Chemical constituents and antioxidant activity from the rhizomes of Zingiber Cassumunar

Abstract

Zingiber cassumunar is one of the species belongs to the genus of Zingiber in the Zingiberaceace family. Hydrodistillation of fresh rhizomes afforded 2.83% of essential oil as a pale yellow liquid with pungent smell. Chemical compositions of the oils were determined by gas chromatography and gas chromatography-mass spectrometry techniques. Twenty-nine compounds were found in the rhizome essential oil which contributed to 78.74% of the total oil. The compounds have been classified as monoterpenes (75.9%), sesquiterpenes (1.8%) and ester (0.8%). The major constituents were found to be terpinen-4-ol (31.35%) (1)and sabinene (23.37%)(2). The dried rhizome of Z. cassumunar was also extracted with chloroform using Soxhlet extraction for twenty hours. Fractionation of the crude extract using silica gel vacuum liquid chromatography, followed by repeated purification using silica gel gravity column chromatography afforded two compounds. The structure of these compounds were elucidated by infrared and nuclear magnetic resonance spectroscopies as trans-1-(3,4-dimethoxyphenyl)butadiene (3)and trans-4-(3,4-dimethoxyphenyl)but-3-en-1-yl acetate(4). DPPH antioxidant screening using DPPH free radical scavenging activity showed that the essential oil of the rhizome of Z. cassumunar gave weak antioxidant property and chloroform crude extract gave positive antioxidant result at higher concentration.