Isoalliin

The ability of callus tissues induced from three Allium plants to accumulate health-beneficial natural products, S-alk(en)ylcysteine sulfoxides.[Pubmed:35691991]

J Nat Med. 2022 Jun 13. pii: 10.1007/s11418-022-01631-4.

S-Alk(en)ylcysteine sulfoxides (CSOs), such as methiin, alliin, and Isoalliin, are health-beneficial natural products biosynthesized in the genus Allium. Here, we report the induction of multiple callus tissue lines from three Allium vegetables, onion (A. cepa), Welsh onion (A. fistulosum), and Chinese chive (A. tuberosum), and their ability to accumulate CSOs. Callus tissues were initiated and maintained in the presence of picloram and 2-isopentenyladenine as auxin and cytokinin, respectively. For all plant species tested, the callus tissues almost exclusively accumulated methiin as CSO, while the intact plants contained a substantial amount of Isoalliin together with methiin. These results suggest that the cellular developmental conditions and the regulatory mechanisms required for the biosynthesis of methiin are different from those of alliin and Isoalliin. The methiin content in the callus tissues of onion and Welsh onion was much higher compared to that in the intact plants, and its cellular concentration could be estimated as 1.9-21.7 mM. The activity of alliinase that degrades CSOs in the callus tissues was much lower than that of the intact plants for onion and Welsh onion, but at similar levels as in the intact plants for Chinese chive. Our findings that the callus tissues of onion and Welsh onion showed high methiin content and low alliinase activity highlighted their potential as a plant-based system for methiin production.

Non-volatile cysteine sulphoxides and volatile organosulphur compounds in cloves of garlic (Allium sativum L.) and elephant garlic (Allium ampeloprasum L.) local accessions from northern and central Italy.[Pubmed:35211974]

J Sci Food Agric. 2022 Feb 24.

BACKGROUND: Garlic (Allium sativum L.) and other species of genus Allium are popular vegetables and food seasonings, owing to their spicy flavour and richness in health-promoting compounds. Several local garlic types are still grown on a small scale in different Italian regions, not being however yet properly characterized for their chemical composition. RESULTS: In the present investigation ten garlic and four elephant garlic (Allium ampeloprasum L.) populations cultivated in northern and central Italy were evaluated for their alk(en)yl cysteine sulphoxide (ACSO) and volatile compound profiles. Three non-volatile ACSOs (methiin, alliin, and Isoalliin) and 27 volatile compounds were identified and quantified. A high and significant within-type variability was detected, with total ACSOs in the range 2759-5756, 4533-15 520, and 6565-10 643 mg kg(-1) of fresh weight (f.w.). in elephant, white and red garlic, respectively. Elephant garlic showed a total sulphoxide content and a relative alliin amount significantly lower than white and red garlic. Remarkable within-type differences were also assessed for volatile compound content, ranging 260-599, 333-981, and 618-845 mg kg(-1) f.w. in elephant, white, and red garlic, respectively. Diallyl trisulphide was the major individual compound, accounting for more than 0.30 mg mg(-1) of volatiles in all the analysed samples. The three garlic types were clearly separated by discriminant analysis of analytical traits. CONCLUSION: This study investigated for the first time different Italian garlic and elephant garlic populations with respect to non-volatile and volatile organosulphur compound content, allowing the possibility of selecting garlic accessions according to the bioactive content. (c) 2022 Society of Chemical Industry.

Hydrogen/Deuterium Exchange Aiding Metabolite Identification in Single-Cell Nanospray High-Resolution Mass Spectrometry Analysis.[Pubmed:34931818]

Anal Chem. 2022 Jan 18;94(2):650-657.

The identification of metabolites in single-cell or small-volume tissue samples using single-cell mass spectrometry (MS) is challenging. In this study, hydrogen/deuterium (H/D) exchange was combined with microsampling nanospray high-resolution mass spectrometry (HRMS) to improve the efficiency and confidence level of metabolite identification in a single cell using commercial software. A nanospray ion source showed an improved reaction depth of 8% for H/D exchange compared with an electrospray ion source. In total, 273 metabolites were identified in Allium cepa L. single cells by searching commercial databases. Generally, more than one candidate is given for a precursor ion by MS or tandem MS (MS(2)) databases such as ChemSpider, MetDNA, MassBank, and mzCloud. With the help of the H/D exchange technique, the number of candidates decreased and reduction of the search space by a factor of 8 was achieved. In addition, two enzymolysis products of Isoalliin, the transient intermediate and its isomer, were tracked at the single-cell level using the proposed method.