Helmut Wiedenfeld

Hypoglycemic effect of Cecropia obtusifolia on streptozotocin diabetic rats

The hypoglycemic effects of water and butanolic extracts prepared from leaves of Cecropia obtusifolia (Cecropiaceae) were examined in streptozotocin induced diabetic rats. A single oral administration of a water extract at doses of 90 and 150 mg/kg and of a butanol extract at doses of 9 and 15 mg/kg significantly (P<0.05) lowered the plasma glucose levels in diabetic rats after 3 h administration. Glibenclamide was used as reference and showed similar hypoglycemic effect to the tested extracts at a dose of 3 mg/kg. The flavone, isoorientin and 3-caffeoylquinic acid (chlorogenic acid), were isolated as the important constituents of the plant and were identified as the main constituents in both extracts, too.

Hypoglycemic effect of Equisetum myriochaetum aerial parts on streptozotocin diabetic rats.

The hypoglycemic effect of water as well as butanolic extracts prepared from aerial parts of Equisetum myriochaetum (Equisetaceae) was examined in streptozotocin induced diabetic rats. A single oral administration of the water extract (WE) at doses of 7 and 13 mg/kg and of the butanol extract (BE) at doses of 8 and 16 mg/kg significantly (P<0.001) lowered the plasma glucose levels in diabetic rats after three hours of the administration. As a reference drug glibenclamide was used and showed, at a dose of 3 mg/kg, similar hypoglycemic effect like the tested extracts. Three kaempferol glucosides and one caffeoyl glucoside were isolated from the drug and were shown to be the main constituents in both extracts.

Plants containing pyrrolizidine alkaloids: toxicity and problems

Pyrrolizidine alkaloids (PA) are toxic for human and livestock. They undergo a metabolic toxication process in the liver which is the first target organ for PA poisoning. Worldwide many episodes of human PA intoxications are well reported. In many cases the reason for these intoxications has been PA contamination in food. The main tools for analysing food and fodder on PA content are based on GC and HPLC separation, followed by MS(-MS) detection. Actual incidents with toxic PA are the ‘Jacobaea vulgaris (syn. Senecio jacobaea) problem’ in Europe and the ‘Ageratum conyzoides problem’ in Ethiopia.

Toxicity of pyrrolizidine alkaloids to humans and ruminants

Abstract1,2-dehydro pyrrolizidine ester alkaloids (PA) are toxic for human and livestock. The PAs undergo a metabolic toxication process in the liver which is the first target organ for PA poisoning. World-wide many episodes of PA intoxications have been reported involving humans as well as ruminants. This intoxication is not only related to the amount and duration of the exposure to PAs but also to species, age and gender. Besides the metabolic toxification, detoxication processes are also important. The paper discusses the toxification and detoxication processes and gives an overview about PA poisoning cases in humans and ruminants.

Camptothecin and 10-hydroxycamptothecin in callus and plantlets of t Camptotheca acuminata

The process of callus induction, organogenesis and plantlets regeneration of Camptotheca acuminata Decne is reported. The highest growth rate of callus was observed on MS medium with 1 mg l−1 NAA, 1 mg l−1 kinetin and 60 g l−1 sucrose. All tissues and organs developed in vitro contain camptothecin and 10-hydroxycamptothecin. The presence of 10-hydroxycamptothecin in shoots and callus of Camptotheca acuminata Decne is reported for the first time. The alkaloids were detected and identified using HPLC methods.

Hypoglycemic effect of Equisetum myriochaetum aerial parts on type 2 diabetic patients

The hypoglycemic effect of a water extract from aerial parts (0.33 g/kg) of Equisetum myriochaetum Schlecht and Cham (Equisetaceae) was analyzed in 11 recently diagnosed type 2 diabetic patients. A single dose of this extract was orally administered. Glucose and insulin were determined at 0, 30, 60, 90,120 and 180 min after administration. The same patients served as the control group and received only colored water as placebo. The administration of the extract significantly reduced the blood glucose levels of the type 2 diabetic patients within 90, 120 and 180 min. There were no significant changes in the insulin levels. The results demonstrate that the water extract of the aerial parts of E. myriochaetum shows a hypoglycemic effect in type 2 diabetic patients starting 90 min after its administration.

A New High Performance Liquid Chromatography Method for the Simultaneous Quantitative Analysis of Pyrrolizidine Alkaloids and their N-Oxides in Plant Material

A new high performance liquid Chromatography (HPLC) method is described for the simultaneous quantitative determination of pyrrolizidine alkaloids and their yV-oxides. The method is based on ion pair HPLC using LiChrospher 60 RP-select B as the stationary phase. The method has been applied to the analysis of senecionine, seneciphylline and spartioidine and their /V-oxides which were isolated from Senicio leucophyllus and identified by nuclear magnetic resonance spectroscopy. The method has also been used to quantify the alkaloidal contents of plant extracts which resulted from various extraction procedures.

Two pyrrolizidine alkaloids from Gynura scandens

Abstract Two new pyrrolizidine alkaloids have been isolated from Gynura scandens and their structures analysed by spectroscopic methods. The names gynuramine and acetylgynuramine are proposed.

Pyrrolizidine alkaloids from Alkanna tinctoria

Abstract Three pyrrolizidine alkaloids were isolated from Alkanna tinctoria and their structures analysed by spectroscopic methods. One of them is new and the name dihydroxytriangularine is proposed for it.

Quantitative Photometric Determination of Senkirkine in Farfarae Folium

A colour reaction for unsaturated pyrrolizidine alkaloids is made applicable for the first time to otonecine alkaloids and is used for the photometric determination of senkirkine in coltsfoot. The method allows the determination of 1 μg of alkaloid in 1 g of dried drug (i.e. 1 p.p.m.) and is therefore a useful alternative to the more exacting gas chromatographic determination.