Phytochemical analysis, antioxidant, and anticholinesterase activities of ethanolic extracts from five ginger plants in Thailand.

Five selected medicinal plants in the family Zingiberaceae, Alpinia nigra, Boesenbergia maxwellii, Etlingera araneosa, Meistera koenigii, and Wurfbainia biflora, were collected from Thailand. HPLC was used to determine the content of phenolic compounds in their ethanolic extracts. The total phenolic contents and the total flavonoid contents of M. koenigii were found to be higher than that of the others. The antioxidant activity of the extracts was assayed by two methods, namely ABTS and DPPH assays using HPTLC and a microplate spectrophotometer. Anticholinesterase activity was screened by the Ellman method against acetylcholinesterase, the chief enzyme of Alzheimer's disease. The results showed mild acetylcholinesterase effects. The results indicated that these five ginger species, especially M. koenigii have the potential to be a good source of natural antioxidants and anticholinesterase agents that could be further applied in the pharmaceutical industry.