terpenoids, types of terpenoids, terpenoid structure, biosynthesis of terpenoids, and terpenoids in medicinal chemistry.
🌿 Chemistry of Terpenoids: Structure, Classification & Applications
Terpenoids, also known as isoprenoids, are a large and diverse class of naturally occurring organic compounds derived from five-carbon isoprene units. Found abundantly in plants, especially in essential oils and resins, terpenoids are responsible for a wide array of aromas, flavors, and biological activities.
🔬 What Are Terpenoids?
Terpenoids are modified terpenes, containing additional functional groups, usually involving oxygen. Their basic structural unit is isoprene (C₅H₈), and they follow the isoprene rule, where most terpenoids are composed of multiples of C₅ units.
🧪 Classification of Terpenoids
Terpenoids are categorized based on the number of isoprene units:
| Type | Number of Isoprene Units | Carbon Atoms | Example |
|---|---|---|---|
| Hemiterpenoids | 1 | C₅ | Isoprene |
| Monoterpenoids | 2 | C₁₀ | Limonene |
| Sesquiterpenoids | 3 | C₁₅ | Farnesol |
| Diterpenoids | 4 | C₂₀ | Taxol |
| Triterpenoids | 6 | C₃₀ | Squalene |
| Tetraterpenoids | 8 | C₄₀ | β-Carotene |
| Polyterpenoids | Many | Variable | Natural rubber |
⚛️ Chemical Structure and Biosynthesis
Terpenoids are biosynthesized via two major pathways:
- Mevalonate Pathway (MVA): Operates in the cytosol, mainly in higher eukaryotes.
- Methylerythritol Phosphate Pathway (MEP): Found in plastids, especially in bacteria and plants.
These pathways convert acetyl-CoA or pyruvate/glyceraldehyde-3-phosphate into IPP (isopentenyl pyrophosphate) and DMAPP (dimethylallyl pyrophosphate), which are then polymerized to form various terpenoids.
🧬 Terpenoids in Nature and Medicine
Terpenoids serve diverse functions in plants and animals:
- Plant defense (antibacterial, antifungal, insecticidal)
- Attractants (pollinators via volatile monoterpenoids)
- Medicinal applications:
- Artemisinin (antimalarial)
- Taxol (anticancer)
- Menthol (analgesic)
Source of Terpenoids
🌿 1. Menthol – Source: Peppermint (Mentha spp.)
- Type: Monoterpenoid
- Use: Found in toothpaste, balms, cough drops, and chewing gum for its cooling effect.
🌳 2. Limonene – Source: Citrus peels (Orange, Lemon)
- Type: Monoterpenoid
- Use: Used in cleaning products, perfumes, and as a natural insect repellent.
🌾 3. Artemisinin – Source: Artemisia annua (Sweet Wormwood)
- Type: Sesquiterpenoid
- Use: Life-saving antimalarial drug recommended by WHO.
🌲 4. Taxol (Paclitaxel) – Source: Taxus brevifolia (Pacific Yew Tree)
- Type: Diterpenoid
- Use: Chemotherapy drug used to treat breast, ovarian, and lung cancers.
🧴 5. Squalene – Source: Shark Liver Oil, Olive Oil, Amaranth Seeds
- Type: Triterpenoid
- Use: Used in cosmetics, skincare products, and as a vaccine adjuvant.
🥕 6. β-Carotene – Source: Carrots, Sweet Potatoes, Spinach
- Type: Tetraterpenoid
- Use: Provitamin A; also used as a natural orange food colorant.
🌸 7. Geraniol – Source: Rose Oil, Citronella Oil
- Type: Monoterpenoid
- Use: Widely used in perfumes and insect repellents.
💊 8. Ginkgolides – Source: Ginkgo biloba
- Type: Diterpenoids
- Use: Known for neuroprotective effects, used in memory-enhancing supplements.
📈 Importance in Modern Chemistry
Due to their structural complexity and biological activities, terpenoids are a hot topic in natural product chemistry, medicinal chemistry, and biotechnology. Synthetic modification of terpenoids is being explored to develop novel drugs and eco-friendly pesticides.
🔍 Conclusion
The chemistry of terpenoids bridges the gap between natural products and applied sciences. From aromatic essential oils to life-saving drugs, terpenoids are nature’s versatile gift to science and industry.