A new esterified furocoumarin from Heracleum pastinacifolium

Abstract

A new esterified furocoumarin (C 17 H 16 O 7 , mp 151-153°C) of the psoralen group was isolated from the roots of Heracleum pastinacifolium. Its structure was established based on chemical and spectral data.Coumarin derivatives from the roots of Heracleum pastinacifolium C. Koch (Apiaceae Lindl.) were previously reported [1,2].In continuation of the chromatographic separation of total extracted substances from the roots of this plant over a column of Al 2 O 3 , a crystalline compound of formula C 17 H 16 O 7 , mp 151-153°C (CHCl 3 :Me 2 CO), was isolated from fractions 65-66 that were obtained by elution with C 6 H 6 :Me 2 CO (3:1).The IR spectrum of 1 exhibited absorption bands of hydroxyls (3550, 3300 cm 1 ), CO of a G-lactone ring and ester (strong bands at 1740, 1300, and 1140), and an aromatic system (1630).Singlets (3H, Table 1 lists chemical shifts of PMR and 13 C NMR resonances of psoroheraclin and its diacetate) for methyls in the PMR spectrum together with a doublet for a methylene and triplet for a gem-hydroxyl methine indicated that the molecule contained a group that was apparently bonded through an ester bond [OCOCH 2 CHOHCOH(CH 3 ) 2 ]. Broad singlets at 3.65 and 5.15 ppm (1H) belonged to protons of two hydroxyls. In addition to these resonances, the PMR spectrum of 1 showed resonances for furocoumarin skeletal protons (H-3, H-4, H-5, H-8, H-2c).The 13 C NMR spectrum of 1 taken with full suppression of proton spin-spin coupling showed 17 singlets, indicating that the molecule comprised 17 C atoms.It was concluded by comparing the physicochemical properties and spectral data (IR, PMR, 13 C NMR, Dept 135, Dept 90) that 1 was a new coumarin derivative that we called psoroheraclin.According to the Dept 135 13 C NMR spectrum, the molecule contained nine resonances belonging to nine protonated C atoms: 25.0 (CH 3 ), 28.0 (CH 3 ), 71.5 (CH 2 O), 75.0 (CHOH), 91.5 (CH=), 97.0 (CH=),103.5 (CH=), 112.0 (CH=), and 149.0 ppm (CH=). According to the Dept 90 13 C NMR spectrum, six of these belonged to one methine (75.0) and five aromatic C atoms (91.5, 97.0, 103.5, 112.0, 149.0 ppm).Thus, eight resonances that did not appear in the Dept 135 spectrum but were seen in the 13 C NMR spectrum of the compound were related to unprotonated C atoms (C-2, C-6, C-7, C-9, C-10, C-3c, C-2s, C-5s).Acetylation of 1 produced the diacetyl derivative (2) of formula C 21 H 20 O 9 , mp 120-122°C, the IR spectrum of which contained strong absorption bands at 1750, 1280, 1270, and 1250 cm 1 that were characteristic of CO of a G-lactone ring and three esters and at 1625 cm 1 (aromatic C=C). The results from the acetylation showed that 1 contained two hydroxyls. Despite the formation of the diacetyl derivative, one of the hydroxyls was tertiary in nature according to the PMR and 13 C NMR spectra of both 1 and its diacetate (Table 1).Thus, the formation of diacetylpsoroheraclin [2] was confirmed by the PMR spectrum where two 3H singlets characteristic of acetyl methyls were observed in the spectrum of the diacetyl derivative in the ran...

The Genus Heracleum: A Comprehensive Review on Its Phytochemistry, Pharmacology, and Ethnobotanical Values as a Useful Herb

“…A recent study reported the presence of a new esterified furocoumarin as a psoralen derivative from the roots of H. pastinacifolium . It was called psoroheraclin 26 and its structure was established by chemical and spectral data (Kasumova and Serkerov ). A new methoxyfurocoumarin named furomethoxyheraclin 27 was isolated from H. transcaucasicum .…”