Mixing water and ethanol together (hydroethanolic), in different proportions, determines the overall polarity of the solvent mixture. The higher the water percentage and the lower the ethanol, the higher the overall polarity (since water is more polar than ethanol). Conversely, the lower the water percentage and the higher the ethanol, the lower the overall polarity will be (since ethanol is less polar than water). So a 24 % EtOH tincture would have 76 % water and would be very polar, while a 95 % EtOH tincture would have only 5 % water and would be much less polar.
For detailed solubility of individual, isolated molecules, consult the Merck Index (Merck & Co., Inc., Whitehouse Station, NJ).
Solubility in a given solvent is influenced by the polarity of a molecule’s skeleton and functional groups, the molecular size, temperature, the pH of the solution, and other factors. The solubility of an isolated compound is easy to determine, but this may change in the complex matrix of a medicinal plant extract. The general principle: like dissolves like. A high-polarity solvent will pull high-polarity molecules out of the herbal material; a low-polarity solvent will select for low-polarity molecules.