Normally, we use the classic process to obtain and to isolate flavonoids from medicinal plants which we don't know.  Each plant has a different chemical composition and we can find a different sctructural variety of flavonoids. So, you should use the classic methods and after to try optmize the extraction and purification of flavonoids of interest.  

Hello, 

I have attached a papers. 

Hello,

for rat or other animals administration you should not exceed the 50% of methanol concentration for the phenolic and flavonoid extraction from plants

Dear Abusufyan

Threads attached by Ali Abdil and Packia are useful and will definitely help you in isolation of flavonoids.

Best Wishes

Several literature is available and you can find different extract methods, a general method easy to carry out is extract the vegetal material with methanol or aqueous methanol and then do a partition into ethyl acetate... I think it works, best wishes

The dried samples were separately

soxhlet extracted in 80% methanol (100 ml/

gm dry weight) on a water bath for 24 hrs

(Subramanian and Nagarajan, 1969). Each

of the extracts was concentrated and

reconcentrated in petroleum ether (40°-

60°C) (fraction-I), ethyl ether (fraction-II)

and ethyl acetate (fraction-III) in succession.

Each of the steps was repeated three times

to ensure complete extraction in each case.

Fraction I was rejected since it was rich in

fatty substances whereas fraction II was

analysed for the free flavonoids in each of the

samples.

Fraction III of each of the test samples

was hydrolysed by refluxing with 7% H2SO4

(10 ml/gm residue) for 5 hours. The mixture

was filtered and the filtrate extracted with

ethyl acetate in a separating funnel. The ethyl

acetate layer was washed with distilled water

till neutrality and dried in vacuo. The

residues were taken up in small volumes of

ethanol separately and then subjected to

various tests for flavonoids.

Several medicinal plants contains glandular trichomes, that are specialized hairs found on the surface of about 30% of all vascular plants and are responsible for a significant portion of a plant’s secondary metabolites. The trichomes contain mixtures of flavonoids and terpenoids.

1.- Aerial parts of the plant are extracted by dipping the fresh plant material with CH2Cl2 at room temperature during 30 s. This procedure is repeated twice to assure the total and selective extraction of the epicuticular components. The combined CH2Cl2 extracts are evaporated, and the residue is fractionated by CC (silica gel). This allows selective removal of methylated flavonoids.

2.-The material extracted with CH2Cl2 is dried, ground and extracted with methanol-H2O (80:20). The methanol is then evaporated and the remaining aqueous solution extracted successively with ethyl acetate and butanol. Both extracts contain the more polar flavonoids.

If the plant has no trichomes, only point 2 is performed with the defatted plant (petroleum ether).

Respected Sir,

Please try with the following method by Eom et al., 2007.

Eom, S.H., Cheng, W.J., Hyoung, J.P. Kim, E.H., Chung, M.I., Kim, M.J., Yu, C.Y. and Cho, D.H. 2007. Far infrared ray irradiation stimulates antioxidant activity in Vitis flexuosa Thunb. Berries. Kor. J. Med. Crop Sci. 15: 319.323.

Estimation of Flavonoids

The total flavonoids content was determined according to Eom et al. (2007). An aliquot of 0.5 ml of sample (1 mg/ml) was mixed with 0.1 ml of 10% aluminium chloride and 0.1 ml of potassium acetate (1 M). In this mixture, 4.3 ml of 80% methanol was added to make 5 ml volume. This mixture was vortexed and the absorbance was measured spectrophotometrically at 415 nm.

Good Luck

Dear All,

Thanks a lot for your valuable suggestions.

Dear Abusufyan

Pl go through the attached book which will give you complete idea of flavonoids including extraction and isolation (Chapter-1).  

Best wishes

http://www.sciencedirect.com/science/article/pii/S1878535211001687