Allixin, a phytoalexin produced by garlic, and its analogues as novel exogenous substances with neurotrophic activity

A review on the effect of garlic on diabetes, BDNF, and VEGF as a potential treatment for diabetic retinopathy

BACKGROUND

Garlic is one of the favorite herbs in traditional medicine that has been reported to have many medicinal features. The aim of the current study is to review the latest documents on the effect of garlic on diabetes, VEGF, and BDNF and, finally, to review the existing studies on the effect of garlic on diabetic retinopathy.

MAIN TEXT

The therapeutic effect of garlic on diabetes has been investigated in various studies. Diabetes, especially in advanced stages, is associated with complications such as diabetic retinopathy, which is caused by the alteration in the expression of molecular factors involved in angiogenesis, neurodegeneration, and inflammation in the retina. There are different in-vitro and in-vivo reports on the effect of garlic on each of these processes. Considering the present concept, we extracted the most related English articles from Web of Science, PubMed, and Scopus English databases from 1980 to 2022. All in-vitro and animal studies, clinical trials, research studies, and review articles in this area were assessed and classified.

RESULT AND CONCLUSION

According to previous studies, garlic has been confirmed to have beneficial antidiabetic, antiangiogenesis, and neuroprotective effects. Along with the available clinical evidence, it seems that garlic can be suggested as a complementary treatment option alongside common treatments for patients with diabetic retinopathy. However, more detailed clinical studies are needed in this field.

The impact of chitosan on the early metabolomic response of wheat to infection by Fusarium graminearum

BACKGROUND

Chitosan has shown potential for the control of Fusarium head blight (FHB) disease caused by Fusarium graminearum. The objective of this study was to compare the effect of chitosan hydrochloride applied pre- or post-fungal inoculation on FHB and to better understand its' mode of action via an untargeted metabolomics study.

RESULTS

Chitosan inhibited fungal growth in vitro and, when sprayed on the susceptible wheat cultivar Remus 24 hours pre-inoculation with F. graminearum, it significantly reduced the number of infected spikelets at 7, 14 and 21 days post-inoculation. Chitosan pre-treatment also increased the average grain weight per head, the number of grains per head and the 1000-grain weight compared to the controls sprayed with water. No significant impact of chitosan on grain yield was observed when the plants were sprayed 24 hours post-inoculation with F. graminearum, even if it did result in a reduced number of infected spikelets at every time point. An untargeted metabolomic study using UHPLC-QTOF-MS on wheat spikes revealed that spraying the spikes with both chitosan and F. graminearum activated known FHB resistance pathways (e.g. jasmonic acid). Additionally, more metabolites were up- or down-regulated when both chitosan and F. graminearum spores were sprayed on the spikes (117), as compared with chitosan (51) or F. graminearum on their own (32). This included a terpene, a terpenoid and a liminoid previously associated with FHB resistance.

CONCLUSIONS

In this study we showed that chitosan hydrochloride inhibited the spore germination and hyphal development of F. graminearum in vitro, triggered wheat resistance against infection by F. graminearum when used as a pre-inoculant, and highlighted metabolites and pathways commonly and differentially affected by chitosan, the pathogen and both agents. This study provides insights into how chitosan might provide protection or stimulate wheat resistance to infection by F. graminearum. It also unveiled new putatively identified metabolites that had not been listed in previous FHB or chitosan-related metabolomic studies.

The antibiotic doxycycline mimics the NGF signaling in PC12 cells: A relevant mechanism for neuroprotection

Doxycycline has been used as antibiotic since the 1960s. Recently, studies have shown that doxycycline is neuroprotective in models of neurodegenerative diseases and brain injuries, mainly due to anti-inflammatory and anti-apoptotic effects. However, it is not known if doxycycline has neurotrophic potential, which is relevant, considering the role of axonal degeneration at the early stages of neurodegeneration in Alzheimer's disease, Amyotrophic Lateral Sclerosis and Parkinson's disease as well as in normal aging. Axons are preceded by the formation of neurites, the hallmark of the neuronal differentiation induced by neurotrophins like NGF. Therefore, the modulation of neurotrophin receptors aimed at formation and regeneration of axons has been proposed as a strategy to delay the progression of neurodegeneration and has gained relevance as new techniques for early diagnosis arise. Based on these premises, we investigated the potential of doxycycline to mimic the effects of Nerve Growth Factor (NGF) with focus on the signaling pathways and neuronal modulators of neurite initiation, growth and branching. We used PC12 cells, a neuronal model widely employed to study the neurotrophic pathways and mechanisms induced by NGF. Results showed that doxycycline induced neurite outgrowth via activation of the trkA receptor and the downstream signaling pathways, PI3K/Akt and MAPK/ERK, without inducing the expression of NGF. Doxycycline also increased the expression of GAP-43, synapsin I and NF200, proteins involved in axonal and synaptic plasticity. Altogether, these data demonstrate, for the first time, the neurotrophic potential of doxycycline, which might be useful to restore the neuronal connectivity lost at the initial phase of neurodegeneration.

Pharmacological characterization of a new series of carbamoylguanidines reveals potent agonism at the H2R and D3R

Even today, the role of the histamine H₂ receptor (H₂R) in the central nervous system (CNS) is widely unknown. In previous research, many dimeric, high-affinity and subtype-selective carbamoylguanidine-type ligands such as UR-NK22 (5, pK_i = 8.07) were reported as H₂R agonists. However, their applicability to the study of the H₂R in the CNS is compromised by their molecular and pharmacokinetic properties, such as high molecular weight and, consequently, a limited bioavailability. To address the need for more drug-like H₂R agonists with high affinity, we synthesized a series of monomeric (thio)carbamoylguanidine-type ligands containing various spacers and side-chain moieties. This structural simplification resulted in potent (partial) agonists (guinea pig right atrium, [³⁵S]GTPγS and β-arrestin2 recruitment assays) with human (h) H₂R affinities in the one-digit nanomolar range (pK_i (139, UR-KAT523): 8.35; pK_i (157, UR-MB-69): 8.69). Most of the compounds presented here exhibited an excellent selectivity profile towards the hH₂R, e.g. 157 being at least 3800-fold selective within the histamine receptor family. The structural similarities of our monomeric ligands to pramipexole (6), a dopamine receptor agonist, suggested an investigation of the binding behavior at those receptors. The target compounds were (partial) agonists with moderate affinity at the hD_2longR and agonists with high affinity at the hD₃R (e.g. pK_i (139, UR-KAT523): 7.80; pK_i (157, UR-MB-69): 8.06). In summary, we developed a series of novel, more drug-like H₂R and D₃R agonists for the application in recombinant systems in which either the H₂R or the D₃R is solely expressed. Furthermore, our ligands are promising lead compounds in the development of selective H₂R agonists for future in vivo studies or experiments utilizing primary tissue to unravel the role and function of the H₂R in the CNS.

Chemistry of aged garlic: Diversity of constituents in aged garlic extract and their production mechanisms via the combination of chemical and enzymatic reactions

Raw garlic contains characteristic compounds, such as S-alk(en)ylcysteine sulfoxides, γ-glutamyl-S-alk(en)-ylcysteines and polysaccharides. These compounds undergo various transformation processes during the aging process. Among these compounds, the change of sulfur-containing molecules is diverse and time-dependent. Previously, by means of the liquid chromatography (LC)/LC-mass spectrometry (MS) method, a number of unidentified peaks corresponding to candidates of sulfur-containing molecules were detected in the chromatogram of aged garlic extract (AGE), and identified using MS and nuclear magnetic resonance (NMR). The production mechanisms of these compounds were then examined by model reactions and laboratory experiments mimicking the aging process. Three γ-glutamyl tripeptides [γ-glutamyl-γ-glutamyl-S-methylcysteine, γ-glutamyl-γ-gluta-myl-S-allylcysteine (GGSAC), γ-glutamyl-γ-glutamyl-S-1-propenylcysteine], γ-glutamyl-S-allylmercaptocysteine (GSAMC) and cis-S-1-propenylcysteine (cis-S1PC) were isolated and identified. GGSAC was produced from GSAC through the enzymatic reaction catalyzed by γ-glutamyltranspeptidase (GGT), and two other tripeptides could be produced in similar reactions. GSAMC was produced by the reaction between γ-glutamyl dipeptides and allicin. Furthermore, GSAMC was a precursor compound of S-allyl-mercaptocysteine (SAMC), and thus it was produced from GSAMC by GGT. cis-S1PC was produced from trans-S1PC by the isomerization reaction. A number of other compounds were also identified, including Maillard reaction products; however, their production mechanisms have not been elucidated. In this review, we present the changes in characteristic constituents in raw garlic and garlic extract during the aging process and discuss their production mechanisms involving the various chemical and enzymatic reactions.

Allyl 6-amino-5-cyano-2-methyl-4-phenyl-4H-pyran-3-carboxylate

In the title compound, C17H16N2O3, the 4H-pyran ring adopts a boat conformation. In the crystal, N—H...N and N—H...O interactions link the molecules, forming an infinite ribbon running along the a-axis direction with N—H...N interactions forming centrosymmetric R 2 2(12) graph-set motifs. The allyl side chain is disordered over two sets of sites with occupancies of 0.720 (7) and 0.280 (7).

The role of hormesis in the functional performance and protection of neural systems

This paper addresses how hormesis, a biphasic dose response, can protect and affect performance of neural systems. Particular attention is directed to the potential role of hormesis in mitigating age-related neurodegenerative diseases, genetically based neurological diseases, as well as stroke, traumatic brain injury, seizure, and stress-related conditions. The hormetic dose response is of particular significance since it mediates the magnitude and range of neuroprotective processes. Consideration of hormetic dose-response concepts can also enhance the quality of study designs, including sample size/statistical power strategies, selection of treatment groups, dose spacing, and temporal/repeat measures’ features.

Glutathione-garlic sulfur conjugates: slow hydrogen sulfide releasing agents for therapeutic applications

Natural organosulfur compounds (OSCs) from Allium sativum L. display antioxidant and chemo-sensitization properties, including the in vitro inhibition of tumor cell proliferation through the induction of apoptosis. Garlic water- and oil-soluble allyl sulfur compounds show distinct properties and the capability to inhibit the proliferation of tumor cells. In the present study, we optimized a new protocol for the extraction of water-soluble compounds from garlic at low temperatures and the production of glutathionyl-OSC conjugates during the extraction. Spontaneously, Cys/GSH-mixed-disulfide conjugates are produced by in vivo metabolism of OSCs and represent active molecules able to affect cellular metabolism. Water-soluble extracts, with (GSGaWS) or without (GaWS) glutathione conjugates, were here produced and tested for their ability to release hydrogen sulfide (H₂S), also in the presence of reductants and of thiosulfate:cyanide sulfurtransferase (TST) enzyme. Thus, the TST catalysis of the H₂S-release from garlic OSCs and their conjugates has been investigated by molecular in vitro experiments. The antiproliferative properties of these extracts on the human T-cell lymphoma cell line, HuT 78, were observed and related to histone hyperacetylation and downregulation of GAPDH expression. Altogether, the results presented here pave the way for the production of a GSGaWS as new, slowly-releasing hydrogen sulfide extract for potential therapeutic applications.

Colloidal drug formulations can explain "bell-shaped" concentration-response curves

Drug efficacy does not always increase sigmoidally with concentration, which has puzzled the community for decades. Unlike standard sigmoidal curves, bell-shaped concentration-response curves suggest more complex biological effects, such as multiple-binding sites or multiple targets. Here, we investigate a physical property-based mechanism for bell-shaped curves. Beginning with the observation that some drugs form colloidal aggregates at relevant concentrations, we determined concentration-response curves for three aggregating anticancer drugs, formulated both as colloids and as free monomer. Colloidal formulations exhibited bell-shaped curves, losing activity at higher concentrations, while monomeric formulations gave typical sigmoidal curves, sustaining a plateau of maximum activity. Inverting the question, we next asked if molecules with bell-shaped curves, reported in the literature, form colloidal aggregates at relevant concentrations. We selected 12 molecules reported to have bell-shaped concentration-response curves and found that five of these formed colloids. To understand the mechanism behind the loss of activity at concentrations where colloids are present, we investigated the diffusion of colloid-forming dye Evans blue into cells. We found that colloidal species are excluded from cells, which may explain the mechanism behind toxicological screens that use Evans blue, Trypan blue, and related dyes.

Garlic sprouting is associated with increased antioxidant activity and concomitant changes in the metabolite profile

Although garlic (Allium sativum) has been extensively studied for its health benefits, sprouted garlic has received little attention. We hypothesized that sprouting garlic would stimulate the production of various phytochemicals that improve health. Ethanolic extracts from garlic sprouted for different periods had variable antioxidant activities when assessed with in vitro assays, including the 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity assay and the oxygen radical absorbance capacity assay. Extracts from garlic sprouted for 5 days had the highest antioxidant activity, whereas extracts from raw garlic had relatively low antioxidant activity. Furthermore, sprouting changed the metabolite profile of garlic: the metabolite profile of garlic sprouted for 5-6 days was distinct from the metabolite profile of garlic sprouted for 0-4 days, which is consistent with the finding that garlic sprouted for 5 days had the highest antioxidant activity. Therefore, sprouting may be a useful way to improve the antioxidant potential of garlic.

Metallo-allixinate complexes with anti-diabetic and anti-metabolic syndrome activities

Metabolic syndrome and the accompanied diabetes mellitus are both important diseases worldwide due to changes of lifestyle and eating habits. The number of patients with diabetes worldwide is estimated to increase to 300 million by 2025 from 150-220 million in 2010. There are two main types of diabetes. In type 1 diabetes, caused by destruction of pancreatic β-cells resulting in absolute deficiency of intrinsic insulin secretion, the patients require exogenous insulin injections several times a day. In type 2 diabetes, characterized by insulin resistance and abnormal insulin secretion, the patients need exercise, diet control and/or several types of hypoglycemics. The idea of using metal ions for the treatment of diabetes originates from the report in 1899. The research on the role of metal ions that may contribute to the improvement of diabetes began. The orally active metal complexes containing vanadyl (oxidovanadium(iv)) ion and cysteine or other ligands were first proposed in 1990, and a wide class of vanadium, copper and zinc complexes was found to be effective for treating diabetes in experimental animals. We noticed a characteristic compound, allixin, which is a non-sulfur component in dry garlic. Its vanadyl and zinc complexes improved both types of diabetes following oral administration in diabetic animals. We then developed a new zinc complex with thioxoallixin-N-methyl (tanm), which is both a sulfur and N-methyl derivative of allixin, and found that this complex improves not only diabetes but also metabolic syndrome. Furthermore, new zinc complexes inspired from the zinc-tanm were prepared; one of them exceeded the activity of zinc-tanm. The mechanism of such complexes was studied in adipocytes. We describe here the usefulness of the development of metal-based complexes in the context of potential therapeutic application for diabetes and metabolic syndrome.

Amelioration of early cognitive deficits by aged garlic extract in Alzheimer's transgenic mice

Subtle accumulation of beta-amyloid peptide (Abeta) oligomers of Abeta42 species in particular, is known to correlate with cognitive deficits independent of Abeta plaque deposition in the brain. Majority of the research showing behavioral improvement after cerebral Abeta reduction has been reported when the animals carried fewer/abundant amyloid plaques in the brain. Very few studies have addressed whether or not behavioral deficits exist even at the pre-plaque stage or in the absence of plaques that would parallel the mild cognitive impairment (MCI) stage of Alzheimer's disease (AD). Current study was undertaken to determine whether there exists any cognitive impairment during the pre-plaque stage which may parallel the MCI stage of AD, and to confirm whether the observed behavioral deficits correlate with Abeta42 predominance. In addition, the study determined whether anti-amyloidogenic effects of dietary aged garlic extract would prevent progressive behavioral impairment. For this purpose we used Tg2576 model showing slow plaque development with a predominance of Abeta40, and the TgCRND8 model showing accelerated plaque development with a predominance of Abeta42. The results show that at 2 months of age Tg2576 mice did not exhibit behavioral impairment in any of the tasks studied. While 2-month-old TgCRND8 mice displayed only a subtle behavioral deficit that matched the behavioral deficits observed in 7-month-old Tg2576 mice which may correlate with the MCI stage of AD. TgCRND8 mice at 7 months of age exhibited advanced deterioration in all behavioral tasks studied, suggesting that accelerated Abeta accumulation and the predominance of Abeta42 species may account for the pronounced cognitive deficits observed in TgCRND8. Feeding of aged garlic extract prevented deterioration of hippocampal based memory tasks in these mice, suggesting that aged garlic extract has a potential for preventing AD progression.

An efficient synthesis of carboxaldehyde derivatives of 4H-pyran-4-one

We developed a general method for the synthesis of various 2-mono- and 2,6-di-carboxaldehyde substituted derivatives of 3,5-diphenyl-4H-pyran-4-one and 4H-pyran-4-one. 3,5-Diphenyl-6-methyl-4-oxo-4H-pyran-2-carboxaldehyde (4a), 6-methyl-4-oxo-4H-pyran-2-carboxaldehyde (4b), 3,5-diphenyl-4-oxo-4H-pyran-2,6-dicarboxaldehyde (5a), 4-oxo-4H-pyran-2,6-dicarboxaldehyde (5b), 3,5-diphenyl-6-hydroxymethyl-4-oxo-4H-pyran-2-carboxaldehyde (10a), and 6-hydroxymethyl-4-oxo-4H-pyran-2-carboxaldehyde (10b) were obtained from the corresponding di-, tri-, and tetra-bromo derivatives of 2,6-dimethyl-3,5-diphenyl-4H-pyran-4-one (1a) and 2,6-dimethyl-4H-pyran-4-one (1b) by treatment with silver acetate followed by hydrolysis. Compounds 4a and 4b were also obtained by the oxidation of 10a and 10b with barium manganate.Key words: 4H-pyran-4-one, hydroxymethyl and carboxaldehyde derivatives, acetoxylation, hydrolysis, oxidation.

Role of caspase-12 in amyloid beta-peptide-induced toxicity in organotypic hippocampal slices cultured for long periods

Amyloid beta (Abeta) toxicity has been implicated in cell death in the hippocampus, but its specific mechanisms are poorly understood. In this study, Abeta-induced cell death was investigated in organotypic hippocampal slice cultures (OHCs) that were cultured for various periods in vitro. There were no obvious histological differences among slices cultured for 3 to 7 weeks in vitro. Although there was little neurotoxicity after treatment with Abeta25-35 in OHCs cultured for relatively shorter periods (3-5 weeks), age-dependent cell death was evident in OHCs cultured for relatively longer periods (6-7 weeks) after exposure to Abeta25-35. In OHCs cultured for 7 weeks, S-allyl-L-cysteine (SAC), a component of aged garlic extract, protected the cells in areas CA1 and CA3 and the dentate gyrus from Abeta25-35-induced toxicity. The immunoreactivity of cleaved caspase-12 was increased whereas that of glucose-regulated protein 78 was not altered after exposure to Abeta25-35. The increases in the cleaved caspase-12 were also reversed by simultaneously applied SAC. These results suggest that OHCs cultured for relatively longer periods are more susceptible to Abeta-induced toxicity and that the Abeta-induced cell death involves caspase-12-dependent pathways. It is also suggested that SAC is able to protect against the Abeta-induced neuronal cell death through the inhibition of the caspase-12-dependent pathway.

N-acetylcysteine selectively protects cerebellar granule cells from 4-hydroxynonenal-induced cell death

4-hydroxynonenal (HNE), an aldehydic product of membrane lipid peroxidation, has been shown to induce neurotoxicity accompanied by multiple events. To clarify mechanisms of neuroprotective compounds on HNE-induced toxicity, the protective effects of N-acetylcysteine (NAC), alpha-tocopherol (TOC), ebselen and S-allyl-L-cysteine (SAC) were compared in cerebellar granule neurons. The decrease in MTT reduction induced by HNE was significantly suppressed by pretreatment of the neurons with 1000 microM NAC or 10 and 100 microM TOC; however, lactate dehydrogenase (LDH) release and propidium iodide (PI) fluorescence studies revealed that neuronal death was suppressed by NAC but not by TOC. Treatment of these neurons with HNE resulted in a drastic reduction of mitochondrial membrane potential, and this reduction was also prevented by NAC but not by TOC. Ebselen and SAC, a garlic compound, were unable to protect these neurons against HNE-induced toxicity. Pretreatment with NAC also prevented HNE-induced depletion of intracellular glutathione (GSH) levels in these neurons. These results suggest that NAC, but not other antioxidants such as TOC, SAC and ebselen, exerts significant protective effects against HNE-induced neuronal death in cerebellar granule neurons, and that this neuroprotective effect is due, at least in part, to preservation of mitochondrial membrane potential and intracellular GSH levels.

Protective effect of S-allyl-L-cysteine, a garlic compound, on amyloid beta-protein-induced cell death in nerve growth factor-differentiated PC12 cells

Aged garlic extract (AGE) contains several neuroactive compounds, including S-allyl-L-cysteine (SAC) and allixin. We characterized cell death induced by amyloid beta-protein (Abeta), 4-hydroxynonenal (HNE), tunicamycin, an endoplasmic reticulum (ER) stressor, or trophic factor deprivation, and investigated whether and how SAC could prevent this in nerve growth factor (NGF)-differentiated PC12 cells, a model of neuronal cells. Exposure of the cells to amyloid beta-protein(1-40) (Abeta(1-40)) decreased the extent of [3-(4,5)-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium (MTT) reduction activity and loss of neuronal integrity, but these effects were not prevented by Ac-DEVD-CHO, a caspase-3 inhibitor. Simultaneously applied SAC protected the cells against Abeta-induced cell death in a concentration-dependent manner. It also protected them against tunicamycin-induced neuronal death. In contrast, it afforded no protection against cell death induced by HNE and trophic factor deprivation, which is mediated by a caspase-3-dependent pathway. These results suggest that SAC may selectively protect cell death induced by Abeta and tunicamycin, which may be triggered by ER dysfunction in NGF-differentiated PC12 cells.

Garlic and aging: new insights into an old remedy

There has been an impressive gain in individual life expectancy with parallel increases in age-related chronic diseases of the cardiovascular, brain and immune systems. These can cause loss of autonomy, dependence and high social costs for individuals and society. It is now accepted that aging and age-related diseases are in part caused by free radical reactions. The arrest of aging and stimulation of rejuvenation of the human body is also being sought. Over the last 20 years the use of herbs and natural products has gained popularity and these are being consumed backed by epidemiological evidence. One such herb is garlic, which has been used throughout the history of civilization for treating a wide variety of ailments associated with aging. The role of garlic in preventing age-related diseases has been investigated extensively over the last 10-15 years. Garlic has strong antioxidant properties and it has been suggested that garlic can prevent cardiovascular disease, inhibit platelet aggregation, thrombus formation, prevent cancer, diseases associated with cerebral aging, arthritis, cataract formation, and rejuvenate skin, improve blood circulation and energy levels. This review provides an insight in to garlic's antioxidant properties and presents evidence that it may either prevent or delay chronic diseases associated with aging.

Allixin accumulation with long-term storage of garlic

Extremely high accumulation of allxiin, a phytoalexin derived from garlic, was observed in necrotic tissue areas after long-term storage. The allixin produced recrystallized on the surface of the garlic clove. The amount of allixin produced in raw garlic with necrotic tissue areas was 1400 ng/mg wet garlic, which exceeds the minimum exhibitory concentration of allixin. After approximately 2 years of storage, amount of allixin accumulated reached slightly less than 1% of the dry weight of garlic cloves.

Pharmacokinetic study of allixin, a phytoalexin produced by garlic

The pharmacokinetic behavior of allixin (3-hydroxy-5-methoxy-6-methyl-2-penthyl-4H-pyran-4-one) was investigated in an experimental animal, mice. Allixin was administered using an inclusion compound because the solubility of allixin in aqueous solution is very low. The allixin content in serum and in the organs of administered animals was analyzed by liquid chromatography (LC)-MS. Most of the administered allixin disappeared within 2 h, and the bioavailability of allixin was estimated to be 31% by obtained area under the blood concentration-time curve (AUC). The metabolites of allixin were studied using the metabolic enzyme fraction of liver and liver homogenate. Several new peaks corresponding to allixin metabolites were observed in the HPLC chromatoprofile. The chemical structure of the metabolites was investigated using LC-MS and NMR. Three of them were identified as allixin metabolites having a hydroxylated pentyl group.

Dietary flavonoids as potential neuroprotectants

There is an increasing awareness of the role of certain nutritional components, including dietary flavonoids found in fruit, vegetables and beverages, in the maintenance of health and prevention of chronic diseases. In this regard, recent studies highlight an exciting role with respect to their potential neuroprotective actions, in particular towards deficits commonly observed with aging, such as reduced performance of cognitive, memory and learning tasks. These neurological functions, and possible mechanisms involved in controlling them, can be influenced by supplementation of single dietary flavonoids, or as part of a flavonoid-rich preparation. With this, a renewed emphasis is aimed at further understanding their modes and sites of action. Moreover a common theme among many in vitro studies examining mechanisms of neuroprotection is the failure to include biologically relevant metabolites of the flavonoids known to enter the circulation, and thus most likely to be bioavailable to cells and tissues. This oversight will ultimately influence the mechanisms of action proposed to explain the neuroprotection observed in animals and human studies. As such, emerging findings suggest a variety of potential mechanisms of action of flavonoids and their bioavailable metabolites in cytoprotection against oxidative stress, which may be independent of conventional antioxidant reducing activities. Such mechanisms might involve their interaction with cell signalling cascades, their influence on gene expression and the down regulation of pathways leading to cell death.

Synthesis of Some Aldoxime Derivatives of 4H-Pyran-4-ones

Aldoxime derivatives of 4H-pyran-4-ones 4-7a,b have been synthesized by the reaction of di(aminoxymethyl) pyranones 3a,b with aromatic aldehydes.

Allixin induction and accumulation by light irradiation

Allixin, a phytoalexin isolated from garlic, was induced by irradiating fresh garlic cloves with sunlight or UV light. Induced allixin was analyzed by HPLC, and the accumulated amounts of allixin were 3.1-6.3 microg/g under experimental conditions.

Effects of basic fibroblast growth factor on central nervous system functions

Basic fibroblast growth factor (bFGF), initially identified as mitogens with prominent angiogenic properties, is now recognized as multifunctional growth factors with notable actions on neuronal cells. bFGF promotes the survival and neurite growth of brain neurons in vitro and in vivo, suggesting that it functions as a neurotrophic factor. This effect of bFGF could be beneficial for improving the survival of grafted neurons in transplantation. Furthermore, bFGF acutely modulates synaptic transmission in the hippocampus, suggesting that it has a role like a neurotransmitter or neuromodulator. In this article, we make a brief review of multiple biological activities of bFGF for brain neurons and discuss its potential usefulness for the treatment of neurodegenerative disorders including Alzheimer's disease and Parkinson's disease.

Ameliorative effect of S-allylcysteine, a major thioallyl constituent in aged garlic extract, on learning deficits in senescence-accelerated mice

This study examined the effect of S:-allylcysteine (SAC), a major thioallyl compound found in aged garlic extract, on the memory deficit and age-related changes of senescence-accelerated mice. Senescence-accelerated prone P8 mice fed a diet supplemented with 40 mg SAC/kg diet for 8 mo had a significantly attenuated decrease in the conditioned avoidance response compared with those not given SAC. In the elevated plus-maze test using senescence-accelerated prone P10 mice, the percentage of time spent on the open arm was greater compared with the senescence-resistant control mice. Chronic dietary treatment with 40 mg SAC/kg diet decreased the time in the open arm in senescence-accelerated prone P10 mice. These studies suggest that diet supplementation with SAC may reduce age-related learning disabilities and cognitive disorders in senescence-accelerated mice.

Effects of garlic extract (Allium sativum) on neutrophil migration at the cellular level

Studies of the effects of garlic extract on oxidative and lipoprotein levels have yielded widely different findings. Leukocytes play an important role during many processes, including inflammation. They migrate from intravascular spaces into tissues and attack microorganisms. In a recent study, the inhibitory effects of the nonsteroidal antiinflammatory drug, ibuprofen, on leukocyte transmigration were demonstrated using an in vitro assay. Little is known about the cellular effects of garlic extracts (Allium sativum). The aim of the current study was to investigate the influence of garlic extract on leukocyte migration through endothelial cell monolayers and thereby evaluate a possible role in inflammatory processes. Human umbilical endothelial cells were cultured on microporous membranes to make an endothelial cell monolayer (ECM). Freshly isolated neutrophils were used in a recently described migration assay. The amount of untreated neutrophils migrating through the untreated ECM was used as control and set at 100%. Neutrophils and/or ECM were pretreated with garlic extract using moderate, higher, and lower concentrations. Moderate plasma concentrations of garlic extract inhibited neutrophil migration through ECM significantly (64 +/- 5.8% standard deviation [SD]; P < 0.05) when both cell types were treated, (a situation that may have clinical relevance). Treating either neutrophils or ECM alone showed significant reductions in migratory rate (neutrophils treated alone: 81 +/- 7.7% SD, P < 0.05; ECM alone: 70 +/- 6.7%, P < 0.05). Thus, garlic extract is identified as a potent inhibitor of leukocyte migration through endothelial cell monolayers. Treatment of both cell types has an additive effect. Endothelial cells seem to be more affected than neutrophils. Further investigations are necessary to understand the potential clinical consequences.

Garlic extracts stimulate proliferation of rat lymphocytes in vitro by increasing IL-2 and IL-4 production

Garlic components are known to modulate certain immune functions. However, mechanisms of their action are not sufficiently elucidated. This study was, therefore, undertaken to examine the effects of aqueous and ethanolic extracts prepared from a garlic powder sample on proliferation of rat spleen lymphocytes in culture. Cells were stimulated with the combination of phorbol myristate acetate (PMA) and a Ca ionophore (A23187) or R73 monoclonal antibody (mAb) directed to the alphabeta chain of T cell receptor. It has been shown that both extracts significantly stimulated proliferation of lymphocytes. The effect correlated with upregulation of the Interleukin 2 receptor alpha (IL-2R alpha) expression and the increase in IL-2 production. Stimulation of IL-2 production by the extracts was higher in cultures with PMA/Ca ionophore than in cultures with R73 mAb. In contrast, both extracts stimulated production of IL-4 by splenocytes triggered by R73 mAb. The complete dependence of lymphocyte proliferation in cultures with R73 mAb and garlic extracts on IL-2 and IL-4 was demonstrated using neutralising mAbs to IL-2R alpha and IL-4. These results suggest that the potentiating effect of garlic extracts on lymphocyte proliferation in vitro differs depending on specific stimulators of cell proliferation and probably on the type of responding cells.