Formulating Sunscreen with Plant Extracts: Concentration and Form

Your questions are quite technical and relate to the complex process of formulating cosmetics, specifically sunscreens, with plant extracts.

1. Regarding light absorption and concentration: When analyzing an extract's light absorption, you are typically characterizing its properties. The concentration used in the final sunscreen formulation is not simply chosen based on which concentration showed the highest or lowest absorption during analysis. Instead, the formulation concentration is determined based on the desired effect of the extract in the final product (e.g., antioxidant, soothing), its stability, compatibility with other ingredients, safety data, and potentially efficacy testing (though plant extracts are generally not used as primary UV filters and their contribution to SPF is usually minimal compared to dedicated UV filters). The analytical data helps understand the extract, but the formulation concentration is a separate decision based on the final product goals.
2. Regarding the form of the extract: The "concentration of the extract that is added to the cream" refers to the amount of the extract product as it is supplied (which could be a liquid, powder, standardized extract, etc.). It is not necessarily just the clear liquid filtered out, unless the extract is specifically prepared and supplied in that form for formulation. The form and concentration used depend on the supplier's specifications and the formulation requirements.
3. Regarding determining concentration: Determining the appropriate concentration involves considering the extract's potency (often based on standardized active compounds, if available), the desired functional benefit in the sunscreen, potential interactions with other ingredients, safety limits, and cost. It often requires formulation trials and stability testing.

Formulating sunscreens, especially with active ingredients like plant extracts, is a complex process that requires expertise in cosmetic chemistry and formulation science. It involves careful consideration of ingredient interactions, stability, efficacy, and regulatory compliance. I cannot provide specific formulation guidance as it requires detailed knowledge of the specific extract, its properties, and the overall formulation goals.