Kristina Jenett-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 activity of Central American medicinal plants

Summary The in vitro antiplasmodial activities of 14 plant species traditionally used in Central America for the treatment of malaria or fever were evaluated. Lipophilic extracts of Piper hispidum, Siparuna andina, S. pauciflora, S. tonduziana, and Xylopia cf. frutescens, proved to be active against both a chloroquine‐sensitive and a resistant strain of Plasmodium falciparum. IC50 values ranged between 3.0 μg/ml and 21.9 μg/ml; however, moderate cytotoxicity of active extracts was observed. Bioactivity‐guided fractionation of Piper hispidum yielded 2′,4,6′‐trihydroxy‐4′‐methoxydihydrochalcone (asebogenin) as an active compound.

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.

Distribution and taxonomic significance of calystegines in the convolvulaceae

Abstract The GC-MS analysis of 65 convolvulaceous species from many, predominantly tropical provenances, belonging to 22 genera (9 tribes), revealed the occurrence of one to five calystegines in 30 species belonging to 15 genera (8 tribes). This indicates the chemotaxonomic significance of these glycosidase inhibiting polyhydroxy-nortropanes for the Convolvulaceae.

The toxin component of targeted anti-tumor toxins determines their efficacy increase by saponins.

Tumor‐targeting protein toxins are composed of a toxic enzyme coupled to a specific cell binding domain that targets cancer‐associated antigens. The anti‐tumor treatment by targeted toxins is accompanied by dose‐limiting side effects. The future prospects of targeted toxins for therapeutic use in humans will be determined by reduce side effects. Certain plant secondary metabolites (saponins) were shown to increase the efficacy of a particular epidermal growth factor receptor (EGFR)‐targeted toxin, paralleled by a tremendous decrease of side effects.

A convenient method for saponin isolation in tumour therapy.

Saponinum album (Merck), which is a crude mixture of saponins from Gypsophila paniculata L., was shown to improve the anti cancer therapy when used in vivo in combination with saporin-based targeted toxins. Unfortunately saponinum album cannot be used for further development since Merck has ceased its production in the 1990s. As pure saponins are mandatory for use in medical purposes we developed a convenient method for saponin isolation directly from the roots of Gypsophila paniculata L. The developed method is rapid, cheap and scaling up is also possible. By combining dialysis and HPLC three saponins were isolated in a one-step procedure. Chemical structures of the purified saponins were characterized by extensive one and two-dimensional NMR-spectroscopy and by using ESI-TOF-MS. The biological activities of the purified saponins were also investigated. The method presented herein enabled a rapid and cheap isolation of saponins for tumour therapy.

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.

Ipangulines, the first pyrrolizidine alkaloids from the convolvulaceae

Abstract Four novel pyrrolizidine alkaloids were isolated from Ipomoea hederifolia. It could be shown by spectroscopic methods that the compounds represent two pairs of isomeric turneforcidine diesters with either erythro- or threo-2,3-dihydroxy-2-methyl-butyric acid as the acyl moiety at C-9 OH. One pair (ipanguline A/isoipanguline A) is characterized by phenylacetic acid as the second acyl component (at C-7 OH), the other (ipanguline B/isoipanguline B) includes a salicylic acid moiety in this position. The distribution pattern shows the occurrence of the A compounds in the seeds and of the B compounds in the roots, respectively, with all four alkaloids in the aerial parts.