Composition of the essential oil from Alpinia galanga rhizomes and its bioactivity on Lasioderma serricorne

The aim of this research was to determine the chemical constituents and bioactivity of the essential oil derived from Alpinia galanga (L.) Willd. rhizomes against the cigarette beetle Lasioderma serricorne (F.) (Coleoptera Anobiidae) adults. The essential oil of A. galanga obtained by hydrodistillation was investigated by gas chromatography-mass spectrometry (GC-MS). The main components of the essential oil were identified to be eucalyptol (22.63%), (1S)-(1)-β-pinene (14.36%), 1R-α-pinene (10.89%), α-terpineol (8.59%) and L(-)-borneol (8.41%) followed by (-)-camphor (4.21%) and camphene (4.14%). Eucalyptol, β-pinene, α-pinene, α-terpineol and borneol were separated and purified by silica gel column chromatography and preparative thin layer chromatography, and further identified by means of physicochemical and spectrometric analysis. The essential oil of A. galanga rhizomes was found to possess strong contact toxicity against L. serricorne adults with LD50 value of 12.2 μg/adult, and also showed strong fumigant toxicity against L. serricorne adults with LC50 value of 3.5 mg/L. α-Terpineol and eucalyptol showed strong contact toxicity against L. serricorne (LD50 = 13.3 and 15.6 μg/adult, respectively) and fumigant toxicity against L. serricorne (LC50 = 2.8 and 5.2 mg/L air, respectively). Moreover, the essential oil and eucalyptol also exhibited the strong repellency against L. serricorne adults whereas borneol exhibited weaker repellency relative to the positive control, DEET. The study revealed that the bioactivity properties of the essential oil can be attributed to the synergistic effects of its diverse major and minor components. The results indicate that the essential oil of A. galanga and the isolated compounds have potential to be developed into natural insecticides or repellents in controlling insects in stored grains and traditional Chinese medicinal materials.