Characterization of phytochemicals from twisted-leaf garlic (Allium obliquum L.) using liquid chromatography coupled with electrospray ionization quadrupole time-of-flight mass spectrometry.

INTRODUCTION: Twisted-leaf garlic (Allium obliquum L.) is a wild Allium species, which is traditionally used as aroma plant for culinary purposes due to its unique, garlic-like flavor. It represents an interesting candidate for domestication, breeding and cultivation. OBJECTIVES: The objective of this work was to explore and comprehensively characterize polar and semi-polar phytochemicals accumulating in leaves and bulbs of A. obliquum. METHOD: Plant material obtained from a multiyear field trial was analyzed using a metabolite profiling workflow based on ultra-high performance liquid chromatography-coupled electrospray ionization quadrupole time-of-flight mass spectrometry (UHPLC/ESI-QTOFMS) and two chromatographic methods. For annotation of metabolites, tandem mass spectrometry experiments were carried out and the resulting accurate-mass collision-induced dissociation (CID) mass spectra interpreted. Onion and garlic bulb extracts were used as reference samples. RESULTS: Important metabolite classes influencing nutritional, sensory and technological properties were detected and structurally characterized including fructooligosaccharides with a degree of polymerization of 3-5, S-alk(en)ylcysteine sulfoxides and other S-substituted cysteine conjugates, flavonoids including O- and C-glycosylated flavones as well as O-glycosylated flavonols, steroidal saponins, hydroxycinnamic acid conjugates, phenylethanoids and free sphingoid bases. In addition, quantitative data for non-structural carbohydrates, S-alk(en)ylcysteine sulfoxides and flavonoids are provided. CONCLUSION: The compiled analytical data including CID mass spectra of more than 160 annotated metabolites provide for the first time a phytochemical inventory of A. obliquum and lay the foundation for its further use as aroma plant in food industry.

Application of ATR-FTIR spectroscopy for profiling of non-structural carbohydrates in onion (Allium cepa L.) bulbs.

Qualitative and quantitative composition of non-structural carbohydrates comprising glucose, fructose, sucrose and fructooligosaccharides (FOS) is one of the key determinants of market suitability, storability and technological processability of onions. To develop a cost-effective and rapid tool for carbohydrate profiling, applicability of attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy of onion juice was investigated with special regard to FOS patterns. As reference, detailed carbohydrate profiles of onion juices were generated by high-performance liquid chromatography coupled with evaporative light scattering detection (HPLC-ELSD). Hierarchical cluster analysis (HCA) of ATR-FTIR spectra was successfully applied for classifying onions into fresh market, storage and dehydrator type according to HPLC-ELSD profiles. A bootstrapping method for automatized test-set validation by projection to latent structures (PLS) algorithms using HPLC and ATR-FTIR spectroscopy data was developed. Model statistics showed promising perspectives for reliable quantification of individual saccharides and sum parameters. The presented methodology allows estimating the nutritional and pre-biotic value directly during cultivation and processing.

Effect of Cultivar and Cultivation Year on the Metabolite Profile of Onion Bulbs ( Allium cepa L.).

This study investigated the variation of metabolite profiles of onion bulbs ( Allium cepa L.) depending on genetic and environmental factors. Nine onion cultivars ("Corrado", "Cupido", "Forum", "Hytech", "Picador", "Redlight", "Snowpack", "Stardust", "Sturon") with different scale color and dry matter content were grown in a two-year field trial. Using a recently established metabolite profiling approach based on liquid chromatography-coupled electrospray ionization quadrupole time-of-flight mass spectrometry, 106 polar and semipolar metabolites which belong to compound classes determining nutritional, sensory, and technological quality of onion bulbs such as saccharides, flavonoids, S-substitued cysteine conjugates, amino acids, and derived γ-glutamyl peptides were relatively quantitated in parallel. Statistical analyses of the obtained data indicated that depending on the compound class genetic and environmental factors differently contributed to variation of metabolite levels. For saccharides and flavonoids the genetic factor was the major source of variation, whereas for cysteine sulfoxides, amino acids, and peptides both genetic and environmental factors had a significant impact on corresponding metabolite levels.

Determination of the melatonin content of different varieties of tomatoes (Lycopersicon esculentum) and strawberries (Fragariaananassa).

Melatonin has recently been detected in various plants and foods. However, data regarding the food composition of melatonin are too scarce to evaluate dietary intake. This paper aims to identify melatonin unequivocally using LC-MS in a wide set of varieties of tomatoes (Lycopersicon esculentum) and strawberry (Fragariaananassa). Furthermore, a validated LC fluorescence was developed. This is the first time melatonin has been identified in Bond, Borsalina, Catalina, Gordal, Lucinda, Marbone, Myriade, Pitenza, Santonio, Perlino, Platero, and RAF varieties of tomatoes, as well as in strawberry (Fragaria ananassa): Camarosa, Candonga, Festival, and Primoris. Melatonin concentration was shown to vary greatly depending on the tomato varieties and harvests (2009, 2010), ranging from 4.11ng/g to 114.52ng/g fresh weight. However, the four varieties of strawberries collected during the two harvests showed greater similarity in melatonin (1.38-11.26ng/g fresh weight).

Pharmacokinetics of the soybean isoflavone daidzein in its aglycone and glucoside form: a randomized, double-blind, crossover study.

BACKGROUND: There are conflicting results in the literature on the bioavailability of isoflavones in the aglycone and the glucoside forms. OBJECTIVE: The objective was to investigate the pharmacokinetics of the soy isoflavone daidzein (DAI) on oral administration of both the aglycone and glucoside form in a human intervention study. In addition, the pharmacokinetics of the bacterial and oxidative metabolites of DAI was assessed. DESIGN: Seven German men aged 22-30 y participated in a randomized, double-blind study in a crossover design. After ingestion of pure DAI or pure daidzein-7-O-beta-d-glucoside (DG) (1 mg DAI aglycone equivalent/kg body weight), blood samples were drawn before isoflavone administration and 1, 2, 3, 4.5, 6, 8, 10, 12, 24, and 48 h after the dose. Urine was collected before and 0-6, 6-12, and 12-24 h after the intake of the isoflavones. The concentrations of DAI and its major bacterial and oxidative metabolites in plasma and urine were measured with isotope dilution capillary gas chromatography-mass spectrometry. RESULTS: The systemic bioavailability (area under the curve; AUC(inf)), the maximal plasma concentration (C(max)), and the cumulative recovery of DAI in urine after administration of DG were 3-6 times greater than after the ingestion of DAI. Except for equol, which was formed by only one volunteer, all other quantified metabolites exhibited 2-12 times greater AUC(inf), C(max), and urinary recoveries after consumption of DG. CONCLUSION: Our results show that DG exhibits a greater bioavailability than its aglycone when ingested in an isolated form.

Preparative isolation of isoflavones from soy and red clover.

Numerous studies have demonstrated the potential of isoflavones occurring in soy (Glycine max L.) and red clover (Trifolium pratense L.) to alleviate climacteric complaints. They have also shown beneficial effects on the cardiovascular system and in the prevention of osteoporosis. As a result, several companies offer nutraceuticals based on soy or red clover extracts. The aim of the present study was the isolation of pure isoflavones on a preparative scale, in order to obtain standards for biological tests and for the quantification of isoflavones in nutraceuticals and foods. High-speed countercurrent chromatography, a special type of liquid-liquid partition chromatography, was applied to the preparative isolation of isoflavones. By using this technique the major monoglucosylated and acetylated isoflavones from soy extracts were obtained after a cleaning-up step on Amberlite XAD-7 material. Furthermore, it was possible to isolate isoflavone aglycones as well as glycosides from a red clover extract. Purity and identity of the isolated isoflavones were confirmed by HPLC with DAD, HPLC-ESI multiple-MS, and NMR spectroscopy.