Sulphur treatment alters the therapeutic potency of alliin obtained from garlic leaf extract

Comparative analysis of two kinds of garlic seedings: qualities and transcriptional landscape

BACKGROUND

Facility cultivation is widely applied to meet the increasing demand for high yield and quality, with light intensity and light quality being major limiting factors. However, how changes in the light environment affect development and quality are unclear in garlic. When garlic seedlings are grown, they can also be exposed to blanching culture conditions of darkness or low-light intensity to ameliorate their appearance and modify their bioactive compounds and flavor.

RESULTS

In this study, we determined the quality and transcriptomes of 14-day-old garlic and blanched garlic seedlings (green seedlings and blanched seedlings) to explore the mechanisms by which seedlings integrate light signals. The findings revealed that blanched garlic seedlings were taller and heavier in fresh weight compared to green garlic seedlings. In addition, the contents of allicin, cellulose, and soluble sugars were higher in the green seedlings. We also identified 3,872 differentially expressed genes between green and blanched garlic seedlings. The Kyoto Encyclopedia of Genes and Genomes analysis suggested enrichment for plant-pathogen interactions, phytohormone signaling, mitogen-activated protein kinase signaling, and other metabolic processes. In functional annotations, pathways related to the growth and formation of the main compounds included phytohormone signaling, cell wall metabolism, allicin biosynthesis, secondary metabolism and MAPK signaling. Accordingly, we identified multiple types of transcription factor genes involved in plant-pathogen interactions, plant phytohormone signaling, and biosynthesis of secondary metabolites among the differentially expressed genes between green and blanched garlic seedlings.

CONCLUSIONS

Blanching culture is one facility cultivation mode that promotes chlorophyll degradation, thus changing the outward appearance of crops, and improves their flavor. The large number of DEGs identified confirmed the difference of the regulatory machinery under two culture system. This study increases our understanding of the regulatory network integrating light and darkness signals in garlic seedlings and provides a useful resource for the genetic manipulation and cultivation of blanched garlic seedlings.

Chemometric origin classification of Chinese garlic using sulfur-containing compounds, assisted by stable isotopes and bioelements

Geographical origin discrimination of agro-products is essential to guarantee food safety and fair trade. Garlic samples cultivated in six provinces or major production regions in China were characterized for stable isotopes (δ¹³C, δ²H, δ¹⁸O, δ¹⁵N, and δ³⁴S), bioelemental contents (% C, % N and % S), and sulfur-containing compounds (8 organosulfur components and 2 amino acids). Results showed that many of the 18 analyzed garlic variables had significant differences among production regions. Some sulfur-containing compounds found in garlic from different provinces had a strong correlation with sulfur isotopes, suggesting garlic sulfur isotopes were also affected by geographical origin. Two supervised pattern recognition models (PLS-DA and k-NN) were developed using stable isotopes, elemental contents, and sulfur-containing compounds, and had a discrimination accuracy of 93.4 % and 87.8 %, respectively. Chemometric classification models using multi-isotopes, elements and sulfur-containing compounds provides a useful method to authenticate Chinese garlic origins.

Parallel analysis of global garlic gene expression and alliin content following leaf wounding

BACKGROUND

Allium sativum (garlic) is an economically important food source and medicinal plant rich in sulfides and other protective substances such as alliin, the precursor of allicin biosynthesis. Cysteine, serine and sulfur is the precursor of alliin biosynthesis. However, little is known about the alliin content under abiotic stress or the mechanism by which it is synthesized.

RESULTS

The findings revealed that the content of alliin was lowest in the garlic roots, and highest in the buds. Furthermore, alliin levels decreased in mature leaves following wounding. Transcriptome data generated over time after wounding further revealed significant up-regulation of genes integral to the biosynthetic pathways of cysteine and serine in mature garlic leaves.

CONCLUSIONS

The findings suggest that differential expression of cysteine, serine and sulfide-related genes underlies the accumulation of alliin and its precursors in garlic, providing a basis for further analyses of alliin biosynthesis.

Identification and expression analysis of S-alk(en)yl-L-cysteine sulfoxide lyase isoform genes and determination of allicin contents in Allium species

Alliinase is the key enzyme in allicin biosynthesis pathway. In the current study, the identification and sequencing of alliinase genes along with determination of allicin contents were reported for Allium species with a novel report for Iranian endemic species. The presence of different isoforms in the Allium being discovered for the first time. In bulbs tissue, the highest allicin concentration was in Allium sativum, A. umbilicatum, and A. fistolosum (1.185%, 0.367%, and 0.34%, respectively), followed by A. spititatum (0.072%), A. lenkoranicum (0.055%), A. atroviolaseum (0.36%), A. rubellum (0.041%), and A. stamineum (0.007%). The highest allicin content in the leaves and roots were in A. sativum (0.13%), and A. stamineum (0.195%), respectively. The ORFs length ranged from 1416 in A. sativum (iso-alliinase2; ISA2) to 1523 bp in A. sativum (alliinase); the identity with A. sativum (alliinase) varies from 95% to 68% for A. ampeloprasum, and A. sativum (iso-alliinase1, ISA1) respectively. These data suggested that both ISA1 and ISA2 had a high expression in the roots and bulbs compared to A. sativum as the control in all species. Note that ISA1 and ISA2 were not expressed in the leaves. The results showed that isoforms expression patterns among different tissues in Allium species were variable. The presence of various isoforms is a possible explanation for the difference between the species in terms of obtained results, especially the amount of allicin.

Selenium and Sulfur to Produce Allium Functional Crops

Selenium is an element that must be considered in the nutrition of certain crops since its use allows the obtaining of biofortified crops with a positive impact on human health. The objective of this review is to present the information on the use of Se and S in the cultivation of plants of the genus Allium. The main proposal is to use Allium as specialist plants for biofortification with Se and S, considering the natural ability to accumulate both elements in different phytochemicals, which promotes the functional value of Allium. In spite of this, in the agricultural production of these species, the addition of sulfur is not realized to obtain functional foods and plants more resistant; it is only sought to cover the necessary requirements for growth. On the other hand, selenium does not appear in the agronomic management plans of most of the producers. Including S and Se fertilization as part of agronomic management can substantially improve Allium crop production. Allium species may be suitable to carry out biofortification with Se; this practice can be combined with the intensive use of S to obtain crops with higher production and sensory, nutritional, and functional quality.

Investigating the chemical constituent and the suppressive effects of alliin hydrolysate on E.coli

The present study investigates the antimicrobial activity of alliin degradation products by enzymatic and alkali-heat treatment. The results suggested that the suppressive effect of enzymatic degradation products (AE) on Escherichia coli was much higher than alkali-heat treatment products (AA). Both AE and AA seriously destroyed the integrity of E. coli cell membrane, decreased the utilisation of intracellular proteins and the absorption of extracellular phosphorus. Furthermore, GC-MS analysis preliminarily confirmed that alliin degradation products contained a variety of sulphur compounds, such as allyl disulphide and dithiene. The antibacterial activities exhibited by AE demonstrate their potential for use as E. coli inhibitor in food.

Chemical composition and bioactive compounds of garlic (Allium sativum L.) as affected by pre- and post-harvest conditions: A review

Garlic (Allium sativum L.) is considered one of the twenty most important vegetables, with various uses throughout the world, either as a raw vegetable for culinary purposes, or as an ingredient of traditional and modern medicine. Furthermore, it has also been proposed as one of the richest sources of total phenolic compounds, among the usually consumed vegetables, and has been highly ranked regarding its contribution of phenolic compounds to human diet. This review aims to examine all the aspects related with garlic chemical composition and quality, focusing on its bioactive properties. A particular emphasis is given on the organosulfur compounds content, since they highly contribute to the effective bioactive properties of garlic, including its derived products. The important effects of pre-harvest (genotype and various cultivation practices) and post-harvest conditions (storage conditions and processing treatments) on chemical composition and, consequently, bioactive potency of garlic are also discussed.

Study on the stability and antioxidant effect of the Allium ursinum watery extract

Background

Organosulfur compounds usually present a reduced stability especially in the presence of oxygen. This research aimed to study the stability and antioxidant potential of the Allium ursinum watery extract.

Results

The decrease of the antioxidant capacity verifies an exponential relation which may be formally associated to a kinetically pseudomonomolecular process. The exponential regression equation allows the half-life of the degradation process to be determined, this being 14 hours and 49 minutes in a watery environment at room temperature.

Conclusions

The watery extract of Allium ursinum changes its proprieties in time. This might be explained by the network of hydrogen bonds in a watery environment which has a protective effect on the dissolved allicin molecule.

Alliin obtained from leaf extract of garlic grown under in situ conditions possess higher therapeutic potency as analyzed in alloxan-induced diabetic rats

CONTEXT

Garlic, Allium sativum L. (Liliaceae), possesses high therapeutic and pharmacological properties. Hypoglycemic activity is attributed to alliin (S-allyl cysteine sulfoxide), the main active principle localized in garlic cloves.

OBJECTIVE

To compare the production and therapeutic efficiency of alliin extracted from garlic leaves of plants grown under ex situ and in situ conditions.

MATERIALS AND METHODS

Alliin content of leaves was quantified and aqueous leaf extracts (from ex situ and in situ grown plants) were given to normal and alloxan-induced diabetic rats for five weeks.

RESULTS

Alliin production noted ~50% enhancement in leaves from plants grown under in situ conditions. Serum glucose, triglycerides, total lipids, total cholesterol, low-density lipoprotein (LDL)-, and very low-density lipoprotein (VLDL)-cholesterol in diabetic rats treated with alliin produced from in situ grown plants noted significant reduction of ~54%, 15%, 14%, 20%, 24%, and 15%, while 35%, 14%, 10%, 12%, 17% and 11% reduction was noted in diabetic rats treated with alliin produced from ex situ grown plants in comparison with those administered with distilled water. High-density lipoprotein (HDL)-cholesterol did not show any significant change. Leaf extract of plants lowered serum enzyme levels (alkaline phosphatase, aspartate aminotransferase, and alanine aminotransferase) toward the norm better than glibenclamide. The histopathological alteration in pancreas caused by alloxan was also reduced by leaf extract.

DISCUSSION AND CONCLUSION

These findings demonstrate leaf extract obtained from plants grown under in situ condition possess higher therapeutic efficiency in comparison with leaf extract obtained from plants grown under ex situ condition. Studies suggest that environmental factors influence production of alliin and its therapeutic potential.

Influence of fertilizer practices on S-containing metabolites in garlic (Allium sativum L.) under field conditions

Cysteine sulfoxides (e.g., alliin) are the characteristic sulfur-containing secondary compounds in garlic, which account for taste and pharmaceutical quality. It was the aim of the present study to investigate the influence of sulfur and nitrogen supply under field conditions on the alliin content and cysteine and glutathione as possible precursors. Sulfur and nitrogen were applied in four different rates, and five samplings were conducted. Sulfur fertilization significantly increased the cysteine, glutathione, and alliin contents of leaves and bulbs, while nitrogen fertilization had no significant influence. Cysteine increased by a factor of 1.3-1.5 in leaves and 1.0-2.0 in bulbs. Glutathione increased significantly in bulbs by a factor of 0.9-1.6 but only at main growth and not at maturity. The alliin concentration in bulbs increased with S fertilization significantly at all harvesting dates and at maturity from 5.1 to 11.2 mg g(-1) of dry weight. High sulfur application in combination with low nitrogen fertilization increased the alliin concentration in garlic significantly during main growth until the beginning of ripening. At the last harvest, 15 kg ha(-1) S resulted in high-quality garlic suitable for consumption and use in plant protection or pharmaceutical industries.

Nutraceutical use of garlic sulfur-containing compounds

Garlic is one of the world's oldest medicines that has been employed not only for flavouring but also as a medical herb for its prophylactic and therapeutic actions. Most garlics' beneficial effects are due to the presence of the organosulphate molecule allicin. Allicin is a highly unstable molecule and, during processing, is rapidly transformed into a variety of organosulfur components. The enzyme alliinase, which is responsible for the conversion of alliin to allicin, is irreversibly destroyed at the acidic environment of stomach. This is the reason why most garlic supplements contain garlic powder or granules, but do not contain allicin itself. Garlic alliinase could be encapsulated and coated with materials which would protect it in the harsh conditions of the stomach. The objective of this chapter is to summarize the most important garlic health benefits and to discuss promising encapsulation/stabilization approaches.