Antitermitic and antifungal properties of enantiopure linalool and furanoid linalool oxide confirmed in Lindera umbellata var. membranacea

Abstract

In this study, antitermitic and antifungal activities of enantiopure linalool and linalool oxide (furanoid) in L. umbellata var. membranacea were evaluated with their racemates. Results of chiral analysis showed that linalool oxide in leaves dominated by (R)-linalool and in twigs dominated by (S)-linalool were (2R,5R)-trans- and (2R,5S)-cis-linalool oxide and (2S,5S)-trans- and (2S,5R)-cis-linalool oxide, respectively. All rac-, (R)-, and (S)-linalool at highest concentration showed termiticidal and antifeedant activities against Reticulitermes speratus. Antitermitic activities of linalool oxides differed depending on their stereostructures, and (2R,5R)-trans-linalool oxide showed the strongest termiticidal activity. (S)-linalool showed significantly stronger antifungal activity than that of rac- and (R)-linalool against Penicillium citrinum and Chaetomium globosum. Racemate of trans- and cis-linalool oxide showed potent activity against P. citrinum, Rhizopus oryzae, and C. globosum; however, the activity decreased in isolated pure enantiomers. These results suggest that linalool and linalool oxide exhibit different antitermitic and antifungal properties.