Influence of harvest time and cultivation region on primary and secondary metabolites of Korean laver (Porphyra spp.)

Laver ( Porphyra spp.) is an economically important red seaweed primarily consumed in East Asia, yet detailed information on its nutritional composition remains limited. This study reports a first pseudo-targeted, in-depth seasonal and regional metabolite profiling of Korean laver harvested between December and March from five major cultivation regions during the 2021–2023 seasons. Using GC-MS/MS and LC-MS/MS, a total of 109 primary and nutrient metabolites were identified. Multivariate analysis (VIP > 1.0) revealed 43 primary metabolites that varied with harvest time and cultivation region in this dataset. Sweet-taste amino acids (alanine, glycine, and serine) and umami-taste amino acids (aspartic acid and glutamic acid) were more abundant in samples harvested in December and January. Additionally, seven carotenoids (fucoxanthin, lutein, zeaxanthin, β-apo-8′-carotenal, β-cryptoxanthin, α-carotene and β-carotene) and seven free phenolic acids (dihydroxyphenylacetic acid, 3,4-dihydroxybenzoic acid, hydroxybenzoic acid hexoside, 4-hydroxybenzoic acid, gallic acid gallate, dimethoxy hydroxycinnamic acid, and salicylic acid) were identified, several of which showed higher levels in early-winter samples. Taken together, these results suggest quality relevant markers for distinguishing harvest times and cultivation regions, thereby providing a scientific basis for product differentiation and the implementation of targeted quality control in laver production. • Metabolite profiles of fresh laver were analyzed across five major Korean regions. • Thirty-seven primary metabolites were newly identified in Korean laver. • Sweet- and umami-related amino acids were more abundant in early-winter laver. • Seasonal and regional variations were observed in carotenoids and phenolic compounds. • Candidate metabolites were proposed to discriminate laver by origin and harvest time.