Analytical method for appreciation of garlic therapeutic potential and for validation of a new formulation.

The consumption of garlic reduces the risk of cardiovascular disease and cancer, S-allylcysteine sulfoxide (alliin), allicin (DATi), diallyl disulfide (DADS), S-allylcysteine (SAC) and several storage dipeptides are the organo-sulphur compounds (OSC) involved in the protective mechanism of garlic against cardiovascular disorders and carcinogenesis. Thus it is very interesting to quantify simultaneously all these compounds in different garlic powders obtained in several cultural conditions. The quantification of OSC by a new ion-pair HPLC method allowed showing the general sulphur-dependence positive effect of garlic on cardiovascular disorder and carcinogenesis and the variable specific activity of each implicated OSC. The screening of 11 garlic tablets proposed on the market showed the variability and particularly the differential instability of each OSC. From these results, a new garlic tablet was realised and each step was controlled by this method. This analytical method proved to be a very powerful tool for the understanding of the garlic protective mechanism against cancer and cardiovascular diseases and the development and quality control of garlic tablets.

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.

Formation of onion bulblets in vitro and viability during medium-term storage.

The influences of light conditions, sucrose and ethylene on in vitro formation and storability of onion (Allium cepa L.) bulblets were studied in various accessions. Light, sucrose and ethylene influenced bulb formation. Storability was primarily enhanced by a high sucrose concentration (100 g/l) in the culture medium. The bulbing process was characterised by changes in bulbing ratio, leaf length, number of leaves and leaf development time. The viability of bulbs after 1 year of in vitro storage at low temperatures was determined by their growth reaction in subsequent subcultures, growth after transfer into the greenhouse and tetrazolium staining. Sufficient sprouting of bulblets previously stored at -1  °C demonstrated the possibility of storing them in a low-temperature, slow-growth culture.

Effect of onion consumption by rats on hepatic drug-metabolizing enzymes.

Fruits and vegetables or their natural constituents which increase detoxication enzymes and/or reduce activating enzymes are considered as good candidates to prevent chemically-induced carcinogenesis. In this study, rats were fed a diet supplemented with 20% onion powder for 9 days. Several cytochrome P450 (CYP)s enzymes (CYP 1A, 2B, 2E1, 3A), which are involved in carcinogen activation, were determined by measuring their enzyme activities using specific substrates. In addition, phase II enzymes activities such as UDP-glucuronosyltransferase (UGT) and glutathione S-transferase (GST), involved in detoxication of carcinogens, were measured. Protein levels of CYPs and GST A1/A2, A3/A5, Ml, M2 and P1 were measured using antibodies in Western blots. Consumption of onion induced CYP 1A and CYP 2B activities while it decreased CYP 2E1 activity. This later modification was accompanied by a decrease of CYP 2E1 levels. The same dietary treatment caused a slight increase of the total GST activity. The relative proportions of GST subunits were modified. GST Al/A2 subunits were increased while GST A3/A5 and GST M2 subunits were decreased and GST M1 and P1 were not modified. Onion consumption also increased p-nitrophenol UGT activity. Taken together, these results suggest that the decrease of CYP 2E1 and the increase of phase II enzymes by onion can afford protection against some carcinogens, while the decrease of some GST subunits could increase the genotoxic effects of other chemicals. The modulating effect of onion could be ascribed to alk(en)yl polysulphides and/or glycosides of flavonols, which were identified in the onion powder.

Changes in non-structural carbohydrate composition during bulbing in sweet and high-solid onions in field experiments.

The composition of non-structural carbohydrate (NSC) content of predominantly long-day onion germplasm has been assessed over several years and in a bi-location trial. It was observed that genetic rather than environmental factors determined the NSC composition of onion bulbs. Glucose was the NSC component which was most closely correlated with genotype. Fructose was the only NSC component that was significantly affected by environment. Sucrose and 1-kestose (DP3 fructans) were not correlated to a large extent to the other NSC components, indicating their transient role in the fructan metabolism. Strong negative correlations were observed between reducing sugars (i.e. fructose and glucose) and dry matter content (DM). Furthermore, it was shown that accessions differed significantly in their fructan accumulation pattern; high DM accessions showed accumulation of fructans over the whole bulbing period, whereas, low DM accessions quickly reached a plateau. Implications for the breeding of high quality onions are discussed.

Establishment of embryogenic cell suspension cultures of garlic (Allium sativum L.), plant regeneration and biochemical analyses.

Embryogenic cell suspension cultures of garlic (Allium sativum L.) were initiated in liquid medium from friable embryogenic tissue. The optimal parameters for culture maintenance were: (1) an initial cell density of 1-4% (v/v); (2) medium renewal every 14 days and subculturing every 28 days; (3) a low 2,4-dichlorophenoxyacetic acid concentration (0.1-0.3 mg/l). Cultures regenerated during a 14-month period. The cell suspension cultures differentiated embryos following transfer to a semi-solid embryo induction medium, with histological studies confirming and characterising the embryogenic nature of the process. Forty percent of these embryos converted into plantlets, which produced micro bulbs in vitro. The composition of the sulphur compounds of the micro bulbs obtained from cell suspension embryo-derived plantlets differed slightly from those produced by in vitro shoot proliferation-derived plantlets, but after two cycles of multiplication in the field these differences had disappeared.

Garlic and health.

Garlic is a worldwide cultivated crop species which is well-known for its health beneficial effects. In this paper an overview is given on a number of important plant and health aspects of garlic. Furthermore an outline is presented of a European initiative which is aimed at the development of high quality garlic and the identification of biomarkers in atherosclerosis and cancer in humans for disease prevention.