Profiling of Nutritionally Vital Bioactive Compounds in Emerging Green Leafy Vegetables: A Comparative Study

Abstract

Green leafy vegetables (GLVs), especially lettuce and spinach, are the key source of bioactive antioxidants in a diet. This research compared the contents and composition of lettuce and spinach bioactive compounds with emerging GLVs, moringa and fenugreek. Liquid chromatography (LC)-mass spectrometry (MS) with single ion monitoring (SIM) was used to examine carotenoids and tocols, while phytosterols were examined using gas chromatography (GC)-MS. Among the studied GLVs, the (all-E)-lutein was the most dominating carotenoid ranging between 31.3 (green/red lettuce)−45.3 % (fenugreek) of total carotenoids, followed by (all-E)-violaxanthin and (all-E)-β-carotene. Surprisingly, (all-E)-β-carotene, a provitamin A carotenoid, was the second most dominating carotenoid in moringa, accounting for 109.2 µg/g fresh weight (FW). Moreover, the significantly highest (p < 0.05; Tukey HSD) contents of total carotenoids (473.3 µg/g FW), α-tocopherol (83.7 µg/g FW), and total phytosterols (206.4 µg/g FW) were recorded in moringa. Therefore, moringa foliage may serve as an affordable source of nutritionally vital constituents in a diet.

Keywords: carotenoids; lutein; phytochemicals; phytosterols; provitamin A; tocopherol; β-carotene.

Figure 1

The representative LC-SIM-MS chromatograms of various carotenoids and α-tocopherol identified in studied GLVs.

Figure 2

The characteristic GC-MS-total ion chromatograms of phytosterols identified in studied GLVs. IS: internal standard. 1, campesterol; 2, stigmasterol; 3, β-sitosterol; 4, α-spinasterol; and 5, 22, 23-dihydrospinasterol. * not a sterol compound.