Neem leaf 90% ethanolic extract became sticky after hot air oven drying (we don't have rotary evaporator) and reconstitution by 50% ethanol is quite impossible let alone weigh it. I will test the antibacterial efficacy.
This could be a practical solution.
You may weight an aliquote of the extract and dissolve it in a suitable and volatile solvent to an exact volume. Then you may take the volume which contains the required quantity and put in a second container. After evaporation of the solvent you may check for the quantity and if necessary add other solution and re-evaporate the solvent . This procedure may be repeated until the required quantity is obtained, then you may obtain the solution at the required concentration.
Dear Zihadi,
I would suggest something that may seem counter-intuitive - add water to the raw extract! Dilute it quite a lot - 1:5 or even 1:10 - you may have to add the water a tiny ammount at a time and mix like crazy ... and then freeze dry it to a powder. If water is not working alone, add a little 1,4-Dioxant or tertiary butanol as you go, or possible even DMSO. That should enable you to get a dry weight. I suspect that you will have to keep the dry samples free from air and moisture, else they'll turn to "goo" again.
Kind regards,
Rob
For the preparation of the extract, 113 or 150 g of Neem leaf powder per liter of water. The decision on the amount of powder to be depend on the quality of the distribution of the extract over the leaves of corn obtained during spraying. For a good distribution of the syrup, it is possible to use less quantity and obtain good results. To
mixing the powder into the water, it should be stirred homogenize the mixture and then leave the resting for 24 hours.
I agree with Alessandro Venditti because the ethanolic extract obtained leads to insoluble residues which, when trying to dissolve it in a rather polar mixture (50% ethanol), is impossible to make a complete solution.
Make an extraction of the ethanolic extract by removing an aliquot and weighing it in a second vessel and then drying the solvent until reaching the desired weight.
Subsequently reconstitute in volumetric balloon to reach the desired concentration.
Thanks all. I found that neem extract is completely miscible with 99% ethanol but with the addition of water the extract just precipitate. But i needed 50% ethanol as i will test the antibacterial efficacy. Whatever, may be DMSO would be the best. Thanks again.
DMSO = dimethyl sulfoxide - it dissolves almost everything organic, but be careful to use the correct PPE as it goes straight through most gloves, and your skin, carrying the chemical dissolved in it.
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