Onion inhibition

Nishimura and coworkers57-59 studied the y-radiolysis of aqueous solutions of sulfoxide amino acids. Sulfoxide amino acids are the precursors of the flavors of onions (S-propyl-L-cysteine sulfoxide, S-methyl-L-cysteine sulfoxide and S-(l-propenyl)-L-cysteine sulfoxide) and garlic (S-allyl-L-cysteine sulfoxide). In studies on sprout inhibition of onion by /-irradiation it was found that the characteristic flavor of onions became milder. In the y-radiolysis of an aqueous solution of S-propyl-L-cysteine sulfoxide (PCSO)57,58 they identified as the main products alanine, cysteic acid, dipropyl disulfide and dipropyl sulfide. In the radiolysis of S-allyl-L-cysteine sulfoxide (ACSO) they found that the main products are S-allyl-L-cysteine, cysteic acid, cystine, allyl alcohol, propyl allyl sulfide and diallyl sulfide. The mechanisms of formation of the products were partly elucidated by the study of the radiolysis in the presence of N20 and Br- as eaq - and OH radicals scavengers, respectively. 

The dlterpene lactone 17-acetoxyacanthoaustralide (25) has minor effects, showing promotion of clover (112%), cucumber (109%) and Palmer amaranth (111%) and inhibition of carrot germination (91%). The flavonoid artemetin (26) at 0.05 mM concentrations slightly affects onion (93%), oat (91%) and promotes seed germinations In carrot (116%) and Palmer amaranth (113%). In closing, it is noteworthy to point out that lettuce and cress are not significantly affected by all ten sesquiterpene lactones as well as the dlterpene (25) and artemetin (26). 

Dilution to 1 20 eliminated inhibition in onion, oat, ryegrass, red clover, and cheatgrass. Further dilution to 1 40 limited inhibition to lettuce, carrot, and Palmer amaranth. At this concentration lovegrass germination was promoted. The addition of 0.1%... 

Oparka, K.J., Murant, E.A., Wright, K.M., Prior, D.A.M., and Harris, N. (1991) The drug probenecid inhibits the vacuolar accumulation of fluorescent anions in onion epidermal cells. J. Cell Sci. 99, 557-563. 

The experiment with 0.5 g/mL of erode extracts of different parts of Allium plants (bulb, green leaf, white stalk) showed the inhibition of acrosin and trypsin activities, mostiy the red onion and garlic extracts. These results demonstrated that spermicidal effect of Allium extracts is determined also by their capacity of protease inhibition. The red onion extract shows the higher antioxidant capacity and a very low cytotoxicity. 

The values of acrosin activity obtained by the method based on the Kennedy et al. assay are summarized in Table 41.1. The boar semen ( 6.5 x 10 spermatozoa/mL) was treated, or not, with plant extract (0.5 g/mL) and the inhibition of acrosin activity indicates the spermicidal effect of plant extracts, about 50% for red onion extract and 25% for garlic extract, for instance. 

Trypsin inhibition activity was determined by measuring the decrease of trypsin activity in the presence of Allium extracts. The results obtained with different types of extracts (bulb, stalk, green leaf-0.5 g/iuL) are presented in Fig. 41.2. All determinations were carried out in triplicate. The higher inhibition activity was obtained with red onion bulb extract (18.55 0.14 Ul/min or 27.94 0.21 U/g fresh plants). Onion bulb extract shows also a high trypsin inhibition (18.48 0.035 UFmin, 27.83 0.053U/g), and all extracts of garlic (bulb, leaf and stalk) show activities between 11.05 1.615 - 13.185 0.205 Ul/min (16.64 2.42 - 19.86 0.31 U/g). 

Srivastava KC. (1984). Aqueous extracts of onion, garlic and ginger inhibit platelet aggregation and alter arachidonic acid metabolism. Biomed Biochim Acta. 43(8-9) S335-46. 

Other compounds containing heteroatom-heteroatom bonds have been reported as 5-LO inhibitors. Diphenyldisulphides and substituted analogues, as well as disulphiram (108), inhibited cRBL and LT release from zymosan-stimulated mouse macrophages (0.3-20 / M) [277, 278]. A number of thiosulphinate esters such as (109) and related compounds, isolated from onion and garlic, were likewise active in cells and cell-free enzymes over the... 

The dose required to inhibit sprouting of onions, shallots, and garlics is 0.03-0.12 kGy. For good sprout control of tubers such as potatoes and yams, somewhat higher doses, 0.08-0.14 kGy, are required. Because of decreased wound-healing ability after irradiation, doses in excess of 0.15-0.2 kGy may induce increased microbial rot in storage [24]. 

The ICGFI [149] estimates that irradiation cost range from 10 to 15 per tonne for a low-dose application (e.g., inhibition of sprouting of potatoes or onions), and 100 to 250 per tonne for a high-dose application (e.g., to ensure hygienic quality of spices). These unit costs are considered to be competitive with alternative treatments. 

A recent survey about essential oils and their pure constituents used to control Varroa jacobsoni, contained three interesting tables that reported the toxicity of essential oils for V. jacobsoni and Apis mellifera after 24, 48 and 72 hours in a topical application and in an evaporation test, and the effects of essential oils on behavior and reproduction of V jacobsoni and on the bee brood [63]. The most interesting oils were those of cinnamon and clove, with 100% mite mortality after 24 h and no significant toxicity on honey bees. Furthermore, clove essential oil produced small brood mortality, and it was an inhibitor of mite reproduction. Other effective oils were anise, fennel, lavender, rosemary and wintergreen, which killed 100% mites after 48-72 hours. On the contrary, the oils obtained from garlic, onion, oregano and thyme, were found to be very toxic for honey bees. Among pure constituents, camphor, linalool, linalyl acetate and pinene resulted small brood mortality and inhibited mite reproduction. 

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