A comprehensive insight into the metabolic landscape of fruit pulp, peel, and seed in two longan (Dimocarpus longanLour.) varieties

Abstract

Longan is an ancient and popular plant with highly nutritious fruit. The pulp is the main part of the fruit which is consumed. However, the potentials of other longan fruit parts such as the peel and the seed as reservoirs of important bioactive components have not yet fully been explored. This study aimed at exploring the diversity of primary and secondary metabolites in two commercial longan varieties, i.e., Shixia and Chuliang, concerning fruit, pulp, peel, and seed based on a widely targeted metabolomics approach. A total of 706 metabolites were identified grouped into eight diverse classes of metabolites, including flavonoids, amino acids and its derivatives, alkaloids, tannins, phenolic acids, organic acids, nucleotides and derivatives, lipids, and lignans. Chuliang peel showed a higher accumulation of metabolites viz. flavonoids, alkaloids, and tannins, while Shixia seeds showed abundance in amino acids, organic acid, nucleic acids and its derivatives. Chuliang pulp showed relatively higher accumulation of lipids when compared with other fruit parts. Differential metabolome profiling between fruit parts indicates the prevalence of key metabolites, i.e., O-Phosphocholine, betaine, piperidine, L-Arginine, and L-Phenylalanine, in seed and peel of the longan fruit. The findings in this research provide a new glance on the nutritional value and biochemical basis of longan fruit pharmaceutical value, with emphasis on valorization of longan peel and seed tissues for their pharmaceutical properties and nutritional values.

Genomic insights into longan evolution from a chromosome-level genome assembly and population genomics of longan accessions

“…KEGG (Kyoto Encyclopedia of Gene and Genomes) enrichment of expanded and contracted gene families ( P < 0.05 ) showed that the 312 expanded gene families were significantly enriched with “phenylpropanoid biosynthesis”, “phenylalanine metabolism”, “anthocyanin”, “sesquiterpenoid and triterpenoid biosynthesis”, “monoterpenoid biosynthesis” (Figure 3D). Longan is rich in flavonoids and polyphenols, with anti-cancer, anti-oxidant properties in leaf, flower, fruits, and seeds 24, 31, 32, 33 , which are derived primarily through phenylpropanoid pathways. The branches of phenylpropanoid metabolism produce end products such as flavonoids, hydrox-ycinnamic acid esters, hydroxycinnamic acid amides (HCAAs), and the precursors of lignin, lignans, and tannins 34 .…”

“…Longan leaf, flower, fruits, and seeds 9,10 are rich in polyphenols with anti-cancer, anti-oxidant properties, biosynthesized primarily through the shikimic acid, flavonoid and phenylpropanoid pathways. Phenylpropanoid pathway is one of the most extensively investigated specialized metabolic pathways.…”

Free Amino Acids Profile and Expression Analysis of Core Genes Involved in Branched-Chain Amino Acids Metabolism during Fruit Development of Longan (Dimocarpus longan Lour.) Cultivars with Different Aroma Types

“…Khan et al [ 35 ] identified a total of 27 FAAs in dried longan pulp. Based on a widely targeted metabolomics approach, Wang et al [ 6 ] had identified 706 metabolites (including ~98 FAAs and their derivatives) from fruit pulp, peel, and seed in two longan varieties i.e., ‘Shixia’ and ‘Chuliang’. Besides, Huang et al [ 21 ] determined 18 kinds of FAAs in ‘Lidongben’ during the fruit development phase and tree hanging phase (3 stages each), the total content of the 18 FAAs ranged from 7.6 to 9.1 g∙kg −1 , but the selected variety was a non-aromatic genotype.…”

“…is an economically important crop in tropical and subtropical regions of Southeast Asia i.e., China, Thailand, Vietnam, etc. Longan possesses numerous nutritional and functional components, including polysaccharides [ 1 ], amino acids [ 2 , 3 ], polyphenols and alkaloids [ 4 , 5 ], flavonoids, lipids [ 6 ], organic acids, vitamin C, minerals [ 7 , 8 ], and volatile compounds [ 9 ]. Amino acids exist in both bound and free forms in plants.…”

Differential metabolome landscape of Kadsura coccinea fruit tissues and potential valorization of the peel and seed tissues

“…Previous studies emphasized valorization of plant biowaste by utilizing a broad spectrum of bioactive compounds present in plant parts generally considered biowaste. Deng et al (2020) and Wang et al (2020a), in their studies on banana pseudo-stem and longan fruit parts (skin and seed), respectively, demonstrated the potential valorization of biowaste by exploiting the metabolome and identified several compounds with nutraceutical properties. Hence, investigating the metabolome composition of black tiger fruit parts could open a new avenue towards a better valorization of the fruit and the development of the industry.…”