This document discusses terpenes, a class of plant secondary metabolites. It begins by defining secondary metabolites and dividing them into three major groups, with terpenes being the largest group. Terpenes are formed from fused five-carbon isoprene units and are classified based on this number, with monoterpenes having two units. There are two pathways for terpene biosynthesis, one involving mevalonic acid and the other methylerythritol phosphate. Important terpenes include lycopene, beta-carotene, and squalene. Terpenes have various biological effects and historical economic uses, such as menthol in medicines and fragrances.

1. TERPENES
INTRODUCTION,CLASSIFICATION,
BIOSYNTHESIS AND IMPORTANCE
BY NAVEED UL MUSHTAQ

2. SECONDARY METABOLITES
• Plants produce a large, diverse array of organic
compounds that appear to have no direct function
in growth, development, photosynthesis,
respiration, solute transport, translocation, protein
synthesis, nutrient assimilation differentiation, or
the formation of carbohydrates.
• These substances are known as secondary
metabolites, secondary products, or natural
products.
• Secondary metabolites also differ from primary
metabolites in having a restricted distribution in
the plant kingdom.

3. Secondary Metabolites Are Divided into
Three Major Groups
• Plant secondary metabolites can be divided
into three chemically distinct groups:
Terpenes(25,000 types)
Phenolics (8,000 types) and
Nitrogen- containing compounds
• The terpenes, or terpenoids, constitute the
largest class of secondary products.
• Terpenoids - oxygen-containing terpenes.

4. Pie chart representing the major groups of
plant secondary metabolites

5. TERPENES
• The term terpenes originates from turpentine
(lat. balsamum terebinthinae). Turpentine, the
so-called "resin of pine trees", is the viscous
pleasantly smelling,insoluble in water which
flows upon cutting or carving the bark and the
new wood of several pine tree species
(Pinaceae).
• Turpentine contains the "resin acids" and
some hydrocarbons, which were originally
referred to as terpenes.

6. Terpenes are Formed by the Fusion of Five-
Carbon Isoprene Units
• All terpenes are derived from the union of five-
carbon elements that have the branched carbon
skeleton of isopentane.
• The basic structural elements of terpenes are
sometimes called isoprene units because
terpenes can decompose at high temperatures to
give isoprene.
• All terpenes are occasionally referred to as
isoprenoids.

7. CLASSIFICATION OF TERPENES
• Terpenes are classified by the number of five-
carbon units they contain.
• Ten-carbon terpenes, which contain two C5 units,
are called monoterpenes
• 15-carbon terpenes (three C5 units) are
sesquiterpenes
• 20-carbon terpenes (four C5 units) are
diterpenes.
• Larger terpenes include triterpenes (30 carbons),
tetraterpenes (40 carbons),and poly terpenoids
([C5]n carbons, where n > 8).

9. There Are Two Pathways for Terpenes
Biosynthesis
• Terpenes are biosynthesized from primary
metabolites in at least two different ways. In the
well-studied mevalonic acid pathway, three
molecules of acetyl-CoA are joined together
stepwise to form mevalonic acid.
• This key six-carbon intermediate is then
pyrophosphorylated, decarboxylated, and
dehydrated to yield isopentenyl diphosphate
(IPP).
• IPP is the activated five-carbon building block of
terpenes.

10. Biosynthesis
• IPP also can be formed from intermediates of
glycolysis or the photosynthetic carbon reduction
cycle via a separate set of reactions called the
methylerythritol phosphate (MEP) pathway
• It operates in chloroplasts and other plastids
• Glyceraldehyde-3-phosphate and two carbon
atoms derived from pyruvate appear to combine
to generate an intermediate that is eventually
converted to IPP.

13. Squalene has a natural and vital part in the synthesis of all
plant and animal sterols, including cholesterol, steroid
hormones, and vitamin D in the human body

14. Lycopene is responsible for the red color in tomatoes and watermelon
-carotene is the compound that causes carrots and apricots to be orange
14
Lycopene's conjugated double bonds give it its deep red
color and are responsible for its antioxidant activity.

15. IMPORTANCE
• Biologically, the monoterpenes have been found to possess a
variety of biological effects, including antibacterial, sedative,
antitumor, cytotoxic, anti-inflammatory, insecticidal,
molluscidal and others.
• They have historically been important ingredients individually
in medicinal and economic products including cosmetics and
other fragrant products.
• One of the best known and most often used monoterpenes is
menthol which has been used as a topical antipruritic, a
counterirritant in external analgesic preparations, as
antiseptic and as a flavoring agent in chewing gums,
toothpaste and tobacco products such as cigarettes.

16. IMPORTANCE
• In drug discovery research reports, linalool, a
monoterpene alcohol found in the essential oils
from many aromatic plants was determined to
be able to moderately inhibit cell proliferation.
• Miliusol, miliusate and miliusane demonstrated
potent cytotoxic activity against a panel of cancer
cell lines.
• Horticulturally, the pyrethrins from Pyrethrum
cinerariaefolium flowers have been used as
potent natural insecticides.

17. IMPORTANCE
• Cumene is a terpene that has been used in
bioremediation studies