Compounds of plant secondary metabolites

Presently more than 100,000 secondary metabolites are known, and with there being at least 250,000 different works species, each with an infinite figure of interactions possible with their environment, many are thought to be undiscovered ( Pimm, et Al. 1995 ) .Generally our cognition of secondary metabolites is limited, with there being a big figure of cistrons, some of which being genus or even species specific. There is besides an tremendous chemodiversity between secondary metabolites, taking to a hapless word picture of metabolic tracts at the degree of biosynthetic intermediates and enzymes ( Dixon and Steele 1999 ; Forkmann and Martens 2001 ) .

Secondary metabolite diverseness in workss is an evolutionary driven feature that is mostly influenced by their dynamic environment. There is a huge array of functions that these secondary metabolites are involved in, including protection against herbivores, microbic infection, and attractants for pollinators and allelopathic agents. Of those discovered, most are derived from merely a few edifice blocks, the ethanoate C2 unit ( polyketides ) , the phenylalaine/tryrosine-dervied C9 unit ( phenyl-proanoids ) , the isopentenyl diphosphate C5 unit and some aminic acids ( Verpoorte 1998 ) . Exploitation of secondary metabolites is of immense benefit in the production of pharmaceuticals ( see table 1 ) , dyes, insect powders, nutrient additives and spirits, and cosmetics.

What is Biotechnology?

Biotechnology is the control and calculated use of a life system to develop commercial procedures and a merchandise. In the production of secondary metabolites it offers unprecedented chances to work the cell, tissue, organ or full beings by turning them in vitro and to genetically pull strings them to obtain a coveted merchandise.

Biotechnology provides an alternate to obtaining secondary metabolites from wild and cultivated workss. Reaping from wild programs has built-in jobs due to extinction of the harvest from which the metabolite is isolated, habit devastation and a loss of familial diverseness within works species ( certain species affected include Arcostaphylos uva-vrsa ( bear berry ) and Piper methysticum ( kava ) ) . It is estimated that between 4,000 and 10,000 works species whose secondary metabolites are extracted for medical intents are now endangered ( Edwards, 2004 ) . Conventional agricultural production of secondary metabolites is hapless as the workss of greatest involvement to industry make non turn good when they are cultivated outside of their natural environment. Another danger posed by big field cultivation is the susceptibleness of the workss to pathogen invasion ( anthracnose on Hypericum perforatum ) ( Bourgaud et al.,2001 ) . Chemical synthesis of secondary metabolites is frequently non possible due to their extremely complex constructions and a deficiency of sufficient cognition of specific stereochemical demands needed and besides, the feasibleness of the production procedure can be a hinderance ( Bourgaud et al. , 2001 ) .

Biotechnology presents the possibility for the production of secondary metabolites with higher outputs, a uniformed higher quality merchandise, feasibleness and dependability. Due to a deficiency of cognition of secondary metabolites in the developmental phases, under specific emphasiss, seasonal or alimentary demands in workss, merely a few high value secondary metabolites utilizing a biotechnological attack are successful to day of the month on a commercial graduated table. An illustration is shikonin production by cell suspension civilizations of Lithospermum erythrorhizon.

Chemical categories of Secondary Metabolites.

Secondary metabolites can be classified on the footing of chemical construction, composing, whether or non they are soluble in H2O or the tract by which they are synthesised. There are three chief categories:

  1. Terpenoids
  2. Phenolic resins
  3. Alkaloids.


Terpenoids are the largest group of secondary metabolites ( Verpoorte and Memelink, 2002 ) with more than 30,000 different constructions ( Julsing et al. , 2006 ) . All terpenoids are derived by the insistent merger of bifurcate five C units based on an isopentane skeleton. Terpenoids are frequently referred to as isoprenoids. Terpenoids are classified based on the figure of five Cs units they contain. The smallest of these, is isoprene ( C5 ) which is of import in the commercial production of spirits and aroma additives. Sterols are 30 C molecules called triterpene. They play an of import function in the pharmaceutical industry as a get downing stuff for the synthesis of drugs such as steroid endocrines and preventives. In workss, terpenoids are responsible for the release of volatile compounds in response to herbivore harm. These compounds function in pulling arthropods, which prey on the herbivores. Other categories of terpenoids include phytoalexins, which provide direct defense mechanism against herbivores and microbic pathogens.


Alkaloids are the best studied category of secondary metabolites. More than 12,000 alkaloids have been identified ( Oksman-Caldent, 2004 ) . Alkaloids contain N derived from amino acids ( Julsing et al. , 2006 ) and map is thought to be involved in the defense mechanism of the works. Alkaloids represent a really diverse group of medically important compounds that include good known drugs such as morphia and codeine. See figure 2.

Phenolic resins

Phenolic compounds contain aromatic rings bearing one or more hydroxyl groups ( -OH ) . Nearly 8000 of these phenolic compounds have been discovered to day of the month. They are derived from pentose phosphate, shikimate and phenylpropanoid tracts. They have a wide scope of maps including growing, reproduction and defense mechanism. Flavonoids are the largest group of phenolic compounds, and are found in about all known works species ( Julsing et al. , 2006 ) .