Optimization of green microwave-assisted extraction of essential oil from lemon (Citrus limon) leaves: Bioactive, antioxidant and antimicrobial potential

This research delves into the analysis of essential oil derived from Citrus limon leaves cultivated in the northern region of Bangladesh, focusing on their potential attributes. The essential oil was extracted employing a microwave-assisted gravity station without using solvent. Optimization was carried out in terms of time, temperature and power as a function of oil yield. The study revealed the highest oil yield of 2.5 % after 50 min at 110 °C, maintaining a microwave power of 300 watt. Twenty-four (24) phyto-components were identified by Gas Chromatogram- Mass Spectrometer (GC-MS) where d-Limonene (34.10660 %) was dominant compound. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay was used to assess the antioxidant activity of essential oil. Notably, essential oil displayed superior DPPH radical scavenging activity (IC₅₀ 8.57 ppm) compared to butylated hydroxytoluene (BHT) (IC₅₀ 10.63 ppm), a common antioxidant standard. Furthermore, a variety of harmful microorganisms were used to evaluate the antimicrobial efficacy. The extracted essential oil exhibited the strongest antimicrobial effectiveness against bacteria Staphylococcus aureus (ZOI-27.50 mm, MIC-7.8 μL/mL) and the fungi Candida albicans (ZOI-32.83 mm, MIC-1.95 μL/mL). These findings demonstrate the Citrus limon leaves essential oil contains bioactive components with strong antioxidant and antimicrobial properties. The extracted essential oil holds significant potential for applications in the foods, pharmaceuticals and cosmetic industries.