Edible Flowers of Tagetes erecta L. as Functional Ingredients: Phenolic Composition, Antioxidant and Protective Effects on Caenorhabditis elegans

Abstract

Tagetes erecta L. has long been consumed for culinary and medicinal purposes in different countries. The aim of this study was to explore the potential benefits from two cultivars of T. erecta related to its polyphenolic profile as well as antioxidant and anti-aging properties. The phenolic composition was analyzed by LC-DAD-ESI/MSn. Folin-Ciocalteu, DPPH^·, and FRAP assays were performed in order to evaluate reducing antiradical properties. The neuroprotective potential was evaluated using the enzymes acetylcholinesterase and monoamine oxidase. Caenorhabditis elegans was used as an in vivo model to assess extract toxicity, antioxidant activity, delayed aging, and reduced β-amyloid toxicity. Both extracts showed similar phenolic profiles and bioactivities. The main polyphenols found were laricitin and its glycosides. No acute toxicity was detected for extracts in the C. elegans model. T. erecta flower extracts showed promising antioxidant and neuroprotective properties in the different tested models. Hence, these results may add some information supporting the possibilities of using these plants as functional foods and/or as nutraceutical ingredients.

Keywords: African marigold; Caenorhabditis elegans; antioxidant; edible flowers; neuroprotective potential; polyphenols.

Figure 1

Phenolic profile of T. erecta yellow recorded at 280 nm (A) and 370 nm (B).

Figure 2

Effects of (A) orange cultivar and (B) yellow cultivar of T. erecta flowers extracts on the response to a lethal oxidative stress induced by juglone on C. elegans. Differences compared to the control group were considered significant at p < 0.05 (*) and p < 0.0001 (****).

Figure 3

Effect of the highest dose tested of (A) orange cultivar and (B) yellow cultivar of T. erecta flowers extracts on lifespan of wild-type C. elegans. The mean of the lifespan for orange cultivar were: 18 days (control group), 20 days (50, 75, and 125 µg/mL treated groups) and 22 days (250 µg/mL treated group). For yellow cultivar were: 15 days in all groups except in nematodes treated with 250 µg/mL, which was 18 days. The results of lifespan experiments were analyzed by using the Kaplan-Meier survival model and for significance by using a long rank pairwise comparison test between the control and treatment groups. Differences in survival curves between treatment and control groups were found in: (A) 50 *, 75 ***, 125**, and 250 **** µg/mL. (B): 75 *, 125 *, and 250 *** µg/mL. Differences compared to the control group were considered significant at p < 0.05 (*), p < 0.01(**), p < 0.001 (***), and p < 0.0001 (****).

Figure 4

Effect of (A) orange cultivar and (B) yellow cultivar of T. erecta flower extracts on Aβ-induced paralysis on transgenic C. elegans CL4176. The PT₅₀ for orange cultivar were 50 hours for the control group and 72 hours for all treated groups and for yellow cultivar were 48 hours (control group), 54 hours (50 µg/mL treated group), 72 hours (100 µg/mL treated group), and the PT₅₀ was not achieved in the group treated with 250 µg/mL. Statistical significance of the difference between the experiments was analyzed by a log-rank (Kaplan-Meier) statistical test, which compares the survival distributions between the control and treated groups. Differences in survival tests between treatment and the control group were found in: (A) 50, 100, and 250 µg/mL, p < 0.0001, (B) 50, 100, and 250 µg/mL, p < 0.0001.