CHEMISTRY OF NATURAL PRODUCTS

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What are natural products?


Living organisms, such as plants, animals, fungi, or microorganisms, produce a vast array of organic compounds. Indeed, the very word “organic” which we use nowadays to mean “carbon-containing,” originally meant derived from organisms. Organic chemistry began and developed as the study of these naturally occurring organic compounds. During the past one and a half centuries, the scope of organic chemistry has dramatically expanded beyond these origins. Nevertheless, the study of natural occurring organic compounds continues to play a vital role in organic chemistry. These compounds are usually referred to as natural products.
Natural products are chemical compounds or substances isolated  from  living  organism. The chemistry of the natural product include their biosynthesis, extraction, identification, quantification, structural elucidation, physical and chemical properties and reactions.
 

Natural products are often divided into two major classes:

  • Primary metabolites.
  • Secondary metabolites.

Primary metabolite are those produced by and involved  in primary metabolite processes such as respiration and photosynthesis. They are directly involved in essential cellular functions such as nutrient assimilation, energy production, and growth/development. Primary metabolites include the building blocks required to make the four major macro-molecules within the body: carbohydrates, lipids, proteins, and nucleic acids (DNA and RNA).

Secondary metabolites  are not  directly involved in growth, development  and  reproduction  of  an  organism,  but  they have  an  ecological  function.  Plant  secondary  metabolite can be found in  the leaves, stem, root  or the bark of  the plant depending on the type of secondary metabolite that is been  produced.  The  most  bio-active  secondary metabolite  are the  Alkaloids,  Tannins,  Flavonoids  and Phenolic  compounds. Many of these secondary metabolites are  indigenous plant use as  food, spices  and herbs.

The role of secondary metabolites 

The role of primary metabolites in nature has long been well understood by biochemist. These molecules are involved in the most fundamental processes of life. The exact role of every secondary metabolite is unknown to us. However, some role is obvious. The various pheromones that insect and other creatures have developed to communicate with one another, such as trail pheromones or sex pheromones, have an easily identifiable function. So do the many toxic compounds that various plants, fungi, and animals make; these are chemical defences to ward off predators. Marine organisms are especially skilled at the types of “chemical warfare “and some of deadliest poisons (e.g. tetradotoxin, palytoxin ) come from marine sources.

Many organisms make compounds that repel or attract other organisms, depending on the situation. The attractive smells given off by many flowers attract insects that help  pollinate the plants. Skunks emits the evil - smelling 3-methylbutane-1-thiol which  repels  potential predators.  Fruits  may  taste  good or bad, depending on whether it is useful for them to be eaten or not. Sometimes   the result may be unexpected, For example, chili plants produce the alkaloid capsaicin, which imparts the characteristics hot taste of chilies. Animals which do not like this taste will probably avoid chilies. However, the fact that many human beings love the hot taste of capsaicin has had an unexpected result.

                                                                 capsaicin


Classification of plant secondary metabolites

 Plants  secondary  metabolites  can  be  divided  into  the following broad classes.

Terpenes and terpenoids

  • Steroids
  • Fatty acids
  • Eicosanoids
  • Polyketides  phenols
  • Phenols
  • Carbohydrates
  • Amino acids and peptides
  • Nucleosides and nucleotides
  • Alkaloids

 

Primary metabolite are those produced by and involved  in primary metabolite processes such as respiration and photosynthesis. They are directly involved in essential cellular functions such as nutrient assimilation, energy production, and growth/development. Primary metabolites include the building blocks required to make the four major macro-molecules within the body: carbohydrates, lipids, proteins, and nucleic acids (DNA and RNA).

Secondary metabolites  are not  directly involved in growth, development  and  reproduction  of  an  organism,  but  they have  an  ecological  function.  Plant  secondary  metabolite can be found in  the leaves, stem, root  or the bark of  the plant depending on the type of secondary metabolite that is been  produced.  The  most  bioactive  secondary metabolite  are the  Alkaloids,  Tannins,  Flavonoids  and Phenolic  compounds. Many of these secondary metabolites are  indigenous plant use as  food, spices  and herbs.

 

  

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