Antimicrobial and phytotoxicity activity of essential oils from waste leaves of Curcuma longa.

Curcuma longa L. is a herbaceous crop that is used for wide applications. The economic importance of C. longa is the rhizome but the leaves remain as wastes. The present study aims to extract the essential oils from the waste leaves of four different varieties of C. longa and to evaluate the antimicrobial activity against plant pathogens and phytotoxic activities of essential oils on seed germination. The major components of EO were monoterpenes with abundant percentage varying across the varieties. The major compounds in Rajendra Sonia were α-terpinolene (14.64%), m-cymen-8-ol (14.02%), 5-isopropenyl-2-methyl-7-oxabicyclo [4.1.0]heptan-2-ol (11.13%), in Rajendra Sonali were α-terpinolene (13,91%), m-cymen-8-ol (11.18%), exo-2-hydroxycineole (13.0%), in IISR-Alleppy Supreme were α-phellandrene (12.84%), α-terpinolene (7.77%), and in IISR-Roma were cis-2,3-pinanediol (17.55%), p-cymene (11.76%). EO exhibited notable antimicrobial activity against plant pathogens albeit to a different degree and in a dose-dependent manner. EO from Rajendra Sonali and Roma inhibited 74% of growth of Bipolaris oryzae as compared to the control while EO from IISR-Alleppy and Roma inhibited the growth of Xanthamonas oryzae more effectively as compared to other EO. Furthermore, EO exhibited phytotoxicity effect and inhibited germination of seeds by 62.91% in Triticum aestivum, 76.1% in Panicum sumatrense and 78.6% in Abelmoschus esculentus and inhibition increased significantly with increased concentration of the essential oils with the exception in Zea mays where inhibition was 20.6% and found not significant. The findings from the study suggest that EO from turmeric waste leave could be valorized and have potential for application in pest control management. [ABSTRACT FROM AUTHOR]