C18 HPLC columns will give you a 'good' separation.

Don't reinvent the wheel!  Do a internet/literature search of common extraction and chromatographic techniques used in plant extracts.

Dear Sir. Concerning your issue about the column to use for HPLC chromatographic profile of aqueous extracts of decoctions and maceration in water . You can use an L-7360 column oven and an L-7455 photodiode array detector (PDA) scanning at 200-800 nm with a 1 nm resolution. Or aqueous extraction can be carried out with plant material and water (1:30 (w/v)) at different temperature of 60 °C in the multipoint stirrer with water bath for 1 h. The samples were analyzed by high performance liquid chromatography (HPLC), equipped with a UV detector (Shimadzu, Kyoto, Japan). Phenomenex-C18 Synergi column (150 mm × 4.6 mm, 4 μm) coupled to a refillable pre-column filled with C18 silica was used in the analysis. The mobile phase consisted of a gradient of acetic acid 2% (A) and acetonitrile (B) filtered and degassed. The gradient elution was 17% B in 0.01 min, 17%–20% B in 10 min, 20% B in 15 min, 20%–25% B in 20 min, 25%–27% B in 22 min, 27%–30% B in 25 min, 30%–35% B in 30 min, 35% B in 35 min, 35%–17% B in 40 min. LC system operated at flow rate of 1 mL/min for 45 min at 30°C with the injection volume of 20 μL and the wavelength was adjusted to 327 nm. I think the following below links may help you in your analysis:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4078343/

http://www.ptfarm.pl/pub/File/Acta_Poloniae/2012/3/475.pdf

Thanks

Dear ElGailani

Many thanks for the book, a very interesting source for medicinal plants study.

Warm regards

Bachir

C18 HPLC columns

 Column 18

Dear RG friends

Many thanks for your feedbacks that help us a lot.

Warm regards

Dear Mr. Benarba.

I agree with Dr. Neagle. A first screening about phytochemical classes of the richest components by TLC or spectrometry is recommended. Then, several HPLC and GC techniques for separation of each class can be assayed after the appropriated clean-up/enrichment procedure. To help further investigations, prefer chromatographic conditions in HPLC-MS literature, even thought MS detector is available. This methodology is important for a rational investigation of natural extracts. Chromatography is an excellent technique of investigation when it is known that class of substances should be investigated. A search in the literature is essential.

An aqueous extract means polar in nature so you have to use non-polar column i.e C18 column will be most suitable for the separation as a whole. Depending upon phytoconstituent mobile phase could be Methanol:water or Acetonitrile: water or diluted weak acids like acetic acid, formic acid or phosphoric acid along with methanol or acetonitrile having good impact.

I agree with previous researchers' comments and RP18 ( C18) column is the best for  better separation of your aqueous extract to obtain good chromatographic profile.  

C18 5 µm (3.9 × 150 mm) column