Isolation and Characterization of Ginger Phytochemicals

The ginger extract (50 g) was chromatographed on a Sephadex LH-20 column with 95% ethanol as eluant to remove the nonphenolic compounds (Fraction 1, 21.8 g) and to generate the gingerols and shogaols enriched fraction (Fraction 2, 28 g). Fraction 2 was then loaded into a Diaion HP-20 column eluted first with water to remove the water soluble compounds and then with 40% aqueous ethanol to obtain fraction A (9 g) followed by 95% aqueous ethanol to obtain fraction B (11g). Fraction A (5g) was subjected to a normal phase silica gel column with a stepwise gradient of hexane/ethyl acetate [9:1; 8:2, and 7:3] to give pure [6]- (2g), [8]- (0.5 g), and [10]-gingerol (0.4 g). Fraction B (5 g) was also subjected to a normal phase silica gel column with a stepwise gradient of hexane/ethyl acetate [9:1 and 8:2] to generate 13 fractions. Fraction B5 (1g) was subjected to a C-18 reverse phase column eluted with a stepwise gradient of methanol/water [3:2, 7:3, and 4:1] to give [6]-paradol (40 mg), [1]-dehydrogigerdione (60 mg), and [10]-shogaol (120 mg). Following a similar procedure, fraction B7 (1.5 g) gave 200 mg [8]-shogaol and 1 g of [6]-shogaol. The purification procedure was guided by TLC and HPLC analysis. The structures of these eight compounds were confirmed based on their ¹H and ¹³C NMR analysis (Figure 1).