Functional groups plants

Acrolein, acrylamide, hydroxyalkyl acrylates, and other functional derivatives can be more hazardous from a health standpoint than acryhc acid and its simple alkyl esters. Furthermore, some derivatives, such as the alkyl 2-chloroacrylates, are powerful vesicants and can cause serious eye injuries. Thus, although the hazards of acryhc acid and the normal alkyl acrylates are moderate and they can be handled safely with ordinary care to industrial hygiene, this should not be assumed to be the case for compounds with chemically different functional groups (see Industrial hygiene Plant safety Toxicology). 

The functional groups of abscisin II could easily arise from a precursor like violaxanthin (M), a carotenoid of widespread occurrence (see 11). Whatever the genesis of abscisin II, it is clear that it must be different from that of the bis-sesquiterpenoid, gossypol (N), which also occurs in the cotton plant and has received considerable attention. 

Humic substances can form complexes with metals, including cationic micronutrients (36), thanks to the presence of electron-donor functional groups in these molecules. It therefore appears evident that due to these properties, humic substances can contribute to the regulation of the chemical balances of metals, thus influencing their solubility (5). With regard to plant availability, the molecular dimension and solubility of humic substances are very important. 

Chemical separations may first be accomplished by partitioning on the basis of polarity into a series of solvents from non-polar hexane to very polar compounds like methanol. Compounds may also be separated by molecular size, charge, or adsorptive characteristics, etc. Various chromatography methods are utilized, including columns, thin layer (TLC) gas-liquid (GLC), and more recently, high pressure liquid (HPLC) systems. HPLC has proven particularly useful for separations of water soluble compounds from relatively crude plant extracts. Previously, the major effort toward compound identification involved chemical tests to detect specific functional groups, whereas characterization is now usually accomplished by using a... 

Biosorption is a rather complex process affected by several factors that include different binding mechanisms (Figure 10.4). Most of the functional groups responsible for metal binding are found in cell walls and include carboxyl, hydroxyl, sulfate, sulfhydryl, phosphate, amino, amide, imine, and imidazol moieties.4 90 The cell wall of plant biomass has proteins, lipids, carbohydrate polymers (cellulose, xylane, mannan, etc.), and inorganic ions of Ca(II), Mg(II), and so on. The carboxylic and phosphate groups in the cell wall are the main acidic functional groups that affect directly the adsorption capacity of the biomass.101... 

Other aquatic weeds such as reed mat, mangrove (leaves), and water lily (Nymphaceae family plants) have been found to be promising biosorbents for chromium removal. The highest Cr(III) adsorption capacity was exhibited by reed mat (7.18 mg/g), whereas for Cr(VI), mangrove leaves showed maximum removal capacity (8.87 mg/g) followed by water lily (8.44 mg/g). It is interesting to mention that Cr(VI) was reduced to Cr(III), with the help of tannin, phenolic compounds, and other functional groups on the biosorbent, and subsequently adsorbed. Unlike the results discussed previously for the use of acidic treatments, in this case, such treatments significantly increased the Cr(VI) removal capacity of the biosorbents, whereas the alkali treatment reduced it.118... 

In recent years, extensive attention has been focused on finding cultured plant cells that can be used as catalysts for organic functional group transformations. A number of transformations employing freely suspended or immobilized plant cell cultures have been reported.24 For example, Akakabe et al.25 report that immobilized cells of Daucus carota from carrot can be used to reduce prochiral carbonyl substrates such as keto esters, aromatic ketones, and heterocyclic ketones to the corresponding secondary alcohols in ( -configuration with enantiomeric excess of 52-99% and chemical yields of 30 63%). 

While most alkaloids do not contain aldehydes when they enter mammalian, microbial, or plant tissues, this functional group may become important when formed as a metabolite of alcohols (via alcohol dehydrogenase) or amines (via oxidative dealkylation and oxidative deamination). Aldehyde dehydrogenases catalyze oxidation of aldehydes to the corresponding carboxylic acids. The physical properties, catalytic mechanism, and specificity of this group of enzymes has been reviewed (99). The general reaction catalyzed by aldehyde dehydrogenase is seen in Eq. (9). 

Triterpenoids (C30 compounds) are the most ubiquitous of the terpenoids and are found in both terrestrial and marine flora and fauna (Mahato et al., 1992). Diterpenoids and triterpenoids rarely occur together in the same tissue. In higher plants, triterpenoid resins are found in numerous genera of broad-leaved trees, predominantly but not exclusively tropical (Mills and White, 1994 105). They show considerable diversity in the carbon skeleton (both tetracyclic and pentacyclic structures are found) which occur in nature either in the free state or as glycosides, although many have either a keto or a hydroxyl group at C-3, with possible further functional groups and/or double bonds in the side-chains. 

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