Can Simulated Microgravity and Darkness Conditions Influence the Phytochemical Content and Bioactivity of the Sprouts?-A Preliminary Study on Selected Fabaceae Species

Abstract

Sprouts' consumption has become popular due to their wide availability, easy cultivation process, and proven biological activity. Moreover, stress factors, such as limited access to light or disturbed gravity during growth, may contribute to the increased activity and the synthesis of bioactive compounds. In this study, for the first time, the examination of the impact of darkness and simulated microgravity conditions on the white clover sprouts from the Fabaceae family was conducted. Among several species, used in the preliminary attempts, only white clover was satisfactory sprouting in the disturbed gravity conditions, and thus was chosen for further examination. A random positioning machine setup was used during the cultivation process to simulate microgravity conditions. Additionally, the sprouts were cultivated in total darkness. Simulated microgravity and/or darkness during the first few days of the sprouts' growth caused biomass reduction, the increased synthesis of bioactive compounds (isoflavones and phenolics), and changes in the level of abscisic acid and phenylalanine ammonia-lyase. Moreover, it increased the antioxidant properties of the sprouts, while the enhancement of their cytotoxic impact was observed only for androgen-dependent prostate cancer LNCaP cells. To conclude, the presented results are promising in searching for novel functional food candidates and further studies are necessary, directed at other plant families.

Keywords: Fabaceae; antioxidant; cytotoxic; isoflavones; phenolics; simulated microgravity; sprouts.

Figure 1

White clover sprouts on the 6th day of germination in simulated microgravity ((A), sample 6LM) and normal gravity conditions ((B), sample 6L). Abbreviations of the sprouts’ samples: 6LM—6-days-old sprouts grown in standard light and simulated microgravity conditions; 6L—6-days-old sprouts grown in standard light conditions.

Figure 2

Changes in the biomass of the white clover sprouts presented as % of control (weight of control sprouts 5L, 6L, and 7L). Abbreviations of the sprouts’ samples: L—the sprouts grown in standard light conditions; D—the sprouts grown in darkness; LM—the sprouts grown in standard light and simulated microgravity conditions; DM—the sprouts grown in darkness and simulated microgravity conditions.

Figure 3

Abscisic acid (ABA) amount and phenylalanine ammonia-lyase (PAL) activity in the white clover sprouts presented as the % of control (control: the amount of ABA and PAL activity in the 5L, 6L, and 7L sprouts). Significant differences were calculated for each day of harvesting separately and were marked with pairs of letters a–c (*: p ≤ 0.05). Abbreviations of the sprouts’ samples: L—the sprouts grown in standard light conditions; D—the sprouts grown in darkness; LM—the sprouts grown in standard light and simulated microgravity conditions; DM—the sprouts grown in darkness and simulated microgravity conditions. The numbers placed before each abbreviation indicate harvest days (5, 6, and 7 days).

Figure 4

Viability of the PC3, DU145, and LNCaP cells after 24 h incubation with the white clover sprout extracts used in different concentrations (50, 100, and 200 μg/mL). Significant differences between the cells treated with the extracts from the white clover sprouts grown in microgravity conditions versus control sprouts were marked with an upper black line (***: p ≤ 0.001; **: p ≤ 0.01; *: p ≤ 0.05). Significant differences between different days of harvesting (e.g., 5LM50 vs. 6LM50), concentrations (e.g., 5LM50 vs. 5LM100) of extracts, and light conditions (e.g., 5LM50 vs. 5DM50) were marked with pairs of letters a–z, A–Z, and special signs (@, <, >, ^, %, &, #, +, and $). Abbreviations of the sprouts’ samples: L—the sprouts grown in standard light conditions; D—the sprouts grown in darkness; LM—the sprouts grown in standard light and simulated microgravity conditions; DM—the sprouts grown in darkness and simulated microgravity conditions. The numbers placed before each abbreviation indicate harvest days (5, 6, and 7 days). The numbers placed after each abbreviation indicate concentration (50, 100, and 200 μg/mL).

Figure 5

Viability of the MDA-MB-231 and MCF7 cells after 24 h incubation with the white clover sprout extracts used in different concentrations (50, 100, and 200 μg/mL). Significant differences between the cells treated with the extracts from the white clover sprouts grown in microgravity conditions versus control sprouts were marked with an upper black line (*: p ≤ 0.05). Significant differences between different days of harvesting (e.g., 5LM50 vs. 6LM50), concentrations (e.g., 5LM50 vs. 5LM100) of extracts, and light conditions (e.g., 5LM50 vs. 5DM50) were marked with pairs of letters a–z and A–D. Abbreviations of the sprouts’ samples: L—the sprouts grown in standard light conditions; D—the sprouts grown in darkness; LM—the sprouts grown in standard light and simulated microgravity conditions; DM—the sprouts grown in darkness and simulated microgravity conditions. The numbers placed before each abbreviation indicate harvest days (5, 6, and 7 days). The numbers placed after each abbreviation indicate concentration (50, 100, and 200 μg/mL).

Figure 6

Viability of the PNT2 and MCF10A cells after 24 h incubation with the white clover sprout extracts (200 μg/mL). Significant differences in the viability of the cells treated with the extracts from the white clover sprouts grown in microgravity conditions versus the sprouts grown in normal gravity were marked with an upper black line (***: p ≤ 0.001). Significant differences between different days of harvesting (e.g., 5L vs. 6L) were marked with pairs of letters a,b. Abbreviations of the sprouts’ samples: L—the sprouts grown in standard light conditions; D—the sprouts grown in darkness; LM—the sprouts grown in standard light and simulated microgravity conditions; DM—the sprouts grown in darkness and simulated microgravity conditions. The numbers placed before each abbreviation indicate harvest days (5, 6, and 7 days).