using digital subtraction HPTLC

Allicin is a major thiosulfinate found in garlic and other Allium sp. and it is responsible for their pungent aroma. It is formed during the tissue lysis of garlic, by the initial action of alliinase upon alliin, the major cysteine sulfoxide. Simultaneous detection of these two analytes is usually performed using HPLC. Contrary to the most important phytoconstituents in other samples, allicin is scarcely detected using the simple HPTLC technique, due to challenges caused by its unique structure, despite its simplicity and high needs in the analytical monitoring of the Allium sp. In this work, a cost-effective, simple, sensitive and accurate method was developed for the determination of allicin together with alliin, using HPTLC. Allicin is quickly pre-derivatised with cysteine in excess to the stable S-allylmercaptocysteine that is then simultaneously detected with alliin, using ninhydrin reagent. The method was validated in terms of accuracy (recoveries of 90-120 %), precision (RSD% of 4-12 %), selectivity, robustness, peak purity and limit of detection (LOD = 0.05 μg/band for allicin and LOD = 0.10 μg/band for alliin). The method was successfully applied using real Allium sp. samples and the results were in good agreement with HPLC data.

Generation of garlic flavor after frying by infusing alliin into potato strips using pulsed electric field and assisted infusion methods

A new method of alliin infusion into potato strips to generate garlic flavor upon frying was investigated. Potato strips were treated using pulsed electric field (PEF) and then allin was infused into the treated strips using immersion, ultrasound, or vacuum assisted infusion. Results showed that under lower PEF intensities (0.250, 0.650 and 1.250 kJ/kg), assisted infusion methods significantly improve alliin infusion efficiency (p < 0.05). The kinetics for alliin infusion showed that 1.250 kJ/kg PEF treatment and 35 kHz ultrasound assisted infusion have the highest a values of 94.69 and 94.80 (mg/mL^.h), respectively. Scanning electron microscope (SEM) highlighted different cell structural changes before and after being treated with different PEF intensities and infusion methods. Sensory evaluations confirmed generation of garlic flavor upon frying (p < 0.05).

Alliin alleviates LPS-induced pyroptosis via promoting mitophagy in THP-1 macrophages and mice

Pyroptosis is a new type of programmed cell death associated with inflammation. Excessive pyroptosis can cause body damage. Alliin is an organosulfur compound extracted from garlic, bearing anti-oxidation and anti-inflammatory properties. In this study, we revealed that alliin alleviated LPS-induced macrophage pyroptosis by detecting PI staining, IL-1β and IL-18 release in vitro and in vivo. In the study of mechanism, we found that alliin might reduce the activation of NLRP3 inflammosome by decreasing intracellular ROS generation. Subsequently, we detected the effect of alliin on mitophagy which degraded damaged mitochondria. The results showed that alliin promoted PINK 1/Parkin-mediated mitophagy. After adding the mitophagy inhibitor CsA, the alleviating effect of alliin on mitochondrial damage and mitochondrial ROS were reversed and the relieving effect of alliin on LPS-induced pyroptosis was inhibited. These results suggested that alliin might reduce intracellular ROS production by promoting mitophagy, thus alleviating LPS-induced macrophages pyroptosis. Our study provides a new perspective and theoretical basis for alliin to alleviate pyroptosis which could further induce body damage.

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.

Variability in S-Alk(en)yl-L-Cysteine Sulfoxides in Garlic within a Seven-Month Period Determined by a Liquid Chromatography - Tandem Mass Spectrometry Method

The composition of garlic (Allium sativum L.) may vary among cultivars and, moreover, change over time, thereby affecting both biological activity and flavour. Thus, it is important to identify the trends in the content of bioactive compounds in garlic, by reliable analytical methods. This study was focused on the key sulfur-containing compounds, S-alk(en)yl-L-cysteine sulfoxides (alliin, isoalliin, methiin, propiin), which were quantified by a fast liquid chromatography - tandem mass spectrometry (LC-MS/MS) method. Several garlic cultivars were monitored repeatedly within seven months: one month before harvest maturity; at harvest maturity; and after two and six months of storage. The results showed not only a high variability among individual cultivars, but also among samples of the same cultivar grown at different localities. During storage, a significant increase in isoalliin content (up to 54-fold after six months) occurred. Nevertheless, none of the cultivars showed significantly different properties compared to others, suggesting that many other factors affect garlic composition.

S-Alk(en)ylcysteine sulfoxides in the genus Allium: proposed biosynthesis, chemical conversion, and bioactivities

S-Alk(en)ylcysteine sulfoxides are sulfur-containing natural products characteristic of the genus Allium. Both the flavor and medicinal properties of Allium plants are attributed to a wide variety of sulfur-containing compounds that are generated from S-alk(en)ylcysteine sulfoxides. Previous radiotracer experiments proposed that S-alk(en)ylcysteine sulfoxides are biosynthesized from glutathione. The recent identification of γ-glutamyl transpeptidases and a flavin-containing S-oxygenase involved in the biosynthesis of S-allylcysteine sulfoxide (alliin) in garlic (Allium sativum) provided insights into the reaction order of deglutamylation and S-oxygenation together with the localization of the biosynthesis, although the rest of the enzymes in the pathway still await discovery. In intact plants, S-alk(en)ylcysteine sulfoxides are stored in the cytosol of storage mesophyll cells. During tissue damage, the vacuolar enzyme alliinase contacts and hydrolyzes S-alk(en)ylcysteine sulfoxides to produce the corresponding sulfenic acids, which are further converted into various sulfur-containing bioactive compounds mainly via spontaneous reactions. The formed sulfur-containing compounds exhibit bioactivities related to pathogen defense, the prevention and alleviation of cancer and cardiovascular diseases, and neuroprotection. This review summarizes the current understanding of the occurrence, biosynthesis, and alliinase-triggered chemical conversion of S-alk(en)ylcysteine sulfoxides in Allium plants as well as the impact of S-alk(en)ylcysteine sulfoxides and their derivatives on medicinal, food, and agricultural sciences.

Effects of alliin on LPS-induced acute lung injury by activating PPARγ

Alliin is a garlic organosulfur compound that possesses various pharmacological properties. In the present study, the protective effects and molecular mechanism of alliin on Lipopolysaccharides (LPS)-induced acute lung injury (ALI) were analyzed. LPS-induced ALI was induced in BALB/c mice by intranasal instillation of LPS. Alliin was administered intraperitoneally to mice 1 h after LPS treatment. The results showed that alliin markedly inhibited lung myeloperoxidase (MPO) activity and wet/dry (W/D) ratio induced by LPS. Alliin also inhibited TNF-α and IL-1β in the bronchoalveolar lavage fluid (BALF) induced by LPS. Furthermore, LPS-induced lung pathological injury was attenuated by treatment of alliin. LPS-induced NF-κB activation was significantly inhibited by alliin. In addition, the expression of peroxisome proliferator-activated receptor γ (PPARγ) was up-regulated by treatment of alliin. Taken together, these results suggested that alliin protected against LPS-induced ALI by activating PPARγ, which subsequently inhibited LPS-induced NF-κB activation and inflammatory response. Alliin might be used as an anti-inflammatory agent in the treatment of ALI.

Alliin, a garlic organosulfur compound, ameliorates gut inflammation through MAPK-NF-κB/AP-1/STAT-1 inactivation and PPAR-γ activation

SCOPE

In this study, the anti-inflammatory effects and the molecular mechanism of alliin were analyzed in dextran sulfate sodium (DSS)-induced colitis mice and lipopolysaccharide-stimulated RAW264.7 cell model.

METHODS

The phenotype of mice was recorded in the DSS-induced and/or alliin (500 mg/kg) groups. Histopathological alterations were analyzed by H&E staining. MPO and MDA of colon tissues were measured. The mRNA expression levels of inflammatory factors were determined by qRT-PCR, and protein expressions of inflammatory factors or activation of kinases were determined by Western blotting.

RESULTS

Oral administration of alliin significantly inhibited the decrease of body weight, improved the DAI and decreased the infiltration of inflammatory cells in colonic tissues. The content of NO, MDA, and MPO, the expression of iNOS and inflammatory factors as well as MAPK and the phosphorylation of PPAR-γ were inhibited in alliin-treated group. Treatment with alliin significantly repressed the expression of inflammatory factors in LPS-stimulated RAW264.7 cells. Further research demonstrated that alliin repressed LPS-induced AP-1/NF-κB/STAT-1 activation by inhibiting the phosphorylations of p38, JNK, and ERK1/2-regulated PPAR-γ activation.

CONCLUSION

Our results show that alliin ameliorates DSS-induced ulcerative colitis and inhibits the inflammatory responses in LPS-stimulated RAW264.7 cells partly through inhibiting ERK1/2-, JNK-/PPAR-γ-stimulated NF-κB/AP-1/STAT-1 activations.

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.