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The presentation discusses two themes of current interest in my research group in conjunction with a garlic mimics program. The first involves a new one-pot methodology for preparing unsymmetrical disulfides in high yield using 1-chlorobenzotriazole (BtCl) as oxidant, which can be applied to a range of functional types. The second part of the lecture will discuss the synthesis of derivatives of the garlic-derived natural product ajoene, in conjunction with an anti-cancer screening program. The synthesis has been used to prepare a fluorescently tagged derivative of the natural product that has been used to investigate localization and mode of action within the cancer cell using confocal laser scanning microscopy.

Antioxidative activities of E- and Z-ajoene prepared from Japanese garlic were studied using various radical scavenging effects. Among the various antioxidative activities tested, ajoene was found to show the highest hydroxyl radicals scavenging activity (E-ajoene = 50% and Z-ajoene = 63%). These ajoene were 5.2-13 times less efficient at reducing DPPH radical and 1.1-1.4 times less efficient at hydroxyl radical as compared with authentic α–tocopherol. Essentially E- and Z-ajoene were capable of scavenging superoxide anion (E- ajoene = 0.11%, Z-ajoene = 3.74%), but 80 minutes later antioxidant activity could not be detected. The effectiveness of Z-ajoene is significantly higher than E-ajoene.

Application of ajoene to mayonnaise and its stability were studied. Addition of 5, 10, 15, 20, 25 and 30% garlic oil containing ajoene to mayonnaise recovered E-ajoene 47.7–62.4 μg/10g mayonnaise and Z-ajoene 42–74 μg/10g mayonnaise. After one month storage 99% E- and Z-ajoene remained. In 20% substituted mayonnaise 72% and 69% E- and Z-ajoene respectively were obtained at 80oC. After three days incubation under UV-light and fluorescent light, 92% and 98% E-ajoene; 88% and 98% Z-ajoene respectively remained. Sensory evaluation demonstrated that, 20% substituted mayonnaise was the highest score among others.

SummaryA hydroponic culture system was developed for producing garlic bulbs and roots containing a precursor of ajoene. Garlic plants were cultured in a growth chamber under artificial lighting for 2 months at air temperatures of 25o/21oC (light/dark), relative humidities of 75%/90% (light/dark), a photosynthetic photon flux density of 450 µmol m–2 s–1, and a photoperiod of 12 h d–1. The growth and ajoene concentrations of garlic plants cultured hydroponically with different aeration regimes were compared in order to examine the effects of dissolved O2 levels on these parameters. The four aeration treatments included 12 h dark-time aeration (12 h-D), 12 h illuminated-time aeration (12 h-L), 24 h continuous aeration (24 h) using a pump, or no aeration (control). Dissolved O2 concentrations increased in the order: 24 h >12 h-L >12 h-D > control. Fresh weights (FW), dry weights (DW), and ajoene concentrations were increased in each part of the garlic plants by increasing the levels of dissolved O2. The FWs o...

The E and Z isomers of the antithrombotic ajoene (4,5,9-trithiadodeca-1,6,11-triene 9-oxide), components of garlic (Allium Sativa, L.), were complexed with heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin (TRIMEB) to yield solid inclusion compounds with the compositions TRIMEB·(E)-ajoene·0.5H2O (1) and TRIMEB·(Z)-ajoene (2). These species were investigated by thermal analysis techniques (HSM, TGA, DSC), powder X-ray diffraction (PXRD) and single-crystal X-ray diffraction at 173 K. Thermal analysis of 1 revealed dehydration followed by melting at 143.8°C, and only melting at 140.5°C for 2. The complexes yielded different PXRD traces, indicating crystallization in different arrangements. Single-crystal X-ray methods revealed the space groups P21 (1) and P212121 (2) and the simultaneous presence of the guest stereoisomers in both complexes. Refinement of guest site-occupancies showed that each complex crystal consists of a mixture of diastereomers in 1:1 molar ratio. The different crystal packing arrangements for...

A compound showing antimicrobial activity was isolated from an oil-macerated garlic extract by silica gel column chromatography and preparative TLC. On basis of the results of NMR and MS analyses, it was identified as Z-4,5,9-trithiadeca-1,6-diene-9-oxide (Z-10-devinylajoene; Z-10-DA). Z-10-DA exhibited a broad spectrum of antimicrobial activity against such microorganisms as gram-positive and gram-negative bacteria and yeasts. The antimicrobial activity of Z-10-DA was comparable to that of Z-ajoene, but was superior to that of E-ajoene. Z-10-DA and Z-ajoene are different in respect of substitution of the allyl group by the methyl group flanking a sulfinyl group. This result suggests that substitution by the methyl group would also be effective for the inhibition of microbial growth.

Ajoene, (E, Z) -4, 5, 9-trithiadeca-1, 6, 11-triene 9 oxide, is a compound originally isolated from ethanolic extracts of garlic that impairs platelet aggregation by inhibiting the functional exposure of platelet integrins GPIIb/IIIa. In vitro, Ajoene is toxic for several tumoral cell lines, and exert an antiproliferative effect on T. cruzi and murine malaria parasites. Here we show that Ajoene strongly inhibited the proliferation induced in human lymphocytes by the mitogens phytohemagglutinin (PHA), phorbol myristate acetate (PMA) and anti-CD3, and the capping formation induced in B lymphocytes by anti-IgM antibodies. On macrophages, Ajoene was also found to partially inhibit the lypopolysaccharide-induced production of Tumor Necrosis Factor (TNF), and to decrease the phagocytic activity of thioglycolate-elicited mouse peritoneal macrophages for IgG-opsonized, human erythrocytes. Ajoene also partially prevented the lytic effect of human and rabbit TNF on Actinomycin D-treated WEHI 164 cells. These results strongly suggest that Ajoene is a potent modulator of membrane-dependent functions of immune cells.

Summary Since many centuries Allium species have prophylactic and therapeutic uses. Some recent informations are here given about the biological activities of their sulfur compounds and problems connected with the preparation of extracts are posed. Cytosolic sulfur compounds affect in vitro the main enzyme involved in blood pressure regulation and also the growth of some cancers. Among the compounds released by the activity of the lyase, thiosulfinates are antiinfectious agents. Polysulfures would occur in in vitro carcinogenesis. Allium act as a deterrent in cardiovascular diseases, they have lipid-lowering and increased tendency of thrombocyte aggregation effects. Ajoene and cepaenes would be the most active molecules but some others are involved too.

Summary If the beneficial effects of garlic on blood circulation are known for centuries, the cellular target has been identified only recently, when ajoene was demonstrated to possess a potent anti-platelet action. Ajoene inhibits platelet aggregation induced by all known platelet agonists, and in all species studied. As does aspirin, ajoene prevents the amplification of platelet responses. However, it doesn't affect prostaglandin synthesis, but modifies the platelet membrane structure. In view of the prominent role of platelets in thrombotic diseases, garlic represents an interesting platelet inhibitor with a specific mode of action.

Ajoene, a major compound containing sulfur in oil-macerated garlic products, inhibited in a two-stage carcinogenesis test on mouse skin. Treatment with ajoene suppressed skin tumor formation, depending on the amount. In particular, the group treated with 250 microg of ajoene had only 4.9% the number of tumors per mouse compared with the control group at 18 weeks.

Garlic (Allium sativum L.) has been used for prevention of several human diseases, as a curative measure against snake bite, and inhibitory against insects, protozoa, fungi and viruses (Barone and Tansey, 1977; Cavallito et al., 1944; Fliermans, 1973; Johnson and Vaughn, 1969; Mishra and Dixit, 1986; Moore and Atkins, 1977; Nagai, 1973; Singh et al., 1979; Stoll and Seeback, 1951). However, some other workers (Tynecka and Gos, 1973; Barone and Tansey, 1977; Yoshida et al., 1987) reported variable results of garlic extracts against several fungi including some dermatophytes. Cavallito et al. (1944) isolated a compound called allicin, a putative antimicrobial agent, from garlic extract with ethanol at room temperature. The intact garlic cloves contain 0.24% by weight S-allylcysteine (alliin) (Stoll and Seeback, 1951). An antithrombotic compound called ajoene was recently isolated by Block et al. (1986) from garlic bulbs. Yoshida et al. (1987) and recently Singh et al. (1990) reported for the first time its inhibitory effect on Aspergillus niger van Tiegh, and Candida albicans (Robin) Berkh. and on some plant pathogenic fungi, respectively. Phytophthora drechsleri f. sp. cajani (Pal et al.) Kannaiyan et al. causes stem and leaf blight in pigeonpea (Cajanus cajan (L.) Millsp.) in India (Williams et al., 1968). The disease is difficult to control under field conditions as the pathogen is naturally resistant against metalaxyl, the most commonly used fungicide to control Phytophthora diseases (Chauhan and Singh, 1987). The present experiment deals with the effect ofajoene on mycelial dry weight, sporangium formation and germination, zoospore germination and types of germ tube branching of P. drechsleri f. sp. cajani. The method of preparation of ajoene and its concentrations are described elsewhere (Singh et al., 1990).