Objective Sinojackia oblongicarpa is a wild plant endemic to China and listed as a Class II National Key Protected Wild Plant, The chemical constituents of its fruits have not yet been systematically explored or reported. This study aimed to systematically analyze the metabolic composition and differential metabolite characteristics of fruits from different germplasms of S. oblongicarpa, thereby providing a scientific basis for germplasm resource evaluation, conservation strategy formulation, and utilization value exploitation of this rare species.

Method Mature fruits of two representative germplasms, CCS3 and CCS106, which differed significantly in fruit morphological traits, were used as experimental materials. Ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was employed for qualitative and quantitative metabolite detection, differential metabolite screening, and metabolic pathway enrichment analysis.

Result (1) In positive and negative ion modes, a total of 368 metabolites were identified, mainly including flavonoids, organic acids, amino acids, phenolics, terpenoids, phenylpropanoids, alkaloids, and other categories. Among them, amino acids had the highest relative abundance, followed by alkaloids, phenolics, and flavonoids. (2) In fruits of germplasm CCS3, the metabolites with relatively high abundance were mainly amino acids (histidine, L-glutamine, tryptophan, and L-valine), alkaloids (arecoline and dictamnine), phenolic acids (β-phenylpropionic acid), flavanols (procyanidin B5 and catechin), and sugars (L-rhamnose, galactose, and D-gulose). (3) A total of 196 significantly differential metabolites were screened between the two germplasms, mainly including flavonoids, amino acids, organic acids, and phenolics. Compared with CCS106, 93 and 103 metabolites showed significantly increased and decreased relative accumulation levels in CCS3 fruits, respectively. (4) A total of 71 metabolic pathways were annotated for the differential metabolites, which were mainly enriched in the citric acid cycle (TCA cycle), D-amino acid metabolism, amino acid metabolism, and flavonoid biosynthesis pathways. Among them, the D-amino acid metabolism pathway had the highest number of enriched differential metabolites, including eight metabolites: pyruvate, L-glutamate, oxoglutarate, oxaloacetate, phenylpyruvate, threonine, L-glutamine, and 4-hydroxyproline.

Conclusion The fruits of S. oblongicarpa are rich in various metabolites, including amino acids, flavonoids, and phenolics, and the metabolite composition differed significantly among different germplasms. This study preliminarily analyzed the metabolic composition and inter-germplasm variation patterns of S. oblongicarpa fruits, providing basic data and theoretical support for germplasm resource evaluation, precise conservation, and exploration of potential functional components of this species.