Citrullus lanatus as source of bioactive components: An up-to-date review

Watermelon Derived Urease Immobilized Gold Nanoparticles-Graphene Oxide Transducer for Direct Detection of Urea in Milk Samples

Urea contamination in milk poses significant health risks, including kidney failure, urinary tract obstruction, fluid loss, shock, and gastrointestinal bleeding. This highlights the need for sensitive, rapid, and reliable methods to detect traces amount of urea in milk. In this study, we designed an electrochemical transducer for urea detection by utilizing purified watermelon urease (Urs), gold nanoparticles (AuNPs), and graphene oxide (GO). The nanomaterials and biosensor probe were characterized using UV-vis spectroscopy, XPS, TEM, XRD, FTIR, AFM, CV, EIS, and DPV. The engineered probe (GCE/AuNPs/GO/Urs) demonstrated a broad linear detection range of 5 to 90 mg/dL and a low limit of detection (LOD) of 0.037 (±0.012) mg/dL (RSD < 3.7%). The biosensor was tested for potential interferents that may be present in adulterated milk and an exceptionally low coefficient of selectivity (ksel <0.1) was obtained. Evaluation of milk samples from a local dairy farm showed good recovery rates from 93.13% to. 98.79% (RSD < 4.28%, n = 3), indicating reliable detection capabilities. Stability tests confirmed the sensor's reproducibility and consistent performance. Additionally, a comparison study of the system was carried out using the purified watermelon urease and the commercially available urease. Herein, the results obtained using the sensor probe was finally validated with the gold standard method.

Watermelon Rind Dietary Fibers as Natural Source to Enhance Texture of Wheat Bread

The objective of this study was to explore how watermelon rinds (WMRs) and their derivatives, specifically water-soluble polysaccharides (WMRPs) and hemicellulose (WMRH), as sources of dietary fiber, could enhance the quality of wheat bread. The extraction process yielded 34.4% for WMRP and 8.22% for WMRH. WMR, WMRP, and WMRH exhibited promising functional characteristics and were incorporated separately into wheat flour with low bread-making quality (FLBM) at varying proportions (0.5%, 1%, and 1.5% (w/w)). The volume, texture, and crust and crumb color underwent evaluation and were compared to the control. The findings indicated that incorporating WMR notably enhanced the alveograph profile of the dough, demonstrating a more effective impact than the addition of WMRP and WMRH. Adding WMR, WMRP, and WMRH at a 1% concentration to low-quality wheat flour for bread making increased the deformation work values by 16%, 15%, and 13%, respectively, and raised the P/L ratios by 42%, 36%, and 38%, respectively. Additionally, the assessment of the bread highlighted a substantial enhancement in both volume and texture profile when WMR was added, in contrast to the control bread (made with FLBM). These findings underscore that incorporating 1% WMR into FLBM was the most effective means of improving bread quality based on the results of this study.

Comparative transcriptome analysis of resistant and susceptible watermelon genotypes reveals the role of RNAi, callose, proteinase, and cell wall in squash vein yellowing virus resistance

Watermelon (Citrullus lanatus) is the third largest fruit crop in the world in term of production. However, it is susceptible to several viruses. Watermelon vine decline (WVD), caused by whitefly-transmitted squash vein yellowing virus (SqVYV), is a disease that has caused over $60 million in losses in the US and continues to occur regularly in southeastern states. Understanding the molecular mechanisms underlying resistance to SqVYV is important for effective disease management. A time-course transcriptomic analysis was conducted on resistant (392291-VDR) and susceptible (Crimson Sweet) watermelon genotypes inoculated with SqVYV. Significantly higher levels of SqVYV were observed over time in the susceptible compared to the resistant genotype. The plasmodesmata callose binding protein (PDCB) gene, which is responsible for increased callose deposition in the plasmodesmata, was more highly expressed in the resistant genotype than in the susceptible genotype before and after inoculation, suggesting the inhibition of cell-to-cell movement of SqVYV. The potential role of the RNA interference (RNAi) pathway was observed in the resistant genotype based on differential expression of eukaryotic initiation factor (eIF), translin, DICER, ribosome inactivating proteins, RNA-dependent RNA polymerase (RDR), and Argonaute (AGO) genes after inoculation. The significant differential expression of hormone-related genes, including those involved in the ethylene, jasmonic acid, auxin, cytokinin, gibberellin, and salicylic acid signaling pathways, was observed, emphasizing their regulatory roles in the defense response. Genes regulating pectin metabolism, cellulose synthesis, cell growth and development, xenobiotic metabolism, and lignin biosynthesis were overexpressed in the susceptible genotype, suggesting that alterations in cell wall integrity and growth processes result in disease symptom development. These findings will be helpful for further functional studies and the development of SqVYV-resistant watermelon cultivars.

Phytogenic-Mediated Zinc Oxide Nanoparticles Using the Seed Extract of Citrullus lanatus and Its Integrated Potency against Multidrug Resistant Bacteria

In the current research study, zinc oxide nanoparticles (ZnO-NPs) were synthesized via a green synthesis technique using the seed extract of Citrullus lanatus. The study further intended to evaluate the potential synergistic effects of ZnO-NPs with antibiotics against multidrug resistant (MDR) bacteria. It was observed that C. lanatus seed extracts obtained by n-hexane and methanolic solvents revealed the presence of constituents, such as tannins, flavonoids, and terpenoids. Furthermore, the extract of n-hexane displayed the strongest antibacterial activity against Yersinia species (17 ± 1.2 mm) and Escherichia coli (17 ± 2.6 mm), while the methanolic extract showed the maximum antibacterial activity against E. coli (17 ± 0.8 mm). Additionally, the ZnO-NP synthesis was confirmed by ultraviolet-visible analysis with a characteristic absorption peak at 280 nm. The Fourier transform infrared spectroscopy analysis suggested the absorption peaks in the 500-3800 cm-1 range, which corresponds to various groups of tertiary alcohol, aldehyde, amine, ester, aromatic compounds, thiol, amine salt, and primary amine. The scanning electron microscopy spectra of ZnO-NPs demonstrated the presence of zero-dimensional spherical particles with well-dispersed character. Moreover, encapsulation with ZnO-NPs improved the antimicrobial activity of antibiotics against the panel of MDR bacteria, and the increases in the effectiveness of particular antibiotics against MDR bacteria were significant (P = 0.0005). In essence, the synthesized ZnO-NPs have the potential as drug carriers with powerful bactericidal properties that work against MDR bacterial strains. These outcomes are an indication of such significance in pharmaceutical science, giving possibilities for further research and development in this field.

Impact of sulfite use and acidification on chemical quality components in thermally processed watermelon juices

The present study compared pasteurized and reconstituted (from vacuum-concentrated) watermelon juices with sulfite use (∼40 mg/L) and acidification (pH = 4.2) to fresh watermelon juices. The products were evaluated for phenolics, free amino acids, carotenoids, sugars, organic acids, and alcohols by high-performance liquid chromatography-HPLC and the volatile profile by headspace-gas chromatography/mass spectrometry(HS-GC/MS). Pasteurization had no significant impact on most of the chemical components. Furthermore, it potentiated typical watermelon aromas (E,E)-2,6-nonadienal, (Z)-3-nonen-1-ol, 4-hexen-1-ol, (E,Z)-3,6-nonadien-1-ol, 6-amino-2-methyl-2-heptanol, (E)-6-nonenal, (E)-2-nonenal, pentanal, nonanal and 1-nonanol), without off-flavor compounds formation. On the other hand, the reconstituted juice showed reduced amino acids (serine, glutamine, and tryptophan), phenolics (epicatechin gallate, myricetin, and cis-resveratrol), carotenoids (lycopene, β-carotene, and violaxanthin) and most volatile compounds. Our results showed that sulfite and acidification could maintain watermelon juice's nutritional and quality parameters after pasteurization. The vacuum concentration and reconstitution processes negatively impacted the evaluated compounds. Our findings contribute to improving thermal processes in watermelon juices for better preservation of nutrients, flavor, and bioactive compounds.

Genome-wide association study of soluble solids content, flesh color, and fruit shape in citron watermelon

Fruit quality traits are crucial determinants of consumers' willingness to purchase watermelon produce, making them major goals for breeding programs. There is limited information on the genetic underpinnings of fruit quality traits in watermelon. A total of 125 citron watermelon (Citrullus amarus) accessions were genotyped using single nucleotide polymorphisms (SNPs) molecular markers generated via whole-genome resequencing. A total of 2,126,759 genome-wide SNP markers were used to uncover marker-trait associations using single and multi-locus GWAS models. High broad-sense heritability for fruit quality traits was detected. Correlation analysis among traits revealed positive relationships, with the exception of fruit diameter and fruit shape index (ratio of fruit length to fruit diameter), which was negative. A total of 37 significant SNP markers associated with soluble solids content, flesh color, fruit length, fruit diameter, and fruit shape index traits were uncovered. These peak SNPs accounted for 2.1%-23.4% of the phenotypic variation explained showing the quantitative inheritance nature of the evaluated traits. Candidate genes relevant to fruit quality traits were uncovered on chromosomes Ca01, Ca03, Ca06, and Ca07. These significant molecular markers and candidate genes will be useful in marker-assisted breeding of fruit quality traits in watermelon.

Watermelon (Citrullus lanatus) rind flour: Development and characterization of a novel watermelon byproduct

Watermelon (Citrullus lanatus) is a fruit widely consumed by the Brazilian population; however, its rind is usually discarded, despite its nutritional value. This work aimed to develop a watermelon rind flour (WRF) and a fiber-rich bread. The WRF was submitted to microbiological analysis, proximate composition, antioxidant activity, and a profile of phenolic compounds. Six types of bread were developed: three using WRF (20%, 30%, and 40% of wheat flour replacement) and three control samples (only wheat flour), which were submitted to the same analysis, in addition to colorimetric properties, instrumental texture profile, and sensory evaluation (check-all-that-apply, purchase intent, and acceptance test). A high fiber content was observed in WRF (27.15%). The total concentration of phenolic compounds was 2.38 ± 0.20 mg of gallic acid equivalent per g and benzoic acid was the main compound found (73.50 mg/100 g WRF). The results of the antioxidant capacity through the DPPH method indicated a 30% reduction. The WRF 40% bread had 3.06 g of insoluble fiber, characterizing itself as a source of fiber. In the instrumental texture analysis, it was observed that bread hardness increased significantly as the WRF content increased. The formulation of the bread containing WRF is an alternative for the use of waste, favoring the development of a fiber-source product, with a functional food claim.

From Fruit Waste to Medical Insight: The Comprehensive Role of Watermelon Rind Extract on Renal Adenocarcinoma Cellular and Transcriptomic Dynamics

Cancer researchers are fascinated by the chemistry of diverse natural products that show exciting potential as anticancer agents. In this study, we aimed to investigate the anticancer properties of watermelon rind extract (WRE) by examining its effects on cell proliferation, apoptosis, senescence, and global gene expression in human renal cell adenocarcinoma cells (HRAC-769-P) in vitro. Our metabolome data analysis of WRE exhibited untargeted phyto-constituents and targeted citrulline (22.29 µg/mg). HRAC-769-P cells were cultured in RPMI-1640 media and treated with 22.4, 44.8, 67.2, 88.6, 112, 134.4, and 156.8 mg·mL-1 for 24, 48, and 72 h. At 24 h after treatment, (88.6 mg·mL-1 of WRE) cell proliferation significantly reduced, more than 34% compared with the control. Cell viability decreased 48 and 72 h after treatment to 45% and 37%, respectively. We also examined poly caspase, SA-beta-galactosidase (SA-beta-gal), and wound healing activities using WRE. All treatments induced an early poly caspase response and a significant reduction in cell migration. Further, we analyzed the transcript profile of the cells grown at 44.8 mg·mL-1 of WRE after 6 h using RNA sequencing (RNAseq) analysis. We identified 186 differentially expressed genes (DEGs), including 149 upregulated genes and 37 downregulated genes, in cells treated with WRE compared with the control. The differentially expressed genes were associated with NF-Kappa B signaling and TNF pathways. Crucial apoptosis-related genes such as BMF, NPTX1, NFKBIA, NFKBIE, and NFKBID might induce intrinsic and extrinsic apoptosis. Another possible mechanism is a high quantity of citrulline may lead to induction of apoptosis by the production of increased nitric oxide. Hence, our study suggests the potential anticancer properties of WRE and provides insights into its effects on cellular processes and gene expression in HRAC-769-P cells.

Genetic control of flowering time and fruit yield in citron watermelon

Flowering time and fruit yield are important traits in watermelon crop improvement. There is limited information on the inheritance and genomic loci underlying flowering time and yield performance, especially in citron watermelon. A total of 125 citron watermelon accessions were evaluated in field trials over two growing seasons for days to male and female flowers, fruit count, fruit weight, and fruit yield. The germplasm was genotyped with more than two million single-nucleotide polymorphism (SNP) markers generated via whole-genome resequencing. Trait mapping was conducted using a genome-wide association study (GWAS). Broad-sense heritability for all traits ranged from moderate to high, indicating that genetic improvement through breeding and selection is feasible. Significant marker-trait associations were uncovered for days to female flower (chromosomes Ca04, Ca05, Ca08, and Ca09), fruit count (on Ca02, Ca03, and Ca05), fruit weight (on Ca02, Ca06, Ca08, Ca10, and Ca11), and fruit yield on chromosomes Ca05, Ca07, and Ca09. The phenotypic variation explained by the significant SNPs ranged from 1.6 to 25.4, highlighting the complex genetic architecture of the evaluated traits. Candidate genes relevant to flowering time and fruit yield component traits were uncovered on chromosomes Ca02, Ca04, Ca05, Ca06, Ca09, and Ca11. These results lay a foundation for marker-assisted trait introgression of flowering time and fruit yield component traits in watermelons.

Evaluation of physicochemical, antioxidant, antibacterial activity, and sensory properties of watermelon rind candy

Watermelon (Citrullus lanatus) is consumed all over the world that contains a large number of seeds and rind, which is discarded. These by-products contain phytochemical compounds with great nutritional potential. This study aims to evaluate physicochemical properties and sensory values of watermelon rind candy. In this study in order to make the waste of watermelon a more sustainable and value-added food product, the watermelon rind was dried using an osmotic dehydration technique which comprises gradual impregnation of syrup (50 and 70% w/w - 1 to 5 h) before drying at 40 and 60 °C in 8 and 10 h. Various variables such as moisture content, chemical composition, water loss, solid gain, rehydration water, acidity, pH, antioxidant activity, antibacterial activity, residual toxins, phenolic and flavonoid contents during osmotic dehydration of watermelon were investigated. Results showed by rising temperatures, dehydration becomes more severe. Increasing the temperature in both osmotic samples in a concentrated solution (70%) and in osmotic samples with a dilute solution (50%) can enhance the mass transfer, water loss, solid absorption, as well as dehydration intensity. However, antioxidant activity, phenolic and flavonoid content significantly decreased after osmotic dehydration. TPC decreased from 35.83 mg/100 g to 27.45 mg/100 g and TFC of the watermelon rind (8.71 ± 0.01 mg/100 g) decreased to 2.63 ± 0.02 mg/100 g and also antioxidant activity after the osmotic process decreased from 61% to 40%. Also, osmotic dehydration had no significant impact on acidity and pH. The watermelon rind dehydrated sample (osmosis temperature: 40 °C, osmotic solution concentration: 70%, immersion duration: 5 h) was the best choice of panelists due to the highest score in the sensory evaluation including taste, texture, and overall acceptability. By determining the hardness of the watermelon rind candy and comparing it with the results of texture analysis of other dried products, it can be concluded that this product can be used as a healthy snack with longer shelf life properties.

Antioxidant and Anti-Inflammatory Compounds from Edible Plants with Anti-Cancer Activity and Their Potential Use as Drugs

Food is our daily companion, performing numerous beneficial functions for our bodies. Many of them can help to alleviate or prevent ailments and diseases. In this review, an extensive bibliographic search is conducted in various databases to update information on unprocessed foods with anti-inflammatory and antioxidant properties that can aid in treating diseases such as cancer. The current state of knowledge on inflammatory processes involving some interleukins and tumor necrosis factor-alpha (TNF-α) is reviewed. As well as unprocessed foods, which may help reduce inflammation and oxidative stress, both of which are important factors in cancer development. Many studies are still needed to take full advantage of the food products we use daily.

Bioactive Compounds from Fruits as Preservatives

The use of additives with preservative effects is a common practice in the food industry. Although their use is regulated, natural alternatives have gained more attention among researchers and professionals in the food industry in order to supply processed foods with a clean label. Fruits are essential components in a healthy diet and have also been associated with improved health status and a lower risk of developing diseases. This review aims to provide an overview of the main bioactive compounds (polyphenols, betalain, and terpenes) naturally found in fruits, their antioxidant and antimicrobial activity in vitro, and their preservative effect in different foods. Many extracts obtained from the skin (apple, grape, jabuticaba, orange, and pomegranate, for instance), pulp (such as red pitaya), and seeds (guarana, grape, and jabuticaba) of fruits are of great value due to the presence of multiple compounds (punicalagin, catechin, gallic acid, limonene, β-pinene, or γ-terpinene, for instance). In terms of antioxidant activity, some fruits that stand out are date, jabuticaba, grape, and olive, which interact with different radicals and show different mechanisms of action in vitro. Antimicrobial activity is observed for natural extracts and essential oils (especially from citrus fruits) that limit the growth of many microorganisms (Bacillus subtilis, Escherichia coli, Penicillium digitatum, and Pseodomonas aeruginosa, for instance). Studies in foods have revealed that the use of extracts or essential oils as free or encapsulated forms or incorporated into films and coatings can inhibit microbial growth, slow oxidative reactions, reduce the accumulation of degradative products, and also preserve sensory attributes, especially with films and coatings. Future studies could focus on the advances of extracts and essential oils to align their use with the development of healthier foods (especially for meat products) and explore the inhibition of spoilage microorganisms in dairy products, for instance.

Phenolic Glycosides Citrulluside H and Citrulluside T Isolated From Young Watermelon (Citrullus lanatus) Fruit Have Beneficial Effects Against Cutibacterium acnes-Induced Skin Inflammation

Acne vulgaris, typically caused by Cutibacterium acnes ( C. acnes) involves chronic inflammation of the sebaceous follicles and is the most common skin disease, afflicting 85% of adolescents. We previously isolated 2 novel phenolic glycosides, 2-caffeoyl-3-hydroxy-3-methylbutyric 4′-β-D-glucopyranosyloxy-3′-hydroxybenzyl ester (citrulluside H [CH]) and 2-caffeoyl-3-hydroxy-3-methylbutyric 4′-β-d-glucopyranosyloxybenzyl ester (citrulluside T [CT]), from young fruits of watermelon ( Citrullus lanatus). Both compounds suppressed UVB-induced photoaging in human fibroblasts by scavenging intracellular reactive oxygen species (ROS) and thus might be useful as natural skin care ingredients. In this study, we examined the inhibitory effects of these phenolic glycosides on C. acnes growth and C.acnes-induced inflammation. Neither phenolic glycoside inhibited the growth of C. acnes. However, they both significantly suppressed toll-like receptor (TLR) 1/2 or TLR2/6/nuclear factor κB (NF-κB) signaling in heat-killed C. acnes (hk- C. acnes) -stimulated RAW264.7 cells. Additionally, both phenolic glycosides decreased the expression of M1 macrophage biomarkers (cluster of differentiation [ CD] 80, CD86, and inducible NO synthase [ iNOS]), suggesting that they attenuate M1 macrophage activation. These results indicated that both CH and CT are potential therapeutic substances against C. acnes-induced skin inflammation.

VOCs Analysis of Three Different Cultivars of Watermelon (Citrullus lanatus L.) Whole Dietary Fiber

In this study, the trend of VOCs of dietary fiber samples, coming from three different watermelon cultivars Citrullus lanatus L. (variety Gavina^®®, Crimson Sweet, and Asahi Miyako) was investigated. This foodstuff, obtained as a by-product of residual agri-food production, has gained increasing attention because of its many bioactive components and high dietary fiber content. The result is a fibrous material for specific applications in food manufacturing, such as corrector for some functional and technological properties. In this study, a method based on headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS) was used to characterize the aromatic profiles of the dried raw materials. Therefore, the VOCs of the samples of the three cultivars were investigated. Experimental results have shown that watermelon fibers generate VOCs, which can be grouped into six common classes of analytes. The different distributions of the identified compounds made it possible to effectively differentiate the three cultivars studied based on their peculiar aroma profiles. In particular, Gavina^®® fiber is distinguished by the high content of terpenes, Asahi Miyako by the presence of aldehydes generated as fatty acid metabolites, and Crimson Sweet by the higher content of acetyl esters.

Antispasmodic activity of the ethanol extract of Citrullus lanatus seeds: Justifying ethnomedicinal use in Pakistan to treat asthma and diarrhea

ETHNOPHARMACOLOGICAL RELEVANCE

Citrullus lanatus (Thunb.) belongs to the ground family, Cucurbitaceae, known for edible fruit. Besides nutritional benefits, the traditional herbal practitioners in Pakistan and India used their seeds to treat gastrointestinal, respiratory, and urinary disorders. In Northern Sudan, its seeds are often used as a laxative. Its root is laxative and emetic at a high dose. Its seeds are also used to treat bedwetting and urinary tract obstruction.

AIM OF THE STUDY

This study aimed to elucidate the multi-target mechanisms of Citrullus lanatus seeds to treat asthma and diarrhea. The pharmacological experiments were designed and conducted, along with the pharmacology network and molecular docking predictions, to verify the seeds biopotency for antispasmodic and bronchodilator properties.

METHODS

LC ESI-MS/MS were performed to identify the potentially active compounds in hydroethanolic extract of Citrullus lanatus seeds, then to quantify them by HPLC. The quantified bioactive compounds of Citrullus lanatus, i.e., stigmasterol, quinic acid, malic acid, epicatechin, caffeic acid, rutin, p-coumaric acid, quercetin, ferulic acid, scopoletin, apigenin, and kaempferol were subjected to in silico studies for molecular docking. The hydroethanolic extract of Citrullus lanatus seeds was examined on isolated rabbit tissue, i.e., jejunum, trachea, and urinary bladder. The antiperistalsis, antidiarrheal and antisecretory studies were also performed in animal models.

RESULTS

In silico studies revealed that bioactive compounds of C. lanatus seeds interfere with asthma and diarrhea-associated target genes, which are a member of calcium mediate signaling, regulation of cytosolic calcium concentration, smooth muscle contraction, and inflammatory responses. It was also found that rutin, quercetin, kaempferol, and scopoletin were stronger binding to voltage-gated calcium channels, calcium/calmodulin-dependent protein kinase, myosin light chain kinase, and phosphoinositide phospholipase C, thus, exerting calcium channel blocker activity. The hydroethanolic extract of C. lanatus seeds exerted a concentration-dependent relaxant response for the spasmolytic response on isolated jejunum and trachea preparations and caused relaxation of spastic contraction of K⁺ (80 mM). Furthermore, it caused a non-parallel rightward shift with suppression of calcium concentration-response curves. In animal models, the Cl.EtOH showed antiperistalsis, antidiarrheal and antisecretory response.

CONCLUSION

Thus, we confirm Citrullus lanatus seeds have some medicinal effects by regulating the contractile response through target proteins of calcium mediates signaling and can be a promising component in the medical treatment for asthma and diarrhea.

Selected Species of the Cucurbitaceae Family Used in Mexico for the Treatment of Diabetes Mellitus

In Mexico, Diabetes mellitus (DM) is a serious health problem, and although the current pharmacological treatments for DM such as insulin and oral hypoglycemics are available, the Mexican population continues to use medicinal plants in the treatment of DM. The antidiabetic properties of the plant species that belong to the Cucurbitaceae family has already been recognized worldwide. Since Mexico is one of the most important centers of diversity of Cucurbitaceae, the present work contributes to the review of the most used species of Cucurbitaceae in the treatment of DM in Mexico. The reviewed species (Cucurbita ficifolia, C. maxima, C. moschata, C. pepo, Ibervillea sonorae, Sechium edule, Citrullus lanatus, Cucumis melo, and C. sativus) revealed that the antidiabetic effects exerted are effective in a number of mechanisms involved in the complex pathogenesis of DM: hypoglycemic, antioxidant, anti-inflammatory, anti-obesity, protective effects on diverse organs and cells, as well as in the control of dyslipidemias; furthermore, the select species of the Cucurbitaceae family could also be essential components of diets for the control of DM in patients with the disease. Thus, the Cucurbitaceae species selected in the present work represent a source of antidiabetic agents that perhaps establish the bases for novel clinical treatments.

Free Amino Acids and Volatile Aroma Compounds in Watermelon Rind, Flesh, and Three Rind-Flesh Juices

Watermelon rind is treated as agricultural waste, causing biomass loss and environmental issues. This study aimed to identify free amino acids and volatiles in watermelon rind, flesh, and rind-flesh juice blends with ratios of 10%, 20%, and 30%. Among the 16 free amino acids quantified, watermelon rind alone contained higher total amino acids (165 mg/100 g fresh weight) compared to flesh alone (146 mg/100 g). The rind had significantly higher (1.5×) and dominant amounts of citrulline and arginine (61.4 and 53.8 mg/100 g, respectively) than flesh. The rind, however, contained significantly lower amounts of essential amino acids. Volatile analysis showed that watermelon rind total volatiles (peak area) comprised only 15% of the flesh volatiles. Of the 126 volatiles identified, the rind alone contained 77 compounds; 56 of these presented in all five samples. Aldehydes and alcohols were most prevalent, accounting for >80% of the total volatiles in all samples. Nine-carbon aldehyde and alcohol compounds dominated both the flesh and rind, though the rind lacked the diversity of other aldehydes, alcohols, ketones, terpenes, terpenoids, esters and lactones that were more abundant in the watermelon flesh. Watermelon rind was characterized by the major aroma compounds above their thresholds, including 17 aldehydes and six unsaturated nine-carbon alcohols. This study demonstrated the potential for rind as a food or beverage supplement due to its key features such as concentrated citrulline and arginine, relatively low odor intensity, and valuable volatiles associated with fresh, green, cucumber-like aromas.

In Vitro Cytotoxic Activity and Phytochemical Characterization (UPLC/T-TOF-MS/MS) of the Watermelon (Citrullus lanatus) Rind Extract

Reusing food waste is becoming popular in pharmaceutical industries. Watermelon (Citrullus lanatus) rind is commonly discarded as a major solid waste. Here, the in vitro cytotoxic potential of watermelon rind extracts was screened against a panel of human cancer cell lines. Cell cycle analysis was used to determine the induction of cell death, whereas annexin V-FITC binding, caspase-3, BAX, and BCL-2 mRNA expression levels were used to determine the degree of apoptosis. VEGF-promoting angiogenesis and cell migration were also evaluated. Moreover, the identification of phytoconstituents in the rind extract was achieved using UPLC/T-TOF-MS/MS, and a total of 45 bioactive compounds were detected, including phenolic acids, flavonoids aglycones, and their glycoside derivatives. The tested watermelon rind extracts suppressed cell proliferation in seven cancer cell lines in a concentration-dependent manner. The cytotoxicity of the rind aqueous extract (RAE) was higher compared with that of the other extracts. In addition to a substantial inhibitory effect on cell migration, the RAE triggered apoptosis in HCT116 and Hep2 cells by driving the accumulation of cells in the S phase and elevating the activity of caspase-3 and the BAX/BCL-2 ratio. Thus, a complete phytochemical and cytotoxic investigation of the Citrullus lanatus rind extract may identify its potential potency as an anticancer agent.

Genetic Analysis of Fruit Quality Traits in Sweet Watermelon (Citrullus lanatus var. lanatus): A Review

Fruit quality traits of sweet watermelon (Citrullus lanatus var. lanatus) are crucial for new product development and commercialization. Sweet watermelon fruit quality traits are affected by the compositions of phytochemical compounds, phytohormones, and fruit flesh firmness which are affected by genes, the growing environment and their interaction. These compositions determine fruit ripening, eating quality, and postharvest shelf-life. Knowledge of the genetic profile and analyses of quality traits in watermelon is vital to develop improved cultivars with enhanced nutritional compositions, consumer-preferred traits, and extended storage life. This review aims to present the opportunities and progress made on the genetic analysis of fruit quality traits in watermelon as a guide for quality breeding based on economic and end-user attributes. The first section of the review highlights the genetic mechanisms involved in the biosynthesis of phytochemical compounds (i.e., sugars, carotenoids, amino acids, organic acids, and volatile compounds), phytohormones (i.e., ethylene and abscisic acid) and fruit flesh structural components (i.e., cellulose, hemicellulose, and pectin) elicited during watermelon fruit development and ripening. The second section pinpoints the progress on the development of molecular markers and quantitative trait loci (QTL) analysis for phytochemical compounds, phytohormones and fruit quality attributes. The review presents gene-editing technology and innovations associated with fruit quality traits for selection and accelerated cultivar development. Finally, the paper discussed gene actions conditioning fruit ripening in citron watermelon (C. lanatus var. citroides [L. H. Bailey] Mansf. ex Greb.) as reference genetic resources to guide current and future breeding. Information presented in this review is useful for watermelon variety design, product profiling and development to serve the diverse value chains of the crop.

Integrative analysis of transcriptomic and metabolomic profiles reveals new insights into the molecular foundation of fruit quality formation in Citrullus lanatus (Thunb.) Matsum. & Nakai

In this study, an integrated transcriptome and metabolome analysis was used to explore the molecular foundation of fruit quality in two parent lines of Citrullus lanatus with distinct flesh characteristics, including ‘14-1’ (sweet, red, and soft) and ‘W600’ (bitter, light yellow, and firm), as well as the corresponding F1 population (bitter, light yellow, and firm). Numerous differentially expressed genes (DEGs) were identified in the fruit samples: 3,766 DEGs for ‘14-1’ vs. ‘W600’, 2,767 for ‘14-1’ vs. F1, and 1,178 for F1 vs. ‘W600’ at the transition stage; and 4,221 for ‘14-1’ vs. ‘W600’, 2,447 for ‘14-1’ vs. F1, and 446 for F1 vs. ‘W600’ at the maturity stage. Weighted gene co-expression network analysis (WGCNA) revealed that a gene module including 1,111 DEGs was closely associated with flesh taste and color, and another gene module including 1,575 DEGs contributed significantly to flesh texture. The metabolomic results showed that there were 447 differential metabolites (DMs) for ‘14-1’ vs. ‘W600’ fruits, 394 for ‘14-1’ vs. F1, and 298 for F1 vs. ‘W600’ at the maturity stage. Combining WGNCA and metabolomic results, several DEGs and DMs were further identified as hub players in fruit quality formation: six DEGs with four DMs for flesh sweetness; six DEGs with 13 DMs for bitterness; nine DEGs with 10 DMs for flesh color; and nine DEGs with four DMs for flesh texture. Altogether, these observations not only expand our knowledge of the molecular basis of fruit quality in watermelon, but also provide potential targets for future watermelon improvement.

Kinetics of acid blue 40 dye degradation under solar light in the presence of CuO nanoparticles synthesized using Citrullus lanatus seeds extract

In view of eco-benign nature of green synthesis, in the present investigation, the CuO NPs are prepared using Citrullus lanatus seeds extract and photocatalytic degradation efficiency for Acid Blue 40 (AB-40) was evaluated. The CuO NPs were characterized by XRD (X-ray diffraction), SEM (scanning electron microscopy), EDX (energy dispersive X-ray), and FT-IR (Fourier transform infrared) techniques. The synthesized CuO NPs was in face centered monoclinic crystalline form with particle size in 40–60 nm range. The photocatalytic degradation potential of CuO NPs was assessed for acid blue 40 (AB-40) dye degradation and catalyst dose, concentration of dye, radiation exposure time and pH are considered for dye removal. The CuO NPs exhibited auspicious efficiency, an 84.89% dye removal was attained at optimal conditions and dye degradation followed BMG (Behnajady–Modirshahla–Ghanbery) kinetics model. Results revealed CuO NPs synthesized using C. lanatus seeds extract is photoactive catalyst and green route can be employed for CuO NPs fabrication for photocatalytic applications.

Soybean Oil Enriched with Antioxidants Extracted from Watermelon (Citrullus colocynthis) Skin Sap and Coated in Hydrogel Beads via Ionotropic Gelation

Many plants and fruits are rich in antioxidant and antimicrobial compounds, such as phenolic compounds. Watermelon is one example, as various parts of the fruit present interesting phytochemical profiles. This study demonstrates that a natural C. colocynthis (watermelon) (W) skin sap (SS) extract can effectively improve the oxidative stability of microencapsulated soybean (SB) oil. By employing a combination of alginate–xanthan gums (AXG) in a matrix hydrogel bead model with WSS extract, high encapsulation efficiency can be obtained (86%). The effects of process variables on the ultrasound-assisted extraction (UAE) of phenolic compounds from watermelon (W) skin sap (SS) using the response surface methodology (RSM), as an optimized and efficient extraction process, are compared with the effects of a conventional extraction method, namely the percolation method. The WSS extracts are obtained via UAE and RSM or the conventional percolation extraction method. The two obtained extracts and synthetic antioxidant butylated hydroxytolune (BHT) are added to SB oil separately and their antioxidant effects are tested and compared. The results show the improved oxidative stability of SB oil containing the extract obtained via the optimized method (20–30%) compared to the SB oil samples containing extract obtained via the percolation extraction method, synthetic antioxidant (BHT), and SB oil only as the control (no antioxidant added). According to existing studies, we assume that the use of WSS as an effective antioxidant will ensure the prolonged stability of encapsulated SB oil in hydrogel beads, as it is well known that extended storage under different conditions may lead to severe lipid oxidation.