ABSTRACT
Phytochemical-enriched edible greens, sweet potato leaves (Ipomoea batatas L.), have become popular due to potential health benefits. However, the phytochemical contents in sweet potato leaves and their subsequent change over harvest stages and growth condition are mostly unknown. In this study, the anthocyanin profile and content in leaves of four sweet potato cultivars, i.e., white-skinned and white-fleshed Bonita, red-skinned and orange-fleshed Beauregard, red-skinned and white-fleshed Murasaki and purple-skinned and purple-fleshed P40, were evaluated. Fourteen anthocyanins were isolated and identified by HPLC-MSI/MS. The most abundant was cyanidin 3-caffeoyl-p-hydroxybenzoyl sophoroside-5-glucoside, which comprised up to 20% of the total anthocyanins. Of the young leaves (1st and 2nd slip cuttings), Bonita contained the highest anthocyanin content followed by P40. Of the mature leaves (vine stage), Beauregard had the greatest anthocyanin (592.5 ± 86.4 mg/kg DW) and total phenolic (52.2 ± 3 mg GAE/g DW). It should be noted that the lowest anthocyanin and total phenolic content of shoots were found in P40, while tubers of P40 contain the highest content of each. Furthermore, the increase in leaf anthocyanin content over the growth stages that was observed in three of the cultivars but not in P40. No significant difference of anthocyanin content was found in Beauregard leaves grown in the high tunnels when compared with that in the open field. This study demonstrated for the first time that anthocyanin levels were significantly changed in response to various growth stages but not high tunnel condition, indicating that the effect of anthocyanin biosynthesis in sweet potato leaves is highly variable and genotype specific.
ABSTRACT
This review focused on the influence of environmental systems and/or factors including high tunnel, UV and visible light, fertilization, and irrigation on bioactive compounds in vegetables and fruits. Most studies reported that high tunnel reduced chicoric acid and luteolin in vegetables including lettuce and pac choi, and fruits including raspberry and tomato versus open field, although a few studies demonstrated that high tunnel did not significantly impact on the bioactive compounds. Light including UV such as photosynthetically active radiation (PAR), UV-A, and UV-B, and visible light especially red and blue light, significantly stimulated biosynthesis of anthocyanins, flavonoids, and phenolics, and promoted their contents in vegetables such as onion and spinach, and fruits for example blueberry and strawberry. The effect of fertilization including nitrogen, phosphorus, and potassium on bioactive phytochemicals (carotenoids, flavonoids, polyphenols) in vegetables (broccoli, kale) or fruits (tomato) varied among the cultivars. Water deficit usually increased anthocyanins, flavonoids, and phenolic acids in vegetables such as lettuce and red beet, and fruits including grape and pomegranate. Taken together, the bioactive compounds in vegetables and fruits in response to environmental factors were species- and varieties- dependent. The negative effect of environmental factors on bioactive compounds in vegetables and fruits can be overcome by selecting appropriate cultivars, while the positive effect can be further manipulated in horticultural production for potential consumer’s health benefits.