viridiflorol and ledol

Results from density functional theory computations indicate that a 1,4-alkyl shift proposed as part of the carbocation cyclization/rearrangement leading to ledol, viridiflorol, and related sesquiterpenes is not energetically viable. Instead, a previously proposed mechanism that avoids such a shift is greatly preferred.

Topics: Cyclization; Sesquiterpenes; Stereoisomerism; Terpenes

Topic applications of Calendula officinalis L. lipophilic extracts are used in phytotherapy to relieve skin inflammatory conditions whereas infusions are used as a remedy for gastric complaints. Such a different usage might be explained by some cytotoxicity of lipophilic extracts at gastric level but little is known about this. Therefore, we screened the CH2Cl2 extract from the flowers of C. officinalis by MTT and LDH assays in human epithelial gastric cells AGS. This bioassay-oriented approach led to the isolation of several sesquiterpene glycosides which were structurally characterized by spectroscopic measurements, chemical reactions and MM calculations. The conformational preferences of viridiflorol fucoside were established and a previously assigned stereochemistry was revised. The compounds 1a, 2a and 3f showed comparably high cytotoxicity in the MTT assays, whereas the effect on LDH release was lower. Our study provides new insights on the composition of C. officinalis extracts of medium polarity and identifies the main compounds that could be responsible for cytotoxic effects at gastric level.

Topics: Calendula; Cardiac Glycosides; Esters; Flowers; Glycosides; Humans; L-Lactate Dehydrogenase; Molecular Structure; Nuclear Magnetic Resonance, Biomolecular; Phytotherapy; Plant Extracts; Sesquiterpenes; Stereoisomerism; Terpenes