The Health Promoting Bioactivities of Lactuca sativa can be Enhanced by Genetic Modulation of Plant Secondary Metabolites

Abstract

Plant secondary metabolites are protective dietary constituents and rol genes evidently increase the synthesis of these versatile phytochemicals. This study subjected a globally important vegetable, lettuce (Lactuca sativa) to a combination of untargeted metabolomics (LC-QTof-MS) and in vitro bioactivity assays. Specifically, we examined the differences between untransformed cultured lettuce (UnT), lettuce transformed with either rolABC (RA) or rolC (RC) and commercially grown (COM) lettuce. Of the 5333 metabolite features aligned, deconvoluted and quantified 3637, 1792 and 3737 significantly differed in RA, RC and COM, respectively, compared with UnT. In all cases the number of downregulated metabolites exceeded the number increased. In vitro bioactivity assays showed that RA and RC (but not COM) significantly improved the ability of L. sativa to inhibit α-glucosidase, inhibit dipeptidyl peptidase-4 (DPP-4) and stimulate GLP-1 secretion. We putatively identified 76 lettuce metabolites (sesquiterpene lactones, non-phenolic and phenolic compounds) some of which were altered by several thousand percent in RA and RC. Ferulic acid levels increased 3033–9777%, aminooxononanoic acid increased 1141–1803% and 2,3,5,4′tetrahydroxystilbene-2-O-β-d-glucoside increased 40,272–48,008%. Compound activities were confirmed using commercially obtained standards. In conclusion, rol gene transformation significantly alters the metabolome of L.sativa and enhances its antidiabetic properties. There is considerable potential to exploit rol genes to modulate secondary metabolite production for the development of novel functional foods. This investigation serves as a new paradigm whereby genetic manipulation, metabolomic analysis and bioactivity techniques can be combined to enable the discovery of novel natural bioactives and determine the functional significance of plant metabolites.

Metabolite Profiling of Manilkara zapota L. Leaves by High-Resolution Mass Spectrometry Coupled with ESI and APCI and In Vitro Antioxidant Activity, α-Glucosidase, and Elastase Inhibition Assays

“…Compared to data from HMDB and the literature [ 15 , 16 , 18 , 20 , 29 ], m / z 121.0280, 123.0437, 128.0386, 135.0285, 151.0388, 161.0230, 173.0442, and 177.0179 were characterized as 2-Hydroxybenzaldehyde, guaiacol, pyroglutamic acid, threonic acid, vanillin, 3-Hydroxycumarin, shikimic acid, and esculetin. The peak at m / z 191.0548 [M–H] − was supposed as quinic acid by detecting fragmented peaks at m / z 173.0445, 127.0388, 109.0282, and 93.0333 with the loss of H 2 O, CH 4 O 3 , CH 6 O 4 , and CH 6 O 5 , accordingly ( Figure S7 ) [ 30 ].…”

“…3,4-Hihydroxybenzoic acid was suggested at m / z 153.0179 and it displayed fragment ion at m / z 109.0282 [ 18 ]. Vanillic acid, caffeic acid, ferulic acid, and syringic acid were detected at m / z 167.0336, 179.0336, 193.0591, and 197.0442, comparing the data found in the Human Metabolome Database (HMDB) and literatures [ 15 , 19 , 20 ]. m / z 169.0129 [M–H] − was characterized as gallic acid and yielded a fragmented ion at m/ z 125.0232 corresponding to [M–H–CO 2 ] − ( Figure S4 ) [ 21 ].…”

“…m / z 337.0917 showed fragmented ions at m / z 191.0555, 173.0449, and 163.0393 upon fragmentation at collision energy (CE) 10 eV and it was characterized as 3- p -Coumaroylquinic acid [ 20 , 33 ]. m / z 343.0658 was identified as 3- O -Galloylquinic acid as it produced fragmented ions at m / z 191.0555, 173.0449, 169.0136, and 125.0235, accordingly [ 15 , 34 ].…”

Stem Lettuce and Its Metabolites: Does the Variety Make Any Difference?

“…This diversity is connected with an array of specialized metabolites produced by the plants. Rapid development of hyphenated analytical techniques brought about an increase in number of metabolomic studies devoted to crop plants, including popular vegetables like lettuce [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ]. The studies have been chiefly focused on polyphenols, especially flavonoids and hydroxycinnamates, which are believed to carry some health benefits [ 9 ].…”

“…Pharmacological studies proved that lactucin-type guaianolides isolated from lettuce demonstrated anti-inflammatory and antinociceptive activity [ 14 , 15 ]. Metabolomic studies on the cultivated lettuce plants revealed also the occurrence of lignans [ 2 , 3 , 4 , 6 ]. The group of specialized plant metabolites seems to be of importance as an estrogenic component of human diet.…”