Exploring chemical composition and insecticidal activities of Alpinia calcarata rhizome essential oil against three major storage insects

Alpinia calcarata (Roscoe), generally recognized as snap ginger or lesser galangal of the Zingiberaceae family, undergoes widespread cultivation in tropical nations. It is characterized by its noteworthy pharmacological attributes, such as anti-inflammatory, analgesic, antinociceptive, reproductive, anti-cancer, and gastro-protective effects. Many storage pests now resist traditional chemical pesticides. Transitioning to organic alternatives is a preferable and sustainable solution. This research investigates the insecticidal activity of essential oil from A. calcarata rhizomes, obtained via hydro-distillation. Chemical analysis was conducted, and the study assessed its toxicity and repellent effects on Tribolium castaneum (Herbst), Lasioderma serricorne (F.), and Callosobruchus chinensis (L). A yield of 0.44 ± 0.02 % essential oil was obtained from dry rhizomes. Gas chromatography-mass spectrometry (GC-MS) characterization revealed the major chemical constituents as 1,8-cineole (25.71 %), ethyl iso-allocholate (16.01 %), and fenchyl acetate (15.15 %). The findings from the investigation into the pesticidal characteristics of essential oils derived from the rhizome of A. calcarata unveiled significant contact (LC₅₀ at 24 h was 10.9 mg/cm² for T. castaneum, 1.0 mg/cm² for L. serricorne and 0.5 mg/cm² for C. chinensis) and fumigant toxicity (LC₅₀ at 24 h was 4.05 mg/L air for T. castaneum, 1.75 mg/L air for L. serricorne, and 1.03 mg/L air for C. chinensis). The repellent efficacy was evaluated through an area preference test, revealing robust repellent activity at various concentrations. Undoubtedly, the essential oil extracted from the rhizome of A. calcarata is valuable and has the potential to be a safe, organic pesticide for controlling storage pests.