Solvent-free Microwave and Hydro-distillation Extraction of Essential Oils from the Sawdust of Pines: Correlation with Heat-map

The chemical compositions were investigated for pine essential oils obtained through a solvent-free microwave assistance extraction system (ME) and a conventional hydrodistillation system (HD). The essential oils of P. pinea, P. nigra, P. brutia, and P. sylvestris sawdust were analyzed by gas chromatography and mass spectroscopy (GC-MS). The main components of the pine essential oils were D-limonene (52.8% for ME and 76.6% for HD), beta-caryophyllene (12.4% for ME), beta-myrcene (2.89% for ME and 1.48% for HD), sesquiterpene hydrocarbons (25% for ME and 9.79% for HD), and total sesquiterpene (25.25% for ME and 9.79% for HD) for P. pinea; D-limonene (28.1% for ME and 79.2% for HD) for P. nigra; beta-pinene (76.6% for ME and 77.3% for HD), diterpene hydrocarbons (94.17% for ME and 95.62% for HD), and total diterpenes (94.94% for ME and 96.3% for HD) for P. brutia; beta-pinene (36.7% for ME and 42.4% for HD), terpineol, (13.8% for ME and 6.06% for HD) diterpene alcohol (26% for ME and 12.57% for HD), and total oxygenated terpenes (26% for ME and 12.57% for HD)for P. sylvestris. Moreover, the ME was able to produce more diterpene alcohols and sesquiterpene hydrocarbons while the HD showed higher potential for the diterpene hydrocarbons. According to the heat-map correlation, P. pinea showed high similarity with P. nigra, while P. sylvestris was related to P. brutia.