# Aroma Volatiles in Litchi Fruit: A Mini-Review
###### Abstract  
Aroma is considered a fundamental component of fruit flavor. Variations in the composition and content of volatile organic compounds (VOCs) contribute to noticeable differences in fruit aromas. Litchi is a delicious tropical and subtropical fruit, and a large number of germplasm resources with unique aromas have emerged during the past 2000 years of cultivation. In this review, our aim is to collect, compare, integrate, and summarize the available literature on the profiles of VOCs of 25 litchi cultivars. We showed that a total of 556 VOCs were reported from litchi fruit, and the aroma of litchi is mainly determined from the content and composition of monotereponoids and alcohols, including linalool, geraniol, limonene, terpionolene, \(\beta\)-citronello1, \(p\)-cymene, nerol, \(\alpha\)-terpineol, _cis_-rose oxide, \(\beta\)-mycrene, 4-terpineol, citral, and neral (_cis_-citral), which might contribute to the rose-like or citrus-like aroma of litchi fruit. Moreover, sulfur-containing volatile compounds (VSCs) possibly impart a special flavor to litchi fruit. This review would be a valuable resource for researchers aiming to improve litchi aroma quality by elucidating the possible mechanisms underlying VOC biosynthesis and their metabolism in litchi fruit.  
Litchi chinets Sonn.; volatile organic compounds; monotereponoid; alcohols; volatile sulfur compounds +
Footnote †: journal: _Horticulture_  
0000-0002-0002-0000-0000-0000-0000-0000-0000-0000-0000-0000-00000-0000-0000-00000-00000-00000-00000-00000-00000-00000-00000-00000-00000-00000-000000-  
and organic acid accumulation, VOCs could be active even at picomolar to nanomolar concentrations, which is enough to alter the fruit aroma [15]. In recent years, VOCs have gained attention because the aroma is one of the most appreciated fruit characteristics in fruit quality. [PERSON] et al. [16] found that C\({}_{9}\) alcohols and aldehydes produced by the fatty acid oxygenase pathway are important sources of aroma during the growth and development of watermelon. Among them, the four key C\({}_{9}\) aldehyde compounds, including (E,Z)-2,6-nonadienal, _trans_-2-nonenal, 3,6-nonylidene-1-ol, and _cis_-3-nonen-1-ol, contribute to the unique sweet aroma of watermelon. [PERSON] et al. [17] explored apple VOCs and found that the composition of VOCs had huge differences among different apple cultivars. The main VOCs in the \"pink lady\" and \"Fuji\" apples were esters and terpenoids, while in the \"Ruixue\" apple, the main VOCs were aldehydes and terpenoids. After combining with transcriptome analysis, it was found that the difference in the related synthetic genes and transcription factors in the fatty acid, isoleucine, and sesquiterpenoid metabolic pathways among cultivars led to the diversity of VOCs.  
Litchi (_Litchi chinensis_ [PERSON]), a subtropical and tropical fruit, has captured the heart of consumers worldwide due to its unique taste, exotic flavor, appealing fruit color, and high nutritional profile. Litchi is grown in over 20 countries and has a long cultivation history of more than 2000 years [18]. Through the combination of genomics and bioinformatics, [PERSON] et al. [19] found that litchi originated in the Yunnan Province of China. After a thousand years of domestication and evolution, litchi evolved as an important fruit crop. Previously, researchers paid more attention to the color and nutritional value of litchi fruit than the flavor [20; 21]. However, the unique aromas of fruit crops are also one of the core criteria for the quality evaluation of fruit. Here, we integrated and summarized the available reports on the volatile profiles of diverse litchi cultivars. This review would provide some directions for exploring the possible mechanisms underlying the volatile biosynthesis and metabolism of litchi aromas.