As medicinal cannabis and THC become increasingly acceptable and legally available, a parallel interest is growing in the benefits of another component of cannabis — cannabidiol, or CBD. CBD, a non-THC (non-psychoactive) cannabinoid, can be helpful for a vast number of medical conditions, including anxiety, epileptic seizures, chronic pain and spasticity from multiple sclerosis. Because CBD does not produce psychoactive effects, which can interfere with life functioning, there is a growing demand for products containing isolated extracts of this cannabinoid. Unfortunately, CBD — like THC — is hydrophobic. That is, it does not naturally dissolve in water, which means that it not only resists being dissolved in water-based products but is also not well-absorbed by the body. The good news is that there are ways around this challenge, but before we get into how to make CBD “water soluble”, we need to take a look at what it means for a substance to be water-soluble and why this characteristic is so important.
The Nature of Water Solubility
What makes a substance water-soluble? Beyond the practical definition of dissolving easily in water, the nature of water solubility is related to a molecule’s degree of charge. Fundamentally, charge is related to electrons — tiny, negatively charged subatomic particles that cause attraction and repulsion among atoms, leading to substances either mixing easily or separating.
Charged and Polar Molecules: Opposites Attract
When charged molecules or atoms, known as ions, have opposing charges, they are strongly attracted to each other — strongly enough to form a type of chemical bond called an ionic bond. Other molecules, called polar molecules, have partial charges on their component atoms. Water (H2O) is a polar molecule made up of two hydrogen atoms and one oxygen atom. The three atoms share their electrons, but the large oxygen atom “hogs” the negative electrons, giving it a partial negative charge and leaving the small hydrogen atoms with a partial positive charge. What this means for solubility is that charged compounds — either ionic compounds (with fully charged ions) or polar compounds (partially charged molecules) — readily dissolve in water.
For example, table salt (NaCl) is made up of positively charged sodium (Na+) ions and negatively charged chloride (Cl-) ions; their opposite charges bind them tightly together when dry. When in water, however, the Na+ ions are attracted to the partially negative oxygen end of the water molecule, while the Cl- ions are attracted to the water molecule’s partially positive hydrogen atoms. The water molecule, essentially, gets in between the NaCl “couple,” holding hands with one ion on its right side and the other ion on its left. What this looks like on the macroscopic level is salt dissolving in water. It dissolves completely; you can taste the salt, but you can’t see it floating around, and the solution is homogeneous and translucent.
Nonpolar Molecules Get Left Out
So, what happens to molecules that have no charge — neither full nor partial? The short answer: if they are added to water, they get left out of the mix.
Since nonpolar molecules have no full or partial positive or negative charge to be attracted to the positive or negative poles of H2O, they become isolated from the “hand-holding” charged molecules, which move toward each other and stick together. Because the charged molecules are attracted to their opposites, this leaves the nonpolar molecules grouped together in bubbles or separate layers. A common example of this is oil-and-vinegar salad dressing. The vinegar is a polar solution of acid and water, while the oil is a nonpolar liquid. You can shake them together, but if you let them set, the molecules will separate into polar and nonpolar layers (a layer of oil floating on a layer of vinegar).
Nonpolar molecules are known by other names that reflect their tendency to dissolve in nonpolar solvents rather than polar solvents such as water. These names include: fat-soluble, lipophilic (from the Greek for fat-loving), and hydrophobic (from the Greek for water-fearing). Conversely, polar molecules are known as water-soluble, hydrophilic, and lipophobic.
CBD and Other Hydrophobes
CBD, like other cannabinoids, is nonpolar and therefore hydrophobic. Like the fat-soluble vitamins (including vitamins A, D, E and K) and the essential fatty acids (including linoleic acid, omega 3 fatty acid and omega 6 fatty acid), cannabinoids don’t readily dissolve in water. Of course, they can be extracted from plant matter via a simple deep fry in vegetable oil, and isolated CBD will also happily dissolve in oil. For maximal efficacy, though, it would be ideal to be able to infuse CBD into water.
Why Solubility Is Important
Water solubility is not just important for making attractive beverages, tinctures and other products; it’s also vital to bioavailability. For a substance to be bioavailable (able to have a biological effect in our bodies), it generally must first be absorbed from our gastrointestinal tract into our body tissue. Since the fluids inside our GI tract are mainly composed of water (and, indeed, our bodies in general are mainly composed of water), a substance must be water-soluble in order for it to be well-absorbed.
Miscibility and Emulsions
The ability of different liquids to mix completely into one another is called miscibility. While water-soluble compounds dissolve easily in water and fat-soluble compounds dissolve easily in oils, the two can mix with the help of molecules called emulsifiers. These molecules are large enough that they can be polar on one end and nonpolar on the other end. One well-known natural emulsifier is egg whites. The large protein molecules that make up the egg white have parts that bind with polar molecules and other parts that bind with nonpolar molecules. This is how adding eggs to cake mix allows oil and water to mix together evenly along with the other ingredients. Fortunately for the nutraceutical industry, more sophisticated methods than egg whites have been developed to help make nonpolar substances miscible with water.
Using Nanoemulsion Technology to Make CBD Water-Soluble
Solubility can get quite complicated when it comes to maximizing substance bioavailability, and much work has gone into strategies to enhance bioavailability through manipulation of solubility. The newest and most exciting of these are based on nanoparticles, such as polymeric micelles, which are like tiny bubbles that are nonpolar on the inside but polar on the outside, allowing them to encapsulate hydrophobic molecules; and nanoemulsions, colloidal systems that carry fat-soluble vitamins or fat-soluble substances like CBD. A CBD nanoemulsion can effectively make this highly hydrophobic medicinal compound into a one that behaves as though it is water-soluble.
While developing a stable nanoemulsion require years of work and scientific expertise, you can take advantage of them without needing to reinvent the wheel. The scientists at Axiomm Technologies developed a turnkey system that’s ready for you to use to convert lipophilic CBD to hydrophilic CBD. Plug-and-play products like µMIX and µSHOT serve as ready-made building blocks that allow you to easily utilize water-soluble CBD. All you need to add are the unique ingredients of your product recipe. Axiomm’s nanotechnology solutions do the rest, freeing you to focus on crafting your own unique CBD-infused products — with the health benefits your customers demand and a flavor and aesthetic profile they will love.