A comparison of extraction methods of phenolic acids in wheat and American ginseng soil

We compared and evaluated different solvents [water, dichloromethane, 1 M and 2 M sodium hydroxide solution (NaOH)] to extract the phenolic acids in wheat (Triticum aestivum L.) and American ginseng (Panax quinquefolium L.) cultivated soil. All sample solutions, with or without concentrating, were tested with HPLC. Nine individual phenolic acids (p-hydroxybenzoic acid, vanillic acid, syringic acid, vanillin, p-coumaric acid, ferulic acid, benzoic acid, salicylic acid and cinnamic acid) were detected in 1 M and 2 M NaOH extracts with concentrating, while only 5-phenolic acids (p-hydroxybenzoic acid, vanillic acid, vanillin, p-coumaric acid and ferulic acid) were detected without concentrating. However, the contents of p-hydroxybenzoic acid, vanillin and p-coumaric acid detected after concentrating were significantly less. Only 5-individual phenolic acids in American ginseng soil (p-hydroxybenzoic acid, vanillic acid, syringic acid, vanillin and p-coumaric acid) and 4 in wheat soil (p-hydroxybenzoic acid, vanillic acid, syringic acid and vanillin) were detected in water extracts and none in dichloromethane extracts. The results indicated that NaOH and water recovered different phenolic acids from soil and concentrating might cause loss of certain phenolic acids. Besides, concentrating may make more individual phenolic acids detectable in NaOH extract.