I think you should collect the fruit, freeze it at -80ºC or liquid nitrogen and lyophilize it. You should freeze in the same day to prevent stress (and end up detecting compounds related to it). The extraction itself I don't know how to help you, it will depend of the method you use, if it is chromatography or any other method. Good luck

Flavonoids easily dissolved in a solvent with crushing, i. e - Juice form. Collect that colored solution, and go with column chromatography. For confirmation, do flavonoid test for different fractions. The most favored fraction for flavonoid test- characterized by the specific test for that chemical constituent. 

I think you should dry your fruit by lyophlilization and try some color reaction  like Shinoda reagent or férric chloride to be sure you have flavonoids. Then if you want to sepárate them run a CC may be using Sephadex LH20.

Since the selected plant is seasonal so some matured seeds could be collected for future cultivation under preserved conditions.

The extract of the fresh fruits can be tested for qualitative and quantitative fiavonoid using usual methods.

The fractions could be separated by chromatographic techniques.

hi, 

since it is fruits, take the following forms: 

1. make juice of the fruit and dry it to get powder from

2. dry the fruits in shade or tray drier powder and subject to systmatic extraction.

after this both are dry forms u can use alcohol as solvent to make extracts test for flavonoids. an d proceed with chromatography

all the best