BOTANY WITH BASICS OF HYDROBOTANY (AQUATIC PLANTS OF UKRAINE) - B.Ye. Yakubenko - 2011

IV. PLANT ANATOMY AND MORPHOLOGY

Secondary Plant Metabolites

Essential Oils and Resins

This group comprises substances that are insoluble in Water but readily soluble in organic Solvents. They are synthesized and accumulated in specialized plant structures, such as oil ducts (fruits of Apiaceae species), glandular trichomes and scales (Essential Oils), and resin ducts (resins in pines).

Essential oils undergo oxidation upon contact with atmospheric oxygen, turning into balsams; therefore, herbal Materials containing essential oils should be stored in tightly stoppered Glass containers.

Chemically, essential oils are complex mixtures of various compounds, predominantly consisting of Terpenes and their oxygenated derivatives.

Terpenes are Hydrocarbons with the general formula С₁₀Н₁₆. This group includes myrcene (constituting 30–50% of hop essential oil), linalool (found in lily-of-the-valley flowers), geraniol (eucalyptus leaves), citronellol (rose and geranium oils), limonene (caraway and dill fruits), and menthol (peppermint leaves). Turpentine is a notable mixture of terpenes. Another well-known essential oil derivative is camphor, which is found in the wood and leaves of the camphor tree as well as in the herb of the Santolina wormwood.

Diterpenes (С₂₀Н₃₂) present in plant exudates are known as balsams and resins. A prime example of resins is oleoresin obtained from conifers. Upon distillation of oleoresin, a liquid fraction (turpentine) and a solid residue (rosin) are produced. Plant resins consist of resin acids, resin alcohols, Tannins, and hydrocarbons.

Turpentine is widely used in medicine in the form of turpentine baths (which improve capillary Circulation) and turpentine ointments (for colds, radiculitis, etc.).