10.5.4 Diterpenes
Diterpenes consist of four isoprene units combined together in a head to tail fashion
and the molecular formula is C 20 H 32 . Diterpenes can be divided into different
classes on basis of the number of rings present in the compounds such as (a) acyclic
diterpenes, e.g., phytol (b) monocyclic diterpenes, e.g., retinol (vitamin A) (c) tricyclic diterpenes, e.g., abietic acid (d) tetracyclic diterpenes, e.g., gibberellins
(Fig. 10.24). Diterpenes contain several rings having various sizes. They may be
6-membered ring structures and also they may contain fused 5- and 7-membered
ring structures. Many diterpenes have also additional ring systems. The additional
ring is present in the side substitutions as esters or epoxides [14]. The phytoconstituents containing diterpenoids have great importance for medicinal values.
Phylloquinone, also known as Vitamin K1 having an antihemorrhagic property is a
diterpene that was first discovered in plants in 1929. Vitamin A1, chemically called
retinol is also another diterpenoid that is prepared from a tetraterpenoid, carotene
found in carrot. The bitter principles of Jateorhiza palmata (calumba root) are
under to furanoditerpenes. The diterpenes obtained from Teucrium chamaedrys
(wall germander) and T. scorodonia (wood sage) belonging to the family Labiatae,
both the products show diaphoretics and antirheumatics activity (Papanov et al.
1980). Like all other classes of terpenes, diterpenes have been reported to exhibit a
wide variety of pharmacological activities like as analgesic, antibacterial, antifungal, anti-inflammatory, antineoplastic, antiprotozoal activities and for the treatment
of asthma, glaucoma, as well as congestive cardiomyopathy(Winkel-Shirley.2001).
Few diterpenes isolated from Kalmia latifolia belonging to the family Ericaceae
exhibit antifeedant activity. The gibberellins, plant hormones, first isolated from a
fungus belonging to genus Gibberella and also available in higher plants, are
Table 10.5 The pharmaceutical uses of some important monoterpenes of plant sources
Sl.
No
Name of the
drugs
Uses
1
Menthol
Antipruritic, counterirritant, antiseptic, carminative, flavoring agent,
and stimulant
2
Thymol
Antibacterial, and antifungal
3
Limonene
Flavoring agent, stimulant, stomachic, and carminative
4
Camphor
Rubifacient, counterirritant, antiseptic, antipruritic, carminative,
masking agent in perfumery industry, and insect repellant
5
Eugenol
Analgesic in dental products, flavoring agent, stimulant, antiseptic,
and condiment in cooking
6
Methyl
salicylate
Counter-irritant, antirheumatic, antiseptic, and flavoring agent
7
Cineole
Analgesic in nasal inhaler and spray, antiseptic in mouthwash,
diaphoretic, and expectorant
8
Terpinol
Stimulant and expectorant
358
C. C. Kandar
Diterpenes consist of four isoprene units combined together in a head to tail fashion
and the molecular formula is C 20 H 32 . Diterpenes can be divided into different
classes on basis of the number of rings present in the compounds such as (a) acyclic
diterpenes, e.g., phytol (b) monocyclic diterpenes, e.g., retinol (vitamin A) (c) tricyclic diterpenes, e.g., abietic acid (d) tetracyclic diterpenes, e.g., gibberellins
(Fig. 10.24). Diterpenes contain several rings having various sizes. They may be
6-membered ring structures and also they may contain fused 5- and 7-membered
ring structures. Many diterpenes have also additional ring systems. The additional
ring is present in the side substitutions as esters or epoxides [14]. The phytoconstituents containing diterpenoids have great importance for medicinal values.
Phylloquinone, also known as Vitamin K1 having an antihemorrhagic property is a
diterpene that was first discovered in plants in 1929. Vitamin A1, chemically called
retinol is also another diterpenoid that is prepared from a tetraterpenoid, carotene
found in carrot. The bitter principles of Jateorhiza palmata (calumba root) are
under to furanoditerpenes. The diterpenes obtained from Teucrium chamaedrys
(wall germander) and T. scorodonia (wood sage) belonging to the family Labiatae,
both the products show diaphoretics and antirheumatics activity (Papanov et al.
1980). Like all other classes of terpenes, diterpenes have been reported to exhibit a
wide variety of pharmacological activities like as analgesic, antibacterial, antifungal, anti-inflammatory, antineoplastic, antiprotozoal activities and for the treatment
of asthma, glaucoma, as well as congestive cardiomyopathy(Winkel-Shirley.2001).
Few diterpenes isolated from Kalmia latifolia belonging to the family Ericaceae
exhibit antifeedant activity. The gibberellins, plant hormones, first isolated from a
fungus belonging to genus Gibberella and also available in higher plants, are
Table 10.5 The pharmaceutical uses of some important monoterpenes of plant sources
Sl.
No
Name of the
drugs
Uses
1
Menthol
Antipruritic, counterirritant, antiseptic, carminative, flavoring agent,
and stimulant
2
Thymol
Antibacterial, and antifungal
3
Limonene
Flavoring agent, stimulant, stomachic, and carminative
4
Camphor
Rubifacient, counterirritant, antiseptic, antipruritic, carminative,
masking agent in perfumery industry, and insect repellant
5
Eugenol
Analgesic in dental products, flavoring agent, stimulant, antiseptic,
and condiment in cooking
6
Methyl
salicylate
Counter-irritant, antirheumatic, antiseptic, and flavoring agent
7
Cineole
Analgesic in nasal inhaler and spray, antiseptic in mouthwash,
diaphoretic, and expectorant
8
Terpinol
Stimulant and expectorant
358
C. C. Kandar