Isolation, Characterization and Bioactivities of Bioactive Compounds from Etlingera spp.
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Universiti Malaysia Sarawak
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Etlingera spp. is one of the largest genera in the Zingiberaceae family, traditionally used by local communities in Borneo for medicinal purposes, culinary and as insect repellents. Despite its widespread traditional use, there is still lack of scientific evidence supporting its potential as a natural source of antioxidants and biopesticides. This study focused on the extraction, isolation and characterization of bioactive compounds from Etlingera coccinea, Etlingera foetens and Etlingera nasuta, as well as the evaluation of their antioxidant and repellent activities. Sequential solvent extraction was performed using hexane, dichloromethane and ethyl acetate. Isolation of bioactive compounds was conducted using thin layer chromatography and column chromatography, while characterization was carried out using gas chromatography - mass spectrometry (GC-MS), fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). Essential oils were extracted using the hydrodistillation method and identified by GC-MS supported with Kovats index data. The extract yields ranged from 0.56 % to 14.19 %, while essential oils yields ranged from 0.08 % to 0.42 %. One slightly pure compound, 5-methyl-2-1-methylethenyl acetate was successfully isolated from ethyl acetate extract from E. nasuta. Major constituents of essential oils were 𝛽-chamigrene (57.41 %), 𝛼-copaene (51.63 %) and 𝛾-elemene (31.91 %) in E. coccinea; octanal acetate (85.63 %), 𝛼-gurjunene (47.75 %) and 𝛽-cubebene (14.69 %) in E. foetens; and neo-intermedeol (49.89 %) and 𝛼-muurolene (27.82 %) in E. nasuta. Antioxidant screening based on DPPH free radical scavenging revealed significant activity in hexane extracts and leaves essential oils of E. foetens and E. nasuta, with IC50 values between 20.95 and 25.2 ppm. Similarly, E. coccinea rhizome essential oil and hexane and ethyl acetate extracts also possessed strong antioxidant potential. Repellent activity indicated that dichloromethane and ethyl acetate extracts of all three species demonstrated high iv repellency (71.43 % - 75.00 %) against Sitophilus oryzae, with effectiveness observed within 1 - 3 hours. The findings support the ethnobotanical claims and suggest that these Etlingera species are promising candidates as natural antioxidants and biopesticides.