As one endproduct of the pathway has been elevated, it may well be that other related compounds, including the flavonols, are also found in higher concentrations. Roman lettuce is richer in lutein than head lettuces; and leafy and roman lettuces are richer in quercetin. The Cucurbitaceae family is rich in vitamin C, carotenoids, and tocopherols. Burger et al. in a survey of 350 melon accessions from different horticultural groups of Cucurbita melo observed a 50-fold variation in ascorbic acid content, ranging from 0.7 mg to 35.3 mg/100g of fresh fruit weight. Ascorbic acid and β-carotene content ranged from 7.0 to 32.0 mg/100g and 4.7 to 62.2 μg/100g, respectively in sweet melons.Diet is the primary therapy for this type of diabetes and bitter gourd is particularly critical when pharmaceuticals are not available, as happens in a great part of the developing world. The Chenopodiaceae family is an excellent source of folate and have been shown to inhibit DNA synthesis in proliferating human gastric adenocarcinoma cells. The Chenopodiaceae vegetables are also among the most oxalate dense vegetables. When oxalates become too concentrated in body fluids, they can crystallize and cause health problems such as kidney calcium oxalate stones. All the legumes , mature and imature seeds are good sources of dietary fiber and isoflavonoids. Mallillin et al. determined the total, soluble and insoluble fibre and fermentability characteristics of ten legumes mature seeds and concluded that the dietary fibre content ranged from 20.9 to 46.9 g/100g and that the best sources after in vitro fermentation using human faecal inoculum stimulating conditions in the human collon were pole sitao and mungbean , kidney bean and pigeon pea, , and peanut and cowpea . High-flavonol legumes include sugar snap peas and mange-tout, which were found to contain 98 and 145 µg quercetin/g respectively. Some legumes are also rich in iron. Trinidad et al. determined the mineral availability in vitro of iron, zinc and calcium in ten local legumes .
They found that the highest iron availability among legumes was for lima bean and mung bean while for zinc and calcium, the highest availability was for kidney beans and pigeon peas, respectively. Groundnuts have the lowest Fe , Zn and Ca availability. They concluded that mineral availability of Fe, Zn, and Ca from legumes differs and may be attributed to their mineral content, grow table hydroponic mineral-mineral interaction and from their phytic and tannic acid content. For example mungbean either eaten as whole pod grains or grown to produce bean sprouts, is an important source of iron for women and children throughout South Asia. In this section we will highlight the health benefits of the most studied and consumed vegetables namely crucifer, allium and solanaceous vegetables. Cruciferous vegetables which include, cabbage, brocolli, cauliflower, Brussels sprouts, kales, kailan, chinese cabbage, turnip, rutabaga, radish, horseradish, rocket, watercress, mustards, among other vegetables, provide the richest sources of glucosenolates in the human diet. Most consumers associate cruciferous vegetable consumption with health. They have reasons for that because based on one of the largest and most detailed reviews of diet and cancer, the World Cancer Research Fund in USA concluded that a diet rich in crucifers is likely to protect humans against colon, rectum, and thyroid cancers, and when consumed with vegetables rich in other phytonutriceuticals, can protect against cancer in other organs. Crucifers rich in glucosenolates including broccoli, cabbage, Brussels sprouts, and kale have been shown to protect against lung, prostate cancer, breast cancer, and chemically induced cancers. Epidemiological data show that a diet rich in crucifers can reduce the risk from several types of cancers and that the risk can be significantly reduced by an intake of at least 10 g per day. Epidemiological studies have suggested that diets rich in broccoli, may reduce the risk of prostate cancer, and consumption of one or more portions of broccoli per week can reduce the incidence and the progression from localized to aggressive forms of prostrate cancer. The overwhelming evidence concerning the anticarcinogenic effect of phytonutriceuticals in crucifers were from in vivo studies, mainly with broccoli, using animal models and human Volunteers.
In order to establish the relationship between whole broccoli and cancer prevention, Farnham et al. examined the diversity of induction of the phase II detoxification enzyme quinone reductase, in murine hepatoma cells, by 71 inbred and 5 hybrid lines of broccoli. They found that the rate of induction of quinone reductase in hepa 1c1c7 by the broccoli inbred lines ranged from 0 to 15,000 units and that the rate of induction was highly correlated to the concentration of glucoraphanin in each broccoli inbred. These results suggest that there are significant differences in the health benefits among crucifers, which is important not only from a health point of view, but also as a marketing tool to promote a certain cultivar. Comparative studies of glucosenolate profiles indicate significant quantitative and quailtative differences among accessions within each crucifer, between plant parts, developmental stage, agronomic management, and climatic conditions. Kushad et al. observed in 65 cultivars of brocolli, that glucoraphanin was the major glucosinolate and that there was more than 27-fold difference between the highest concentration in cultivar “Brigadier” and the lowest concentration in cultivar “EV6-1”. Hansen et al. also observed in their study with 21 cultivars of red cabbage and 6 white cabbages, that there was a considerable variation in the concentration of the individual glucosenolates between the cultivars examined. Red cabbage cultivars were found to contain significantly higher concentrations of glucoraphanin compared to white cabbage cultivars. There were also significant differences within the red cabbage cultivars. Of the red cultivars examined “Rodima” had the highest concentration with 7.4 mg/g DW glucoraphanin whereas “Primero” has the lowest concentration containing only 0.6 mg/g DW. The white cabbage cultivars contained significantly higher levels of glucoiberin compared to red cultivars. The white cabbage cultivar “Bartolo” contained the highest level of 7.4 mg/g dry weight, whereas the cultivar “Candela” had the lowest level of 1.7 mg/g dry weight. The red cultivars ranged from approximately 3 mg/g dry weight to 0.3 mg/g dry weight. The red cabbages were also found to contain significantly higher concentration of gluconasturtiin compared to white cabbage cultivars. The cultivar “Amager Garo” had the highest concentration whereas “Primero” had the lowest, 1 and 0.1 mg/g dry weight, respectively. Similar differences were also observed in turnip and rutabagas. Fahey et al. evaluated glucosinolate content of broccoli sprouts and found that they contain nearly 20- to 50-fold higher glucosinolates than tissue from mature plants. In broccoli heads, the most significant glucosinolates are glucoraphanin, glucobrassicin, progoitrin, and gluconasturtiin. In cabbage, Brussel sprouts, cauliflower, kale, tronchuda and collard the predominant glucosinolates are sinigrin, progoitrin, and glucobrassicin.
In turnip and rutabagas, the predominant glucosenolates are glucoerucin, glucoraphanin, and glucobrassicin. In radish, the predominant glucosinolates are glucoerucin, glucoraphanin, and glucobrassicin. Each of these crucifers also contain smaller amounts of other glucosinolates. The bulk of the differences in the aliphatic glucosinolates is genetically regulated. Differences in the indol glucosinolates, in contrast to aliphatic glucosinolates, have been attributed to environmental factors. Even though the glucosinolate content is influenced by environmental conditions the effect of genotype is found to be greater than that of environ- mental factors. Crucifer vegetables are also rich in vitamins, with kale rated as the second highest among 22 vegetables tested. Brussels sprouts and broccoli were also ranked high in their vitamin content containing significant amounts of vitamins C and E, and β-carotene. Evaluation of α- and β-, α-, and γ-tocopherols, and vitamin C in broccoli, Brussels sprouts, cabbage, cauliflower, tronchuda, and kale, showed significant variations between and within these crucifers. Vitamin C is the most abundant vitamin in all five crucifers tested. Kale had the highest amount of these vitamins, followed by broccoli, Brussels sprouts, cabbage and cauliflower. Analysis indicated that 79% of β-carotene, 82% of α-tocopherol, and 55% of vitamin C variability in broccoli were associated with genetic factors. Crucifers are also excellent source of folate. Brussels sprouts and broccoli were ranked among the highest vegetable sources for folate, contributing about 110 to 135 and 70 to 90 μg/100 g, respectively. Crucifers also contain significant amounts of dietary fiber. Dietary fiber content of cauliflower was estimated to be about 5% of the total fresh weight or about 50% of the total dry weight, consisting of about 40% nonstarch polysaccharides. Cellulose and lignin concentrations in Brussels sprouts were estimated to be 36% and 14.5%, while in cauliflower they were estimated to be about 16% and 13% of the total dry matter, respectively. There are plenty of crucifers that are good sources of calcium. Galega kale contains a high content of protein, fiber, calcium, and sulfur when compared to broccoli,grow table the reference within Brassica vegetables. Crucifers are capable of accumulating substantial amounts of selenium when grown on high-selenium soil. Banuelos and Meek reported that broccoli grown on selenium enriched soil accumulated sevenfold more selenium than cabbage, collards and Swiss chard. Broccoli plants grown outdoors on a sphagnum, peatmoss, and vermiculite medium and fertilized with sodium-selenate and selenite accumulated 278 mg/g dry weight selenium, in the edible florets, compared to the nonfertilized control, which accumulated only 0.13 mg/g dry weight. In broccoli, selenium is stored as selenocysteine, which is readily absorved by human tissue. Selenium-enriched broccoli has been found to reduce colon cancer and mammary tumors in animal models. Cabbage sprouts and fully developed heads also accumulated selenium and the accumulation was higher in the sprouts than in the mature heads. Other antioxidants in crucifers include flavonoids. Miean and Mohamed examined the flavonoid content of 62 vegetables and found that broccoli, cauliflower, cabbage, chinese cabbage, and kailan contained between 148 and 219 mg/kg of flavonoids. Broccoli contained myricetin, quercetin, and luteolin; cauliflower contained myricetin and quercetin; kailan contained quercetin and apigenin; while cabbage contained only myricetin. In a similar study, Hertog et al. evaluated the methanolextracted flavonoids from 28 vegetables and found that quercetin levels, in the edible part of most vegetables, were below 10 mg/kg, except in kale , broccoli , and onion . Kale, broccoli and turnip contained 211, 72, and 48 mg/kg of kaempferol, respectively.
Kaempferol had also been detected in cabbage leaves, but Miean and Moamed did not detect kaempferol in any of the tested crucifer vegetables. Alliums vegetables include, garlic, onion, leek, chive, Welsh onion, among other vegetables. They are rich in a wide variety of thiosulfides, which have been linked to reducing various chronic diseases. Similar to glucosinolates in crucifers, the types and amounts of thiosulfides in alliums vary significantly. Typically, they contain 1% to 5% nonprotein sulfur compounds, on a dry weight basis. Kubec et al. reported significantly variability in the total thiosulfide content and in the relative proportion of these compounds between and within alliums, even when grown under identical conditions. Theyfound that the total thiosulfide contents in green onion leaves, chive, and onion bulb were 0.2, 0.72, and 1.02 g/kg fresh weight, respectively. The type of thiosulphides in these vegetables were also variable. For example onion bulbs contained 34% methiin, 5% ethiin, 6% propiin, 5% alliin, and 49% isoalliin, while garlic cloves contained about 92% alliin, 8% methiin, and trace amounts of ethiin, propiin, and isoalliin. The second most important group of phytonutriceuticals in alliums are flavonoids. Two types of flavonoids are found in onion bulbs: anthocyanins in red onions and flavonols like quercetin and kaempferol in most yellow fresh cultivars. Miean and Mohamed reported that onion leaves had the highest total flavonoid content among 62 different vegetables they tested and that total flavonoid content of onion leaves and garlic were about 2.7 and 1.0 g/kg dry weight, respectively. In onion leaves, about 55% of the total flavonoids is quercetin, 31% kaempferol, and 14% luteolin. In onion bulb, more than 95% of the flavonoids is quercetin and only a trace amount of kaempferol. White onion cultivars were reported to have significantly less quercetin than the red ones and most of the quercetin is present in the outer scales. Red onions contained approximately 1350 µg/g fresh weight of total flavonols and white onions contained only 10 µg/g.