Extractions Methods and Biological Applications of Essential Oils

Abstract

Plants produce secondary metabolites for defense and based on the biosynthetic pathway, these chemical compounds are broadly divided into three categories namely nitrogen-containing compounds, phenolic compounds, and terpenes. Essential oils and other such compounds are known for their biological activities. The extraction of essential oils is a challenging aspect for researchers in the field of natural products. Hydrodistillation is a time-consuming and very tedious method. Nowadays, accelerated solvent extraction, supercritical fluid extraction, subcritical water extraction, microwave hydrodiffusion are promising alternatives for conventional methods with several advantages. Essential oils have several biological activities in the field of pharmacological, ethnopharmacological, pesticidal, etc.

Biosynthesis of Nanoparticles Using Plant Extracts and Essential Oils

“…The composition of essential oils from plants is affected by the part of the plant analyzed, growing conditions, variation of species, plant growth conditions, extraction methods, place of origin, and phase of plant growth [ 116 , 121 ]. Among these, the extraction method is an important component in improving the overall yield and quality of the essential oil, which should be low-cost and efficient [ 122 ].…”

“…Expression, or cold pressing, is the oldest extraction method used to extract essential oils from plants, flowers, seeds, and citrus [ 122 , 126 ]. This method is used to extract the citrus peel’s essential oils due to the aldehydes’ thermal instability [ 119 ].…”

“…This method is used to extract the citrus peel’s essential oils due to the aldehydes’ thermal instability [ 119 ]. The expeller-pressed oil, at low temperature and pressure, is 100% pure and retains all plant characteristics [ 122 , 127 ]. First, the whole fruit is placed in a device and then mechanically pressed when the essential oil glands are crushed or broken to release the oil.…”

“…Supercritical fluid extraction is a relatively new technique for obtaining essential oils, using supercritical fluids as the extraction solvent. The most commonly used supercritical fluid is CO 2 because it is non-flammable, non-explosive, non-toxic, accessible at low cost, high purity, easily removed from extracts, and diffusivity is two or three times higher than other fluids [ 122 , 136 ]. The heated and compressed fluid passes through the plant material to extract the compounds from the plant, after which the mixture of carbon dioxide and plant extracts is sent to two separators to separate the plant extracts from the CO 2 by decompression.…”

“…Ultrasounds have mechanical vibrations, which, as they move, create expansion and compression cycles within the medium [ 159 ]. A cavitation phenomenon is created by microscopic bubbles’ production and breakdown, leading to cell membrane damage [ 122 , 160 ]. Ultrasound-assisted extraction can occur in an extraction bath or a glass reactor with a conical ultrasonic system.…”