Dereplication of phenolic derivatives of three Erythroxylum species using liquid chromatography coupled with ESI-MSn and HRESIMS.

INTRODUCTION: Given the diversity of secondary metabolites produced by species of the genus Erythroxylum, in addition to the many methods that have already been described in the literature, modern screening and identification methodologies, such as dereplication, represent an efficient and quick strategy compared to the classic techniques linked to natural product research. OBJECTIVE: The objective of the present study was to determine the phenolic profiles obtained from three species of Erythroxylum (Erythroxylum pauferrense Plowman, Erythroxylum pulchrum A.St.-Hil. and Erythroxylum simonis Plowman) by dereplication using liquid chromatography coupled with ESI-MSn and HRESIMS. MATERIAL AND METHODS: Ethyl acetate and n-butanolic fractions from crude ethanolic extract of Erythroxylum species were analyzed by HPLC-ESI-MSn and HPLC-HRESIMS, in order to identify its corresponding compounds. Experiments were performed in negative ionization mode, and the metabolites were provisionally identified based on deprotonated molecules, molecular formulas, fragmentation patterns and literature data. The corresponding isolated compounds were characterized by 1 H and 13 C NMR spectroscopy. RESULTS: According to the dereplication method, it was possible to establish and compare the phenolic profile of the corresponding species by the assignment of 55 compounds, most of which were first described in these species and among which some were also new to the Erytroxylum genus. Additionally, nine compounds were isolated, including biphenyl-3,3',4,4'-tetraol, where the mass spectral data were not sufficient for their identification, and reported for the first time in the Erythroxylaceae family. CONCLUSION: This research contributes to the phytochemical knowledge of the Erythroxylum genus and demonstrates the importance of the dereplication method regarding the investigation of natural products, enabling accurate identification of the metabolites while avoiding the efforts and material expenses involved in the isolation of known compounds.

Structural elucidation and NMR assignments of a new pyrrolizidine alkaloid from Crotalaria vitellina Ker Gawl.

A new pyrrolizidine alkaloid, named crotavitelin, was isolated from fruits of Crotalaria vitellina, Fabaceae (Papilionoideae). The structure was established by spectroscopic techniques such as one-dimensional and two-dimensional NMR, IR, and MS.

Secondary metabolites from Sida rhombifolia L. (Malvaceae) and the vasorelaxant activity of cryptolepinone.

The phytochemical study of Sida rhombifolia L. (Malvaceae) led to the isolation through chromatographic techniques of eleven secondary metabolites: sitosterol (1a) and stigmasterol (1b), sitosterol-3-O-b-D-glucopyranoside (2a) and stigmasterol-3-O-b-D-glucopyranoside (2b), phaeophytin A (3), 17³-ethoxypheophorbide A (4), 13²-hydroxy phaeophytin B (5), 17³-ethoxypheophorbide B (6), 5,7-dihydroxy-4'-methoxyflavone (7), cryptolepinone (8) and a salt of cryptolepine (9). Their structures were identified by ¹H- and ¹³C-NMR using one- and two-dimensional techniques. In addition, the vasorelaxant activity of cryptolepinone in rat mesenteric artery rings is reported herein for the first time.

Application of UV/VIS spectrophotometry and multivariate analysis to characterization of the species of Solanum sect. Erythrotrichum CHILD.

The UV/VIS spectral characteristics of the standardized extracts of the leaves of 22 Solanum species of the Leptostemonum clade were investigated in the presence of shift reagents with the aid of multivariate analysis, to obtain data in support of the interspecific and subsectional delimitation proposed for Solanum sect. Erythrotrichum. Of these species, 20 belong to the section Erythrotrichum, S. paniculatum is assigned to the section Torva, and S. robustum is not attributed to a defined section. The results indicated characteristic λ(max) (absorbance maxima) for each species as well as the presence of phenolic compounds like flavonoids such as 5-hydroxy flavonols. Hierarchical cluster analysis (HCA) of the data obtained by UV/VIS analysis of the extracts or the extracts with the added shift reagents AlCl3 and HCl showed a cophenetic correlation coefficient above 0.92 and the classification of the data into three groups. The principal-component analysis (PCA) revealed that the first three principal components accounted for over 98% of the total variance and showed results similar to those obtained by HCA. The present results supported the current proposal for interspecific delimitation of the studied species and partially supported the division of the section into two subsections. The UV/VIS spectral characteristics along with multivariate analysis appear to be a useful approach for distinguishing among species of the genus Solanum.

Dolichocarpols A-F, Unprecedented Macrocyclic Humulene-Type Sesquiterpenoids from Anaxagorea dolichocarpa.

Six sesquiterpenoids with unprecedented macrocyclic humulene-type structures, namely, dolichocarpols A-E (1-5) with ether-bridged bicyclic rings between C-10 and C-2, C-10 and C-7, C-10 and C-6 (×2), and C-6 and C-3 and dolichocarpol F (6) cyclized between C-7 and C-2 and with an ether bridge between C-10 and C-3, were isolated from Anaxagorea dolichocarpa roots. The structures of the compounds were elucidated by NMR, MS, and IR data. Absolute configurations of compounds 1-3 and 6 were established on the basis of data from electronic circular dichroism, whereas relative configurations of compounds 4 and 5 were suggested by the NOESY spectrum. In addition, a putative biosynthetic pathway of the compounds is proposed. Furthermore, the cytotoxicity of 3, 4, and 6 against HCT-116 (human colorectal carcinoma) and L929 (murine fibroblast) was evaluated.

Chemical constituents from Tillandsia recurvata.

The CHCl3 extract of Tillandsia recurvata yielded 5,3'-dihydroxy-6,7,8,4'-tetramethoxyflavanone (1), 1,3-di-O-cinnamoyl-glycerol (2) and ethyl ester of caffeic acid. Their structures were elucidated by means of spectroscopic methods such as mass spectroscopy and 1 and 2D-NMR.

Leaf epidermal characters of Solanum sect. polytrichum (Solanaceae) as taxonomic evidence.

The morphological similarities among the species of Solanum are remarkable, and are often very difficult one clear distinction between them. This paper presents a comparative anatomical study of the leaf epidermis of five Brazilian species of Solanum sect. Polytrichum, carried out using light and scanning electron microscopy. The leaf epidermis surfaces were investigated to evaluate their taxonomic significance to be used for separation and delimitation of the species of the section. As results, some micro-morphological characters of the leaf epidermis, such as density, distribution and type of stellate trichomes, and the anticlinal walls of epidermal cells, and also the type and distribution of stomata proved to be the most useful and distinctive characters for the separation and delimitation of the species, and also may contribute as an additional support to the interspecific taxonomy and systematic of Solanum sect. Polytrichum.

Leaf epidermal characteristics of Cissampelos L. (Menispermaceae) species from Northeastern Brazil.

The morphological similarities among the species of Cissampelos are remarkable and the difficult to distinguish them as well. This article presents a comparative anatomical study of the leaves of common Northeastern Brazilian species of Cissampelos, carried out using light and scanning electron microscopy. The leaf epidermal was studied to obtain data on epidermal characteristics and to evaluate their taxonomic significance. As results, some micromorphological characters on the leaf epidermal like the cuticular waxes, the presence of papillae in epidermis and nonglandular trichomes, the anticlinal walls epidermal cells, the distribution, density and type of trichomes, and also the type and distribution of epicuticular wax proved to be the most useful characteristics to distinguish the species in taxonomic studies.