Ingrid Arnault

High-performance ion-pair chromatography method for simultaneous analysis of alliin, deoxyalliin, allicin and dipeptide precursors in garlic products using multiple mass spectrometry and UV detection

The quality of garlic and garlic products is usually related to their alliin content and allicin release potential. Until now no analytical method was able to quantify simultaneously allicin, its direct precursor alliin (S-allyl-L-cysteine sulfoxide), SAC (S-allyl-L-cysteine) as well as various dipeptides that apparently serve as storage compounds in garlic. It is well known that all these intermediates are involved in the allicin biosynthetic pathway. A simple and rapid HPLC method suitable for routine analysis was developed using eluents containing an ion-pairing reagent. Particularly, heptanesulfonate as ion-pairing reagent guarantees a sufficient separation between alliin and the more retained dipeptides at very low pH. Allicin was eluted after 18 min on a 150 x 3 mm column. Synthetic reference compounds were characterized by the same chromatographic method using a diode-array UV detector and an ion trap mass spectrometer (electrospray ionization) in the multiple MS mode. In routine analysis of garlic bulbs, powders and other products, the diode-array detector is sufficient for a relevant quantification. Our method has been used in studies to improve the quality of garlic and its derived products.

Aroma analysis of fresh and preserved onions and leek by dual solid-phase microextraction–liquid extraction and gas chromatography–mass spectrometry

The lachrymatory factor (thiopropanal-S-oxide) was directly analysed on fresh onion (Allium cepa) juice by solid-phase microextraction (polyacrylate fibre) using a fast routine GC-MS method on a 10 m x 0.32 mm I.D. (4 microm thick polydimethylsiloxane film) column with splitless mode injection. The identification and quantification of thiosulphinates and zwiebelanes were obtained on the same juice extracted by diethyl ether after 80 min maceration using the same GC-MS method. Selected ion recording enhanced the differentiation possibilities and the detection limits. This dual method was used to evaluate flavour differences between onion and shallot varieties as it provides accurate profiles of all initially formed compounds. Moreover, this method allowed us to compare qualitatively and quantitatively transformed products: frozen, freeze-dried powders and sterilised products. Excepting the lachrymatory factor, frozen onion compounds were similar compared to those of fresh onion sample. Conversely, the other transformed samples have lost most of the initially formed compounds and produced mainly di- and trisulphides corresponding to the degradation of thiosulphinates and zwiebelanes. These dramatic changes can explain the very different flavours of these manufactured products compared to fresh material.

Diversity in fertility potential and organo-sulphur compounds among garlics from Central Asia

Extending the collection of garlic (Allium sativum L.) accessions is an important means that is available for broadening the genetic variability of this cultivated plant, with regard to yield, quality, and tolerance to biotic and abiotic traits; it is also an important means for restoring fertility and flowering. In the framework of the EU project ‘Garlic and Health’, 120 garlic accessions were collected in Central Asia – the main centre of garlic diversity. Plants were documented and thereafter maintained in field collections in both Israel and The Netherlands. The collection was evaluated for biological and economic traits. Garlic clones vary in most vegetative characteristics (leaf number, bulb size and structure), as well as in floral scape elongation and inflorescence development. A clear distinction was made between incomplete bolting and bolting populations; most of the accessions in the latter populations produced flowers with fertile pollen and receptive stigma. Wide variations were recorded with regard to differentiation of topsets, their size, number and rapidity of development. Furthermore, significant variation in organo-sulphur compounds (alliin, isoalliin, allicin and related dipeptides) was found within garlic collections and between plants grown under differing environmental conditions. Genetic fingerprinting by means of AFLP markers revealed three distinct groups within this collection, differing also in flowering ability and organo-S content.

Possible interest of various sample transfer techniques for fast gas chromatography-mass spectrometric analysis of true onion volatiles.

We improved GC-MS analysis of onion volatiles by comparing organic solvent partition with solid-phase microextraction (SPME) following cryo-trapping isolation and by comparing the same extraction methods on direct onion juice. Cryotrapping produces very small quantities of volatiles and therefore is not a suitable extraction method for GC-MS analysis. We confirm that SPME accelerates the degradation of labile thiosulfinates but the lacrymatory factor remains intact. The identification of Allium thiosulfinates is only obtained on juice extracted by diethyl ether using a fast GC-MS analysis on a 10 m X 0.3 mm column of 4 microm coating, with routine splitless injection. The lacrymatory factor is best analysed directly on fresh onion juice by SPME with the same chromatographic conditions. To characterise and to quantify all the true onion volatiles, we propose to analyse the same sample by successive SPME-GC-MS and solvent extraction-GC-MS.

Soil behaviour of sulfur natural fumigants used as methyl bromide substitutes

Methyl bromide is the most widely used and most effective fumigant and is used extensively for soil fumigation. According to the Montreal Protocol of 1991, methyl bromide is categorised as an ozone-depleting chemical and its use is prohibited from 2005. Many substitutes, such as methyl isothiocyanate and methyl iodide, are not applied as widely as methyl bromide. Moreover, crushed Alliumspp. plants (garlic, leek and onion) produce thiosulfinates (Ti, R–S–SO–R′) and related compounds like disulfides, which have the same pesticide activity as methyl bromide. Therefore Allium tissues or extracts can be used in biological control and Integrated Pest Management in agriculture. The successful application of these compounds, and Allium tissues and extracts, for biological soil disinfection requires more specific knowledge regarding their subsequent fate in the soil. To obtain this, appropriate analytical methods using IR spectroscopy, SPME (solid-phase micro-extraction) and GC-MS techniques were developed and applied in the laboratory on pure compounds and on Allium tissues or extracts. The experiments revealed that thiosulfintes are stable in the atmosphere but in soil they are rapidly degraded into disulfides, which are very stable in soil. For that reason and for their general pesticide effect, disulfides are a promising alternative to methyl bromide.

Comparison of gas chromatography–mass spectrometry and electronic tongue analysis for the classification of onions and shallots

Onions and Jersey shallots belong to the same species (Allium cepa L.), but are from two different groups: cepa and aggregatum. The grey shallot belongs to Allium oschaninii O. Fedtsch. Onions and shallots differ in taste but however both contain same sulfur volatile compounds making sensory evaluation difficult. There is a practical need to reliably discriminate onion from shallot. The aim of this study was to evaluate and compare the classification of several cultivars of onions and shallots by the ‘electronic tongue’ and by the chemical analysis of their fresh aroma. The ‘e-tongue’ is an analytical instrument comprising an array of cross-sensitive chemical sensors. The fresh aroma of onion and shallot due to sulfur compounds (thiosulfinates and zwiebelanes) was analysed by GC-MS. Data processing was performed by PCA. The ‘e-tongue’ and GC-MS chemical analysis were able to separate onions from shallots. The grey shallot and the white onion were separated from all samples by the two techniques, a result which fits well with its botanical nature. The differentiation between seed-propagated cultivars (all onions and a few shallots) from the vegetative produced ones (all the classic shallots) was also done. The two methods appeared compatible and sometimes complementary.

A survey on image-based insect classification

Entomology has had many applications in many biological domains (i.e insect counting as a biodiversity index). To meet a growing biological demand and to compensate a decreasing workforce amount, automated entomology has been around for decades. This challenge has been tackled by computer scientists as well as by biologists themselves. This survey investigates fourty-four studies on this topic and tries to give a global picture on what are the scientific locks and how the problem was addressed. Views are adopted on image capture, feature extraction, classification methods and the tested datasets. A general discussion is finally given on the questions that might still remain unsolved such as: the image capture conditions mandatory to good recognition performance, the definition of the problem and whether computer scientist should consider it as a problem in its own or just as an instance of a wider image recognition problem. Graphical abstractDisplay Omitted HighlightsFourty-four about image-based insect recognition are scrutinized.Each paper is qualified from three perspectives: image capture, feature extraction and classification.Datasets used in the literature are investigated.A discussion is given in which several questions about the problem are raised.

Allium Roseum L. Extract Exerts Potent Suppressive Activities on Chronic Myeloid Leukemia K562 Cell Viability Through the Inhibition of BCR-ABL, PI3K/Akt, and ERK1/2 Pathways and the Abrogation of VEGF Secretion

ABSTRACT Use of plant extracts, alone or combined to the current chemotherapy as chemosensitizers, has emerged as a promising strategy to overcome tumor drug resistance. Here, we investigated the anticancer activity of Allium roseum L. extracts, a wild edible species in North Africa, on human Chronic Myeloid Leukemia (CML) K562 cells. The dehydrated aqueous extract (DAE) disturbed the cell cycle progression and induced the apoptosis of K562 cells. Chemical analysis of DAE showed a diversity of organosulfur compounds S-alk(en)yl-cysteine sulfoxides (RCSO) and high amount of allicin, suggesting that such molecule may be behind its antitumor effect. DAE was efficient in inhibiting K562 cell viability. DAE inhibitory effect was associated with the dephosphorylation of the BCR-ABL kinase and interfered with ERK1/2, Akt, and STAT5 pathways. Furthermore, we found that DAE-induced inactivation of Akt kinase led to the activation of its target FOXO3 transcription factor, enhancing the expression of FOXO3-regulated proapoptotic effectors, Bim and Bax, and cell cycle inhibitor p27. Finally, we found that DAE reduced the secretion of vascular endothelial growth factor. Overall, our data suggest that A. roseum extract has great potential as a nontoxic cheap and effective alternative to conventional chemotherapy.

Différences et similitudes des métabolites secondaires chez deux espèces du genre Allium, Allium roseum L. et Allium ampeloprasum L

Abstract This study deals with the valorisation of medicinal and aromatic Allium to find new bioactive natural products. The phytochemical analyses of A. roseum and A. ampeloprasum powders and their aqueous and organic extracts are achieved. The results show that these species are characterized by the presence, among their components, of three precursors of organosulphurous volatile compounds. They are methiin, isoalliine and alliine in A. roseum and isoalliin and methiin in A. ampeloprasum. These differences in their flavours can correlated with the vicinity of A. roseum with garlic and A. ampeloprasum with onion. Phytochemical screening of Allium roseum shows the presence of active agents such as saponins, tannins, flavonoids, coumarins, steroids, cardiac glycosides, free quinone and iridoids.

Genotype, nitrogen fertility and sulphur availability interact to affect flavour in garlic (Allium sativum L.)

Summary Experiments were carried out to investigate the influence of combined nitrogen (N) and sulphur (S) fertility on the organosulphur compound content of garlic bulbs, especially alliin, as a specific flavour quality trait related to the health-value of garlic. Three cultivars, ‘Printanor’, ‘Morasol’ and ‘Messidrôme’, were grown in the greenhouse and in vitro. Sulphur was increased in the macronutrients within the range 0 – 144 mg l–1. Numerous combinations of both S and N were tested in vitro. In the greenhouse, increasing N levels, from 184.8 mg l–1 to 856.8 mg l–1, were tested with a single high level of S (128 mg l–1). Increasing S alone did not affect the growth or bulb weight of any garlic cultivar, but slightly increased the alliin content of bulbs. No symptoms of S deficiency were observed under greenhouse conditions, although the same garlic cultivars grown in vitro at 0 mg S l–1 clearly suffered, their size being greatly reduced. This suggests an important role for S contamination, such as atmospheric S, in the process of S absorption by garlic plants, which is discussed. Increasing N levels significantly accelerated garlic maturity and decreased bulb yield. The effect of N on the organosulphur compound content of bulbs was cultivar-dependent, but alliin accumulation was not enhanced. ‘Printanor’ and ‘Morasol’ had the highest alliin levels and were negatively influenced by increasing N, while a slight synergistic effect of S and N was observed on ‘Messidrôme’. ‘Messidrôme’ also had the highest flavour potential when including precursors, and was more efficient in accumulating S into organosulphur compounds. It is therefore advisable to choose the most appropriate variety, and to adapt the N S fertilisation regime according to the environment, in order to produce garlic with the highest health-value.