The aim of this research was to determine the chemical composition and insecticidal activity of the essential oil of Curcuma wenyujin Y.H. Chen et C. Ling rhizomes against the booklouse Liposcelis bostrychophila Badonnel and to isolate any insecticidal constituents from the essential oil. The essential oil of C. wenyujin rhizomes was obtained by hydrodistillation and analyzed by GC-MS. A total of 43 components of the essential oil were identified and the principal compounds in the essential oil were 1,8-cineole (15.26%), camphor (10.12%), germacrone (6.86%), β-elemene (6.33%), curzerene (6.70%), and β-elemenone (5.23%). followed by curzerenone (4.52%), curdione (4.45%) and linalool (4.43%). Based on bioactivity-guided fractionation, the two main active constituents were isolated from the essential oil and identified as 1,8-cineole and camphor. The essential oil of C. wenyujin rhizomes exhibited contact toxicity against L. bostrychophila with an LD50 value of 208.85 µg/cm2. Camphor (LD50 = 207.26 µg/cm2) exhibited stronger contact toxicity than 1,8-cineole (LD50 = 1048.75 µg/cm2) against booklouse. The essential oil of C. wenyujin (LC50 = 2.76 mg/L air) also possessed fumigant toxicity against L. bostrychophila, while the two constituents, camphor and 1,8-cineole had LC50 values of 1.03 mg/L air and 1.13 mg/L air, respectively. The results indicate that the essential oil of C. wenyujin rhizomes and its constituent compounds have potential for development as natural insecticides or fumigants for control of insects in stored grains.

The vascular system of plants consists fundamentally of two functional cell types, phloem and xylem. Phloem forms an extensive conduit for the dynamic long-distance transport of a diverse range of macromolecular signals that are required for plant development and defense mechanisms. Vascular tissues contain low levels of signaling peptide molecules, which are technically difficult to identify and characterize. We identified low molecular weight peptides from the phloem sap of Chinese Long cucumber using nano-LC-ESI-MS/MS with high SEQUEST scores. Bioinformatics analyses predicted their biological functions as signaling peptides and/or antimicrobial peptides. Here, we selected two peptides (Cupep-1 and Cupep-2), with highly SEQUEST score, to be synthesized and functionally investigated. Cupep-1 synthetic peptide showed a robust antimicrobial activity against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus subtilis and Candida albicans. These results potentiate the use of Cupep-1 peptide as a natural food preservative. We also show that the Cupep-2 peptide was able to conditionally change plant cell differentiation. Thus we suggest a role of Cupep-2 in plant development.