Karsten Siems

Antiplasmodial activity of naphthoquinones and one anthraquinone from Stereospermum kunthianum.

A lipophilic extract of the root bark of Stereospermum kunthianum revealed antiplasmodial activity in vitro. Bioassay-guided fractionation led to the isolation of four novel naphthoquinones (sterekunthals A and B, pyranokunthones A and B) and one novel anthraquinone (anthrakunthone) together with the known naphthoquinone pinnatal. The structures of the novel compounds were determined by comprehensive analyses of their 1D and 2D NMR data. The antiplasmodial activities and toxicity against the endothelial cell line ECV-304 of the isolated compounds have been assessed.

In Vitro Antiplasmodial Investigation Of Medicinal Plants From El Salvador

In vitro antiplasmodial activities of extracts from Albizia saman, Fabaceae, Calea tenuifolia (C. zacatechichi), Asteraceae, Hymenaea courbaril, Fabaceae, Jatropha curcas, Euphorbiaceae, Momordica charantia, Cucurbitaceae, and Moringa oleifera, Moringaceae were evaluated. From the lipophilic extract of C. tenuifolia five active flavones were obtained. 4′,5- Dihydroxy-7-methoxyflavone [genkwanin] and 5-hydroxy-4′,7-dimethoxyflavone [apigenin 4′,7-dimethylether] exhibited the strongest antiplasmodial activity against a chloroquine-sensitive strain (poW) and a chloroquine-resistant strain (Dd2) of Plasmodium falciparum (IC50 values: 17.1 - 28.5 μm). Furthermore octadeca-9,12-dienoic acid [linoleic acid] {IC50 values of 21.8 μm (poW) and 31.1 μm (Dd2)} and octadeca-9,12,15-trienoic acid (α-linolenic acid) were isolated

Seasonal and interannual dynamics of polyphenols in Myriophyllum verticillatum and their allelopathic activity on Anabaena variabilis

In 4 successive years, we investigated the seasonal and interannual variability of the total polyphenolic pool and of the individual polyphenolic compounds in Myriophyllum verticillatum, as well as their allelopathic activity in a small eutrophic lake. We tested whether nutrient availability explained interannual and seasonal changes in the production of polyphenols. There were no strong interannual variations in plant tissue carbon, nitrogen and phosphorus concentrations, while total phenolic compounds (TPC) significantly differed between years, especially in apical meristems (range: 38 122 mg g 1 dry weight (DW)). Seasonal patterns, with maxima between May and July, changed between years. Partially confirming the carbon nutrient balance hypothesis sensu Bryant et al. [Bryant, J.P., Chapin III, F.S., Klein, D.R., 1983. Carbon/nutrient balance of boreal plants in relation to vertebrate herbivory. Oikos 40, 357 368], we found correlations between TPC and the C/N (carbon/nitrogen) ratio in some but not all years, especially in apical meristems. Plant tissue phosphorus content accounted also for the variability in TPC in some years. Crude extracts of apical meristems always inhibited the growth of Anabaena variabilis, used as a target cyanobacterium. Plant TPC concentration and allelopathic activity were significantly correlated in all years except in 2005. Bioassay directed fractionation of M. verticillatum extracts coupled with LC MS analyses of the respective fractions revealed several isomers of HHDP di and tri galloylglucose apparently responsible for the allelopathic effects. The individual active compounds revealed a more distinct seasonal pattern compared to the pool of phenolic compounds in M. verticillatum, with a clear maximum in May, the ecologically most relevant period for inhibitory effects of submerged macrophytes on phytoplankton.

Herbal Remedies Traditionally Used Against Malaria in Ghana: Bioassay-Guided Fractionation of Microglossa pyrifolia (Asteraceae)

Different extracts from 11 West African plants traditionally used against malaria in Ghana were tested against both the chloroquine-sensitive strain PoW and the chloroquine-resistant clone Dd2 of Plasmodium falciparum. Due to the promising in vitro activity of the lipophilic extract [IC50: 10.5 μg/ml (PoW); 13.1 μg/ml (Dd2)], Microglossa pyrifolia (Lam.) Kuntze (Asteraceae) was chosen for further phytochemical investigation. From active fractions 13 compounds were isolated; their structures were established on the basis of spectroscopic methods. 1-Acetyl-6E-geranylgeraniol-19-oic acid and sinapyl diangelate represent new natural compounds. The two diterpenes E-phytol [IC50: 8.5 μм (PoW); 11.5 μм (Dd2)], and 6Egeranylgeraniol- 19-oic acid [IC50: 12.9 μм (PoW); 15.6 μм (Dd2)] proved to be the most active constituents in our test system.

Pyrrolizidine alkaloids of Ipomoea hederifolia and related species

Abstract The common necine base of the novel pyrrolizidine alkaloids (ipangulines) isolated recently from Ipomoea hederifolia is not turneforcidine but its 1β-epimer, platynecine. Three novel ipangulines were isolated from the aerial parts of I. hederifolia and identified as 9- O -[2-hydroxy-3-(2-acetoxy)-2-methylbutyryl]-7- O -salicyloylplatynecine (ipanguline B 2 ), 9- O -[2-hydroxy-3-(2-methylbutyryloxy)-2-methylbutyryl]-platynecine (ipanguline D 10 ) and 9- O -salicyloylplatynecine (ipanguline D 11 ). Comprehensive GC-mass spectrometric analysis also revealed a great variety of >38 platynecine monoesters and diesters. They are classified as ipangulines A (diesters with one phenylacetic acid moiety), ipangulines B (diesters with one salicylic acid moiety), ipangulines C (diesters with two aliphatic moieties) and ipangulines D (either 7- or 9-monoesters). In shoot tips and young leaves, total ipangulines concentrations are up to 0.45% (on dry wt basis). The ipangulines are stored as tertiary alkaloids and not as N -oxides. Seeds of different provenance showed similar alkaloid patterns. Taxonomically related species, such as I. neei and I. × perigrenium , also contain platynecine esters in their vegetative tissues.

The Phytochemical Glaucarubinone Promotes Mitochondrial Metabolism, Reduces Body Fat, and Extends Lifespan of Caenorhabditis elegans

Naturally occurring compounds that promote energy expenditure and delay aging in model organisms may be of significant interest, since these substances potentially provide pharmaceutical approaches to tackle obesity and promote healthy lifespan in humans. We aimed to test whether pharmaceutical concentrations of glaucarubinone, a cytotoxic and antimalarial quassinoid known from different species of the plant family Simaroubaceae, are capable of affecting metabolism and/or extending lifespan in a nematodal model organism for aging processes, the roundworm Caenorhabditis elegans. Adult C. elegans roundworms, maintained on agar plates, were fed with E. coli strain OP50 bacteria, and glaucarubinone was applied to the agar to test (i) whether it alters respiration rates and mitochondrial activity, (ii) whether it affects body fat content, and (iii) whether it may promote longevity by quantifying survival in the presence and absence of the compound. We have found that glaucarubinone induces oxygen consumption and reduces body fat content of C. elegans. Moreover and consistent with the concept of mitohormesis, glaucarubinone extends C. elegans lifespan when applied at a concentration of 1 or 10 nanomolar. Taken together, glaucarubinone is capable of reducing body fat and promoting longevity in C. elegans, tentatively suggesting that this compound may promote metabolic health and lifespan in mammals and possibly humans.

Phenylethanoid glycosides from Stachytarpheta cayennensis (Rich.) Vahl, Verbenaceae, a traditional antimalarial medicinal plant

The boiled juice of Stachytarpheta cayennensis, Verbenaceae, whole plant material is used ethnomedicinally in different countries of Latin-America to treat symptoms of malaria. In the ethyl acetate extract, five phenylethanoid glycosides could be identified. Three of these phenylethanoid glycosides, leucosceptoside A, martynoside and jionoside D were detected for the first time in the genus Stachytarpheta.

Sipaucins A-C, sesquiterpenoids from Siparuna pauciflora.

The phytochemical investigation of the leaves of Siparuna pauciflora yielded three novel sesquiterpenoids: the germacrane sipaucin A, the elemane sipaucin B and sipaucin C, comprising a new type of carbon skeleton. In addition, four known aporphine alkaloids-nor-boldine, boldine, laurotetanine, and N-methyl-laurotetanine-were obtained. The evaluation of the antiplasmodial activity of the isolated compounds against two strains of Plasmodium falciparum (PoW, Dd2) showed a moderate activity of nor-boldine.

Tropane alkaloids with a unique type of acyl moiety from two Convolvulus species

Abstract An investigation of the roots of Convolvulus siculus and C. sabatius ssp. mauritanicus afforded two new tropan-3 α -ol esters named consiculine and consabatine and the known base merresectine B (3). The acyl residues of the new alkaloids are formed by consiculic acid ( = 1 β ,2 α -dihydroxy-5-prenyl-cyclohex-5-en-4-one carboxylic acid) and its 2-deoxy derivative, respectively.

Triterpene glycosides from the leaves of Pittosporum angustifolium.

Phytochemical investigation of the leaves of Pittosporum angustifolium resulted in the isolation and structural elucidation of nine new triterpene saponins, named pittangretosides A-I (1-9), together with a known compound (10). Mainly by NMR and HRESIMS experiments, eight compounds were identified as A1-barrigenol glycosides (1-7, 10), whereas two compounds exhibited an unusual 17,22-seco-backbone of oleanolic acid (8, 9). All compounds were evaluated for their in vitro cytotoxicities against human urinary bladder carcinoma cells (5637). Only compounds with an angeloyl-residue at C-22 of the aglycone (1-4 and 10) showed antiproliferative effects with IC50 values of 4.1, 5.2, 2.1, 17.9, and 2.4 µM, respectively.