Phytochemistry 1
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Lecture 1
Date : 3/2/2015
Secondary metabolites
Done By : Sanaa Otoom
As we remember previously the photosynthesis , we remember that we have three major criteria very
important for the photosynthesis :
1- Water (they can get it from soil)
2- Sunlight
3- Chlorophyll
That’s mean any plant whether it’s higher plant or lower plant (like algae) ,must contain chlorophyll to have
the ability to do photosynthesis :
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If we go back to the figure above we see Water +Carbon dioxide  Sugar :
This sugar is known as Glucose (C₆H₁₂O₆) , the first product in our photosynthesis is glucose ,also it’s the
most abundant, most important sugar presented in nature ,then we expect all plant whether higher or lower
plant the first product is glucose .
The plant produces 6 mol of C₆H₁₂O₆ :
6 C₆H₁₂O₆
5 mol to krebs cycle
1 mol deposited in the plant
And this process is primary metabolism , and our sugar glucose is known as
Primary
metabolite
Are products that are NOT restricted to any Genera, Species or Family.
-Primary metabolites are universal products and all plants have the ability to produce them . the sugar
glucose is the primary metabolite that produced by most plants in good amounts (glucose is known as
grape sugar) , but other plants produce it in very small amount and produce another sugar called fructose,
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it’s exactly like glucose but glucose is aldose and fructose is keto sugar (fructose is known as fruit sugar).
Both sugars known as carbohydrate (carbohydrate means compounds contains H and O in the same ratio
as water) .
Glucose
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Now other plants like to take their sugar glucose and fructose combined together which known as
Sucrose (table sugar ) found in plants like beet and sugar cane.
Another important carbohydrate is Starch :
If we return back to the cycle , the 1 mol of glucose that deposited in plant will be converted to starch ,
starch consisting of amylose and amylopectin :
6 C₆H₁₂O₆
5 mol to krebs cycle
1 mol deposited in the plant
o Carbohydrate are divided into :
monosaccharides like
glucose
disaccharides like sucrose
maltose,lactose
polysaccharides like
starch,inulin
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Why we need carbohydrates ?
1- We need them as source of energy in our daily life and food.
2- Used in therapy : for example Dextrose as IV injection as energetic source.
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Another carbohydrates and their uses :
1- Cellulose : it’s exactly like starch but the deposition is randomly , it’s found in the woods of
plants.
- Activated charcoal is carbon atoms that are used in medicine as adsorbent in case of
flatulence.
2- Lactose: we have in pharmacy a derivative of lactose which is lactulose, it’s prepared by
epimerization of lactose and it’s used as laxative.
3- Sucralose : we know that sucrose is not recommended for diabetic patients but the semi
synthetic one sucralose (trichlorinated sucrose) used as sweetener.
Primary metabolites
Carbohydrates
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Lipids
Nucleic acids
Lipids :
Lipids can be classified into saturated and non-saturated lipids or also into essential and non-essential
lipids.
Acetic acid
acetate
They are precursors that considered the most important building blocks for the biosynthesis of lipids, for
this reason we never see odd number of carbon atoms ,all of them are even (acetic acid , butyric acid ,
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capric acid ,caproic acid , lauric acid , palmitic acid,stearic acid ) ,since the origin of their synthesis is the
acetate.
**Our focus in this course on Secondary metabolites , they are not like primary , they are not universal ,
they are restricted in certain genera, species or family, not all plants can produce them.
C₆H₁₂O₆
By glycolysis
Glyceraldehyde : is the simplest carbohydrate,we can use it in therapy as glycerin : - laxative as
suppositories
fermentation
Glycerol
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Examples on secondary metabolites :
- Cocaine it’s an alkaloid found in leaves of coca  it’s restricted to this plant,not found in any
other plant.
- Atropine and related compounds  in Solanaceae family.
Note
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in fact the most important and what we use in therapy are secondary metabolites.
Tannins : plant use them in certain stage of his development to protect from insects or
anything, when the plant doesn’t need them anymore it releases them from leaves as waste,
but for us they are not waste we can use them in medicine .An example on tannins :
Isoprenoids : is the precursor in the biosynthesis of volatile oil (essential oil)
Remember : fixed oils from fatty acids .
Isoprenoid
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Examples on prescriptions that are of natural origin :
Cocaine ,morphine ,atropine and Digoxin.
**we do structural modifications of natural products due to their toxicity , Examples :
1- Artimisin that are used in case of malaria , to reduce its side effects there’s derivatives from it.
2- Taxol used originally for ovarian cancer and then they do modifications for treatment of Lung
cancer ,it’s based on natural structure.
Pyruvate is keto
Acid:
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*Each group in secondary metabolites has its own biosynthetic pathway, own precursor (in our course we
are going to discuss acetate ,malonate pathways).
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The research field for natural products based on Ethnopharmacology: using certain plants by certain
ethnic group in certain area for treatment of certain diseases.
Ex. Artimisin obtained from Chinese plant for treatment of malaria.
Good Luck 
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