Assessment and Classification of Volatile Profiles in Melon Breeding Lines Using Headspace Solid-Phase Microextraction Coupled with Gas Chromatography-Mass Spectrometry.

Cucumis melo L is one of the most commercial and economical crops in the world with several health beneficial compounds as such carotenoids, amino acids, vitamin A and C, minerals, and dietary fiber. Evaluation of the volatile organic compounds (VOCs) in different melon (Cucumis melo L.) breeding lines provides useful information for improving fruit flavor, aroma, and antimicrobial levels. In this study, the VOCs in 28 melon breeding lines harvested in 2019 were identified and characterized using head space solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS). This identified 113 VOCs with significant differences in composition and contents of among the breeding lines, including 15 esters, 27 aldehydes, 35 alcohols, 14 ketones, 4 acids, 10 hydrocarbons, 5 sulfurs, and 3 other compounds. The highest average contents of all the VOCs were found in BL-30 (13,973.07 µg/kg FW) and the lowest were in BL-22 (3947.13 µg/kg FW). BL-9 had high levels of carotenoid-derived VOCs. The compounds with the highest contents were benzaldehyde, geranylacetone, and ß-ionone. Quality parameters such as color and sugar contents of melons were also measured. All the melon color readings were within the typical acceptable range. BL-22 and BL-14 had the highest and lowest sugar contents, respectively. Principal component analysis (PCA) produced diverse clusters of breeding lines based on flavor and aroma. BL-4, BL-7, BL-12, BL-20, and BL-30 were thus selected as important breeding lines based on their organoleptic, antimicrobial, and health-beneficial properties.

Transition of aromatic volatile and transcriptome profiles during melon fruit ripening.

Melon (Cucumis melo L.) is an important diploid crop with a wide variety of flavors due to its distinct aromatic volatile organic compounds (VOC). To understand the development of VOC profiles during fruit development, we performed metabolomic and transcriptomic analysis of two cantaloupe varieties over the course of fruit development. A total of 130 metabolites were detected in fruit samples, and 449014207 reads were mapped to the melon genome. A total of 4469 differentially expressed genes in fruits were identified and used to visualize the transition of VOC and transcriptomic profiles during the fruit development. A shift of VOC profiles in both varieties was observed from early-fruit profiles enriched in C5-C8 lipid-derived VOCs to late-fruit profiles abundant in C9 lipid-derived VOCs, apocarotenoids, and esters. The shift coincided with the expression of specific isoforms of lipid and carotenoid metabolizing enzymes as well as transcription factors involved in fruit ripening, metabolite regulation, and hormone signaling.

Multivariate Analysis of Amino Acids and Health Beneficial Properties of Cantaloupe Varieties Grown in Six Locations in the United States.

Cantaloupe is a good dietary source of amino acids, including γ-aminobutyric acid (GABA), glutamine, and citrulline. However, the levels of these amino acids vary among different cantaloupe varieties grown in different locations. Understanding the variation in amino acid contents provides fundamentally important information for quality control and improving melon varieties. To examine this variation, we measured the amino acid contents in cantaloupes grown in six locations in the United States (Texas, Georgia, North Carolina, California, Indiana, and Arizona). Principal component analyses were applied to analyze the effect of growing location on the amino acid profiles in different varieties. The GABA content ranged from 1006.14 ± 64.77 to 3187.12 ± 64.96 µg/g and citrulline ranged from 92.65 ± 9.52 to 464.75 ± 34.97 µg/g depending on the variety and location. Total phenolic contents, α-amylase inhibition, and antioxidant activities were also measured. Tuscan type Da Vinci had significantly higher phenolic contents in Arizona (381.99 ± 16.21 µg/g) but had the lowest level when grown in California (224.56 ± 14.62 µg/g). Our analyses showed significant differences in amino acid levels, phenolics contents, and antioxidant activity in the cantaloupe varieties based on the growing location. These findings underline the importance of considering growing location in the selection and improvement of cantaloupe varieties.

Comparative Metabolomics Profiling of Polyphenols, Nutrients and Antioxidant Activities of Two Red Onion (Allium cepa L.) Cultivars.

Onion is among the most widely cultivated and consumed economic crops. Onions are an excellent dietary source of polyphenols and nutrients. However, onions phytonutrient compositions vary with cultivars and growing locations. Therefore, the present study involved the evaluation of polyphenol, nutritional composition (proteins, nitrogen, and minerals), sugars, pyruvate, antioxidant, and α-amylase inhibition activities of red onion cultivars, sweet Italian, and honeysuckle grown in California and Texas, respectively. The total flavonoid for honeysuckle and sweet Italian was 449 and 345 µg/g FW, respectively. The total anthocyanin for honeysuckle onion was 103 µg/g FW, while for sweet Italian onion was 86 µg/g FW. Cyanidin-3-(6"-malonoylglucoside) and cyanidin-3-(6"-malonoyl-laminaribioside) were the major components in both the cultivars. The pungency of red onions in honeysuckle ranged between 4.9 and 7.9 µmoL/mL, whereas in sweet Italian onion ranged from 8.3 to 10 µmoL/mL. The principal component analysis was applied to determine the most important variables that separate the cultivars of red onion. Overall results indicated that total flavonoids, total phenolic content, total anthocyanins, protein, and calories for honeysuckle onions were higher than the sweet Italian onions. These results could provide information about high quality and adding value to functional food due to the phytochemicals and nutritional composition of red onions.

Review on Bile Acids: Effects of the Gut Microbiome, Interactions with Dietary Fiber, and Alterations in the Bioaccessibility of Bioactive Compounds.

Bile acids are cholesterol-derived steroid molecules that serve various metabolic functions, particularly in the digestion of lipids. Gut microbes produce unconjugated and secondary bile acids through deconjugation and dehydroxylation reactions, respectively. Alterations in the gut microbiota have profound effects on bile acid metabolism, which can result in the development of gastrointestinal and metabolic diseases. Emerging research shows that diets rich in dietary fiber have substantial effects on the microbiota and human health. Plant-based foods are primary sources of bioactive compounds and dietary fiber, which are metabolized by microbes to produce different metabolites. However, the bioaccessibility of these compounds are not well-defined. In this review, we discuss the interaction of bile acids with dietary fiber, the gut microbiota, and their role in the bioaccessibility of bioactive compounds. To understand the possible mechanism by which bile acids bind fiber, molecular docking was performed between different dietary fiber and bile salts.

Optimized method for the quantification of pyruvic acid in onions by microplate reader and confirmation by high resolution mass spectra.

The present study describes the rapid microplate method to determine pyruvic acid content in different varieties of onions. Onion juice was treated with 2,4-dinitrophenylhydrazine to obtain hydrazone, which was further treated with potassium hydroxide to get stable colored complex. The stability of potassium complex was enhanced up to two hours and the structures of hydrazones were confirmed by LC-MS for the first time. The developed method was optimized by testing different bases, acids with varying concentrations of dinitrophenyl hydrazine to get stable color and results were comparable to developed method. Repeatability and precision showed <9% relative standard deviation. Moreover, sweet onion juice was stored for four weeks at different temperatures for the stability; the pyruvate remained stable at all temperatures except at 25°C. Thus, the developed method has good potential to determine of pungency in large number of onions in a short time using minimal amount of reagents.