Solvent-free microwave extraction and hydrodistillation extraction of essential oils from Syzygium cumini leaves: Comparative analysis of chemical constituents, in vitro and in silico approaches

The essential oil (EO) from Syzygium cumini (L.) Skeels leaves holds significant potential due to its various medicinal and aromatic properties. The present study aimed to compare efficiency of EO extraction from S. cumini leaves using two distinct methods: solvent-free microwave extraction (SFME) and hydrodistillation extraction (HDE). Functional groups such as C-H, C=C, -OH and C=O were revealed by FTIR analysis, suggesting the existence of carbonyl compounds, hydroxyl compounds, alkanes, and alkenes. The GC/MS analysis identified total thirty-seven compounds where major components were isoledene (SFME-23.916 ± 0.178 %, HDE-25.332 ± 0.232 %), β-Pinene (SFME-10.662 ± 0.040 %, HDE-11.302 ± 0.010 %), α-Pinene (SFME-12.699 ± 0.239 %, HDE-9.755 ± 0.125 %) and α-ylangene (SFME-10.246 ± 0.167 %, HDE-10.318 ± 0.085 %). The antioxidant activity, total phenolic content and total flavonoid content of SFME were relatively higher (IC₅₀ 13.511 ± 0.102 ppm, 2.557 ± 0.138 mg GAE/g, 3.383 ± 0.125 mg QCE/g) than HDE (IC₅₀ 16.031 ± 0.121 ppm, 1.235 ± 0.110 mg GAE/g and 3.249 ± 0.022 mg QCE/g). The antimicrobial activity was evaluated by measuring zone of inhibition (ZOI) and minimum inhibitory concentration (MIC). EO extracted by SFME showed highest against bacteria S. aureus (ZOI-17.50 ± 1.87 mm, MIC-3.10 μL/mL) compared to HDE where ZOI-12.83 ± 1.03 mm, MIC-6.20 μL/mL for S. aureus. Molecular docking study also correlates antimicrobial test results. This comparative study demonstrates SFME as a promising method for efficiently obtaining quality essential oil from S. cumini leaves.