Recent updates on the chemistry, bioactivities, mode of action, and industrial applications of plant essential oils

Plant extracts - importance in sustainable agriculture

“…The oil composition may vary depending on plant organs, genetics, growth conditions, soil composition, harvest stage, root colonisation by microorganisms (Bajpai et al, 2011;Nikolova and Berkov, 2018;Karalija et al, 2020;Raveau et al, 2020). Essential oils contain a mixture of compounds, specific for each plant, which includes, among others: aldehydes, alkaloids, carotenoids, flavonoids, isoflavones, monoterpenes, phenolic acids, and oxygen-containing, and non-oxygenated terpene hydrocarbons (Zanellato et al, 2009;Fierascu et al, 2020;Ni et al, 2021). Essential oils extracted from aromatic plants can be used not only as sprays, fumigants, or granular formulations but also for seeds coating (Benvenuti et al, 2017;Beni et al, 2020).…”

“…However, due to the low effectiveness of biological and mechanical techniques, worldwide agricultural practices are mostly based on chemical methods (Atak et al, 2016;Shreeya et al, 2016;Fierascu et al, 2020). The chemical interactions among plants could be used as ecological methods to limit the application of synthetic pesticides (Koul et al, 2008;Zanellato et al, 2009;Bajpai et al, 2011;Amri et al, 2013;Taban et al, 2013;Shreeya et al, 2016;Ibáñez and Blázquez, 2018;Saroj et al, 2019;El-rokiek et al, 2020;Fierascu et al, 2020;Mirmostafaee et al, 2020;Raveau et al, 2020;Ni et al, 2021). These interactions include competition (growth inhibition due to the active absorption of limited resources) and allelopathy (growth inhibition due to the release of chemicals).…”

“…Plants release allelochemicals into the environment through leaf or stem leaching (caused by rain, dew, irrigation), tissue decomposition, root exudates, and volatilisation (prevalent in dry and semi-arid conditions) (Atak et al, 2016;Mirmostafaee et al, 2020). The ability of aromatic and medicinal plants to transmit allelochemicals in their essential oils (Benvenuti et al, 2017;Jouini et al, 2020;Mirmostafaee et al, 2020) has attracted much attention due to their phytotoxic activity against weeds and the possibility of the use as potential green pesticides (Koul et al, 2008;Atak et al, 2016;Shreeya et al, 2016;Benvenuti et al, 2017;Raveau et al, 2020;Ni et al, 2021). On average, most plants contain from 1 to 2% of essential oils (ranging from 0.01 to 10%) (Koul et al, 2008).…”

“…On average, most plants contain from 1 to 2% of essential oils (ranging from 0.01 to 10%) (Koul et al, 2008). EOs are synthesised by all plant organs (e.g., herbs, buds, flowers, fruits, leaves, twigs, bark, wood, seeds, roots) (Bajpai et al, 2011;Amri et al, 2013;Taban et al, 2013;Atak et al, 2016;Shreeya et al, 2016;Raveau et al, 2020), and mostly are extracted by hydrodistillation, water and steam distillation, as well as a solvent or supercritical fluid extraction (Miguel, 2010;Bajpai et al, 2011;Nikolova and Berkov, 2018;Raveau et al, 2020;Ni et al, 2021). Essential oils are stored in secretory cells, cavities, canals, epidermic cells, or glandular trichomes (Shreeya et al, 2016;Nikolova and Berkov, 2018;Raveau et al, 2020).…”

“…Plants emit volatile organic compounds to attract pollinators, seed dispersers, and other beneficial organisms (Amri et al, 2013;Taban et al, 2013;Shreeya et al, 2016) as well as to protect themselves against heat and cold and induce defence responses (Koul et al, 2008). Essential oils, a source of bioactive compounds, can exert antibacterial, antifungal, herbicidal, nematicidal, and insecticidal activities which encourage their exploration and utilisation as one of the most promising natural products that could be used as an alternative to synthetic chemical pesticides (Shreeya et al, 2016;Ibáñez and Blázquez, 2018;Saroj et al, 2019;El-rokiek et al, 2020;Fierascu et al, 2020;Karalija et al, 2020;Raveau et al, 2020;Ni et al, 2021). The EOs global market is projected to reach 403.06 kilotonnes by 2025, thus the large-scale production could contribute to the decrement of their production costs (Fierascu et al, 2020).…”