Effects of maturity of harvested flue-cured tobacco on its polyphenol content and composition
The polyphenol contents and composition in fresh and cured tobacco leaves harvested at different maturity stages (unripe, physiological mature, technical mature and over-ripe) were studied. The results showed that: 1) The polyphenol content topped at physiological mature stage for fresh and cured cutters and at technical mature stage for cured upper leaves, which raised with the increase of maturity in fresh upper leaves. 2) Among polyphenols, the rutin content in unripe fresh leaves was the highest, while in the fresh and flue-cured leaves of the other treatments, the polyphenols in the order of content were chlorogenic acid > rutin > 4-O-caffeoylquinic acid > 5-O-caffeoylquinic acid > Kaempferol-3-rutinoside (K-3-Ru) > scopoletin. 3) The percentage of chlorogenic acid increased with the increase of maturity in cured cutters and upper leaves, however decreased slightly at over-ripe stage; while that of 4-O-caffeoylquinic acid and 5-O-caffeoylquinic acid changed on the contrary way. There was no obvious difference for other polyphenols in cured leaves among these treatments. 4) The polyphenol content was obviously higher in cured leaves than in fresh leaves, in cured-leaves the raise of polyphenol contents with the increase of maturity gradually slowed. The percentage of chlorogenic acid was higher in cured leaves than in corresponding fresh leaves, while that of rutin or Kaempferol-3-rutinoside was on the contrary.