Discovery and Identification of the Key Contributor to the Bitter Taste in Oriental Melon after Forchlorfenuron Application

Forchlorfenuron is a cytokinin-like plant growth regulator, which on application to oriental melon fruit often produces a bitter taste due to the accumulation of cucurbitacin. In the present study, the relationship between forchlorfenuron treatment and bitterness in oriental melon fruit was revealed by human sensory analysis coupled with highly sensitive quantitative analyses. Nine cucurbitacins as the major bitter compounds were identified in the oriental melon, with their concentration ranging from 0.001 to 32.263 mg/kg. And these cucurbitacins mainly accumulated in the peel and pedicle pulp of oriental melon fruits at maturation. Application of forchlorfenuron increased the concentration of cucurbitacin B and decreased arvenin I in total cucurbitacins for the oriental melons. Calculation of the impact of the bitter taste of these compounds based on a dose/activity relationship indicated that cucurbitacin B and arvenin I were the key contributor to the bitter taste in oriental melon fruit after high-dose forchlorfenuron application. These results are helpful in understanding the source of bitterness of oriental melon and provide a practical guide on the rational use of forchlorfenuron.