Decrypting solvent-free microwave as a dual green extraction: studying simultaneous extraction of essential oil and phenolics from the same biomass - valorization and outperforming traditional approaches

BACKGROUNDThe current research work focuses on the sustainable utilization of plant biomass so that two separate classes of phytocompounds (volatile and non-volatile principles) can be extracted from the same biomass simultaneously. The hydro-diffusion and gravity variant of solvent-free microwave-based extraction (MHG-SFME) was attempted for the extraction of Piper betle L. essential oil (PBEO).RESULTSThe threat of milky emulsion has been exemplified for the first time which is likely to occur when the biomass temperature exceeds a critical value (85 degrees C). A microwave power level of 255 W with 25 min of extraction time produced PBEO with eugenol content 123% more than that obtained with steam distillation (SD). The said optimal MHG-SFME conditions returned PBEO with the highest phenolic (20.8 mg GAE g-1 of oil) and eugenol (657.57 mu g g-1) contents. PBEO showed better thermal behavior when compared to the EO obtained from SD.CONCLUSIONThe proposed method was capable of retaining non-volatile principles, as the retention of total phenolics in biomass after MHG-SFME was found to be 95%, indicating reusability of the biomass for the extraction of non-volatile principles. In contrast, the retention factor of phenolics content for SD was found to be 17.7% only. Real-time evidence in the form of chemo-microscopy and scanning electron microscopy was generated to understand the retention of phenolics and ultrastructural changes upon microwave exposure. Complete glandular rupture was evident in the biomass subjected to MHG-SFME while the oil glands appeared squeezed for the biomass which underwent SD. Complete profiling of phenolics and flavonoid principles of the leftover biomass was carried out. (c) 2024 Society of Chemical Industry (SCI).