Optimization, chemical constituents and bioactivity of Baeckea frutescens L. essential oil extracted by microwave-assisted hydro-distillation

The objective of this study was to optimize the extraction of essential oil from Baeckea frutescens leaves using microwave-assisted hydro-distillation (MAHD) combined with response surface methodology (RSM). This approach aimed to improve extraction efficiency and maximize essential oil yield. The chemical composition of the extracted oil was subsequently analyzed using gas chromatography-mass spectrometry (GC-MS) to identify its principal constituents. The optimal extraction conditions were determined to be a microwave power of 550 W, an extraction time of 89 min and a liquid-to-material ratio of 9.5:1. Under these conditions, the essential oil yield was 3.96 ± 0.02 % (w/w), which represents a high extraction efficiency. GC-MS analysis revealed that the major constituents of the essential oil were α-thujene (26.81 %), α-humulene (15.35 %), trans-caryophyllene (12.29 %) and 3-carene (10.20 %). In addition, biological activity assays indicated that the essential oil exhibited notable antibacterial and antioxidant activities. It significantly inhibited the growth of Escherichia coli and Salmonella typhi, with minimum inhibitory concentrations (MICs) below 100 µg/mL. These findings suggest that Baeckea frutescens essential oil has strong potential as a natural antimicrobial and antioxidant agent, supporting its application in pharmaceutical and industrial products.