CHAPTER II REVIEW OF LITERATURE REVIEW OF LITERATURE CHAPTER II REVIEW OF LITERATURE Review of literature revealed that the selected wild edible plants are not studied so far bionutritional point of view. Hence, detailed plant food chemistry of selected wild edible plants from India and Iran has been carried out to investigate nutritional values. Our method covers a considerable scope of the literature and highlights the variability that can occur in the quantity and quality of information available. Less thorough searches could, as was the case with Moringa oleifera leaves, have serious research and operational implications, mainly in the overestimation of intake or the discounting of useful species for the prevention of micronutrient malnutrition. The wide variation in the basis of expression makes the use of some information particularly difficult if a practitioner is not specialized in the compilation of food composition information. In some cases, published nutritional data are inaccurate and valueless for work relating to human nutrition. This could be prevented by journals involved in publishing nutrient values in relation to human nutrition adopting conventions easily understood by the end user (Salih et al. 1991). A diversity of scientific disciplines involved in the investigation of wild food plants is always encouraging, however, the lack of collaboration and 42 REVIEW OF LITERATURE standardization in methodology is not published. Research on the nutritional value of wild food plants requires the coirect presentation of botanical information, chemical analysis and nutritional data, otherwise the results cannot be inteipreted fully. This can only be achieved by well-organized and focused collaboration between all disciplines involved. The investment required for the thorough investigation of a particular food plant is fully justified. If wild food plants are to be utilized for diet diversification during times of famine and food insecurity, sound empiric data must be available to researchers for their investigation. The collection and assessment of available information is the first step in this process. Once undertaken, researchers may be able to use information already collected or decide to undertake their own analysis on the species in question (Onyechi et al. 1988). Health promoting compounds in vegetables and fruits: Optimization of composition of plant-derived food would be a very cost-effective method for disease prevention, since diet-induced health improvements would not carry any added costs for the health sector If improvements can be obtained with existing or slightly adapted food technology, the production costs will be similar. Many epidemiological studies show negative correlations between the intake of vegetables and fruits and the incidence of several important diseases, including cancer and atherosclerosis (Trichopoulou et al. 2003). Vegetables and fruits are 43 REVIEW OF LITERATURE known to contain components with several types of health promoting actions (as vitamins, as essential minerals, as antioxidants and as pre-biotic (fibers)) and most of these have been evaluated in intervention studies. In general, health benefits from supplementation have been proved only for groups that had particularly low intake of these compounds, e.g. due to malnutrition, while supplementations at high levels generally provided only minor additional improvements, and in some cases even showed adverse effects, as is the case for y5-carotene. However, the data from epidemiological studies shows sufficient linearity across the range to allow calculations of the benefits of substantial increases in the intake of fruits and vegetables to 400 g per day ( Van et al. 2000) or even higher ( Gundgaard et al. 2003). This should be compared with the lower levels (approx. 200 g per day) needed to ensure against deficiencies of the known beneficial compounds in the absence of supplementation or other dietary sources ( Ali & Tsou, 2002). Those levels are lower than the average intake in European countries. In addition, a few compounds are known or suspected to benefit health by other, less understood mechanisms, such as protection against cardiovascular disease by sulfoxides and/or flavonoides from Alliums ( Griffiths et al. 2002) or anticancer effects of glucosinolates and their derivatives ( Lund, 2003 ) from Brassicas . However, the epidemiological correlations are not confined to these two types of vegetables. 44 REVIEW OF LITERATURE While the consensus is that most people should eat more vegetables and fruit, rather than pills supplying adequate amounts of the relevant nutrients, it is not known why this is in fact better, nor how to advice people who cannot or will not eat the full selection in large amounts. As long as the compounds that make the greatest difference for health have not been identified, knowledge of the fate of plant constituents during cooking and storage cannot be used to conclude to what extent raw plant foods are better or worse than cooked ones or if a storage method increases or decreases the value for health. Similarly, the knowledge on biodiversity and plant composition does not tell us to what extent certain species, cultivars or cultivation conditions are important for this value. So while very specific and practically useful dietary recommendations are provided for groups of people who are at risk for malnutrition (Darmon et al. 2002), the advice to the affluent populations is to use a variety of species and preparation methods for the vegetables and fruit ( Trichopoulou et al. 2003). At present the primary background for this recommendation is our ignorance, diversity maximizes the random chance of obtaining sufficient amounts of the crucial, largely unknown compounds, as long as we do not know which foods are the best sources ( Trichopoulou et al. 2003). Once we have identified these compounds and sources, will probably still recommend diversity, but then the advice will be based on we 45 REVIEW OF LITERATURE knowledge, and it will become possible to adjust and optimize the recommendations for people with special needs or preferences. Specifically, the present information shows that compounds with already investigated beneficial properties, for example antioxidants, either have additional or unknown benefits and properties, or foods from plants simply contain other health promoting compounds with unknown effects, that have until now been overlooked. Many studies, including several EU-projects, such as QLKl-CT- 2001-01080, QLKl-CT-1999-00830, QLKl-CT-1999-00505, QLKl-CT-1999- 00498, QLKl-CT-1999-00124, BMH4960726 and COST 916, aim at investigating new properties and/or interactions of known compounds. In contrast, few studies focus on the identification of new types of health promoting compounds from vegetables and fruits. The multidisciplinary project "Health promoting compounds from vegetables'" described in the present paper was designed to initiate a systematic approach for screening for novel compounds from edible plants that are likely to have important effects on health. Alocacia indica It is a stout herb. The roots tock is sub erect, 3-8 ft. long, 1-6 in. thick with few soboli. Leaves are large, ovate, deeply sagittately cordate, lobes rounded and the sinus narrow. The spathe is 8-12 in. long and pale yellowish-green and bears 46 REVIEW OF LITERATURE unisexual, flowers. The female flower lie below on the axis and male flowers lie at the of the axis. Uses In tribal areas of India, especially in Konkan the stem slices are fried and consumed during fasting. The stem is very rich in starch and also contents of raphides. Asparagus officinalis: II is a peremiial growing to 1.5m by 0.75m. It is hardy to zone and is not bearing frost tender. It bears flower in August, and the seeds ripen from September to October. The flowers are dioecious (individual flowers are either male or female, but only one sex is to be found on any one plant so both male and female plants must be grown if seed is required) and are pollinated by Bees. The plant is not self-fertile. The plant prefers light (sandy), medium (loamy) and heavy (clay) soils and requires well- drained soil. The plant prefers acid, neutral and basic (alkaline) soils and can grow in Asparagus is a dioecious perennial herb with scale-like leaves and an erect, much- branched stem that grows to a height of up to 3 meters. Asparagus is native to Europe and Asia and is cultivated widely. The part used as a vegetable consists of the aerial stems, or spears, arising from rhizomes. The fleshy roots and, to a lesser degree, the seeds have been used for medicinal purposes. 47 REVIEW OF LITERATURE History Asparagus spears are used widely as a vegetable and frequently are blanched before use. Extracts of the seeds and roots have been used in alcoholic beverages, with the maximum levels averaging 16 ppm. The seeds have been used in coffee substitutes, diuretic preparations, laxatives, remedies for neuritis and rheumatism, to relieve toothache, to stimulate hair growth, and as cancer treatments. Chinese medicine has used them to treat parasitic diseases. Extracts are said to have sei-ved as contraceptives. Home remedies have employed the topical application of preparations containing the shoots and extracts to cleanse the face and dry acneform lesions. very acid, very alkaline and saline soils. It can grow in semi-shade (light woodland) or no shade. It requires moist soil. The plant can tolerate maritime exposure. Uses Asparagus has been cultivated for over 2,000 years as a vegetable and medicinal herb. Both the roots and the shoots can be used medicinally; they have a restorative and cleansing effect on the bowels, kidneys and liver. Young shoots are consumed as a- raw or cooked. It is considered as a gourmet food. The shoots are harvested in the spring. It is preferred as a raw in salads, with a hint of onion in their flavor. They are normally boiled or steamed and used as a vegetable. Male plants produce the best shoots.