Terpenoidid

Terpenoidid (terpenoids) are a large and diverse class of natural organic compounds built from isoprene units. They are widespread in nature, especially in plants, where they contribute to essential oils, aromas, flavors, pigments, and defense chemicals. Terpenoids are derived from the building blocks isopentenyl pyrophosphate (IPP) and dimethylallyl pyrophosphate (DMAPP) through a series of enzyme-catalyzed condensations and cyclizations.

Biosynthesis of terpenoids occurs via two main pathways. The mevalonate (MVA) pathway operates in the cytosol of fungi and animals, while the methylerythritol phosphate (MEP) pathway functions in plastids of plants and many bacteria. Tubular and ring-forming reactions by terpene synthases generate the core hydrocarbon skeletons, which are then modified by oxidation, reduction, glycosylation and other reactions to yield a vast array of terpenoids.

Classification commonly follows the number of isoprene units. Monoterpenoids (C10), sesquiterpenoids (C15), diterpenoids (C20), sesterterpenoids (C25), triterpenoids (C30), and tetraterpenoids (C40) are examples, with many being oxygenated or rearranged to form diverse structures. Distinctions are often made between terpenes (hydrocarbon precursors) and terpenoids (oxygen-containing derivatives or modified forms).

Biological roles include ecological interactions such as deterring herbivores, attracting pollinators, and signaling. In organisms, terpenoids also serve as membrane components (e.g., sterols) and pigments (carotenoids). Industrially, they are valued for fragrances, flavors, and pharmaceutical properties, with notable examples including menthol, limonene, artemisinin, and many essential oils.