods for the synthesis of this compound have not been described in the literature. The best condition was the neat reaction with N-iodo-succinimide with 68% yield in just a few minutes. All product yields are after column chromatography using silica gel, and characterized by usual methods, including 1H-NMR, 13C-NMR, IR and MS-TOF.

The phytochemical investigation of Clusia lanceolata leaves yielded fourteen compounds including six flavones, vitexin, isovitexin, isovitexin-2"-O-α-L-rhamnopyranoside, vitexin-2"-O-α-L-rhamnopyranoside, orientin and isoorientin, two phaeophytins [132-hydroxy-(132-S-)-phaeophytin a and 132-hydroxy-(132-R)-phaeophytin a], two triterpenes, α- and β-amyrin, and four steroids, β-sitosterol, stigmasterol, sitosterone and stigmasterone. Their structures were assigned based on spectroscopic analysis, including two-dimensional NMR techniques and comparison with literature data. The antioxidant capacity in vivo of vitexin and mixing isovitexin-2"-O-α-L-rhamnopyranoside and vitexin-2"-O-α-L-rhamnopyranoside was evaluated using the yeast Saccharomyces cerevisiae as the biological system model and hydrogen peroxide as a stressor agent. The results showed that the tested flavonoids were able to protect the yeast cell against the oxidative damage caused by H2O2.

O estudo fitoquímico de Solanum crinitum Lam forneceu quatro flavonóides: tilirosídeo (1), astragalina (2), kaempferol (3) e biochanina A-7-O-β-D-apiofuranosil-(1→5)-β-D-apiofuranosil-(1→6)-β-D-glucopiranosideo (7), ácido 4-hidroxibenzoico (12), e quatro derivados do ácido cinâmico: cis- e trans- cumárico (10 e 11), cis- e trans- cumarato de etila (8 e 9), isolados de tricomas do fruto. Do extrato metanólico de frutos verdes foram isolados três alcalóides esteroidais glicosilados: solamargina (13), 20-epi-solamargina (14) e solasonina (16). Os derivados 3,5,7,4'-tetra-O-metil-kaempferol (4), 3,7,4'-tri-O-metil-kaempferol (5), 3,7,4'-tri-O-metil-5-O-acetil-kaempferol (6), peracetil-epi-solamargina (15) e peracetil-solasonina (17) foram sintetizados e estão sendo registrados pela primeira vez na literatura. As estruturas foram definidas através de análise de dados espectrométricos.

The phytochemical investigation of Solanum crinitum Lam led to the isolation from the fruit trichomes of four flavonoids, tiliroside (1), astragalin (2), kaempferol (3), biochanin A-7-O-β-D-apiofuranosyl-(1→5)-β-D-apiofuranosyl-(1→6)-β-D-glucopyranoside (7), along with 4-hydroxybenzoic acid (12), and four cinnamic acid derivatives, cis- and trans- coumaric acids (10 and 11) and cis- and trans- ethyl coumarate (8 and 9). Three tri-glycosyl-steroidal alkaloids, solamargine (13), 20-epi-solamargine (14) and solasonine (16) were isolated from the methanolic extract of the green fruits. The derivatives 3,5,7,4'-tretra-O-methyl-kaempferol (4), 3,7,4'-tri-O-methyl-kaempferol (5), 3,7,4'-tri-O-methyl-5-O-acetyl-kaempferol (6), the peracetyl-epi-solamargine (15) and peracetyl-solasonine (17) were prepared. The structures were established through the analysis of their spectral data. The complete ¹H and 13C NMR data assignments of the new peracetyl derivatives of the alkaloids were made.