Effect of harvest time on the levels of phytochemicals, free radical‐scavenging activity, α ‐amylase inhibition and bile acid‐binding capacity of spinach ( Spinacia oleracea )

BACKGROUND Spinach is a green leafy vegetable that is rich in health‐promoting compounds. The present study analyzed the levels of phytochemicals and health‐promoting properties of spinach harvested at 20, 30, 40, 50 and 60 days after planting. RESULTS The time of harvest had a significant effect on nitrate levels, which increased from 1909 ± 70.6 µg g −1 (20 days) to 3668 ± 101.3 µg g −1 (40 days) and then decreased to 974 ± 164 µg g −1 (60 days). Lutein and chlorophylls a and b were found to be maximum at 60 days, whereas β ‐carotene was higher at 50 days. Liquid chromatography/high‐resolution quadrupole time‐of‐flight tandem mass spectrometry (LC/HR‐QTOF‐MS) was used to identify 12 flavonoids, and their tentative fragmentation pathways have been proposed. Spinach harvested at 30 and 60 days exhibited significantly higher 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) and 2,2′‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid) (ABTS) free radical‐scavenging activities and inhibition of amylase. The levels of total phenolics ranged from 885 ± 35.1 to 1162 ± 112.4 µg g −1 in the samples. In vitro bile acid‐binding capacity showed that glycochenodeoxycholate and glycodeoxycholate were bound to maximum levels in all spinach samples. CONCLUSION The harvest time has a major effect on the levels of phytochemicals and health‐beneficial properties, which indicates that consumption of both baby and mature spinach will provide maximum health benefits. © 2017 Society of Chemical Industry