Chemistry and biological properties of onions and garlic

Emission of volatile organic compounds during open fire cooking with wood biomass: Traditional three-stone open fire vs. gasifier cooking stove in rural Kenya

Cooking with wood biomass fuels releases hazardous air pollutants, including volatile organic compounds (VOCs), that often disproportionally affect women and children. This study, conducted in Kwale and Siaya counties in Kenya, employed thermal desorption gas chromatography - mass spectrometry to analyse VOC emissions from cooking with a wood biomass three-stone open fire vs. top-lit updraft gasifier stove. In kitchens with adequate ventilation, total VOC levels increased from 35-252 μg∙m-3 before cooking to 2235-5371 μg∙m-3 during open fire cooking, whereas use of a gasifier stove resulted in reduced emissions from cooking by 48-77 % (506-2778 μg∙m-3). However, in kitchens with poor ventilation, there was only a moderate difference in total VOC levels between the two methods of cooking (9034-9378 μg∙m-3 vs. 6727-8201 μg∙m-3 for the three-stone open fire vs. gasifier stove, respectively). Using a non-target screening approach revealed significantly increased levels of VOCs, particularly benzenoids, oxygenated and heterocyclic compounds, when cooking with the traditional open fire, especially in closed kitchens, highlighting the effects of poor ventilation. Key hazardous VOCs included benzene, naphthalene, phenols and furans, suggesting potential health risks from cooking. In kitchens with good ventilation, use of the gasifier stove markedly reduced emissions of these priority toxic VOCs compared to cooking with an open fire. Thus, substituting open fires with gasifier stoves could help to improve household air quality and alleviate health risks. The study revealed that VOCs were present prior to cooking, possibly originating from previously cooked food (buildup) or the outside environment. VOC emissions were also exacerbated by reduced air flow in high humidity during rainfall, suggesting an area for further research. The findings underscore the importance of adopting cleaner cooking technologies and enhancing kitchen ventilation to mitigate the impacts of VOCs in developing countries.

Diversity of the Morphometric and Biochemical Traits of Allium cepa L. Varieties

Several Allium cepa L. varieties, representing a versatile set of vegetables widely utilized by consumers, are appreciated for their bioactive properties, including antimicrobial, anticarcinogenic, and antioxidant capacities. The aim of this study is to compare the morphometric characteristics and biochemical profiles of four cultivars of A. cepa, two of them represented by the perennial Sicilian landrace "Cipudda agghiarola" (Allium × proliferum (Moench) Schrader), widely known as the Egyptian walking onion (WO), and by the landrace "Cipudduzza" belonging to the variety known as aggregatum (ON), which were compared with two commercial cultivars of A. cepa var. cepa (onion), Stoccarda (OS) and Rossa Carmen (OR). The experimental trial was conducted in Catania (Sicily), following organic growing practices. The randomized complete block experimental design was adopted with one experimental factor, the genotype (GE) effect. The harvested plants were characterized for their main morphometric parameters, according to the International Plant Genetic Resources (IGPR) descriptors. The biochemical activity was assessed by analyzing the total phenolic content (TPC) and the total flavonoid content (TFC). The antioxidant capacity was determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, ferric reducing antioxidant power (FRAP), and oxygen radical absorbance capacity (ORAC). The sugar profile (total sugars, sucrose, glucose, fructose, and fructooligosaccharides-FOS) and the volatile compounds by headspace-gas chromatography/mass spectrometry (HS-GC/MS) were also determined. The OR bulb exhibited the highest TPC (16.3 mg GAE/g d.w., p < 0.01) and TFC (8.5 mg QE/g d.w., p < 0.01), with the highest antioxidant capacity measured by the FRAP (27.1 µmol TE/g d.w., p < 0.01) and DPPH assays (46.2 µmol TE/g d.w., p < 0.01). The ON bulb showed the highest ORAC value (209 µmol TE/g d.w., p < 0.01). Generally, the bulbs were richer in sugars (584 mg/g d.w., p < 0.01) than the leaf blade (239 mg/g d.w., p < 0.01), except for OR. Significant interaction between the genotype and plant organ was noted in the volatile compound profiles (p < 0.05) except for total ketones and carboxylic acids, where higher content was observed in the leaf blade compared to the bulb, regardless of the genotype. These findings highlight WO's potential for use in ready-to-eat products, enhancing its market value.

An Overview of the Potential of Medicinal Plants Used in the Development of Nutraceuticals for the Management of Diabetes Mellitus: Proposed Biological Mechanisms

Diabetes mellitus (DM) is a chronic metabolic disorder in which the pancreas does not produce enough insulin or the body cannot effectively use it. The prevalence of diabetes is increasing steadily, making it a global public health problem. Several serious complications are associated with this disease. There are a number of different classes of antidiabetic medications. Interestingly, traditional medicine can also be used for the development of novel classes of hypoglycemic therapeutics. This article summarizes an update of the potential of various important medicinal plants used in the development of nutraceuticals for the management of diabetes mellitus, and a proposal of their biological mechanisms.

Morphological and molecular characterization of garlic (Allium sativum L.) genotypes sampled from Turkey

Garlic is a vegetable widely used both in food and as a pharmaceutical raw material in the world due to its contents. Although morphological differences are observed in garlic, which is obligatory apomictically propagated, clonal propagation causes narrowing variation, a genetic bottleneck. This situation complicates breeding programs aiming improvements in preferred agronomic characteristics. For this reason, determining the morphological and molecular differences between garlic genotypes originating from Turkey is important for breeding studies. In this study, morphological and molecular characteristics of 39 garlic genotypes, which are widely cultivated in Turkey, were determined. Kahramanmaraş4 genotype was different from other genotypes in terms of some morphological features (fresh weight, dry weight, and bulb diameter). In the molecular characterization study, 10 Inter-Simple Sequence Repeats (ISSR) primers were used, and it was determined that the genotype TekDiş31 of Tunceli region was different from other garlic genotypes. Genetic similarity coefficient was found to be high (0.85-1.0) in genotypes except for TekDiş31 garlic genotype. In general, some garlic clones (Maraş3 and Kayseri30, Urfa33 and Topaklı35, Kastamonu22 and Kastamonu28, Urfa10 and Kastamonu14, Kastamonu29 and Bademci23) were completely similar to each other, while few differences were found among others. In conclusion, this study revealed that the garlic plant, despite its clonal propagation, consisted of some level of morphological and partially molecular variation. Due to its mode of reproduction (vegetative), this variation may largely be due to point or chromosomal mutation. Furthermore, the 10 identified ISSR primers can generate valuable information for genetic diversity for use by garlic breeders.

In Vitro Antioxidant and In Vivo Lipid-Lowering Properties of Zingiber officinale Crude Aqueous Extract and Methanolic Fraction: A Follow-Up Study

Over the past decades, cardiovascular diseases have become the leading cause of death all over the world, and among these diseases there is atherosclerosis caused mainly by an increase in plasmatic cholesterol levels and by strong oxidation caused by free radicals. For these reasons and others, we explored in this report the hypolipidemic and the antioxidant effects of Zingiber officinale crude aqueous and methanolic extract. The hypolipidemic study was carried out in high-fat-fed mice model. Animals were subdivided into four groups and were orally treated with the aqueous extract once daily for twelve weeks at two doses: 250 and 500 mg/Kg. During the treatment, the body weight, total cholesterol, triglycerides, and high-density lipoproteins have been defined every four weeks. The antioxidant activity has been studied using radical scavenging activity, β-carotene bleaching, reducing power assay, and the TBARs tests. The daily oral administration of the extracts for twelve weeks significantly improved the lipid profile in a dose-dependent manner, from the first until the twelfth week, and also showed a significant antioxidant effect. These findings may be potentially contributive to the validation of the medicinal use of Z. officinale to treat hyperlipidemia and cardiovascular complications.

Impact of Mannanase-Producing Bacillus spp. on the Accuracy of the 3M Petrifilm Aerobic Count Method

Consistent deviations of the 3M Petrifilm aerobic counts (AC) from the standard pour plate aerobic plate count (APC) were observed with dehydrated onion and garlic products. A large study was designed to determine the relationship of these two methods and the root cause for the deviations. A total of 3,800 dehydrated onion and garlic samples were analyzed by both the Petrifilm AC and the standard pour plate APC method. Large spreader-like liquefied areas were observed on numerous Petrifilm plates. These liquefied areas made enumeration inaccurate. "Liquefier" microorganisms from Petrifilm plates were isolated and identified to species level by 16S rRNA and gyrB gene sequencing. Enzyme diffusion assay was performed to determine potential enzymatic degradation of guar gum, the gelling agent used in Petrifilm plates. The results indicated that the correlation between Petrifilm AC and standard APC is relatively low. Paired t test results suggested that the Petrifilm AC method produced significantly different results compared with standard APC. The discrepancies were attributable at least partly to a liquefier organism that hydrolyzed guar gum, leading to liquefaction. Liquefaction of Petrifilm plates seems to have two effects on accuracy: (i) liquefied areas may allow motile organisms to move and multiply in the liquefied area during the incubation period, yielding more than one colony from one cell and, as a result, leading to overestimation of the microbial load and (ii) the blurred areas obscure other colonies, leading to potential underestimation. The liquefier organism was identified as Bacillus amyloliquefaciens , a potent mannanase producer and heat-resistant spore former. Enzyme diffusion assay confirmed that mannanase contained in the cell-free supernatant of B. amyloliquefaciens can hydrolyze the 1,4-β-mannopyranosyl bond, the backbone of guar gum. This is the first report of the role of B. amyloliquefaciens in the liquefaction of Petrifilm plates and its negative impact on accuracy.

Ethnobotanical survey of medicinal plants used in the traditional treatment of diabetes in Chtouka Ait Baha and Tiznit (Western Anti-Atlas), Morocco

ETHNOPHARMACOLOGICAL RELEVANCE

In Morocco, diabetes mellitus is a major public health problem with more than 1.5 million cases in 2014. Medicinal plants are widely used by the Moroccan population to treat the illness.

AIM OF THE STUDY

The aim of this work is to make an inventory of plant species used in folk medicine for the management of diabetes in Chtouka Ait Baha and Tiznit provinces.

MATERIALS AND METHODS

The survey was carried out by means of semi-structured questionnaires. A total of 380 interviews were conducted with traditional health practitioners and knowledgeable villagers. The data were analyzed through use value (UV), fidelity level (FL) and relative frequency of citation (RFC).

RESULTS

In total, 48 plant species belonging to 25 families were reported. Lamiaceae, Asteraceae and Apiaceae were reported as the most represented families. Six plants are reported for the first time as used in traditional treatment of diabetes and one plant species was previously unknown for its medicinal use to treat diabetes in Morocco. The most frequently cited plant species are Allium sativum L., Salvia officinalis L., Marrubium vulgare L. and Lavandula dentata L. Leaves were the most cited plant part used, decoction is the preferred mode of preparation.

CONCLUSION

This study showed the importance of folk medicine in the healthcare system for the local people living in the study area. The current study represents a useful documentation, which can contribute to preserving knowledge on the use of medicinal plants in this region and to explore the phytochemical and pharmacological potential of medicinal plants.

Nanocellulose-Zeolite Composite Films for Odor Elimination

Free standing and strong odor-removing composite films of cellulose nanofibrils (CNF) with a high content of nanoporous zeolite adsorbents have been colloidally processed. Thermogravimetric desorption analysis (TGA) and infrared spectroscopy combined with computational simulations showed that commercially available silicalite-1 and ZSM-5 have a high affinity and uptake of volatile odors like ethanethiol and propanethiol, also in the presence of water. The simulations showed that propanethiol has a higher affinity, up to 16%, to the two zeolites compared with ethanethiol. Highly flexible and strong free-standing zeolite-CNF films with an adsorbent loading of 89 w/w% have been produced by Ca-induced gelation and vacuum filtration. The CNF-network controls the strength of the composite films and 100 μm thick zeolite-CNF films with a CNF content of less than 10 vol % displayed a tensile strength approaching 10 MPa. Headspace solid phase microextraction (SPME) coupled to gas chromatography-mass spectroscopy (GC/MS) analysis showed that the CNF-zeolite films can eliminate the volatile thiol-based odors to concentrations below the detection ability of the human olfactory system. Odor removing zeolite-cellulose nanofibril films could enable improved transport and storage of fruits and vegetables rich in odors, for example, onion and the tasty but foul-smelling South-East Asian Durian fruit.

Enhancing Effect of Lipids and Emulsifiers on the Accumulation of Quercetin Metabolites in Blood Plasma after the Short-term Ingestion of Onion by Rats

The effects of co-ingested lipids and emulsifiers on the accumulation of quercetin metabolites in blood plasma after the short-term ingestion of onion by rats were investigated. Plasma extracts of rats that had been fed onion-containing diets for one and two weeks were analyzed by HPLC with electrochemical detection after a treatment with sulfatase/beta-glucuronidase. Almost all of the quercetin metabolites in the plasma were sulfate/glucuronide conjugates of quercetin and isorhamnetin. More than 4.6% (w/w) of soybean oil in the diets significantly enhanced the accumulation of quercetin metabolites in the plasma. Fish oil and beef tallow increased this to an extent similar to that with soybean oil, and lecithin was more effective than the other three lipids. Two emulsifiers, sodium caseinate and sucrose fatty acid ester, also showed an enhancing effect on the accumulation of quercetin metabolites. These results indicate that co-ingested lipids and emulsifiers could enhance the bioavailability of quercetin glucosides in onion.

Identification of (S,S)-γ-glutamyl-(cis-S-1-propenyl)thioglycine, a naturally occurring norcysteine derivative, from the Chinese vegetable Toona sinensis

Extracts of Toona sinensis shoots were studied to identify the precursors of volatile sulfur-containing flavor molecules. T. sinensis was found to contain new compounds (S,S)-γ-glutamyl-(cis-S-1-propenyl)thioglycine, 1, (S,S)-γ-glutamyl-(trans-S-1-propenyl)thioglycine, 2, and γ-glutamyl-(cis-S-1-propenyl)-cysteine, 3. The structures of these compounds were determined by interpretation of multistage mass spectrometric (MS(n)), 1D, and 2D NMR data. The absolute configuration of 1 was established by comparison of experimental with computed infrared and vibrational circular dichroism spectra. Because of the flexibility of the molecule and the novelty of the structure, the configuration was further confirmed by X-ray crystallography. Compounds 1 and 2 are the first examples of norcysteine-containing metabolites reported from nature. They may release thiols via cleavage of the amide bond by proteases, followed by spontaneous decomposition of the resulting unstable alk(en)yl norcysteine moiety.

Dietary spices as beneficial modulators of lipid profile in conditions of metabolic disorders and diseases

Spices are valued for their medicinal properties besides their use as food adjuncts to enhance the sensory quality of food. Dietary garlic, onion, fenugreek, red pepper, turmeric, and ginger have been proven to be effective hypocholesterolemics in experimentally induced hypercholesterolemia. The hypolipidemic potential of fenugreek in diabetic subjects and of garlic and onion in humans with induced lipemia has been demonstrated. Capsaicin and curcumin - the bioactive compounds of red pepper and turmeric - are documented to be efficacious at doses comparable to usual human intake. Capsaicin and curcumin have been shown to be hypotriglyceridemic, thus preventing accumulation of fat in the liver under adverse situations by enhancing triglyceride transport out of the liver. Capsaicin, curcumin, fenugreek, ginger, and onion enhance secretion of bile acids into bile. These hypocholesterolemic spices/spice principles reduce blood and liver cholesterol by enhancing cholesterol conversion to bile acids through activation of hepatic cholesterol-7α-hydroxylase. Many human trials have been carried out with garlic, onion, and fenugreek. The mechanism underlying the hypocholesterolemic and hypotriglyceridemic influence of spices is fairly well understood. Health implications of the hypocholesterolemic effect of spices experimentally documented are cardio-protection, protection of the structural integrity of erythrocytes by restoration of membrane cholesterol/phospholipid profile and prevention of cholesterol gallstones by modulation of the cholesterol saturation index in bile.

Studies on purification of allicin by molecular distillation

BACKGROUND

With recent improvements in living standards, people have been giving more consideration to the healthcare effects of foods. In this respect, allicin, which is the most important organosulfur compound in garlic and plays a key role in physiological function, has been receiving much attention.

RESULTS

Allicin obtained from garlic by supercritical CO(2) extraction was purified by molecular distillation (MD). The effects of operating conditions such as absolute pressure (AP), distillation temperature (DT) and feed flow rate (FFR) on allicin purity and yield were studied. The optimal AP, DT and FFR levels in first-stage MD were found to be 200 Pa, 50 °C and 15 mL min(-1) respectively. After three stages of MD the contents of allicin, diallyl disulfide (DADS) and diallyl trisulfide (DATS) were 68.04, 9.19 and 5.91% (w/w) respectively.

CONCLUSION

This study has provided a safe and effective method for the purification of allicin.

Garlic improves insulin sensitivity and associated metabolic syndromes in fructose fed rats

BACKGROUND

Type 2 diabetes mellitus, characterized by peripheral insulin resistance, is a major lifestyle disorder of the 21st Century. Raw garlic homogenate has been reported to reduce plasma glucose levels in animal models of type 1 diabetes mellitus. However, no specific studies have been conducted to evaluate the effect of raw garlic on insulin resistance or type 2 diabetes mellitus. This study was designed to investigate the effect of raw garlic on fructose induced insulin resistance, associated metabolic syndrome and oxidative stress in diabetic rats.

METHODS

Male Sprague Dawley rats weighing 200-250 gm body weight were divided into 3 groups (n = 7 per group) and fed diet containing 65% cornstarch (Control group) and 65% fructose (Diabetic group) for 8 weeks. The third group (Dia+Garl group) was fed both 65% fructose and raw garlic homogenate (250 mg/kg/day) for 8 weeks. Whole garlic cloves were homogenized with water to make a fresh paste each day.

RESULTS

At the end of 8 weeks, serum glucose, insulin, triglyceride and uric acid levels, as well as insulin resistance, as measured by glucose tolerance test, were significantly (p < 0.01) increased in fructose fed rats (Diabetic group) when compared to the cornstarch fed (Control) rats. Administration of raw garlic to fructose fed rats (Dia+Garl group) significantly (p < 0.05) reduced serum glucose, insulin, triglyceride and uric acid levels, as well as insulin resistance when compared with fructose fed rats. Garlic also normalised the increased serum levels of nitric oxide (NO) and decreased levels of hydrogen sulphide (H2S) after fructose feeding. Although body weight gain and serum glycated haemoglobin levels of fructose fed rats (Diabetic group) were not significantly different from control rats, significant (p < 0.05) reduction of these parameters was observed in fructose fed rats after garlic administration (Dia+Garl group). Significant (p < 0.05) increase in TBARS and decrease in GSH was observed in diabetic liver. Catalase was not significantly affected in any of the groups. Administration of raw garlic homogenate normalised both hepatic TBARS and GSH levels.

CONCLUSIONS

Our study demonstrates that raw garlic homogenate is effective in improving insulin sensitivity while attenuating metabolic syndrome and oxidative stress in fructose-fed rats.

Color, flavor, texture, and nutritional quality of fresh-cut fruits and vegetables: desirable levels, instrumental and sensory measurement, and the effects of processing

The color, flavor, texture, and the nutritional value of fresh-cut fruit and vegetable products are factors critical to consumer acceptance and the success of these products. In this chapter, desirable and undesirable quality attributes of fresh-cut fruit and vegetable products are reviewed. Both instrumental and sensory measurements for determining these critical quality attributes are discussed. The advantages and disadvantages of sensory and instrumental quality measurements are described. A review of typical unit operations involved in the production of fresh-cut products is presented. The effects of fresh-cut processing techniques and treatments on sensory quality, including the appearance, texture, flavor (taste and aroma) of vegetables, and fruits are detailed.

Antifungal activity of the aqueous extract of Ilex paraguariensis against Malassezia furfur

Malassezia furfur is a lipodependent, dimorphic and saprophyte fungus which causes pityriasis versicolor, dandruff and seborrheic dermatitis in humans. The drugs available to treat this fungal infection are few. These drugs are highly toxic and are costly when used in prolonged treatments. For these reasons, it is necessary to find new compounds to treat these infections. Ilex paraguariensis St Hilaire is a plant that grows in Argentina, Brazil and Paraguay. The aim of this study was to evaluate the effect of the aqueous extract of Ilex paraguariensis on the growth of M. furfur. High performance liquid chromatography (HPLC) was employed to identify and isolate compounds of I. paraguariensis and the agar-well diffusion method was used to assess the antifungal activity of the extract. The fungicidal/fungistatic effect was evaluated by the modified Thompson assay. The results demonstrated that the aqueous extract of Ilex paraguariensis (1000 mg/ml) possesses inhibitory activity against M. furfur. This antimalassezial activity was equivalent to 2.7 microg/ml of ketoconazole. Therefore, the topical use of Ilex paraguariensis extract as alternative antifungal agent can be suggested.

Alterations in the blood glucose, serum lipids and renal oxidative stress in diabetic rats by supplementation of onion (Allium cepa. Linn)

This study examined the anti-diabetic effect of onion (Allium cepa. Linn) in the streptozotocin (STZ)-induced diabetic rats. Male Sprague-Dawley rats were divided into normal rats fed control diet or supplemented with onion powder (7% w/w) and diabetic rats fed control diet or supplemented with onion powder. Diabetes was induced by a single injection of STZ (60 mg/kg, ip) in citrate buffer. The animals were fed each of the experimental diet for 5 weeks. Blood glucose levels of rats supplemented with onion were lower than those of rats fed control diet in the diabetic rats. Onion also decreased the total serum lipid, triglyceride, and atherogenic index and increased HDL-cholesterol/total cholesterol ratio in the diabetic rats. Glutathione peroxidase, glutathione reductase and glutathione S-transferase activities were high in the diabetic rats compared to normal rats and reverted to near-control values by onion. These results indicate that onion decreased blood glucose, serum lipid levels and reduced renal oxidative stress in STZ-induced diabetic rats and this effect might exert the anti-diabetic effect of onion.

Antidiabetic effect of Korean traditional Baechu (Chinese cabbage) kimchi in a type 2 diabetes model of rats

The present study was conducted to examine the antidiabetic effects of two dietary dosages (0.5% and 2.0%) of freeze-dried Korean traditional Baechu (Chinese cabbage) kimchi in a high-fat (HF) diet-fed, streptozotocin (STZ)-induced type 2 diabetes (T2D) rat model. Five-week-old male Sprague-Dawley rats were fed HF diet for 2 weeks and then randomly divided into four groups of eight animals: normal control (NC), diabetic control (DBC), kimchi low (KML) (0.5%), and kimchi high (KMH) (2.0%) groups. Diabetes was induced by an intraperitoneal injection of STZ (40 mg/kg of body weight) in all groups except the NC group. After 4 weeks of feeding of experimental diets, serum insulin concentrations and Homeostatic Model Assessment pancreatic beta-cell function were increased and blood glycated hemoglobin was decreased in the kimchi-fed groups compared to the DBC group, while a significant (P < .05) difference was observed only in the KMH group for serum insulin concentration. Lower fasting blood glucose and better glucose tolerance were observed in the KMH group compared to the DBC and KML groups; however, differences were not significant. Food intake, body weight gain, Homeostatic Model Assessment insulin resistance index, and serum lipid profiles were not significantly influenced by kimchi-containing diets. Data of this study suggest that dietary Baechu kimchi has some antidiabetic effects even when fed with a HF-containing diet. Better results are possible if it is consumed with normal or low-fat rather than HF-containing diet.

S-alkenyl cysteine sulfoxide and its antioxidant properties from Allium cepa var. tropeana (red onion) seeds

A new cysteine sulfoxide, (S(S)R(C))-S-(3-pentenyl)-L-cysteine sulfoxide (1), was identified from the seeds of Allium cepa var. tropeana, together with the known methiin, etiin, alliin, isoalliin, propiin, and butiin. The structure of compound 1 was established by analysis of its physical and spectroscopic data. The antioxidant activity of an extract containing cysteine sulfoxides and compound 1 was evaluated using the FRAP and DPPH tests.

Antidiabetic effect of garlic (Allium sativum L.) in normal and streptozotocin-induced diabetic rats

OBJECTIVE

The antidiabetic effect of garlic ethanolic extract (Allium sativum L.) was investigated in normal and streptozotocin-induced diabetic rats.

RESEARCH METHODS AND PROCEDURE

In the present study, oral administration of garlic extract (0.1, 0.25 and 0.5 g/kg body wt.) for 14 days on the level of serum glucose, total cholesterol, triglycerides, urea, uric acid, creatinine, aspartate amino transferase (AST) and alanine amino transferase (ALT) in normal and streptozotocin-induced diabetic rats were evaluated.

RESULTS

Oral administrations of the garlic extract significantly decreased serum glucose, total cholesterol, triglycerides, urea, uric acid, creatinine, AST and ALT levels, while increased serum insulin in diabetic rats but not in normal rats (p<0.05). A comparison was made between the action of garlic extract and glibenclamide (600 microg/kg), the known antidiabetic drug. The antidiabetic effect of the extract was more effective than that observed with glibenclamide.

CONCLUSION

It is concluded that the plant must be considered as excellent candidate for future studies on diabetes mellitus.

In vitro antifungal activities of Allium cepa, Allium sativum and ketoconazole against some pathogenic yeasts and dermatophytes

By using an agar dilution assay, the antifungal activity of aqueous extracts prepared from Allium cepa (onion; AOE) and Allium sativum (garlic; AGE) were evaluated against Malassezia furfur (25 strains), Candida albicans (18 strains), other Candida sp. (12 strains) as well as 35 strains of various dermatophyte species and compared with the activity of a known antifungal drug, ketoconazole (KTZ). All the AOE, AGE and KTZ were found to be able to inhibit growth of all fungi tested in a dose-dependent manner with maximum of 100% at defined concentrations. The results indicate that onion and garlic might be promising in treatment of fungal-associated diseases from important pathogenic genera Candida, Malassezia and the dermatophytes.

Quantitation of the intense aroma compound 3-mercapto-2-methylpentan-1-ol in raw and processed onions (Allium cepa) of different origins and in other Allium varieties using a stable isotope dilution assay

A stable isotope dilution assay was developed for the quantitation of the potent onion odorant 3-mercapto-2-methylpentan-1-ol (1) using mass chromatography and synthesized [(2)H(2)]-3-mercapto-2-methylpentan-1-ol as the internal standard. Application of the newly developed method on onions from different origins revealed amounts between 8 and 32 microg/kg in raw onions, whereas 34-246 microg was found in sliced, stored (50 min), and then cooked onions. In extracts prepared by simultaneous steam distillation-extraction the highest concentrations of 1 were formed, amounting to >1200 microg/kg. The much higher content of 3-mercapto-2-methylpentan-1-ol in cooked onions suggested its formation from specific, yet unkown, precursors enzymatically formed during cutting of raw onions. 1 was for the first time identified and also quantified in other Allium species such as chives, scallions, and leek, whereas surprisingly garlic and bear's garlic did not contain the aroma compound.

Onions--a global benefit to health

Onion (Allium cepa L.) is botanically included in the Liliaceae and species are found across a wide range of latitudes and altitudes in Europe, Asia, N. America and Africa. World onion production has increased by at least 25% over the past 10 years with current production being around 44 million tonnes making it the second most important horticultural crop after tomatoes. Because of their storage characteristics and durability for shipping, onions have always been traded more widely than most vegetables. Onions are versatile and are often used as an ingredient in many dishes and are accepted by almost all traditions and cultures. Onion consumption is increasing significantly, particularly in the USA and this is partly because of heavy promotion that links flavour and health. Onions are rich in two chemical groups that have perceived benefits to human health. These are the flavonoids and the alk(en)yl cysteine sulphoxides (ACSOs). Two flavonoid subgroups are found in onion, the anthocyanins, which impart a red/purple colour to some varieties and flavanols such as quercetin and its derivatives responsible for the yellow and brown skins of many other varieties. The ACSOs are the flavour precursors, which, when cleaved by the enzyme alliinase, generate the characteristic odour and taste of onion. The downstream products are a complex mixture of compounds which include thiosulphinates, thiosulphonates, mono-, di- and tri-sulphides. Compounds from onion have been reported to have a range of health benefits which include anticarcinogenic properties, antiplatelet activity, antithrombotic activity, antiasthmatic and antibiotic effects. Here we review the agronomy of the onion crop, the biochemistry of the health compounds and report on recent clinical data obtained using extracts from this species. Where appropriate we have compared the data with that obtained from garlic (Allium sativum L.) for which more information is widely available.

In vitro stability and chemical reactivity of thiosulfinates

A model reaction system was used to generate pure thiosulfinates (3) from S-alk(en)yl-L-cysteine sulfoxides (1) to facilitate studies on the intrinsic pH and thermal sensitivities of individual thiosulfinate species. Thiosulfinate decay could be characterized as first-order processes over the pH range of 1.2-9.0 and at 20-80 degrees C. The stability of thiosulfinates was greatest at pH 4.5-5.5, followed by pH 1.2, pH 6.5-7.5, and pH 8.0-9.0. Thiosulfinates with longer and saturated alk(en)yl groups were generally more stable than those with shorter and unsaturated alk(en)yl groups. Thiosulfinates underwent thioalkyl-exchange reactions at pH 8-9 without loss of total thiosulfinate levels within 60-90 min at 20 degrees C.

Antioxidant functions of selected allium thiosulfinates and S-alk(en)yl-L-cysteine sulfoxides

Pure thiosulfinates, R-S(O)S-R (2), where R = Me (2a), Pr (2b), or All (2c), at levels up to 4 mM were not capable of scavenging hydrogen peroxide or superoxide anion. Relative to standard antioxidants (ascorbic acid, n-propyl gallate, butylated hydroxytoluene, Trolox, and reduced glutathione), these thiosulfinates were 1-3 orders of magnitude less efficient at reducing 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, 0.5-2 orders of magnitude less efficient at quenching singlet oxygen, and about equally effective at scavenging hydroxyl radical. Generally, AllS(O)SAll (2c) was the most effective and PrS(O)SPr (2b) was the least effective thiosulfinate in these assays, except that MeS(O)SMe (2a) exhibited no quenching effect toward singlet oxygen. These thiosulfinates were also incapable at levels up to 0.1 mM (where they were toxic) of in vitro induction of quinone reductase (QR) in murine hepatoma (hepa 1c1c7) cells. However, S-1-propenyl-L-cysteine sulfoxide (isoalliin, 1a) and cycloalliin (3) induced QR in this system at 2 mM and 1 mM, respectively, although doubling of QR required levels of 10-15 mM.

Biomonitoring the intake of garlic via urinary excretion of allyl mercapturic acid

Allium vegetables (onions, leeks, chives) and in particular garlic have been claimed to have health-promoting potential. This study was conducted to get insight into the perspectives for monitoring the intake of garlic by a biomarker approach. Chemically, the biomarker results from exposure to gamma-glutamyl-S-allyl-l-cysteine, which is first hydrolysed by gamma-glutamine-transpeptidase resulting in the formation of S-allyl-l-cysteine. The latter compound is subsequently N-acetylated by N-acetyltransferase into S-allyl-mercapturic acid (ALMA) and excreted into urine. The mercapturic acid was measured in urine using gaschromatography with mass spectrometry. Thus the intake of garlic was determined to check the compliance of garlic intake in a placebo-controlled intervention study. Results indicate that S-allyl-mercapturic acid could be detected in 15 out of 16 urine samples of garlic supplement takers, indicating good compliance. In addition, the intake of garlic was also monitored in a cross-section study of vegans versus controls in Finland, in which no differences in garlic consumption nor in ALMA output were recorded between vegans and controls. These data indicate good possibilities for further studies in the field of biomarkers to investigate the putative chemopreventive effects of garlic and garlic-containing products.

Biologically active peptides and enzymatic approaches to their production

This review briefly surveys various classes of biologically active and flavor peptides that have been isolated and characterized in recent years, and analyzes emerging trends and advances in biotechnological methods for their production.