New Phenolic Glycosides from the Seeds of Cucurbita moschata

Abstract

Pumpkin, the fruits of Cucurbita moschata (Cucurbitaceae), has been used as a popular vegetable in cooking since antiquity and the pumpkin seeds are utilized in several countries as snacks after salting and roasting. The pumpkin seeds are also an important Traditional Chinese Medicine in the treatment of cestodiasis, ascariasis, and schistosomiasis. 1)Pharmacological studies on the seeds have demonstrated hepatoprotective 2) and antitumor activities.3) To our knowledge, most of the chemical studies on pumpkin seeds were carried out on lipids in the pumpkin seed oil, [4][5][6] and no report has been published concerning the water-soluble constituents. The nutritive value and potential medicinal importance prompted us to investigate its chemical constituents, which resulted in the isolation of five new phenolic glycosides, cucurbitosides A-E (1-5). This paper deals with the isolation and structural elucidation of the new constituents on the basis of spectroscopic analysis and chemical evidence.The seeds of C. moschata purchased in Harbin, China, were extracted with methanol. The methanolic extract was partitioned between ethyl acetate and water. The water layer was passed through a Diaion HP-20 column, and washed with methanol. The methanolic eluate was evaporated and applied to an ODS column chromatography (CC). Further purification by repeated reverse-phase HPLC gave five new phenolic glycosides, which were termed as cucurbitosides A-E (1-5).Cucurbitoside A (1) was isolated as an amorphous powder. The molecular formula was established as C 26 H 32 O 12 by high-resolution (HR)-FAB-MS. On acid hydrolysis, 1 afforded D-glucose and D-apiose as component sugars, which was identified by GLC analysis of its trimethylsilyl thiazolidine derivative.7) The 1 H-and 13 C-NMR spectra of 1 (Table 1) also revealed the presence of glucopyranose and apiofuranose moieties. The b-anomeric configuration for the glucopyranose was determined from a large 3 J H1,H2 coupling constant value (7.5 Hz). The b-anomeric configuration for the apiofuranose was suggested by the chemical shift of its anomeric carbon (d 110.5).8) Besides the signals due to sugars, the 1 H-NMR spectrum of 1 also showed a set of proton signals due to 1,4-disubstituted aromatic ring at d 6.95 (2H, dd, Jϭ8.9, 1.9 Hz) and 6.91 (2H, d, Jϭ8.9 Hz), as well as a benzylic methylene at d 2.65 (2H, td, Jϭ7.1, 1.9 Hz) and a hydroxymethyl at d 3.62 (2H, t, Jϭ7.1 Hz), indicating the presence of a 2-(4-hydroxyphenyl)ethanol moiety. Furthermore, the signals attributable to a monosubstituted aromatic ring were observed at d 7.94 (2H, dd, Jϭ8.3, 1.4 Hz), 7.41 (2H, t, Jϭ8.3 Hz) and 7.58 (1H, tt, Jϭ8.3, 1.4 Hz), in combination with the signal for a carbonyl carbon at d 167.8 in the 13 C-NMR spectrum, suggesting a benzoyl moiety in 1. The connection of the aforementioned structural units was determined by the 1 H-detected heteronuclear multiple bond connectivity (HMBC) data (Fig. 1). The b-D-glucopyranose was found to be connected to 4-OH of the 2-(4-hydroxy)phenylethanol moiety by ob...

A Review on Pharmacological Activities and Utilization Technologies of Pumpkin

“…However, the presence of antinutrients in pumpkin seeds which have been shown to have detrimental physiological effects on growing rats and chicks limits its nutritional value and hence limits the usefulness of fresh pumpkin seed as a protein source for human food [31][32][33]. Several phytochemicals such as polysaccharides, phenolic glycosides, 13-hydroxy-9Z, 11E-octadecatrienoic acid from the leaves of pumpkin, proteins from germinated seeds, have been isolated [34][35][36][37][38].…”

In vitro health beneficial activities of Pumpkin seeds from Cucurbita moschata cultivated in Lemnos

“…Traditionally, the nutrition quality factor comprises major nutrients such as carbohydrates, fats and proteins, as well as minor components such as minerals, vitamins, fibers (Bourne, 2002) and the well studied phenolics or not extensively studied various others (Jiang & Du, 2011;Koike, Li, Liu, Hata, & Nikaido, 2005;Li et al, 2009) or still unidentified minor food compounds. In the last decades many studies have revealed that minor food components such as various lipids (Demopoulos, Karantonis, & Antonopoulou, 2003;Fragopoulou, Demopoulos, & Antonopoulou, 2009;Nasopoulou, Karantonis, Detopoulou, Demopoulos, & Zabetakis, 2014) and phenolics (Del Rio et al, 2013) exert beneficial effects in human health by preventing chronic disease development in humans such as cardiovascular diseases and diabetes type II.…”

The hypoglycaemic effect of pumpkins as anti-diabetic and functional medicines

“…Polysaccharides, proteins and peptides, para-aminobenzoic acid, and sterols are biologically active components, which are contained within pumpkins (Appendino, Jakupovic, Belloro, & Marchesini, 1999;Kuhlmann, Koetter, & Theurer, 1999). The leaves of pumpkins contain phytochemicals such as phenolic glycosides, 13-hydroxy-9Z, 11E-octadecatrienoic acid, in addition to proteins from germinated seeds (Bang et al, 2002;Koike, Li, Liu, Hata, & Nikaido, 2005). Much research has been written on the medicinal activities of these polysaccharides and proteins such as: 1) antibacterial (Hammer, Carson, & Riley, 1999); 2) hypocholesterolaemic and antioxidant (Kong, 2000); 3) immunomodulatory (Xu, 2000); 4) antimutagenic (Ito, Maeda, & Sugiyama, 1986); 5) anthelmintic (Diaz Obregon, Lloja, Lozano, & Carbajal Zuniga, 2004) and 6) anticancer properties (Xie, 2004).…”