Physicochemical characterisation and antimicrobial potential of leaf, rhizome, and root essential oils from turmeric (Curcuma longa): a comparison of conventional and microwave-assisted hydrodistillation techniques
摘要
Curcuma longa L. is well known for its appealing culinary, cosmetic, and therapeutic applications. The purpose of this work was to compare the yield and metabolite profile of C. longa extracted by conventional hydrodistillation (CHD) and microwave-assisted hydrodistillation (MAHD). The volatile metabolites were extracted using CHD and MAHD and analysed by GC-FID and GC-MS. The non-volatile metabolites were extracted by a solvent extraction method and analysed by HPLC-PDA. MAHD yielded 1.5% essential oil at 75 min, whereas CHD failed to reach this level even after 6 h of continuous heating (1.4%). The results showed that the extraction speed of MADH was approximately five times faster than that of CHD. Even though the CHD and MAHD produced essential oils with comparable physicochemical profiles, the concentrations of curcumin and total curcuminoids in the spent rhizome decreased as the extraction time increased. Further, the essential oil yield in crop wastes: senescent leaves and roots was 3.8 ± 0.2% and 0.5 ± 0.0%, respectively. Altogether, 42 constituents, forming 90.0-97.9% of the total oil compositions, were identified. Monoterpenoids (97.3%) and sesquiterpenoids (82.9–83.3%) dominated the leaf and rhizome essential oils, respectively. However, mono- and sesquiterpenoids (51.5% and 42.8%) both constituted the root essential oil. The essential oils from different plant parts exhibited antimicrobial activity against the test microorganism. This study highlighted the superiority of MAHD, which reduced extraction time by 75% compared to CHD.