Hi José

When you say DMSO 0.5% or Tween 1%, what are the remaining 99.5/99%?

If you extract with Chloroform, you will get mainly lipids and other nonpolar compounds, you will have to take that into account when choosing your solvent for the bioassay.

Many thanks Christian. We performed the bioassay with physiological serum, so the remaining 99.5/99% is serum. I have read that Tween or DMSO are common used when you have to evaluate the effects of nonpolar compounds in biological systems (animals, cells, etc).

José,

I don't think that little DMSO and/or Tween in your serum will do much to solubilise a dried chloroform extract... Also I'm not sure how you go from extract to assay, you may have to give some more detail about your extraction and cleanup steps, beginning with how much sample you process, how much chloroform etc

Hi Christian,

The extraction was as follow:

1.- 2.5 g of Caulerpa filiformis powder were extracted with 25 ml of chloform for 2 days, at room temperature, magnetic agitation and in the dark.

2.- After the 2 days, the extract was filtered and the chloforom were evaporated at 40°C all night. 

3.- The extract was resuspended with Tween 0.1% and then filtered with a 0.25 um filter. With the Tween solution the bioassays were performed

That are the main steps. 

Many thanks

OK, couple options here...

You have not mentioned how much (dry weight) extract you recovered from the Chloroform. That will determine (empirically) how much solvent you need to resuspend it all. I recommend using a small volume straight DMSO (or ACN, or IPA, or MeOH, or THF, or ...) to resuspend the dried extract.

Would it be possible to move away from Chloroform for the extraction entirely and use something like MeOH (or a combination of solvents)? Might save you a lot of headache... you could also think about using normal phase SPE if you have to use Chloroform...

Hi Christian,

With 5 ml of Tween 0.1 I recovered 15 mg of the extract (originally, it weighted 65 mg). I have also used methanolic extracts for evalute its effects on human sperm, so my objective is to compare it with the chloroformic extract. What about report the 15 mg per 5 ml (or 3 mg/ml) as my highest concentration? So, the effects can only be attributed to the part of the extract that was resuspended.

Well, I have no experience using Tween in extracts (I do a lot of LC-MS work on biological extracts, so I normally avoid any surfactants like hell), again, my recommendation is resuspending the extract in as little organic solvent (NOT serum) as possible and adding that to the sperm. Ideally you would also want to get an Idea what is in your reconstituted extract (my guess, it will be a different composition than before drying).

Ok Christian! Many thanks for your advice. That helps me a lot :D!!!