Changes in free amino acid, protein, and flavonoid content in jujube (Ziziphus jujube) fruit during eight stages of growth and antioxidative and cancer cell inhibitory effects by extracts.

Jujube (Ziziphus jujube) was analyzed at eight stages of ripeness (S1-8) for protein, by HPLC and mass spectroscopy for free amino acids and flavonoids, and by colorimetry for total flavonoids and antioxidative activity. The ripe fruit had lower levels of protein, flavonoids, and antioxidative activity than that of the unripe fruit. Free amino acids levels peaked at S5, due mainly to an increase in free asparagine. Extracts were also tested against four cell lines using the MTT cell viability assay. All growth stages dose-dependently inhibited HeLa cervical cancer cells, whereas the inhibition of Hel299 normal lung and A549 lung cancer cells decreased as the fruit matured and was well correlated with the flavonoid content and antioxidative activity. Chang normal liver cells were inhibited by only the S5 extract. U937 lymphoma cells were unaffected by the extracts. These results show the effect of fruit maturity on nutritional and health-promoting components.

Structure-activity relationships of α-, ß(1)-, γ-, and δ-tomatine and tomatidine against human breast (MDA-MB-231), gastric (KATO-III), and prostate (PC3) cancer cells.

Partial acid hydrolysis of the tetrasaccharide (lycotetraose) side chain of the tomato glycoalkaloid α-tomatine resulted in the formation of four products with three, two, one, and zero carbohydrate side chains, which were separated by high-performance liquid chromatography (HPLC) and identified by thin-layer chromatography (TLC) and liquid chromatography ion-trap time-of-flight mass spectrometry (LCMS-IT-TOF). The inhibitory activities in terms of IC(50) values (concentration that inhibits 50% of the cells under the test conditions) of the parent compound and the hydrolysates, isolated by preparative HPLC, against normal human liver and lung cells and human breast, gastric, and prostate cancer cells indicate that (a) the removal of sugars significantly reduced the concentration-dependent cell-inhibiting effects of the test compounds, (b) PC3 prostate cancer cells were about 10 times more susceptible to inhibition by α-tomatine than the breast and gastric cancer cells or the normal cells, (c) the activity of α-tomatine against the prostate cancer cells was 200 times greater than that of the aglycone tomatidine, and (d) the activity increased as the number of sugars on the aglycone increased, but this was only statistically significant at p < 0.05 for the normal lung Hel299 cell line. The effect of the alkaloids on tumor necrosis factor α (TNF-α) was measured in RAW264.7 macrophage cells. There was a statistically significant negative correlation between the dosage of γ- and α-tomatine and the level of TNF-α. α-Tomatine was the most effective compound at reducing TNF-α. The dietary significance of the results and future research needs are discussed.

Free amino acid and phenolic contents and antioxidative and cancer cell-inhibiting activities of extracts of 11 greenhouse-grown tomato varieties and 13 tomato-based foods.

Tomato (Solanum lycopersicum) plants synthesize nutrients, pigments, and bioactive compounds that benefit nutrition and human health. The nature and concentrations of these compounds are strongly influenced by varietal factors such as size and color as well as by processing. To better understand how these factors affect the concentration of nutrients and bioactive compounds, we analyzed 11 Korean tomato varieties grown under the same greenhouse conditions and 13 processed commercial tomato products for free amino acids and amino acid metabolites by HPLC, for individual phenolics by HPLC-MS, for total phenolics by the Folin-Ciocalteu method, for antioxidative activity by the FRAP and DPPH methods, and for cancer cell-inhibiting effects by the MTT assay. We also determined the protein content of the tomatoes by an automated Kjeldahl method. The results show that there is a broad range of bioactive compounds across tomato varieties and products. Small tomatoes had higher contents of bioactive compounds than the large ones. The content of phenolic compounds of processed products was lower than that of fresh tomatoes. Tomato extracts promoted growth in normal liver (Chang) cells, had little effect in normal lung (Hel299) cells, mildly inhibited growth of lung cancer (A549) cells, and first promoted and then, at higher concentrations, inhibited growth in lymphoma (U937) cells. The relationship of cell growth to measured constituents was not apparent. Dietary and health aspects of the results are discussed.

Distribution of free amino acids, flavonoids, total phenolics, and antioxidative activities of Jujube (Ziziphus jujuba) fruits and seeds harvested from plants grown in Korea.

Fruit pulp and seeds from the jujube plant possess nutritional and medicinal properties. The bioactive components have been shown to vary both with cultivar and with growing conditions. Most studies report the components of varieties from China. We measured free amino acid, individual phenolic, and total phenolic content, and antioxidative activities in three jujube fruit pulp extracts from Boeun-deachu, Mechu, and Sanzoin cultivars and two seed extracts (Mechu and Sanzoin) from plants grown in Korea. In g/100 g dry weight, total free amino acid content measured by ion-exchange chromatography ranged from 5.2 to 9.8 in the pulp and from 4.0 to 5.3 in the seed. Total phenolic content measured by Folin-Ciocalteu ranged from 1.1 to 2.4 in the pulp and from 3.6 to 4.6 in the seed. Flavonoids were measured by HPLC and ranged from 0.7 to 1.8 in the pulp and from 3.2 to 4.0 in the seed. Flavonoids were identified by HPLC elution position and UV/vis and mass spectra. Fruits contained the following flavonoids: procyanidin B2, epicatechin, quercetin-3-O-rutinoside (Q-3-R), quercetin-3-O-galactoside (Q-3-G), kaempferol-glucosyl-rhamnoside (K-G-R), and two unidentified compounds. Seeds contained the following flavonoids: saponarin, spinosin, vitexin, swertish, 6'''-hydroxybenzoylspinosin (6'''-HBS), 6'''-feruloylspinosin (6'''-FS), and one unidentified substance. Dimensions and weights of the fresh fruit samples affected phenolic content. The distribution of the individual flavonoids among the different samples varied widely. Data determined by the FRAP antioxidative assay were well correlated with total phenolic content. In a departure from other studies, data from the DPPH free radical assay were not correlated with FRAP or with any of the measured compositional parameters. Because individual jujube flavonoids are reported to exhibit different health-promoting effects, knowledge of the composition and concentration of bioactive compounds of jujube products can benefit consumers.

Changes in free amino acid, phenolic, chlorophyll, carotenoid, and glycoalkaloid contents in tomatoes during 11 stages of growth and inhibition of cervical and lung human cancer cells by green tomato extracts.

Tomato ( Solanum lycopersicum ) plants synthesize nutrients, pigments, and secondary metabolites that benefit nutrition and human health. The concentrations of these compounds are strongly influenced by the maturity of the tomato fruit on the vine. Widely consumed Korean tomatoes of the variety Doturakworld were analyzed for changes in the content of free amino acids, phenolic compounds, chlorophylls, carotenoids, and glycoalkaloids at 11 stages (S1-S11) of ripeness. The results show that (a) the total content (in mg/100 g of FW) of the free amino acids and other nitrogen-containing compounds in the extracts ranged from about 41 to 85 in the green tomato extracts S1-S7 and then increased to 251 (S9) in the red extracts, followed by a decrease to 124 in S11 red extracts; (b) the total initial concentration and composition of up to 12 phenolic compounds of approximately 2000 microg/100 g of FW varied throughout the ripening process, with the quantity decreasing and the number of individual compounds increasing in the red tomato; (c) chlorophyll a and b content of tomatoes harvested during S1 was 5.73 mg/100 g of fresh pericarp and then decreased continuously to 1.14 mg/100 g for S11; (d) the concentration (in mg/100 g of FW) of lycopene in the S8 red extract of 0.32 increased to 1.27 in S11; and (e) tomatoes harvested during S1 contained 48.2 mg of dehydrotomatine/100 g of FW, and this value continually decreased to 1.5 in S7, with no detectable levels in S8-S11. The corresponding alpha-tomatine content decreased from S1 (361) to S8 (13.8). The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cell assay IC(50) values showed that Hel299 lung cells, A549 lung cancer cells, and HeLa cervical carcinoma cells were highly susceptible to inactivation by glycoalkaloid-rich green tomato extracts. Chang normal liver cells and U937 lymphoma cells were less susceptible. The possible significance of the results for plant physiology and the diet is discussed.

Changes in the composition of raw tea leaves from the Korean Yabukida plant during high-temperature processing to pan-fried Kamairi-cha green tea.

To develop a better understanding of compositional changes occurring during the production of commercial teas, we determined by high-performance liquid chromatography (HPLC) changes in ingredient levels during each of several manufacturing steps used to produce Kamairi-cha, a premium green tea. Kamairi-cha uses pan-frying instead of the usual blanching technique to inactivate the enzymes responsible for producing traditional black tea. The resulting tea lacks the characteristic bitterness of green tea, producing a green tea that is described as sweet tasting. The processing steps used to produce this pan-fried tea were as follows: 1st roasting, 1st rolling, 2nd roasting, 2nd rolling, 1st firing, and 2nd firing. The results show that during production at temperatures up to 300 degrees C, raw leaves lost (in percent) 97.3 water, 94 two chlorophylls, 14.3 seven catechins, and 2.75 caffeine. A separate analysis showed that the final product contained 21.67 mg/g dry wt of the biologically active amino acid theanine. The results of this 1st report on changes in individual catechins and other tea ingredients in tea leaves during pan-frying make it possible to select production conditions that maximize levels of beneficial tea ingredients. The possible significance of the results for the human diet is discussed.

Tomatine-containing green tomato extracts inhibit growth of human breast, colon, liver, and stomach cancer cells.

Tomato plants ( Lycopersicon esculentum ) synthesize the glycoalkaloids dehydrotomatine and alpha-tomatine, possibly as a defense against bacteria, fungi, viruses, and insects. Six green and three red tomato extracts were investigated for their ability to induce cell death in human cancer and normal cells using a microculture tetrazolium (MTT) assay. Compared to untreated controls, the high-tomatine green tomato extracts strongly inhibited the following human cancer cell lines: breast (MCF-7), colon (HT-29), gastric (AGS), and hepatoma (liver) (HepG2), as well as normal human liver cells (Chang). There was little inhibition of the cells by the three low-tomatine red tomato extracts. Cell death induced by the pure glycoalkaloids dehydrotomatine and alpha-tomatine isolated from green tomatoes and characterized by HPLC, GC, and GC-MS, as well as their respective aglycones tomatidenol and tomatidine, was also evaluated. alpha-Tomatine was highly effective in inhibiting all of the cell lines. Dehydrotomatine, tomatidenol, and tomatidine had little, if any, effect on cell inhibition. The results show that the susceptibility to destruction varies with the nature of the alkaloid and plant extract and the type of cancer cell. These findings extend related observations on the anticarcinogenic potential of glycoalkaloids and suggest that consumers may benefit by eating not only high-lycopene red tomatoes but also green tomatoes containing glycoalkaloids. Possible mechanisms of the anticarcinogenic and other beneficial effects and the significance of the cited observations for breeding improved tomatoes and for the human diet are discussed.

Distribution of glycoalkaloids in potato tubers of 59 accessions of two wild and five cultivated Solanum species.

Steroidal glycoalkaloids are naturally occurring, secondary plant metabolites that are found in foods, including potatoes and tomatoes. Their content in plants is controlled by both genetic and environmental factors. Glycoalkaloid profiles can be passed to progenies during breeding and hybridization of wild and cultivated potatoes designed to develop improved potatoes. The most common potato, Solanum tuberosum, contains primarily the glycoalkaloids, alpha-solanine and alpha-chaconine. However, wild-type potatoes being used for breeding new varieties contain other, less common glycoalkaloids. Because glycoalkaloid composition is a major criterion for the release of new potato cultivars, we used HPLC, TLC, GC, and GC/MS to determine their nature and content in several Solanum species widely used in potato breeding and hybridization programs. Solanum tuberosum, as well as S. andigena and S. stenotomum, contained alpha-solanine and alpha-chaconine. S. canasense was found to contain only dehydrocommersonine. S. acaule contained alpha-tomatine and demissine. S. juzepczukii and S. curtilobum contained demissine and two previously unidentified glycoalkaloids. We characterized them as demissidine-glucose/rhamnose (1/1 ratio) and demissidine-galactose/glucose/rhamnose (1/1/1 ratio), tentatively named dihydro-beta(1)-chaconine and dihydrosolanine, respectively. We found extensive variability in the glycoalkaloid profiles in the tested potato varieties. The possible significance of these findings for plant breeding and food safety is discussed.

Flavonoid content in fresh, home-processed, and light-exposed onions and in dehydrated commercial onion products.

Onion plants synthesize flavonoids as protection against damage by UV radiation and by intracellular hydrogen peroxide. Because flavonoids also exhibit health-promoting effects in humans, a need exists to measure their content in onions and in processed onion products. To contribute to the knowledge about the levels of onion flavonoids, HPLC and LC-MS were used to measure levels of seven quercetin and isorhamnetin glucosides in four Korean commercial onion bulb varieties and their distribution within the onion, in scales of field-grown onions exposed to home processing or to fluorescent light and in 16 commercial dehydrated onion products sold in the United States. Small onions had higher flavonoid content per kilogram than large ones. There was a graduated decrease in the distribution of the flavonoids across an onion bulb from the first (outside) to the seventh (innermost) scale. Commercial, dehydrated onion products contained low amounts or no flavonoids. Losses of onion flavonoids subjected to "cooking" (in percent) ranged as follows: frying, 33; sauteing, 21; boiling, 14-20; steaming, 14; microwaving, 4; baking, 0. Exposure to fluorescent light for 24 and 48 h induced time-dependent increases in the flavonoid content. The results extend the knowledge about the distribution of flavonoids in fresh and processed onions.

Analysis of phenolic compounds by high-performance liquid chromatography and liquid chromatography/mass spectrometry in potato plant flowers, leaves, stems, and tubers and in home-processed potatoes.

Potato plants synthesize phenolic compounds as protection against bruising and injury from bacteria, fungi, viruses, and insects. Because antioxidative phenolic compounds are also reported to participate in enzymatic browning reactions and to exhibit health-promoting effects in humans, a need exists for accurate methods to measure their content in fresh and processed potatoes. To contribute to our knowledge about the levels of phenolic compounds in potatoes, we validated and used high-performance liquid chromatography and liquid chromatography/mass spectrometry to measure levels of chlorogenic acid, a chlorogenic isomer, and caffeic acid in flowers, leaves, stems, and tubers of the potato plant and in home-processed potatoes. The total phenolic acid content of flowers (626 mg/100 g fresh wt) was 21 and 59 times greater than that of leaves and stems, respectively. For all samples, chlorogenic acid and its isomer contributed 96-98% to the total. Total phenolic acid levels (in g/100 g fresh wt) of peels of five potato varieties grown in Korea ranged from 6.5 to 42.1 and of the flesh (pulp) from 0.5 to 16.5, with peel/pulp ratios ranging from 2.6 to 21.1. The total phenolic acid content for 25 American potatoes ranged from 1.0 to 172. The highest amounts were present in red and purple potatoes. Home processing of pulp with various forms of heat induced reductions in the phenolic content. The described methodology should facilitate future studies on the role of potato phenolic compounds in the plant and the diet.

Structure-activity relationships of tea compounds against human cancer cells.

The content of the biologically active amino acid theanine in 15 commercial black, green, specialty, and herbal tea leaves was determined as the 2,4-dinitrophenyltheanine derivative (DNP-theanine) by a validated HPLC method. To define relative anticarcinogenic potencies of tea compounds and teas, nine green tea catechins, three black tea theaflavins, and theanine as well as aqueous and 80% ethanol/water extracts of the same tea leaves were evaluated for their ability to induce cell death in human cancer and normal cells using a tetrazolium microculture (MTT) assay. Compared to untreated controls, most catechins, theaflavins, theanine, and all tea extracts reduced the numbers of the following human cancer cell lines: breast (MCF-7), colon (HT-29), hepatoma (liver) (HepG2), and prostate (PC-3) as well as normal human liver cells (Chang). The growth of normal human lung (HEL299) cells was not inhibited. The destruction of cancer cells was also observed visually by reverse phase microscopy. Statistical analysis of the data showed that (a) the anticarcinogenic effects of tea compounds and of tea leaf extracts varied widely and were concentration dependent over the ranges from 50 to 400 microg/mL of tea compound and from 50 to 400 microg/g of tea solids; (b) the different cancer cells varied in their susceptibilities to destruction; (c) 80% ethanol/water extracts with higher levels of flavonoids determined by HPLC were in most cases more active than the corresponding water extracts; and (d) flavonoid levels of the teas did not directly correlate with anticarcinogenic activities. The findings extend related observations on the anticarcinogenic potential of tea ingredients and suggest that consumers may benefit more by drinking both green and black teas.

Antimicrobial activities of tea catechins and theaflavins and tea extracts against Bacillus cereus.

We evaluated the antimicrobial activities of seven green tea catechins and four black tea theaflavins, generally referred to as flavonoids, as well as the aqueous extracts (infusions) of 36 commercial black, green, oolong, white, and herbal teas against Bacillus cereus (strain RM3190) incubated at 21 degrees C for 3, 15, 30, and 60 min. The results obtained demonstrate that (i) (-)-gallocatechin-3-gallate, (-)-epigallocatechin-3-gallate, (-)-catechin-3-gallate, (-)-epicatechin-3-gallate, theaflavin-3, 3'-digallate, theaflavin-3'-gallate, and theaflavin-3-gallate showed antimicrobial activities at nanomolar levels; (ii) most compounds were more active than were medicinal antibiotics, such as tetracycline or vancomycin, at comparable concentrations; (iii) the bactericidal activities of the teas could be accounted for by the levels of catechins and theaflavins as determined by high-pressure liquid chromatography; (iv) freshly prepared tea infusions were more active than day-old teas; and (v) tea catechins without gallate side chains, gallic acid and the alkaloids caffeine and theobromine also present in teas, and herbal (chamomile and peppermint) teas that contain no flavonoids are all inactive. These studies extend our knowledge about the antimicrobial effects of food ingredients.

Antioxidative, antimutagenic, and anticarcinogenic activities of rice bran extracts in chemical and cell assays.

Ethanol-water (70:30 v/v) extracts from rice brans removed from seeds of two blackish-purple pigmented (Sanhaehyanghyulla and Suwon 415) and one nonpigmented (Chuchung) brown rice cultivars were evaluated for antioxidative, anti-tumor-promoting, and anticarcinogenic activities in chemical assays and in mammalian cells (human leukemia HL-60, marmoset B lymphoblastoid B95-8, and Chinese hamster V79 lung cells) by the following tests: inhibition of xanthine oxidase activity; chelation of ferrous ions; reduction of potassium ferricyanide; scavenging of superoxide anions, hydroxyl radicals, and intracellular peroxides; inhibition of 4-nitroquinoline N-oxide-induced mutagenesis; and inhibition of phorbol ester-induced tumor promotion. The extracts from the pigmented rice seeds had generally higher activities in all tests than did the extract from the nonpigmented variety. The results suggest that brans from pigmented rice varieties may provide a source of new natural antioxidants and anticarcinogens and that such rice cultivars with high antioxidative potential also provide a genetic resource for the development of new, improved rice cultivars that may make it possible to enhance both the nutritional and medical value of rice-based diets.

Distribution of ascorbic acid in potato tubers and in home-processed and commercial potato foods.

HPLC was used to analyze the content of ascorbic acid (AA) in tubers of four Korean potato cultivars (Chaju, Sumi, Deso, and Dejima), in a series of baked, boiled, braised, fried, microwaved, pressure-cooked, and sauteed potato slices from the Dejima cultivar and in 14 commercial Korean and 14 processed potato foods sold in the United States (chips, snacks, mashed potatoes, fries). The AA content for the four cultivars ranged from 16 to 46 mg/100 g of fresh weight. The distribution of AA in each of the eight potato slices (sticks, plugs) cut horizontally from the stem end of the Dejima potato ranged from 6.8 to 19.3% of the total. The corresponding distribution in seven sticks cut vertically was much narrower, ranging from 11.7 to 17.5% of the total. Losses of AA in water (pH 5.2) were significantly greater than in 5% metaphosphoric acid (pH 1.0). Less degradation occurred in water solutions of the vitamin stored at 1 degree C than at 25 degrees C. Losses of AA observed during home-processing of three varieties with low (Dejima, 16 mg/100 g), intermediate (Sumi, 32 mg/100 g), and high (Chaju, 42 mg/100 g) AA contents were as follows: boiling in water, 77-88%; boiling in water containing 1-3% NaCl, 61-79%; frying in oil, 55-79%; sauteing, 61-67%; pressure-cooking in water, 56-60%; braising, 50-63%; baking, 33-51%; and microwaving, 21-33%. The content of the Korean foods ranged from trace amounts to 25 mg/100 g and that of the U.S. foods from 0.4 to 46 mg/100 g. These results permit optimization of the vitamin C content of the diet by (a) using high-vitamin C potato varieties such as Chaju, (b) selecting sticks cut horizontally for frying, (c) baking or microwaving rather than boiling or frying, and (d) selecting commercial potato foods with a high vitamin C content.

Glycoalkaloids and metabolites inhibit the growth of human colon (HT29) and liver (HepG2) cancer cells.

As part of an effort to improve plant-derived foods such as potatoes, eggplants, and tomatoes, the antiproliferative activities against human colon (HT29) and liver (HepG2) cancer cells of a series of structurally related individual compounds were examined using a microculture tetrazolium (MTT) assay. The objective was to assess the roles of the carbohydrate side chain and aglycon part of Solanum glycosides in influencing inhibitory activities of these compounds. Evaluations were carried out with four concentrations each (0.1, 1, 10, and 100 microg/mL) of the the potato trisaccharide glycoalkaloids alpha-chaconine and alpha-solanine; the disaccharides beta(1)-chaconine, beta(2)-chaconine, and beta(2)-solanine; the monosaccharide gamma-chaconine and their common aglycon solanidine; the tetrasaccharide potato glycoalkaloid dehydrocommersonine; the potato aglycon demissidine; the tetrasaccharide tomato glycoalkaloid alpha-tomatine, the trisaccharide beta(1)-tomatine, the disaccharide gamma-tomatine, the monosaccharide delta-tomatine, and their common aglycon tomatidine; the eggplant glycoalkaloids solamargine and solasonine and their common aglycon solasodine; and the nonsteroidal alkaloid jervine. All compounds were active in the assay, with the glycoalkaloids being the most active and the hydrolysis products less so. The effectiveness against the liver cells was greater than against the colon cells. Potencies of alpha-tomatine and alpha-chaconine at a concentration of 1 microg/mL against the liver carcinoma cells were higher than those observed with the anticancer drugs doxorubicin and camptothecin. Because alpha-chaconine, alpha-solanine, and alpha-tomatine also inhibited normal human liver HeLa (Chang) cells, safety considerations should guide the use of these compounds as preventative or therapeutic treatments against carcinomas.

Dehydrotomatine and alpha-tomatine content in tomato fruits and vegetative plant tissues.

Tomato plants (Lycopersicon esculentum) synthesize the glycoalkaloids dehydrotomatine and alpha-tomatine, possibly as a defense against bacteria, fungi, viruses, and insects. We used a high-performance liquid chromatography method with UV detection at 208 nm for the analysis of these compounds in various tissues. An Inertsil ODS-2 column with a mobile phase of acetonitrile/20 mM KH2PO4 (24/76, v/v) afforded good separation of the two glycoalkaloids in mini-tomato extracts, fruit harvested at different stages of maturity, and calyxes, flowers, leaves, roots, and stems. The two peaks appeared at approximately 17 and approximately 21 min. Recoveries from tomato fruit extracts spiked with dehydrotomatine and alpha-tomatine were 87.7 +/- 6.8 and 89.8 +/- 3.4% (n = 5), respectively. The detection limit is estimated to be 0.39 microg for dehydrotomatine and 0.94 microg for alpha-tomatine. The dehydrotomatine and alpha-tomatine content of tomatoes varied from 42 to 1498 and 521 to 16 285 microg/g of fresh weight, respectively. The ratio of alpha-tomatine to dehydrotomatine ranged from 10.9 to 12.5 in tomatoes and from 2.3 to 7.8 in the other plant tissues. These results suggest that the biosynthesis of the glycoalkaloids is under separate genetic control in each plant part. Degradation of both glycoalkaloids occurred at approximately the same rate during maturation of the tomatoes on the vine. An Inertsil NH2 column, with acetonitrile/1 mM KH2PO4 (96/4, v/v) as the eluent, enabled the fractionation of commercial tomatidine into tomatidenol and tomatidine, the aglycons of dehydrotomatine and alpha-tomatine, respectively. The information should be useful for evaluating tomatoes and vegetative tissues for dehydrotomatine/alpha-tomatine content during fruit development and their respective roles in host-plant resistance and the diet.

Glycoalkaloid and calystegine contents of eight potato cultivars.

Diverse procedures have been reported for the separation and analysis by HPLC of the two major glycoalkaloids present in potatoes, alpha-chaconine and alpha-solanine. To further improve the usefulness of the HPLC method, studies were carried out on the influence of several salient parameters on the analysis of the two potato glycoalkaloids. Effects on retention (elution, separation) times of the (a) composition and pH of the mobile phase (acetonitrile and phosphate buffer), (b) concentration of the phosphate buffer, (c) capacity values of column packing of four commercial HPLC amino columns, (d) column temperature were studied. Except for pH, all of the variables significantly influenced the retention times. The results make it possible to select analysis conditions that produce well-separated as well as symmetrical peaks of the two glycoalkaloids. This improved HPLC method (limit of detection of approximately 150 ng) was evaluated with extracts from the cortex of one whole potato variety (May Queen) grown in Japan and the freeze-dried peel and flesh from the following eight cultivars grown in the United States: Atlantic, Dark Red Norland, Ranger Russet, Red Lasoda, Russet Burbank, Russet Norkota, Shepody, and Snowden. In addition, the same samples were analyzed by GC-MS for the presence of two water-soluble nortropane alkaloids, calystegine A(3) and calystegine B(2), reported to be potent glycosidase inhibitors. The following ranges for the eight varieties of total glycoalkaloid and calystegine levels were observed: dry flesh, 5-592 and 6-316 mg/kg; dry peel, 84-2226 and 218-2581 mg/kg; dry whole potatoes, 40-883 and 34-326 mg/kg; wet flesh, 1-148 and 1-68 mg/kg; wet peel, 12-429 and 35-467 mg/kg; wet whole potatoes, 7-187 and 5-68 mg/kg. The possible significance of the results to plant and food sciences is discussed.