Common plant foods

There are few dietary sources of cholecalciferol. The richest sources are oUy fish (especially fish liver oUs), although eggs also contain a relatively large amount, and there is a modest amount in mUk fat and animal liver. In many countries, margarine is fortified with vitamin D. No common plant foods contain vitamin D, although some tropical plants contain calciferol glucuronides that are hydrolyzed in the intestinal lumen and are a source of the vitamin. Indeed, this can be a cause of hypervitaminosis and calcinosis in grazing animals. 

EXAMPLE 12.4 Most fruits and vegetables do not contain significant amounts of triglyceride. Some common plant foods are exceptions avocados are approximately 22% by weight triglyceride, and nuts such as macadamias are up to 75% by weight triglyceride. 

FIGURE 7.1 Conversion pathways of the common plant food lignans to the enterolignans enterolactone and enterodiol. Solid arrows indicate known pathways. Dashed arrows indicate theoretical pathways. Adapted from Clavel et... 

Although iron deficiency is a common problem, about 10% of the population are genetically at risk of iron overload (hemochromatosis), and elemental iron can lead to nonen2ymic generation of free radicals. Absorption of iron is stricdy regulated. Inorganic iron is accumulated in intestinal mucosal cells bound to an intracellular protein, ferritin. Once the ferritin in the cell is saturated with iron, no more can enter. Iron can only leave the mucosal cell if there is transferrin in plasma to bind to. Once transferrin is saturated with iron, any that has accumulated in the mucosal cells will be lost when the cells are shed. As a result of this mucosal barrier, only about 10% of dietary iron is normally absorbed and only 1-5% from many plant foods. 

Fig. 15.2 Example chemical structures of phytochemicals in common dietary food plants.

Because plants are able to synthesize carotenoids de novo, the carotenoid composition of plant foods is enriched by the presence of small or trace amounts of biosynthetic precursors, along with derivatives of the main components. Although commonly thought of as plant pigments, carotenoids are also encountered in some animal foods. Animals are incapable of carotenoid biosynthesis thus their carotenoids need to be derived from the diet. Selectively or unselectively absorbed, carotenoids accumulate in animal tissues unchanged or slightly modified into typical animal carotenoids. 

Khanum F, Swamy MS, Sudarshana Krishna KR, Santhanam K and Viswanathan KR. 2000. Dietary fiber content of commonly fresh and cooked vegetables consumed in India. Plant Foods Hum Nutr 55 207-218. 

We are exposed to plant products (many of the earlier drugs and most of the herbal pharmacopoeia in use today are crude plant extracts), some of which are potentially toxic, as, less commonly, are foods of animal origin. Medicinal drugs are just one of a set of chemicals which are exposed to the range of defence mechanisms put up by the body to protect it from the onslaught of foreign chemicals. 

The data in Table 4.9 Table 4.12 are comprehensive estimates of five classes of flavonoids in commonly available foods in the United Kingdom. Moreover, these estimates are derived from critically assessed published sources and the evaluation procedures adopted ensured the inclusion of content values for edible parts of plant materials available to the UK consumer. A USDA compiled database (http //www.nal.usda.gov/fnic/foodcomp/Data/Flav/flav.pdf) aimed primarily at the North American diet is also available. These databases are in contrast to another literature-derived database that is available for flavonoids where data quality was not formally assessed and flavonoid values determined using semiquantitative methods were also included. 

Flavonols are present in plant foods mainly in the leaves and in the outer parts of plants with quercetin and kaempferol the most common ones. Quercetin and its glycoside are ubiquitous in fruits and vegetables. Conversely, kaempferol and myricetin are less distributed (Table 7) [21-23]. 

Table 1 Chemical Nomenclature and Provitamin A Activity of Some Common Carotenoids of Plant Foods...

Uma Pradeep, K., Geervani, P. and. Eggum, B.O. (1 993) Common Indian spices nutrient composition, consumption and contribution to dietary value. Plant Foods for Human Nutrition (formerly Qualitas Plantarum) 44(2),1 37-1 48. 

Phenols and substituted phenols such as chlorinated phenols and related aromatic compounds are known to be usual components of industrial wastes. Some of the larger and more common sources of wastewater containing phenolic compounds are pulp and paper mills, petrochemical refineries, plastics and glue manufacturers, coke plants, food industries and leachate from municipal waste dumps (Rao et al. 2002). Many phenolic compounds are thought to be highly toxic and carcinogenic so they are considered to be priority pollutants. 

SEE is very suitable for extracting thermolabUe compounds, as it allows the possibility to perform fast extractions at moderate temperatures (around 40°C). " Therefore numerous applications of the technique have been reported. A large field has been covered environmental matrices, plants, foods and fats, and polymers. As legislation will tend to restrict, or even ban, the use of many common solvents, recent extraction techniques will. 

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