The alkaloids of leaves and flowers of 18 populations of four Pleurothallis (Orchidaceae) species were characterized. Both leaves and flowers of individuals from all populations have two diasteroisomers of 1-hydroxymethylpyrrolizidine (RI=1290 and 1311). The 1290 isomer was the most abundant in all populations of P. johannensis (74-93%) and P. fabiobarrosii (63-93%), two morphologically closed ...

Pyrrolizidine alkaloids (PAs) are a class of secondary metabolites found in various unrelated angiosperm lineages including cool-season grasses (Poaceae, subfamily Pooideae). Thesinine conjugates, saturated forms of PA that are regarded as non-toxic, have been described to occur in the two grass species Lolium perenne and Festuca arundinacea (Poaceae, subfamily Pooideae). In a wider screen, we ...

Two new antifungal withanolides, (1) and (2) have been isolated from the defatted methanolic extract of Ajuga parviflora. Their structures were established as 3/3,17/3,20-trihydroxyl-oxo-(20/?, 22/?)-witha-5,14,24-trienolide (1), 28-hydroxy-14,20-epoxy-l-oxo-(22/?)-witha2,5,24-trienolide (2) on the basis of spectroscopic data including two dimensional NMR tech­ niques. The pyrrolizidine alkaloi...

Dehydroheliotridine, a major pyrrolic metabolite of heliotridine-based pyrrolizidine alkaloids, interacted with both native and heat-denatured DNA in vitro under mildly acid conditions to form a soluble non-diffusible complex as shown by spectral data. The complex formed with heat-denatured DNA was more resistant than heat-denatured DNA alone to the combined action of deoxyribonuclease and phos...

Due to its tropical location, chains of mountains, inter-Andean valleys, Amazon basin area, eastern plains and shores on both the Atlantic and Pacific Oceans, Colombia has many ecosystems and the second largest plant biodiversity in the world. Many plant species, both native and naturalized, are currently recognized as toxic for both animals and humans, and some of them are known to cause their...

A concise and flexible approach for the asymmetric syntheses of polyhydroxylated pyrrolizidine alkaloids hyacinthacines A(2) and A(3) has been developed using iterative reductive alkylation of O,O'-dibenzyltartarimide (5) as key steps. The ambiguity about the structure of synthetic hyacinthacine A(3) due to the differences in the NMR data of the synthetic material (2) and the natural product (h...

Humans are exposed to pyrrolizidine alkaloids (PA) through different sources, mainly from contaminated foodstuff. Teas and herbal infusions (T&HI) can be contaminated by PA producing weed. PA can possess toxic, mutagenic, genotoxic, and carcinogenic properties. Thus, possible health risks for the general population are under debate. There is a strong safety record for T&HI and additiona...