High Growing Temperature Changes Nutritional Value of Broccoli (Brassica oleracea L. convar. botrytis (L.) Alef. var. cymosa Duch.) Seedlings

Abstract

High temperature (HT) causes physiological and biochemical changes in plants, which may influence their nutritional potential. This study aimed to evaluate the nutritional value of broccoli seedlings grown at HT on the level of phytochemicals, macro- and microelements, antioxidant capacity, and their extracts' in vitro cytotoxicity. Total phenols, soluble sugars, carotenoids, quercetin, sinapic, ferulic, p-coumaric, and gallic acid were induced by HT. Contrarily, total flavonoids, flavonols, phenolic acids, hydroxycinnamic acids, proteins, glucosinolates, chlorophyll a and b, and porphyrins were reduced. Minerals As, Co, Cr, Hg, K, Na, Ni, Pb, Se, and Sn increased at HT, while Ca, Cd, Cu, Mg, Mn, and P decreased. ABTS, FRAP, and β-carotene bleaching assay showed higher antioxidant potential of seedlings grown at HT, while DPPH showed the opposite. Hepatocellular carcinoma cells were the most sensitive toward broccoli seedling extracts. The significant difference between control and HT-grown broccoli seedling extracts was recorded in mouse embryonal fibroblasts and colorectal carcinoma cells. These results show that the temperature of seedling growth is a critical factor for their nutritional value and the biological effects of their extracts and should definitely be taken into account when growing seedlings for food purposes.

Keywords: Brassicaceae; antioxidant capacity; climate change; food quality; global warming; in vitro cytotoxicity; macro- and microelements; phytochemical composition.

Figure 1

MTT assay showing the viability, expressed in IC50 values, of HaCaT, HepG2, HCT116, and H460 cells after exposure to the extracts of broccoli seedlings grown under room (RT) and high temperature (HT). Values represent mean ± standard deviation of three biological replicates and three technical replicas. Different letters indicate a significant difference among the values for each cell type separately (ANOVA, Duncan’s test, p ≤ 0.05). HaCaT = normal human keratinocytes, HepG2 = hepatocellular carcinoma cells, HCT116 = colorectal carcinoma cells, and H460 = lung carcinoma cells.

Figure 2

Viability of (A) MEF, (B) HaCaT, (C) HepG2, (D) HCT116, and (E) H460 cells measured by means of neutral red uptake after incubation with different concentrations of extracts of broccoli seedlings grown under room (RT) and high temperature (HT). Values represent mean ± standard deviation of three biological replicates and three technical replicas. Different letters indicate a significant difference among the values for each extract concentration separately (ANOVA, Duncan’s test, p ≤ 0.05). MEF = mouse embryonal fibroblasts, HaCaT = normal human keratinocytes, HepG2 = hepatocellular carcinoma cells, HCT116 = colorectal carcinoma cells, and H460 = lung carcinoma cells.

Figure 3

Principal component analysis of the groups of broccoli seedlings: (A) score plot separating the samples based on the measured phytochemicals (individual and groups), macro- and microelements, antioxidant capacity, and in vitro cytotoxicity, and (B) loading plot of the measured variables.

Figure 4

Hierarchical clustering, expressed as Euclidean distance, of control and treated groups of plants, based on the measured total and individual bioactive compounds, their pigments, oxidative stress parameters, antioxidant potential, and ability to inhibit enzymes α-amylase, α-glucosidase, and lipase. HT = plants watered with high temperature water, CT = plants watered with cold water, and Con = plants watered with room temperature water.