Page 138 - phytochemistry I - PharmD Clinical

commonly referred to as Band I (usually 300 – 380 nm), and Band II
(usually 240 – 280 nm). Band I is considered to be associated with
absorption due to the B-ring cinnamoyl system, and Band II with
absorption involving the A-ring benzoyl system.

Band II Band I

250 350

Pharmacokinetics of flavonoids:

• Flavonoid-O-glycosides are converted into the aglycone by bowel
flora.

• Levels of a flavonoid aglycone in the blood stream will vary
according to:
- Whether it is administered as an aglycone or glycoside.
- If given as a glycoside, the form of the glycosidic pro-drug.
- The nature of the individual bowel flora, which is partly
dependent on the individual diet.

• Oral doses of flavonoid aglycones are less bioavailable than their
glycosides because they are more susceptible to ring fission. The
ring fission is the process of the breakdown of the central ring in the
flavonoid structure to give two different phenolic products. The
following is an example of C-ring fission.

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