Cryopreservation in liquid nitrogen (LN, −196 °C) is a unique option for the long-term conservation of threatened plant species with non-orthodox or limitedly available seeds. In previous studies, a systematic approach was used to develop a droplet-vitrification (DV) cryopreservation protocol for Postemon yatabeanus shoot tips that includes preculture with 10% sucrose, osmoprotection with C4-35%, cryoprotection with A3-80% vitrification solution, and a three-step regrowth starting with the ammonium-free medium. The tricarboxylic acid (TCA) cycle is a crucial component of plant cell metabolism as it is involved in redox state regulation and energy provision. We hypothesized that organic acids (OAs) associated with the TCA and its side reactions indirectly indicate metabolism intensity and oxidative stress development in shoot tips under the cryopreservation procedure. In this study, the contents of 14 OAs were analyzed using gas chromatography–tandem mass spectrometry (GC-MS/MS) in P. yatabeanus shoot tips in a series of treatments including individual steps of the DV procedure, additional stress imposed by non-optimum protocol conditions (no preculture, no osmoprotection, various vitrification solution composition, using vials instead of aluminum foils, etc.) and regrowth on different media with or without ammonium or growth regulators. The possible relation of OA content with the total cryoprotectant (CPA) concentration and shoot tips regeneration percentage was also explored. Regeneration of cryopreserved shoot tips reduced in descending order as follows: standard protocol condition (91%) > non-optimum vitrification solution (ca. 68%) > non-optimum preculture (60–62%) > regrowth medium (40–64%) > no osmoprotection, cryopreservation in vials (28–30%). Five OAs (glycolic, malic, citric, malonic, and lactic) were the most abundant in the fresh (control) shoot tips. The dynamic pattern of OAs during the DV procedure highly correlated (r = 0.951) with the total CPA concentration employed: it gradually increased through the preculture, osmoprotection, and cryoprotection, peaked at cooling/rewarming (6.38-fold above control level), and returned to the fresh control level after 5 days of regrowth (0.89-fold). The contents of four OAs (2-hydroxybutyric, 3-hydroxypropionic, lactic, and glycolic) showed the most significant (10-209-fold) increase at the cooling/rewarming step. Lactic and glycolic acids were the major OAs at cooling/rewarming, accounting for 81% of the total OAs content. The OAs were categorized into three groups based on their dynamics during the cryopreservation protocol, and these groups were differently affected by protocol step modifications. However, there was no straightforward relationship between the dynamics of OAs and shoot tip regeneration. The results suggest that active modulation of OAs metabolism may help shoot tips to cope with osmotic stress and the chemical cytotoxicity\ of CPAs. Further intensive studies are needed to investigate the effect of cryopreservation on cell primarily metabolism and identify oxidative stress-related biomarkers in plant materials.

Three new depsipeptides, homiamides A–C (1–3), were isolated from a marine sediment-derived strain of Streptomyces sp., ROA-065. The planar structures of homiamides A–C (1–3) were elucidated using mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopic data. The absolute configurations of 1–3 were deduced from the application of the Marfey’s method and GC-MS analysis after formation of the O-trifluoroacetylated (S)-(+)-methyl-2-butyl ester derivatives of amino acids. Compounds 1–3 exhibited weak anti-bacterial activities against both Gram-positive bacteria and Gram-negative bacteria, with compound 1 showing MIC values of 32–64 μg/mL. In antifouling assays, compounds 1 and 2 displayed moderate activity against Micrococcus luteus KCTC 3063, while compound 3 exhibited weak activity against all tested bacteria.

Barley (Hordeum vulgare) is a major cereal grain grown in temperate climates globally and provides various nutrients in a peeled form after milling. However, milling causes changes in nutritional composition, including metabolites. Thus, a metabolomics study was conducted to monitor the changes in nutritional composition before and after the milling of Hordeum vulgare seeds (Saechalssal, Hinchalssal, and Yeongbaekchal) focusing on the development and application of new analytical methods for organic acids (OA) and amino acids (AA). Profiling analyses of OAs and AAs were performed using GC-MS/MS. This analytical method showed good linearity (r ≥ 0.995) with limit of detection (0.1 ng, 21.2 ng) and limit of quantitation (0.3 ng, 63.6 ng), respectively. Repeatability varied from 0.1 to 12.4 (% RSD) and accuracy varied from –12.3 to 14.8 (% RE), respectively. Altered levels of 36 metabolites (16 OAs, 20 AAs) were monitored post-milling and compared with pre-milling in the three Hordeum vulgare cultivars. Radar plots of OAs and AAs to corresponding mean levels of each pre-milling group in the three Hordeum vulgare cultivars were easily distinguished from those in each post-milling group. The pre-and post-milling groups of the three Hordeum vulgare cultivars were completely separated by partial least square discriminant analysis, and the lysine, cysteine, glutamic acid, asparagine, 4-hydroxyphenylacetic acid, and citric acid were significantly different. Therefore, this study will be useful for monitoring altered metabolites following milling and discrimination of varieties.