Gas-phase dissociation study of erythrinian alkaloids by electrospray ionization mass spectrometry and computational methods.

Alkaloids from plants of the genus Erythrina display important biological activities, including anxiolytic action. Characterization of these alkaloids by mass spectrometry (MS) has contributed to the construction of a spectral library, has improved understanding of their structures and has supported the proposal of fragmentation mechanisms in light of density functional calculations. In this study, we have used low-resolution and high-resolution MSn analyses to investigate the fragmentation patterns of erythrinian alkaloids; we have employed the B3LYP/6-31+G(d,p) model to obtain their reactive sites. To suggest the fragmentation mechanism of these alkaloids, we have studied their protonation sites by density functional calculation, and we have obtained their molecular electrostatic potential map and their gas-phase basicity values. These analyses have indicated the most basic sites on the basis of the proton affinities of the nitrogen and oxygen atoms. The protonated molecules were generated by two major fragmentations, namely, neutral loss of CH3 OH followed by elimination of H2 O. High-resolution analysis confirmed elimination of NH3 by comparison with the losses of H2 and •CH3 . NH3 was eliminated from compounds that did not bear a substituent on ring C. The benzylic carbocation initiated the dissociation mechanism, and the first reaction involved charge transfer from a lone pair of electrons in the oxygen atoms. The second reaction consisted of ring contraction with loss of a CO molecule. The presence of hydroxy and epoxy groups could change the intensity or the occurrence of the fragmentation pathways. Given that erythrinian alkaloids are applied in therapeutics and are promising leads for the development of new drugs, the present results could aid identification of several analogues of these alkaloids in biological samples and advance pharmacokinetic studies of new plant derivatives based on MSn and MS/MS analyses. Copyright © 2017 John Wiley & Sons, Ltd.

Chemical constituents of Lychnophora pohlii and trypanocidal activity of crude plant extracts and of isolated compounds.

Crude extracts of Lychnophora pohlii were tested in vitro against trypomastigote forms of Trypanosoma cruzi, and the dichloromethane and methanol crude extracts from leaves plus inflorescences were found to have trypanocidal activity. The bioassay-guided fractionation of the extracts yielded seven active compounds: the sesquiterpene lactones lychnopholide, centratherin, goyazensolide and 15-desoxygoyazensolide in the dichloromethane extract, and caffeic acid and the flavonoids luteolin and vicenin-2 in the methanol extract. One active caffeoyl quinic acid derivative was isolated from the inactive hydroalcoholic extract of leaves plus inflorescences. Chemically, the plant has sesquiterpene lactone type furanoheliangolides, flavonoids, caffeic acid, a caffeoyl quinic acid derivative, which are characteristic of the Vernonieae.

Inhibitory activity of flavonoids from Lychnophora sp. on generation of reactive oxygen species by neutrophils upon stimulation by immune complexes.

Formation of circulating immune complexes (ICs) is essential for clearance of invading agents. In some circumstances ICs might deposit on host tissues, leading to an inflammatory process that involves massive activation of neutrophils (PMNs), release of reactive oxygen species (ROS) and lysosomal enzymes and damage to the host tissue. Extracts of plants from Lychnophora sp. are used in Brazilian folk medicine as antiinflammatory agents. In this study, we evaluated the effect of eight flavonoids isolated from L. granmongolense, L. salicifolia and L. ericoides on the generation of ROS by rabbit PMNs stimulated with two kinds of ICs: particles of serum-opsonized zymosan (OZ) and insoluble ICs (ICIgG). ROS production was measured by chemiluminescence (CL) assay. We observed that 5- and 7- dihydroxylated compounds at 5 micromol/L inhibited almost totally ICIgG- and OZ-triggered luminol-CL and OZ-triggered lucigenin-CL. The degree of inhibitory effect among the other flavonoids was different, depending on the kind of ICs used to trigger ROS generation by PMNs and the number and position of methoxy groups. Moreover, under the conditions assessed, the studied flavonoids were not toxic to the rabbit PMNs. These results suggest that the actions of flavonoids on ROS generation by stimulated PMNs are highly dependent on their structures.

Trypanocidal activity of Lychnophora staavioides Mart. (Vernonieae, Asteraceae).

In the continuing search for new compounds with trypanocidal activity for use in blood banks to prevent the transmission of Chagas' disease, a trypanocidal extract of Lychnophora staavioides Mart. (Vernonieae, Asteraceae) was fractionated using several chromatographic techniques and afforded the following flavonoids: tectochrysin, pinostrobin, pinobanksin, pinobanksin 3-acetate, pinocembrin, chrysin, galangin 3-methyl ether, quercetin 3-methyl ether, chrysoeriol and vicenin-2. The most active compound was quercetin 3-methyl ether, which showed no blood lysis activity and which represents a promising compound for use against T. cruzi in blood banks.

Antimalarial activity of crude extracts from Brazilian plants studied in vivo in Plasmodium berghei-infected mice and in vitro against Plasmodium falciparum in culture

1. Ninety-five crude extrat obtained with either organic solvents or water from 48 Brazilian plants or parts of plants were evaluated experimentally as blood schizontocides. Seventy-three extracts wee obtained from 33 plants randomly collected using an empirical approach, and 22 from 15 "medicinal" plants. 2. The crude extracts were screened in vivo at up to 1.0g/Kg, po, for 4 days in mice infected with blood forms of Plasmodium berghei and parasitemia was determined on the fifth day. 3. Six plants, 2 randomly collected, Vernonia brasiliana and Eupatorium squalidum, and 4 "medicinal" plants, Acanthospermum australe, Esenbeckia febrifuga, Lisianthus speciosus, and Tachia guianensis, were partly active aginst the rodent malaria, i.e., they showed 40-50% inhibition of P. berghei multiplication. Forthy-two plants whose extracts presented no antimalarial activity are reported. 4. Four extracts with antimalarial activity were also tested in vitro using P. falciparum cultures and two of them, V. brasiliana and A. australe, were active. Extracts of V. brasiliana caused about 50% inhibition of parasite multiplication at relatively low doses (40ng/ml) as compared to chloroquine (30ng/ml) and quinine (50ng/ml). The relatively high percentage of positive results obtained here for "medicinal" plants vs randomly chosen plants demonstrates the effectiveness of the ethnopharmacological approach to drug testing