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The realisation of manned space exploration requires the development of Bioregenerative Life Support Systems (BLSS). In such self-sufficient closed habitats, higher plants have a fundamental role in air regeneration, water recovery, food production and waste recycling. In the space environment, ionising radiation represents one of the main constraints to plant growth.• In this study, we explore whether low doses of heavy ions, namely Ca 25 Gy, delivered at the seed stage, may induce positive outcomes on growth and functional traits in plants of Solanum lycopersicum L. 'Microtom'. After irradiation of seed, plant growth was monitored during the whole plant life cycle, from germination to fruit ripening. Morphological parameters, photosynthetic efficiency, leaf anatomical functional traits and antioxidant production in leaves and fruits were analysed.• Our data demonstrate that irradiation of seeds with 25 Gy Ca ions does not prevent achievement of the seed-to-seed cycle in 'Microtom', and induces a more compact plant size compared to the control. Plants germinated from irradiated seeds show better photochemical efficiency than controls, likely due to the higher amount of D1 protein and photosynthetic pigment content. Leaves of these plants also had smaller cells with a lower number of chloroplasts. The dose of 25 Gy Ca ions is also responsible for positive outcomes in fruits: although developing a lower number of berries, plants germinated from irradiated seeds produce larger berries, richer in carotenoids, ascorbic acid and anthocyanins than controls.• These specific traits may be useful for 'Microtom' cultivation in BLSS in space, in so far as the crew members could benefit from fresh food richer in functional compounds that can be directly produced on board.Plant Biology 21 (2019) 615-626

Peel, pulp and seed extracts of three mandarin varieties, namely Phlegraean mandarin (Citrus reticulata), Kumquat (Citrus japonica), and Clementine (Citrus clementina) were compared and characterised in terms of photosynthetic pigment content, total polyphenols amount, antioxidant activity and vitamin C to assess the amount of functional compounds for each cultivar. The highest polyphenols content was found in the Phlegraean mandarin, especially in peel and seeds, whereas Kumquat exhibited the highest polyphenols amount in the pulp. The antioxidant activity was higher in the peel of Phlegraean mandarin and clementine compared to Kumquat, which showed the highest value in the pulp. The antioxidant activity peaked in the seeds of Phlegraean mandarin. The vitamin C in the Phlegraean mandarin was the highest in all parts of the fruit, especially in the seeds. Total chlorophyll content was comparable in the peel of different cultivars, in the pulp the highest amount was found in clementine, whereas kumquat seeds showed the greatest values. As regards total carotenoids, peel and pulp of clementine exhibited higher values than the other two cultivars, whereas the kumquat seeds were the richest in carotenoids. Among the analysed cultivars Phlegraean mandarin may be considered the most promising as a source of polyphenols and antioxidants, compared to the clementine and Kumquat, especially for the functional molecules found in the seeds. Moreover, regardless of cultivars this study also highlights important properties in the parts of the fruit generally considered wastes.

No abstract

In this work, we assess the potential of waste products of Phlegrean mandarin (Citrus reticulata Blanco), namely seeds and peel, to be reutilized as a source of bioactive compounds beneficial for the human diet. Starting from the evidence that the by-products of this specific cultivar are the most powerful sources of antioxidants compared to pulp, we have investigated if and how the bioactive compounds in peel and seeds may be affected by fruit ripening. Three stages of fruit ripening have been considered in our study: unripe fruits = UF, semi-ripe fruits = SRF, ripe fruits = RF. The overall results indicated that RF showed the highest concentration of antioxidants. Among fruit components, peel was the richest in total antioxidant capacity, total polyphenol content, total flavonoids, total chlorophylls and carotenoids, while seeds exhibited the highest concentration of total condensed tannins and ascorbic acid. The liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay indicates the occurrence, in peel extracts, of 28 phenolic compounds, mainly flavonoids (FLs); in seeds, 34 derivatives were present in the first stage (UF), which diminish to 24 during the ripening process. Our data indicated that the content of phytochemicals in citrus strongly varies among the fruit components and depends on the ripening stage. The higher antioxidant activity of peel and seeds, especially in RF, encourage a potential use of by-products of this specific citrus cultivar for industrial or pharmacological applications. However, to maximize the occurrence of desired bioactive compounds, it is important also to consider the ripening stage at which fruits must be collected.