Comparative evaluation of bioactive phytochemicals in Spinacia oleracea cultivated under greenhouse and open field conditions

Various factors related to growing conditions can influence the nutritional quality of plants, including vegetable crops, especially the contents of health-promoting phytochemicals. In this study, the phytochemical contents of spinach (Spinacia oleracea) cultivated under greenhouse and open field conditions were comparatively analyzed using a metabolomic approach with Mass Profiler Professional (MPP) software. S. oleracea, which is one of the well-known leafy vegetables belonging to the family Chenopodiaceae, is cultivated worldwide. Although the nutritional value of spinach is high, the phytochemical contents of spinach cultivated under greenhouse and open field conditions have not been comparatively analyzed. Metabolomic analysis of the methanol (MeOH) extracts of greenhouse-cultivated spinach (GS) and open field-cultivated spinach (OFS) using ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS), followed by principal component analysis (PCA) with MPP demonstrated the differential metabolite profiles of GS and OFS. The active compounds 1-3 were isolated and identified using LC-Q-TOF-MS-guided fractionation. Among these, 5,3',4'-trihydroxy-3-methoxy-6,7-methylenedioxyflavone 4'-glucuronide (2) exhibited growth-inhibitory activities against Helicobacter pylori 51. Distribution analysis of compound 2 revealed that the anti-H. pylori compound 2 is an OFS-specific bioactive phytochemical. This indicates that the phytochemical quality of OFS is better than that of GS. These findings will aid in providing vital data for vegetable processors, dieticians, nutritionists, and consumers to select optimal green leafy vegetables.