Characterization of homoisoflavonoids in different cultivation regions of Ophiopogon japonicus and related antioxidant activity

Homoisoflavonoids were identified in Ophiopogon japonicus of two cultivation regions in China: Hang-maidong (grown in Zhejiang province) and Chuan-maidong (grown in Sichuan province). Liquid chromatography (LC), coupled with electrospray ionization (ESI) tandem mass spectrometry (MS), was developed to analyze homoisoflavonoids in these two areas. Based on LC-MS/MS data, 24 homoisoflavonoid compounds--19 in Hang-maidong and 17 in Chuan-maidong--were identified or tentatively characterized. The homoisoflavonoids in the two regions were similar in chemical profile, but distinctive in their combination and ratio. Methylophiopogonanone A and methylophiopogonanone B were the major contributors to the total homoisoflavonoid content. Hang-maidong had a higher total homoisoflavonoid content and better DPPH (2,2-diphenyl-1-picryl-hydrazyl) radical-scavenging activity than that of Chuan-maidong. The total phenolic content showed no significant difference between the two regions. This study allows a clear chemical differentiation of Hang-maidong from Chuan-maidong.