457 DELIVERING SUSTAINABLE SOLUTIONS TO IMPROVE WELLBEING
environmental concerns. Subcritical water is one of these opportunities. While subcritical
water extractions are not new to the chemical industry, the application of this technology
in the production of personal care products is new! Subcritical water is the application of
heat and pressure within specific ranges to allow water to maintain its liquid form at higher
temperatures (Figure 1). Temperature ranges of 100°C to 374°C and pressures between 1
and 218 atm decrease the water polarity to allow the medium to non-polar compounds
to be extracted from botanical materials. This polarity shift mimics that of other organic
solvents without the additional hazards or processing steps (Figure 2). By extracting more
from botanical materials with only water as a solvent, a wider range of phytoactives can be
produced to meet a growing demand for more sustainable products.
An analytical examination of the phytoactive composition of botanical extracts prepared by
traditional water and aqueous glycerin solvent extractions and subcritical water extraction
technology is illustrated here with a representative example of a S rebaudiana leaf/stem
extract. The S rebaudiana extract is a vegan-friendly extract with retinoid-like results that
minimizes the appearance of wrinkles for younger looking skin. Hot water and aqueous
glycerin extracts of the botanicals were completed to be used as baselines for temperature
and solvent variables.
Stevia extracts contain proteins, carbohydrates, lipids, and phenolic compounds (Figure 3).
The subcritical water extract contained almost five times greater protein than the hot water.
The carbohydrate content of the subcritical water extract is more than twice that of the hot
water and glycerin extractions. Regarding the lipid content, the subcritical water extract
contained 17% content less than the hot water extract and 42% less than the aqueous
glycerin extraction. The phenolic compound content of the subcritical water extract was six
times greater than the hot water extraction.
Figure 1. The dielectric constant of water changes at different temperatures, thus making its polarity similar
to other organic solvents.

458 JOURNAL OF COSMETIC SCIENCE
Analysis of the individual caffeoylquinic acid derivatives in the stevia extracts demonstrates
that these compounds are not well extracted by hot water or aqueous glycerin (Figure
4). Steric hindrance may contribute to the decreased extraction of the caffeoylquinic acid
derivatives with larger branched compounds extracting less with the hot water and aqueous
glycerin techniques. Extracting the 3,4-di-o-caffeoylquinic acid and 4,5-di-o-caffeoylquinic
compounds highlights the ability of subcritical water to better extract more complex
nonpolar compounds than hot water and aqueous glycerin, which is specifically 450 to
550 times more. The other caffeoylquinic acid derivatives have similar results. These data
demonstrate that subcritical water extracts caffeoylquinic acid derivatives from stevia at
efficacious levels that are not possible with hot water and aqueous glycerin.
Figure 2. Changes in the polarity modify the behavior of water to extract a broader range of compounds.
Figure 3. Comparison of extraction efficiencies of phytochemical families.