ok., firstly I will assume that your plant weight (1g) is on a dry basis. Also, that you have obtained all the amount of extract, and that extract is also dry. (70 mg).

With that extract and prepared a solution of 2mg/mL and obtained a concentration of 0.132 mg/mL of flavonoids in that solution.

Since the volume units are the same, you can do:

0.132/2*100=6.6%

Its also valid to simply do 132ug/2mg = 66 ug/mg= 66mg/g dry extract.

To get the amount of flavonoids in the plant (assuming 1g of plant =70 mg extract ) you can do a simple proportion:

and you get 4.62 mg Flavenois equivalents /g dry plant

Please read the aluminium chloride colorimetric assay of flavonoids determination in attached paper