An experiment with the cultivation of sweet potatoes (Ipomoea batatas L.) took place in a protected area (plastic greenhouse) and outdoors at the Laboratory field at the Biotechnical Faculty in Ljubljana (altitude 305 m; φ = 46° 3'23"; λ = 14° 30' 29"). The purpose of the experiment was to determine how different production systems influence the content of total and individual sugars in the tubers and individual and total polyphenol contents (TPC) in the sweet potato leaves. The plants were transplanted to the ground covered with black polyethylene foil at a spacing of 0.5 x 0.5 m. An experiment with two Slovenian ones ('Lučka' with brown orange skin and orange meat and 'Janja' with white meat and white colored skin) and two foreign varieties ('Purple Speclet' with red violet meat and purple skin and 'Okinawian' with white purple marbled meat and light brown skin) was designed in four random blocks. The content of selected bioactive substances was determined with the using of the high performance liquid chromatography (HPLC) and spectrophotometric analysis. We found that, unlike hydroxycinnamic acid derivatives and TPC, the location of cultivation affects the content of total sugars and total quercetin derivatives. Varieties were characterized by differences in the content of quercetin-, kaempferol- and isorhamnetin derivatives and total sugars.
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