Liquorice root contains amino acids, flavonoids, phytosterols like ß-sitosterol and stigmasterol, coumarins, chalcones, polysaccharides, glucides, and triterpenes. Although these are all great to have in our creations, it's the glycyrrhizic acid and flavonoids that mostly give liquorice its wonderful features.
Glycyrrhizic acid is a triterpene with many awesome qualities. It is a decongestant and sweetener considered strong than sugar. What appeals to us as bath and body product makers is the anti-inflammatory, anti-allergic, analgesic, anti-pyretic (anti-fever), and anti-viral features that makes this a powerful healing agent for skin ailments like eczema and psoriasis. Glycyrrhizic acid and its derivatives show anti-inflammatory benefits than those achieved by hydrocortisone. Liquorice root extracts should be standardized to include no less than 4% glycyrrhizic acid. This triterpene is the reason for the possibly toxic effects of ingesting too much liquorice - it can be toxic at high doses, so stick to de-glycyrrhized liquorice like the Allsorts in the picture above. (It is a good expectorant and laxative, so you get an idea of what the path to toxicity looks like!)
The isoflavone glabridin has been found to work very effectively as an anti-inflammatory ingredient at 0.5% in a water solution. Studies have been conducted for this isoflavone and acne, thanks to the anti-bacterial potential, and reduction of oil production. It is showing great promise in helping reduce sebum production and decrease acne outbreaks.
Liquorice root contains the compound anethole, an aromatic unsaturated ether that is more soluble in alcohol than water. It's found in anise and fennel, and offers the liquorice-y taste we like! It has the ability to spontaneously form micro-emulsions, called the "ouzo effect" that gives alcohol drinks a cloudy appearance. It offers anti-microbial features to our products and is showing promise as an insecticide. (There are studies showing essential oils or extracts containing this aromatic compound may be effective as bug sprays to repel mosquitoes and flies. Nothing firm yet, but it is an interesting thought - campgrounds and beaches reeking of liquorice with no bugs to be found!)
Asparagine shows up at 2% to 4% in liquorice root (also found in comfrey root), an amino acid that offers moisturizing and soothing of skin. The polysaccharides (also found in cucumber, aloe vera, ginseng, and horsetail root) offer moisturizing and emolliency through the formation of a light gel layer on our skin. The coumarins in liquorice root offer anti-fungal, anti-bacterial, and anti-inflammatory properties, reducing redness and possible UV protection. The other flavonoids offer anti-oxidizing and anti-inflammatory benefits. The phytosterols can help with weather damaged skin, a reduction in inflammation, and help with repairing the skin's barrier protection. Lignans behave as anti-oxidants and phytoestrogens in our body.
So does liquorice root extract deserve a place in our workshops and formulations? I think the answer is yes! We can use it at up to 1% (the level generally regarded as safe) in our creations, but I'd start at 0.5% and work your way up to see how your skin likes it. (Although it offers anti-irritancy features, it can - ironically- cause an allergic reaction). It offers great anti-inflammatory, anti-oxidant, anti-microbial, and anti-redness features for any product. And it might have the added benefit of offering protection from biting insects who want to ruin summer time fun!
If you are formulating for skin lightening, it is suggested to have at least 0.5% in your product. As liquorice extract contains about 0.35% to 0.4% glabridin, this would require a little more than 1%, which is higher than the recommended amount. So I'm not going to offer any suggestions for this, other than possibly sourcing out pure glabridin.
As I have not formulated with this extract, I can't offer any recipes, but if you are interested in using it, try it in a toner to see what your skin thinks about liquorice!