Carbon-13 NMR spectroscopic analysis of 24-methyl-Δ5,22-sterols in rape and mustard seed oils

Depsides: lichen metabolites active against hepatitis C virus

A thorough phytochemical study of Stereocaulon evolutum was conducted, for the isolation of structurally related atranorin derivatives. Indeed, pilot experiments suggested that atranorin (1), the main metabolite of this lichen, would interfere with the lifecycle of hepatitis C virus (HCV). Eight compounds, including one reported for the first time (2), were isolated and characterized. Two analogs (5, 6) were also synthesized, to enlarge the panel of atranorin-related structures. Most of these compounds were active against HCV, with a half-maximal inhibitory concentration of about 10 to 70 µM, with depsides more potent than monoaromatic phenols. The most effective inhibitors (1, 5 and 6) were then added at different steps of the HCV lifecycle. Interestingly, atranorin (1), bearing an aldehyde function at C-3, inhibited only viral entry, whereas the synthetic compounds 5 and 6, bearing a hydroxymethyl and a methyl function, respectively, at C-3 interfered with viral replication.

Soyasapogenol B and trans-22-dehydrocam- pesterol from common vetch (Vicia sativa L.) root exudates stimulate broomrape seed germination

BACKGROUND

Orobanche and Phelipanche species (the broomrapes) are root parasitic plants, some of which represent serious weed problems causing severe yield losses on important crops. Control strategies have largely focused on agronomic practices, resistant crop varieties and herbicides, albeit with marginal success. An alternative control method is the induction of suicidal seed germination with natural substances isolated from root exudates of host and non-host plants.

RESULTS

Soyasapogenol B [olean-12-ene-3,22,24-triol(3β,4β,22β)] and trans-22-dehydrocampesterol [(ergosta-5,22-dien-3-ol, (3β,22E,24S)] were isolated from Vicia sativa root exudates. They were identified by comparing their spectroscopic and optical properties with those reported in the literature. Soyasapogenol B was very specific, stimulating the germination of O. minor seeds only, whereas trans-22-dehydrocampesterol stimulated P. aegyptiaca, O. crenata, O. foetida and O. minor.

CONCLUSION

Soyasapogenol B and trans-22-deydrocampesterol were isolated for the first time from Vicia sativa root exudates, and their biological activity as stimulants of Orobanche or Phelipanche sp. seed germination was reported.