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PubMed2003

The effects of frozen storage conditions on lycopene stability in watermelon tissue.

The purpose of this investigation was to evaluate the rate of deterioration of lycopene in watermelon tissue during frozen storage, because little is known about the stability of watermelon tissue lycopene under cold storage conditions. Heart tissue from each of nine individual watermelons was stored at -20 or -80 degrees C as either small chunks or puree and periodically sampled over a year's time. Initial freeze-thaw experiments indicated that a small percentage of lycopene, approximately 4-6%, degraded during an initial freeze-thaw. Analyses of the samples showed a loss of approximately 30-40% lycopene over a year's storage at -20 degrees C and a loss of approximately 5-10% over the same period at -80 degrees C. Lycopene was slightly more stable in pureed compared with diced watermelon tissue at -20 degrees C, but not at -80 degrees C. The kinetic data were best fitted by application of two simultaneous, first-order decay processes. HPLC analysis of the samples after a year's storage suggested that beta-carotene was more stable during storage at -20 degrees C than was lycopene.

Carotenoids↗
PubMed2005

Carotenoid pigmentation affects the volatile composition of tomato and watermelon fruits, as revealed by comparative genetic analyses.

Tomato near-isogenic lines differing in fruit carotenogenesis genes accumulated different aroma volatiles, in a strikingly similar fashion as compared to watermelon cultivars differing in fruit color. The major volatile norisoprenoids present in lycopene-containing tomatoes and watermelons were noncyclic, such as geranial, neral, 6-methyl-5-hepten-2-one, 2,6-dimethylhept-5-1-al, 2,3-epoxygeranial, (E,E)-pseudoionone, geranyl acetone, and farnesyl acetone, seemingly derived from lycopene and other noncyclic tetraterpenoids. Beta-ionone, dihydroactinodiolide, and beta-cyclocitral were prominent in both tomato and watermelon fruits containing beta-carotene. Alpha-ionone was detected only in an orange-fleshed tomato mutant that accumulates delta-carotene. A yellow flesh (r) mutant tomato bearing a nonfunctional psy1 gene and the yellow-fleshed watermelon Early Moonbeam, almost devoid of carotenoid fruit pigments, also lacked norisoprenoid derivatives and geranial. This study provides evidence, based on comparative genetics, that carotenoid pigmentation patterns have profound effects on the norisoprene and monoterpene aroma volatile compositions of tomato and watermelon and that in these fruits geranial (trans-citral) is apparently derived from lycopene in vivo.

Acyclic Monoterpenes↗
PubMed2005

A simple and efficient system for green note compound biogenesis by use of certain lipoxygenase and hydroperoxide lyase sources.

Six-carbon (C(6)) aldehydes and alcohols are important components of the aroma and flavor of fruits and vegetables. Soybean lipoxygenase (LOX) isozyme LOX 3 was reported not only to produce less 13-hydroperoxides, precursors of C(6) aldehydes, but also to convert them to ketodiene products. Here, we examined the effects of LOX 3 on hexenal formation from linolenic acid homogenized with watermelon 13-hydroperoxide lyase (HL)-overexpressing Nicotiana tabacum leaves and soybean acetone powder. Compared to the wild type, which contains LOXs 1, 2, and 3, the elimination of LOX 3 in LOX 1 + 2 facilitates greater production of hexenals. The use of LOX 2 alone yielded the highest hexenal production, while a two-step conversion was required for LOX 1 to produce hexenals at high levels due to different pH optima of the enzymes involved. These results clearly demonstrate that the soybeans lacking LOX 3 in combination with watermelon HL-overexpressing leaf tissues greatly enhance hexenal formation.

Alcohols↗
PubMed2006

Carotenoid content of 50 watermelon cultivars.

The lycopene content of 50 commercial cultivars of seeded and seedless red-fleshed watermelons was determined. Scanning colorimetric and spectrophotometric assays of total lycopene were used to separate watermelon cultivars into low (<50 mg/kg fw), average (50-70 mg/kg fw), high (70-90 mg/kg fw), and very high (>90 mg/kg fw). Cultivars varied greatly in lycopene content, ranging from 33 to 100 mg/kg. Most of the seeded hybrid cultivars had average lycopene contents. Sixteen of the 33 seedless types had lycopene contents in the high and very high ranges. All-trans-lycopene was the predominant carotenoid (84-97%) in all watermelon cultivars measured by high-performance liquid chromatography, but the germplasm differed in the relative amounts of cis-lycopene, beta-carotene, and phytofluene. Red-fleshed watermelon genotypes vary extensively in carotenoid content and offer opportunities for developing watermelons with specifically enhanced carotenoids.

Carotenoids↗
PubMed2006

Carotenoid changes of intact watermelons after storage.

Watermelon contains lycopene, a red carotenoid pigment that has strong antioxidant properties. The lycopene content of watermelon is substantial, contributing 8-20 mg per 180 g serving. There are no reports on carotenoid changes in whole watermelon during storage. Three types of watermelon, open-pollinated seeded, hybrid seeded, and seedless types, were stored at 5, 13, and 21 degrees C for 14 days and flesh color, composition, and carotenoid content were compared to those of fruit not stored. Watermelons stored at 21 degrees C had increased pH, chroma, and carotenoid content compared to fresh fruit. Compared to fresh fruit, watermelons stored at 21 degrees C gained 11-40% in lycopene and 50-139% in beta-carotene, whereas fruit held at 13 degrees C changed little in carotenoid content. These results indicate that carotenoid biosynthesis in watermelons can be affected by temperature and storage.

Antioxidants↗
PubMed2006

Quality changes and nutrient retention in fresh-cut versus whole fruits during storage.

The influences of processing and storage on the quality indices and nutritional content of fresh-cut fruits were evaluated in comparison to whole fruits stored for the same duration but prepared on the day of sampling. Fresh-cut pineapples, mangoes, cantaloupes, watermelons, strawberries, and kiwifruits and whole fruits were stored for up to 9 days in air at 5 degrees C. The postcutting life based on visual appearance was shorter than 6 days for fresh-cut kiwifruit and shorter than 9 days for fresh-cut pineapple, cantaloupe, and strawberry. On the other hand, fresh-cut watermelon and mango pieces were still marketable after 9 days at 5 degrees C. Losses in vitamin C after 6 days at 5 degrees C were < or = 5% in mango, strawberry, and watermelon pieces, 10% in pineapple pieces, 12% in kiwifruit slices, and 25% in cantaloupe cubes. No losses in carotenoids were found in kiwifruit slices and watermelon cubes, whereas losses in pineapples were the highest at 25% followed by 10-15% in cantaloupe, mango, and strawberry pieces after 6 days at 5 degrees C. No significant losses in total phenolics were found in any of the fresh-cut fruit products tested after 6 days at 5 degrees C. Light exposure promoted browning in pineapple pieces and decreased vitamin C content in kiwifruit slices. Total carotenoids contents decreased in cantaloupe cubes and kiwifruit slices, but increased in mango and watermelon cubes in response to light exposure during storage at 5 degrees C for up to 9 days. There was no effect of exposure to light on the content of phenolics. In general, fresh-cut fruits visually spoil before any significant nutrient loss occurs.

Actinidia↗
PubMed2006

Characterization and semiquantitative analysis of volatiles in seedless watermelon varieties using solid-phase microextraction.

Seedless triploid watermelons have increased in popularity since the early 1990s, and the demand for seedless fruit is on the rise. Sweetness and sugars are crucial breeding focuses for fruit quality. Volatiles also play an important role; yet, we found no literature for seedless varieties and no reports using solid-phase microextraction (SPME) in watermelon. The objective of this experiment was to identify volatile and semivolatile compounds in five seedless watermelon varieties using carboxen divinylbenzene polydimethylsiloxane solid-phase microextraction (SPME) with gas chromatography-mass spectrometry (GC-MS). Fully ripe watermelon was squeezed through miracloth to produce rapid juice extracts for immediate headspace SPME GC-MS. Aldehydes, alcohols, ketones, and one furan (2-pentyl furan, a lipid oxidation product) were recovered. On the basis of total ion count peak area, the most abundant compounds in five varieties were 3-nonen-1-ol/(E,Z)-2,6-nonadienal (16.5-28.2%), (E)-2-nonenal (10.6-22.5%), and (Z)-6-nonenal (2.0-11.3%). Hexanal was most abundant (37.7%) in one variety (Petite Perfection) [corrected] The most abundant ketone was 6-methyl-5-hepten-2-one (2.7-7.7%). Some sensory attributes reported for these compounds are melon, citrus, cucumber, orange, rose, floral, guava, violet, vegetable, green, grassy, herbaceous, pungent, fatty, sweet, and waxy. Identifying and relating these compounds to sensory attributes will allow for future monitoring of the critical flavor compounds in seedless watermelon after processing and throughout fresh-cut storage.

Alcohols↗
PubMed2006

Interaction of sodium dodecyl sulfate with watermelon chromoplasts and examination of the organization of lycopene within the chromoplasts.

The properties of plant-derived precipitates of watermelon lycopene were examined in aqueous sodium dodecyl sulfate (SDS) as part of an ongoing effort to develop simpler, more economical ways to quantify carotenoids in melon fruit. Levels of SDS >0.2% were found to increase the water solubility of lycopene in the state in which it was isolated from watermelon. Electron microscopy and chemical analyses suggested that the watermelon lycopene as isolated is packaged inside a membrane to form a chromoplast. Spectral peaks in the visible region of the watermelon chromoplasts in SDS exhibited a bathochromic shift from those in organic solvent. Watermelon chromoplasts in SDS exhibited pronounced circular dichroic activity in the visible region. Binding measurements indicated that about 120 molecules of SDS were bound per molecule of lycopene inside the chromoplast; likely, the detergent molecules are bound to the chromoplast membrane. Around 80% of the chromoplast-SDS complexes were retained on a 0.45 mum membrane filter. Together, these observations are consistent with lycopene in a J-type chiral arrangement inside a membrane to form a chromoplast. The binding of SDS molecules to the chromoplast membrane form a complex that is extensively more water-soluble than the chromoplast alone.

Carotenoids↗
PubMed2005

[Pharmaco-toxicological and clinical studies with colocynth pulp extracts (Extr. colocynthidis fructus)].

Colocynth pulp extract is a long-serving laxative. Contesting the official characterizations "drastic irritant action, no longer defensible" by suitable pharmacotoxicologic studies, extracts of the drug with increasing concentrations of the effective constituant "Cucurbitacins" were prepared in order to define efficacy ranges lethal to rats and mice. The extract Koloquinthentrockenextrakt Alpha with the highest content of Cucurbitacins (23,2 % delta 232,64 mg/g) permitted the definition of the LD50 for female (tentative because of death inhibition under maximal doses) and male rats; the mean LD50 = 281,8 and 525,6 mg/kg extract, respectively, equivalent to 66 and 122 mg/kg Cucurbitacins. This corresponds to 660- to 1220-fold therapeutic doses. Repeated administrations of 10- and 50-fold therapeutic doses to rats for 30 days produced no negative effects. The symptoms of rodent poisoning are described in detail. Pharmacologic doses were not toxic on rat liver slices, did not influence breathing and circulation parameters in guinea pigs (under the maximal dose of 41,6 mg/kg Cucurbitacins, 3/10 animals died of breathing failure) nor the behaviour of mice, nor were they mutagen (Ames test). Colocynth pulp extract weakly inhibited the growth of MDA-MB435 mamma carcinoma cells, but had no influence on the growth of B16 mouse melanoma cells. P388 mouse leukemia cells and L 929 mouse fibroblasts were not significantly influenced. High doses of Colocynth pulp extract inhibited diuresis and electrolyte excretion in rats. The Cucurbitacins E and I were rapidly metabolized in S9-supernatants of rat livers. A dried ethanolic Salvia fruit extract alleviated the toxicity of lethal doses of Colocynth pulp extract when administered simultaneously. A field study with 200 patients and a phase I study with 60 volunteers were conducted in Germany with Colocynth pulp extract from April to October 1998, andfrom December 2002 to March 2003, respectively. Data on the tolerance of the highest allowed dose and of a half-maximal dose administered to volunteers for 14 days in comparison to placebo, as well as data on the efficacy of a treatment course of 3 days of patients with obstipation, were to be gained. Clinical laboratory investigations of volunteers gave no indication of pathological changes even under the highest dose. In patients with obstipation and associated complaints, the administration for 3 days at maximum led to an increased frequency of bowel movements. At the same time, the discomforts accompanying obstipation were significantly relieved. Patients with obstipation defined tolerance as good. Volunteers, on the other hand, judged the tolerance of the drug significantly inferior ("good" - "average") to that of placebo ("very good" - "good"). The low risk potential of Colocynth pulp extract documented in pharmaco-toxicological studies was confirmed during administration to humans.

Animals↗
PubMedDate not supplied

Consumer acceptability of low-sugar watermelon sweetened with non-calorie sweetener by a Native American community.

Watermelons are a good source of lycopene, a carotenoid that exhibits antioxidant activity and may protect against some cancers. However, intake of watermelon may be restricted for individuals who have diabetes or those who limit carbohydrate intake. A low-sugar watermelon was developed at Lane, Oklahoma using traditional plant breeding techniques. The objective of this study was to determine whether the artificially sweetened low-sugar watermelon was acceptable with Native Americans, a group with a high incidence of diabetes. The red flesh from a low-sugar watermelon and a commercial variety of watermelon was removed and cut into cubes. Low and high levels of artificial sweetener were added to the low-sugar watermelon. Students at a Native American school (Grades 1-12) and adults at a Native American Feeding Center were asked to rate how much they liked or disliked the watermelon using a seven-point hedonic scale. Sugar composition, pH, lycopene and other carotenoids were analyzed from samples using established methods. The pH, lycopene, beta-carotene and total carotenoid levels were similar among fruit. Artificially sweetened fruit were rated slightly more acceptable in taste than the commercial control watermelons by both age groups. The low-sugar watermelons were lower in sugar composition but were comparable with conventional melons in all other quality factors and were found acceptable in taste by a broad age group of Native American consumers.

Adolescent↗
PubMed2003

Comparison of chitin and Amberlite IRA-938 for alpha-galactosidase immobilization.

Watermelon alpha-galactosidase (EC 3.2.1.22) was immobilized on a natural (chitin) and a synthetic anion-exchange (Amberlite IRA-938) support by covalent coupling methods. The procedure entails the activation of supports with 1,1'-carbonyldiimidazole (CDI), followed by immobilization of the enzyme on to these supports without and with a spacer arm; gamma-aminobutyric acid (GABA). Optimization of activation was performed by changing the CDI concentrations and coupling efficiencies. The comparison of two immobilization techniques for both chitin and Amberlite IRA-938 was made by comparing different enzyme concentrations against enzyme activity yield. Furthermore, the storage stability of the immobilized enzymes was also investigated and chitin immobilized alpha-galactosidase was found to be better. Although the activity yield of immobilized enzymes were the same for both supports, the short storage stability of immobilized enzyme on Amberlite IRA-938 is currently a drawback to its applications.

Anion Exchange Resins↗
PubMed2003

Preparation and properties of alpha-galactosidase chemically attached to activated chitin.

alpha-Galactosidase (alpha-D-galactoside galactohydrolase, EC 3.2.1.22) from watermelon was covalently immobilized on chitin. The immobilized alpha-galactosidase exhibited an activity of 0.61 U per g of carrier and an activity yield of 67%. The properties of free and immobilized alpha-galactosidase were also searched and compared. The results showed that, optimum conditions for activity were not affected by immobilization. The optimum pH and temperature for free and immobilized enzyme found as pH 6.0 and 65 degress C, respectively. Compared with the free enzyme, the temperature and pH stabilities of the immobilized enzyme were similar. Both the enzymes were stable between pH 2-10 and below 50 degrees C. The Km values for free and immobilized enzyme were determined using p-nitrophenyl-alpha-D-galactopyranoside (PNPG) and raffinose as substrates. Operational stability of the immobilized enzyme was investigated by using both substrates. The operational half-life (t 1/2) was calculated as 34 h for PNPG and 28 h for raffinose. The immobilized alpha-galactosidase was also utilized in the hydrolysis of raffinose. The immobilization procedure on chitin was cheap and also easy to carry out, and the immobilized enzyme had good properties that the potential for practical application is considerable.

Chitin↗
PubMed2002

Citrulline and DRIP-1 protein (ArgE homologue) in drought tolerance of wild watermelon.

Drought-affected plants experience more than just desiccation of their organs due to water deficit. Plants transpire 1000 times more molecules of water than of CO2 fixed by photosynthesis in full sunlight. One effect of transpiration is to cool the leaves. Accordingly, drought brings about such multi-stresses as high temperatures, excess photoradiation and other factors that affect plant viability. Wild watermelon serves as a suitable model system to study drought responses of C3 plants, since this plant survives drought by maintaining its water content without any wilting of leaves or desiccation even under severe drought conditions. Under drought conditions in the presence of strong light, wild watermelon accumulates high concentrations of citrulline, glutamate and arginine in its leaves. The accumulation of citrulline and arginine may be related to the induction of DRIP-1, a homologue of ArgE in Escherichia coli, where it functions to incorporate the carbon skeleton of glutamate into the urea cycle. Immunogold electron microscopy reveals the enzyme to be confined exclusively to the cytosol. DRIP-1 is also induced by treating wild watermelon with 150 mM NaCl, but is not induced following treatment with 100 microM abscisic acid. The salt treatment causes the accumulation of gamma-aminobutyrate, glutamine and alanine, in addition to a smaller amount of citrulline. Citrulline may function as a potent hydroxyl radical scavenger.

Abscisic Acid↗
PubMed2001

Small, repetitive DNAs contribute significantly to the expanded mitochondrial genome of cucumber.

Closely related cucurbit species possess eightfold differences in the sizes of their mitochondrial genomes. We cloned mitochondrial DNA (mtDNA) fragments showing strong hybridization signals to cucumber mtDNA and little or no signal to watermelon mtDNA. The cucumber mtDNA clones carried short (30-53 bp), repetitive DNA motifs that were often degenerate, overlapping, and showed no homology to any sequences currently in the databases. On the basis of dot-blot hybridizations, seven repetitive DNA motifs accounted for >13% (194 kb) of the cucumber mitochondrial genome, equaling >50% of the size of the Arabidopsis mitochondrial genome. Sequence analysis of 136 kb of cucumber mtDNA revealed only 11.2% with significant homology to previously characterized mitochondrial sequences, 2.4% to chloroplast DNA, and 15% to the seven repetitive DNA motifs. The remaining 71.4% of the sequence was unique to the cucumber mitochondrial genome. There was <4% sequence colinearity surrounding the watermelon and cucumber atp9 coding regions, and the much smaller watermelon mitochondrial genome possessed no significant amounts of cucumber repetitive DNAs. Our results demonstrate that the expanded cucumber mitochondrial genome is in part due to extensive duplication of short repetitive sequences, possibly by recombination and/or replication slippage.

Base Sequence↗
PubMed2003

Watermelon growth, fruit yield and plant survival as affected by squash bug (Hemiptera: Coreidae) feeding.

Adult squash bugs, Anasa tristis (De Geer) (Heteroptera: Coreidae), were confined on watermelon plants at differing phenological stages and at densities of zero to four per plant in one trial and zero to 32 per plant in three additional trials. Squash bugs were allowed to feed on the plants until plants died or fruit matured. Plant foliage, roots, and fruit were harvested and weighed to determine effects on growth and productivity. Growth and fruit production was regressed on number of squash bugs and results indicated that an increasing density of squash bugs feeding on vining and flowering stage plants resulted in significant reductions in plant growth and fruit yield. When plants were infested at the fruit set stage of growth, there was either less effect or no effect on plant growth and fruit production. Plant mortality increased as the density of squash bugs increased regardless of the stage of growth when plants were infested with squash bugs.

Animals↗
PubMed2003

Consumption of watermelon juice increases plasma concentrations of lycopene and beta-carotene in humans.

Watermelon is a rich natural source of lycopene, a carotenoid of great interest because of its antioxidant capacity and potential health benefits. Assessment of bioavailability of lycopene from foods has been limited to tomato products, in which heat processing promotes lycopene bioavailability. We examined the bioavailability of lycopene from fresh-frozen watermelon juice in a 19-wk crossover study. Healthy, nonsmoking adults (36-69 y) completed three 3-wk treatment periods, each with a controlled, weight-maintenance diet. Treatment periods were preceded by "washout" periods of 2-4 wk during which lycopene-rich foods were restricted. All 23 subjects consumed the W-20 (20.1 mg/d lycopene, 2.5 mg/d beta-carotene from watermelon juice) and C-0 treatments (controlled diet, no juice). As a third treatment, subjects consumed either the W-40 (40.2 mg/d lycopene, 5.0 mg/d beta-carotene from watermelon juice, n = 12) or T-20 treatment (18.4 mg/d lycopene, 0.6 mg/d beta-carotene from tomato juice, n = 10). After 3 wk of treatment, plasma lycopene concentrations for the W-20, W-40, T-20 and C-0 treatments were (least squares means +/- SEM) 1078 +/- 106, 1183 +/- 139, 960 +/- 117 and 272 +/- 27 nmol/L, respectively. Plasma concentrations of beta-carotene were significantly greater after W-20 (574 +/- 49 nmol/L) and W-40 (694 +/- 73 nmol/L) treatments than after the C-0 treatment (313 +/- 27 nmol/L). Plasma lycopene concentrations did not differ at wk 3 after W-20, W-40 and T-20 treatments, indicating that lycopene was bioavailable from both fresh-frozen watermelon juice and canned tomato juice, and that a dose-response effect was not apparent in plasma when the watermelon dose was doubled.

Adult↗
PubMed2002

Cloning of gibberellin 3 beta-hydroxylase cDNA and analysis of endogenous gibberellins in the developing seeds in watermelon.

We have isolated Cv3h, a cDNA clone from the developing seeds of watermelon, and have demonstrated significant amino acid homology with gibberellin (GA) 3 beta-hydroxylases. This cDNA clone was expressed in Escherichia coli as a fusion protein that oxidized GA(9) and GA(12) to GA(4) and GA(14), respectively. The Cv3h protein had the highest similarity with pumpkin GA 2 beta,3 beta-hydroxylase, but did not possess 2 beta-hydroxylation function. RNA blot analysis showed that the gene was expressed primarily in the inner parts of developing seeds, up to 10 d after pollination (DAP). In the parthenocarpic fruits induced by treatment with 1-(2-chloro-4-pyridyl)-3-phenylurea (CPPU), the embryo and endosperm of the seeds were undeveloped, whereas the integumental tissues, of maternal origin, showed nearly normal development. Cv3h mRNA was undetectable in the seeds of CPPU-treated fruits, indicating that the GA 3 beta-hydroxylase gene was expressed in zygotic cells. In our analysis of endogenous GAs from developing seeds, GA(9) and GA(4) were detected at high levels but those of GA(20) and GA(1) were very low. This demonstrates that GA biosynthesis in seeds prefers a non-13-hydroxylation pathway over an early 13-hydroxylation pathway. We also analyzed endogenous GAs from seeds of the parthenocarpic fruits. The level of bioactive GA(4 )was much lower there than in normal seeds, indicating that bioactive GAs, unconnected with Cv3h, exist in integumental tissues during early seed development.

Amino Acid Sequence↗