A Multi-lensed Comparative Analysis of Select Secondary Metabolites Produced by Kale, Brassica oleracea, in Simulated Microgravity Versus Gravity Conditions

Abstract

Extended journeys through space are a goal of NASA. Yet, astronauts will face elevated health risks from microgravity and radiation as journeys continue for longer time periods. Approaches to combatting these health risks consist of growing fresh super foods in space for astronaut consumption while in flight. However, while a great deal is known about the effects of microgravity of humans, little is known about its effects on the nutrient profiles of plants. Endeavors towards understanding more about these effects are currently funded by NASA grants. Kale, a metabolite and specifically a flavonoid-rich crop, stands as a promising candidate for growth on space flights. We observed the effects of simulated microgravity broadly on the F1 cultivar, Starbor Kale metabolomics, and further focused on flavonoid content, using a 2-D clinostat. Extracts of kale were analyzed by proton nuclear magnetic resonance (1H NMR), and high-performance thin layer chromatography (HPTLC). 1H NMR spectra of clinostat-grown kale showed that samples from simulated microgravity conditions had an increased number of peaks in the aromatic region (6.5 to 8.5 ppm) when compared with gravity grown kale. HPTLC confirmed greater banding in medium- and high-polarity solvent systems, while low-polarity extracts showed no differences. Overall, we noted that the microgravity grown kale had greater amounts of bands present. These results signal that microgravity stressors may be connected to the increased secondary metabolite production in kale. Our findings underscore kale to be a prospective crop to be grown in space flight to combat effects of microgravity.