A novel approach to the rapid assignment of (13)C NMR spectra of major components of vegetable oils such as avocado, mango kernel and macadamia nut oils

Sensitivity of Proton NMR Relaxation and Proton NMR Diffusion Measurements to Olive Oil Adulterations with Vegetable Oils

Olive oils and, in particular, extra-virgin olive oils (EVOOs) are one of the most frauded food. Among the different adulterations of EVOOs, the mixture of high-quality olive oils with vegetable oils is one of the most common in the market. The need for fast and cheap techniques able to detect extra-virgin olive oil adulterations was the main motivation for the present research work based on ¹H NMR relaxation and diffusion measurements. In particular, the ¹H NMR relaxation times, T₁ and T₂, measured at 2 and 100 MHz on about 60 EVOO samples produced in Italy are compared with those measured on four different vegetable oils, produced from macadamia nuts, linseeds, sunflower seeds, and soybeans. Self-diffusion coefficients on this set of olive oils and vegetable oil samples were measured by means of the ¹H NMR diffusion ordered spectroscopy (DOSY) technique, showing that, except for the macadamia oil, other vegetable oils are characterized by an average diffusion coefficient sensibly different from extra-virgin olive oils. Preliminary tests based on both NMR relaxation and diffusometry methods indicate that eventual adulterations of EVOO with linseed oil and macadamia oil are the easiest and the most difficult frauds to be detected, respectively.

Novel Strategy for the Recognition of Adulterant Vegetable Oils in Essential Oils Commonly Used in Food Industries by Applying 13C NMR Spectroscopy

Essential oils (EOs) are valuable products commonly employed in the food industry and intensively studied as biopreservatives for the extension of food shelf-life. Unfortunately, EOs might be counterfeit to increase industrial profits. Among the possible adulterants, vegetable oils (VOs) must be considered for their characteristics and low costs. We aimed to apply nuclear magnetic resonance (NMR) spectroscopy for the detection and identification of VOs in mixtures with EOs. This innovative strategy is based on comparing the peak area ratio matrices of characteristic VO ¹³C NMR fatty acid signals with those of adulterated EOs. The identification of the VOs was achieved by calculating the matrix similarity at different confidence levels. The strategy demonstrated the capacity to efficiently recognize the presence of adulteration and the type of VO adulterant in mixtures. Thus, the method was applied to 20 commercial EOs, and VOs were detected and then identified in four samples.

Theoretical prediction of 13C NMR spectrum of mixed triglycerides by mean of GIAO calculations to improve vegetable oils analysis

This pioneering study based on GIAO-DFT methods is aimed to the best prediction of ¹³C Nuclear Magnetic Resonances (NMR) arising from triglycerides (and also glycerols), known to be the main component of vegetable oils. Provided that fatty esters bound to the glycerol moiety are not affected by the other esterification chains, and slightly affected by their own esterification position (2- internal, or 1/3- external), eight natural molecules are first optimized despite the challenging presence of many non-hydrogen atoms and the large conformational freedom. This preliminary study sheds light on the total chemical shift prediction concerning five fatty esters (Oleic, Palmitic, Linoleic, Stearic and Linolenic) either present in internal or external positions (ten fragments in total); these results display a very good matching to the experimental profile recorded for several vegetable oils chosen as natural mixtures of glycerides. In order to further improve the theoretical to experimental matching, ten simplified triglycerides with the mentioned fatty esters in the two different esterification positions, and flanked by acetyl esters, were studied and optimized. Beyond the best matching reached so far, we notice that the theoretical rationalisation of the overcrowding in the 28.7-29 ppm spectral region in unable to decode the necessary resolution, nonetheless the same theoretical prediction can still drive the appropriate assignments (as for the fifth and sixth carbon attribution of every chain) even against actual misleading reports.

Quantification of Fatty Acids and their Regioisomeric Distribution in Triacylglycerols from Porcine and Bovine Sources Using 13 C NMR Spectroscopy

The uptake of specific fatty acids in humans is dependent on their position on the glycerol backbone. There is a great interest in methods that can access this information fast and accurately. By way of high-resolution NMR, we have analyzed TAG extracted from pig and beef tissues and obtained quantitative data for the composition and regioisomeric distribution of all major unsaturated fatty acids usually found in these source materials, using a combination of manual integration and deconvolution of ¹³ C NMR spectra. In addition, we have developed a method for determining composition and regioisomeric distribution of the two main saturated fatty acids found in pork (16:0, 18:0). The results are discussed in relation to species-specific genetic characteristics of fatty acid and TAG biosynthesis. The developed method could support decisions related to breeding for desired fatty acid profiles, and stimulate further methodology developments using high field NMR.

Oleic Acid Is not the Only Relevant Mono-Unsaturated Fatty Ester in Olive Oil

(1) Background: Extra-virgin olive oil (EVOO) is a precious and universally studied food matrix. Recently, the quantitative chemical composition was investigated by an innovative processing method for the nuclear magnetic resonance (NMR) experiments called Multi-Assignment Recovered Analysis (MARA)-NMR. (2) Methods: Any EVOO 13-carbon NMR (¹³C-NMR) profile displayed inconsistent signals. This mismatch was resolved by comparing NMR data to the official gas-chromatographic flame ionization detection (GC-FID) experiments: the analyses concerned many EVOOs but also the "exotic" Capparis spinosa oil (CSO). (3) Results: NMR and GC-FID evidenced the overwhelming presence of cis-vaccenic esters in the CSO and, more importantly, cis-vaccenic ¹³C-NMR resonances unequivocally matched the misunderstood ¹³C-NMR signals of EVOOs. The updated assignment revealed the unexpected relevant presence of cis-vaccenic ester (around 3%) in EVOOs; it was neglected, so far, because routine and official GC-FID profiles did not resolve oleic and cis-vaccenic signals leading to the total quantification of both monounsaturated fatty esters. (4) Conclusions: The rebuilt MARA-NMR and GC-FID interpretations consistently show a meaningful presence of cis-vaccenic esters in EVOOs, whose content could be a discrimination factor featuring specific cultivar or geographical origin. The study paves the way toward new quantification panels and scientific research concerning vegetable oils.

Avocado Oil: Characteristics, Properties, and Applications

Avocado oil has generated growing interest among consumers due to its nutritional and technological characteristics, which is evidenced by an increase in the number of scientific articles that have been published on it. The purpose of the present research was to discuss the extraction methods, chemical composition, and various applications of avocado oil in the food and medicine industries. Our research was carried out through a systematic search in scientific databases. Even though there are no international regulations concerning the quality of avocado oil, some authors refer to the parameters used for olive oil, as stated by the Codex Alimentarius or the International Olive Oil Council. They indicate that the quality of avocado oil will depend on the quality and maturity of the fruit and the extraction technique in relation to temperature, solvents, and conservation. While the avocado fruit has been widely studied, there is a lack of knowledge about avocado oil and the potential health effects of consuming it. On the basis of the available data, avocado oil has established itself as an oil that has a very good nutritional value at low and high temperatures, with multiple technological applications that can be exploited for the benefit of its producers.

Similarity and differential NMR spectroscopy in metabolomics: application to the analysis of vegetable oils with 1H and 13C NMR

INTRODUCTION

In NMR based metabolomics there is a need for tools to easily compare spectra and to extract the maximum of information from the data.

OBJECTIVES

The calculation of similarity and performing differential NMR spectroscopy provides important additional information for classification and validation in metabolomics experiments.

METHODS

From 13 different vegetable oils samples were analysed by ¹H and ¹³C NMR. The similarity between spectra was calculated and differential NMR spectroscopy was used to discover marker compounds.

RESULTS

The similarity between the individual spectra was calculated for the spectra of all samples. The similarity was used to verify and improve the alignment. For vegetable oils which showed a high similarity, e.g. chia seed oil and linseed oil, differential NMR spectroscopy was used to discover marker compounds.

CONCLUSIONS

The calculation of similarity is an important tool to reveal variability between samples and spectra and can be used to verify data sets and improve alignment or binning procedures. With differential spectroscopy marker compounds are easily discovered. The methods can be seen as an important addition to the routine procedures of metabolomics experiments.

Anti-Inflammatory Constituents from Bidens frondosa

A new polyacetylene glucoside (3E,5E,11E)-tridecatriene-7,9-diyne-1,2,13-triol-2-O-β-D-glucopyranoside (1), a new phenylpropanoid glucoside 2'-butoxyethylconiferin (2), and a new flavonoid glycoside 8,3',4'-trihydroxyflavone-7-O-(6''-O-p-coumaroyl)-β-D-glucopyranoside (3), have been isolated from Bidens frondosa together with fifty-three known compounds 4-56. The structures of these compounds were established by spectroscopic methods. mainly ESIMS, 1D- and 2D-NMR spectroscopic data. and comparison with literature data. Compounds 1-34, 36, 39, 43, 47, 51, and 52 were tested for inhibition of nuclear factor kappa B (NF-κB) in 293-NF-κB-luciferase report cell line induced by lipopolysaccharide (LPS), and compounds 1, 2, 3, 9, 15, 21, 24 and 51 were tested for the production of TNF-α, IL-1β, IL-6, IL-10 in RAW 264.7 macrophages induced by LPS. In conclusion, the isolated compounds 1, 2, 3, 9, 15, 21, 24 and 51 exhibited significant activity in anti-inflammatory activity assays.

Properties of sesame oil by detailed 1H and 13C NMR assignments before and after ozonation and their correlation with iodine value, peroxide value, and viscosity measurements

Gaseous ozone chemically reacts with unsaturated triglyceride substrates leading to ozonated derivatives with a wide potential applications, ranging from the petrochemical to the pharmaceutical industry. To date, an ultimate understanding of the ozone reactivity during sesame oil ozonation process as well as detailed (1)H and (13)C NMR assignments are lacking. A practical advantage of NMR is that a single NMR sample measurement can explain many issues, while similar analysis by traditional methods may require several independent and time-consuming measurements. Moreover, significant relationships among NMR spectra and both conventional chemical analysis and viscosity measurements have been found. Eventually, NMR could play an important role for quality attributes of ozonated oil derivatives.