Structure Determination of Bisacetylenic Oxylipins in Carrots (Daucus carota L.) and Enantioselective Synthesis of Falcarindiol

Abstract

Although bisacetylenic oxylipins have been demonstrated to exhibit diverse biological activities, the chemical structures of many representatives of this class of phytochemicals still remain elusive. As carrots play an important role in our daily diet and are known as a source of bisacetylenes, an extract made from Daucus carota L. was screened for bisacetylenic oxylipins, and, after isolation, their structures were determined by means of LC-MS and 1D/2D NMR spectroscopy. Besides the previously reported falcarinol, falcarindiol, and falcarindiol 3-acetate, nine additional bisacetylenes were identified, among which six derivatives are reported for the first time in literature and three compounds were previously not identified in carrots. To determine the absolute stereochemistry of falcarindiol in carrots, the (3R,8R)-, (3R,8S)-, (3S,8R)-, and (3S,8S)-stereoisomers of falcarindiol were synthesized according to a novel 10-step total synthesis involving a Cadiot-Chodkiewicz cross-coupling reaction of (S)- and (R)-trimethylsilanyl-4-dodecen-1-yn-3-ol and (R)- and (S)-5-bromo-1-penten-4-yn-3-ol, respectively. Comparative chiral HPLC analysis of the synthetic stereoisomers with the isolated phytochemical led to the unequivocal assignment of the (Z)-(3R,8S)-configuration for falcarindiol in carrot extracts from Daucus carota L.

Natural products possessing protein tyrosine phosphatase 1B (PTP1B) inhibitory activity found in the last decades

“…Zheng et al reported the first stereoselective synthesis of 298 from L-tartaric acid and D-xylose via the Cadiot-Chodkiczwicz reaction as a key step [209] . Further synthetic studies have reported several strategies for the stereoselective synthesis of 298 [210][211][212] . Further research on the chemical constituents of the EtOH extract of the plant Ardisia japonica by Li et al led to the isolation of [1,4]benzoquinones 299-302 [213] .…”

Characterisation of polyacetylenes isolated from carrot (Daucus carota) extracts by negative ion tandem mass spectrometry

“…Carrot roots ( Daucus carota ) generally contain three polyacetylenes of the falcarinol type: falcarinol [( Z )‐heptadeca‐1,9‐dien‐4,6‐diyn‐3‐ol], falcarindiol [( Z )‐heptadeca‐1,9‐dien‐4,6‐diyn‐3,8‐diol] and falcarindiol‐3‐acetate [( Z )‐3‐acetoxyheptadeca‐1,9‐dien‐4,6‐diyn‐8‐ol] (Fig. ) . In addition to their presence in terrestrial plants, polyacetylenes have also been shown to be present in many marine organisms most notably sponges .…”

“…Since the importance of polyacetylenes has only recently become apparent, it is not possible to purchase commercial authenticated standards of any of the compounds present in these vegetables. Therefore, isolation, purification and identification of these compounds from their native source are essential steps for quantification and evaluation of their bioactivity . Preliminary identification of the purified polyacetylenes can be achieved by comparing their characteristic ultraviolet (UV) spectra with published spectroscopic data .…”

“…Mass spectrometry (MS) has been used for the identification and quantification of various polyacetylenes in food of plant origin, marine sponges and in medicinal plants since the mid‐1960s. The most widely used methods in the investigation of polyacetylenes have been electron impact (EI) and/or fast atom bombardment (FAB)‐MS .…”

“…Electrospray ionisation (ESI)‐MS, despite exponential growth of its application in health and life sciences since the 1990s, is a relatively new analytical tool in food research and industry. To date, few literature reports of ESI‐MS coupled to a liquid chromatography (LC) system have been made for the characterisation of the polyacetylenes . The ESI‐MS data reported to date have been almost exclusively obtained in the positive ion mode where the sodium or solvent adducts dominated the mass spectra.…”