Kaffir Lime Essential Oil Variation in the Last Fifty Years: A Meta-Analysis of Plant Origins, Plant Parts and Extraction Methods

Kaffir lime has been widely researched for use as an essential oil, alongside its main function as an Asian spice, due to the needs of numerous industries. A meta-analysis was used to summarize the variation in yield and main components of kaffir lime essential oils in response to differences in plant origins, plant parts, and extraction methods during the last fifty years. A database was constructed from 85 data items from 36 single studies, prepared by following PRISMA-P. The result showed no significant effect of extraction method on variation in oil yield and main components. In contrast, after integrating numerous single studies under a statistical approach, some interesting facts emerged, such as (i) plant origin significantly affected the citronellol, i.e., subtropical conditions were more favorable than tropical ones; (ii) caryophyllene was found in all countries, from subtropical America and tropical Asia to tropical East Africa; (iii) the richest parts of citronellal, citronellol, citronellyl acetate, and sabinene were leaves, blossoms, twigs, and fruit peels, respectively; and (iv) due to significant interaction of plant origin and plant parts, a very challenging issue in boosting oil yield could be answered by formulating location-specific and organ-specific culture practices. This study had succeeded in providing further research directions.