Dissolving Boswellia Serrata and Centella Pure TECA in Toner Formulation

Question

Dear Expert,

I need assistance with dissolving Boswellia Serrata Extract (Boswellic Acid) and Centella Pure TECA 95% (Cica Extract) for my toner formulation.

What temperature and how much Propylene Glycol is required to dissolve the Boswellia Serrata Extract powder?
For the Centella Pure TECA 95%, what temperature, quantity, and type of glycol should be used?
Is it necessary or recommended to stabilize the mixture with PEG-40 Hydrogenated Castor Oil after dissolution?

Proposed Formulation:

Premix 1: 0.3% Boswellia Acid powder + 2% Propylene Glycol + 1.5% DMI
Premix 2: 0.2% Centella Cica powder + 3% Pentylene Glycol + 1.5% DMI
Method: Combine both premixes and stabilize with 0.5% PEG-40 HCO.

I cannot exceed a total of 5% glycol in the formulation. Could you please advise if this approach is correct or what I should do?

Answer 1

Based on the ingredients and your proposed formula, here are the technical recommendations for dissolving these active powders in your toner:

1. Boswellia Serrata Extract (Boswellic Acid)

Solvent & Ratio: Using 2% Propylene Glycol for 0.3% Boswellia Serrata Extract is appropriate. The recommended ratio is at least 6 parts glycol to 1 part extract.
Temperature: Do not use heat. Boswellia should be dissolved in Propylene Glycol at room temperature.
pH: Ensure the final toner pH is between 4.0–6.5 for stability.

2. Pure-TECA™ (Centella Asiatica Extract 95%)

Solvent Choice: While you mentioned Pentylene Glycol, Propylene Glycol is a more effective solvent for Pure-TECA™.
Temperature: You must use heat (70-80°C) to dissolve TECA in the glycol/DMI mixture. Stir until the powder is fully dispersed or dissolved.
Solubility Warning: TECA is extremely difficult to dissolve. The manufacturer recommends a 1:100 ratio (e.g., 1% TECA in 99% Glycol) for a clear solution. Your proposed ratio of 0.2% TECA in 3% Glycol (1:15) is very concentrated and will likely result in a cloudy (opaque) toner or potential precipitation over time.

3. Stabilization with PEG-40 HCO

Recommendation: Yes, using PEG-40 Hydrogenated Castor Oil is highly recommended. It acts as a solubilizer and stabilizer to help keep the poorly water-soluble Boswellic acid and TECA dispersed in the water-based toner.
Usage: 0.5% is a good starting point, but if the solution remains unstable or shows heavy precipitation, you may need to increase it to 1%.

Suggested Procedure (Staying within 5% Glycol limit):

TECA Premix: Mix 0.2% Pure-TECA™ with 3% Propylene Glycol and 1.5% Dimethyl Isosorbide (DMI). Heat to 70-80°C until dissolved. Allow it to cool to room temperature.
Boswellia Premix: In a separate container, dissolve 0.3% Boswellia Serrata Extract in 2% Propylene Glycol at room temperature.
Combination: Combine the two premixes. Add 0.5% PEG-40 Hydrogenated Castor Oil to this mixture and stir well.
Final Step: Slowly add this combined mixture into your water phase (the rest of the toner) while stirring.

Note: Due to the low amount of glycol relative to the TECA concentration, the toner will likely be cloudy rather than crystal clear. To achieve a clear solution, you would typically need to significantly increase the glycol content or decrease the TECA percentage.