1. Chemistry of natural products

2. Classification of Natural product
There is no rigid scheme for classifying natural products—their immense diversity in structure, function, and biosynthesis is too great to allow them to fit neatly into a few simple categories
Five main classes of natural products:
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3. Terpenoids and Steroids, Fatty Acid–derived Substances and Polyketides, Alkaloids, Non Ribosomal Polypeptides, and Enzyme Cofactors.
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4. Natural Products (secondary metabolites)
Terpenoids, Steroids
Alkaloids
Fatty acids, Polyketides
Non ribosomal polypeptides
Enzyme cofactors
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5. Terpenoids and steroids
Are a vast group of substances—more than 35,000 are known—derived biosynthetically from
Isopentenyl diphosphate.
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6. Alkaloids
Are a large and diverse class of compounds, with more than 12,000 examples known at present.
They contain a basic amine group in their structure and are derived biosynthetically from amino acids.
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7. Fatty acid
Derived substances and polyketides, of which more than 10,000 are known, are biosynthesized from simple acyl precursors such as acetyl CoA, propionyl CoA, and methyl malonyl CoA.
Natural products are derived from fatty acids, such as the eicosanoid prostaglandin E1,but polyketides, such as the antibiotic erythromycin A often have many oxygen substituents remaining.
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8. Nonribosomal polypeptides
They are peptide like compounds that are biosynthesized from amino acids by a multifunctional enzyme complex without direct RNA transcription.
The penicillins are good examples
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9. Enzyme cofactors
Cofactors, mostly metal ions or coenzymes, are inorganic and organic chemicals that assist enzymes during the catalysis of reactions.
Coenzymes are non-protein organic molecules that are mostly derivatives of vitamins soluble in water by phosphorylation; they bind apoenzyme to proteins to produce an active holoenzyme.
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10. Terpenoids
Have an immense variety of apparently unrelated structures, while steroids have a common tetracyclic carbon skeleton and are modified terpenoids that are biosynthesized from the triterpene lanosterol
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11. Introduction to Natural Products
Natural products are products from various natural sources, plants, microbes and animals.
Natural products can be an entire organism (e.g. a plant, an animal or a micro-organism), a part of an organism (e.g. leaves or flowers of a plant, an isolated animal organ), an extract of an organism or part of an organism and an exudate, or pure compound (e.g. alkaloids, coumarins, flavonoids, lignans, steroids and terpenoids) isolated from plants, animals or micro-organisms.
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12. However, in practice, the term natural product refers to secondary metabolites, small molecules (molecular weight < 1500 amu), produced by an organism, but not strictly necessary for the survival of the organism.
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13. CHAPTER-1 CHEMISTRY OF NATURAL PRODUCTS, Prepared by Dr. Khalid Shadid
29/07/1440
The 18th century …
At the end of the 18th century, crude drugs were still being used as powders, simple extracts, or tinctures.
The era of pure compounds (In 1803, a new era in the history of medicine)
Isolation of morphine from opium
Strychnine (1817)
Quinine and caffeine (1820)
Nicotine (1828)
Atropine (1833)
Cocaine (1855)
morphine
Nicotine
Strychnine
caffeine
Quinine
Atropine
Cocaine
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14. CHAPTER-1 CHEMISTRY OF NATURAL PRODUCTS, Prepared by Dr. Khalid Shadid
29/07/1440
In the 19th century, the chemical structures of many of the isolated compounds were determined
In the 20th century, the discovery of important drugs from the animal kingdom, particularly hormones and vitamins. In addition, microorganisms have become a very important source of drugs
Captopril
Epibatidine
Penicillin
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15. Epibatidine has a high analgesic potency
Epibatidine is a putative  alkaloid that is secreted by the Ecuadoran frog Epipedobates Anthonyi
 It was discovered by  John W. Daly in 1974, but its structure was not fully elucidated until Whether Epibatidine is the first observed example of a chlorinated alkaloid
Epibatidine has a high analgesic potency
Captopril is used to treat high blood pressure (hypertension), congestive heart failure, kidney problems caused by diabetes, and to improve survival after a heart attack. 
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16. CHAPTER-1 CHEMISTRY OF NATURAL PRODUCTS, Prepared by Dr. Khalid Shadid
29/07/1440
Compounds from natural sources play significant roles in modern medicine:
They provide a number of extremely useful drugs that are difficult, if not impossible, to produce commercially by synthetic means
Natural sources also supply basic compounds that may be modified slightly to render them more effective or less toxic
Their utility as prototypes or models for synthetic drugs possessing physiologic activities similar to the originals
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17. Ibuprofen
salicylic acid
Aspirin
Spirea
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18. Overview of a bioassay-guided traditional natural product drug discovery process
Source materials
(e.g. plant)
Extract (s)
Active extract (s)
Extraction
Chromatographic fractionation
Bioassay
Chromatographic fractions
Active fraction (s)
Isolation and purification
Bioassay
Isolated compounds
Active compound (s)
Identification by spectroscopic techniques, e.g. UV, IR, MS, NMR
Bioassay
Identified compounds
Identified bioactive compound (s)
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19. Thank You
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