PURAC: lactic acid, lactates and gluconates

Natural active ingredients

Today's cosmetics industry includes not only preparations for cleaning and beautifying the face and body, but also products that have special functions. There has been an increasing demand in the cosmetic markets for more cosmetics products with special applications and functions.

The table below provides an overview of the most important applications with the preferred products and functionalities.

Application	Product	Main functionality
Skin care	PURAC L(+)-lactic acid	AHA, pH regulator, bacteriostatic agent
Skin care	PURASAL salt of L(+)-lactic acid	AHA, Skin lightening, Moisturizer, bacteriostatic agent
Toiletries /Antiperspirants	PURAC L(+)-lactic acid	pH regulator, bacteriostatic agent
	PURASALsalt of L(+)-lactic acid	Moisturizer, humectant, bacteriostatic agent
	PURAMEXmetal salt of L(+)-lactic acid	Astringent agent
Hair care	PURAC L(+)-lactic acid	pH regulator
Hair care	PURASALsalt of L(+)-lactic acid	Moisturizer
Oral care	PURACALcalcium L(+)-lactate	Calcium source, anti-tartar agent
Oral care	PURAMEXmetal salt of L(+)-lactic acid	Antimicrobial agent, astringent agent

When lactates are incorporated as the active ingredient in your formulation, they provide other benefits in addition to their functionality as the active ingredient. These additional lactate functionalities include: humectancy, bacteriostatic, increasing ceramide level.

* NOTE: the graphs on these WebPages are based on standard products: PURASAL S 60% and PURAC 90%

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L(+)-lactic acid is the human body's own mild AHA

Alpha hydroxy acids, also called fruit acids, have been used in cosmetics for several years. They have now become standard ingredients in a broad range of personal care formulations.

Not all AHAs are equally effective. Lactic acid - especially the natural L(+) form - has been widely investigated. Numerous scientific publications have reported that L(+)-lactic acid is the mildest and most effective AHA available. Compared with other AHAs such as glycolic, citric and malic acid, lactic acid is the most widely used AHA in cosmetic products.

A well-known method for determining the performance is measuring the Therapeutic Index or Activity Index (cell renewal increase divided by clinical irritation). This gives an indication of the total performance of a hydroxy acid. The graph shows this parameter for the most important AHAs (International Journal of Cosmetic Science 18, 75-83, 1996).

Citric acid and malic acid have a low therapeutic index; cell renewal is very low and the irritation potential high. The relatively poor performance of glycolic acid is solely related to its irritation potential. Natural L(+)-lactic acid shows the highest therapeutic index and performs best in this test. Lactic acid combines a high cell renewal rate with a very low irritation level.

Beta hydroxy acids have become quite popular among some cosmetic formulators. The most widely used acid in the BHA group today is salicylic acid. Salicylic acid occurs naturally in willow bark, but in cosmetics a synthetic form is often used.

A comparison of the performance of AHA and BHA can be seen in the graph. Salicylic acid and lactic acid were tested alone and in mixtures (Source: WO 94/06440). The results of this experiment show that the effectiveness of salicylic acid is comparable with lactic acid in terms of cell renewal. However, salicylic acid causes more irritation. As a result, the therapeutic index is slightly lower for salicylic acid. Mixing lactic acid and salicylic acid in a ratio of 2:1 results in a pronounced synergistic effect with a sharp increase in cell renewal and a drop in irritation. Other acids tested in the same experiments did not reveal any synergistic effects.

It is generally recognized that lactic acid is the best performing hydroxy acid. Of all AHAs and BHAs, lactic acid is one of the mildest hydroxy acids and exhibits excellent cell renewal activities. Lactic acid exhibits additional properties as well: it moisturizes and possesses the ability to increase ceramide levels.

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Lactates are safe and effective skin-lightening agents

There is a worldwide demand for products able to inhibit or prevent pigmentation of the skin. With the increasing use of lightening ingredients, it is apparent that other factors, such as safety and mildness, are just as crucial as the effectiveness of lightening formulations today. Moreover the cost price of both the formulations and their ingredient is also playing an increasingly important role.

Melanin is the skin's natural pigment. The formation of melanin proceeds by a multi-step mechanism in which tyrosinase is the key enzyme:

In theory, three different mechanisms are involved in the operation of lightening ingredients:

A.Direct reduction of melanin
B.Inhibition of tyrosinase activity
C.Suppression of the formation of tyrosinase

The lightening action of lactates is based on the suppression of the formation of tyrosinase (action C). This mechanism is completely different from the lightening action of conventional ingredients such as Vitamin C, Arbutin and Kojic acid (action B) and Hydroquinon (action A).

A lactate concentration equivalent to 8% lactic acid is sufficient to achieve a significant lightening effect. The graph shows the lightening power of lactates compared with that of other ingredients. A clinical lightening trial was conducted for 12 weeks. The lightening effect was measured using a Melanometer.

The graph shows the difference in lightening compared with the baseline reading. Lactates are clearly the best lightening performers compared with other well-known ingredients such as Licorice, Kojic acid and Arbutin. Lactates can also be used in combinations with these products in order to increase their efficiency.

Lactates have been shown to exhibit synergistic effects when used in combination with Vitamin C, as can be seen in the graph.

Combinations of Vitamin C and lactates were tested (pH 5.5) as well as both ingredients alone. The results show a pronounced synergistic skin-lightening effect when a combination of lactic acid and Vitamin C is used. The reported lightening result of the combination was better and faster compared to hydroquinon.

As stated above, the lightening effects of natural L(+)-lactic acid and of lactates are the result of the suppression of the formation of tyrosinase. The formulations were all tested under relatively skin-neutral conditions (pH 5.5). The exfoliative action of lactic acid is very modest at these pH levels, since almost all of the lactic acid is present in its salt form (e.g. sodium lactate).

Formulating at a lower pH (with the addition of lactic acid) will presumably increase the effectiveness of lightening formulations. Possible explanations for this are the better penetration of the lactate ion and the exfoliating action of lactic acid at lower pH values.

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Active ingredients for oral care

One trend in oral care products is the addition of calcium for healthier teeth. The high solubility of calcium lactate, plus its neutral taste, make PURACAL - natural calcium salt base on lactic acid - a very suitable calcium source in oral care products. Moreover, clinical tests show that PURACAL also reduces the formation of tartar on the teeth (Source: M. Schaeken, Caries Res., 24 (1990) and 27 (1993)).

The first clinical test was carried out with a mouthwash containing 5% PURACAL, which was used for three months by the test subjects. It was found that the use of these mouthwashes reduced the calculus deposition on the teeth.

	Tartar score (DM calcus Index)
Baseline Water PURACAL Mouthwash	4.7 ± 4.6 4.6 ± 4.3 2.9 ± 3.4

Tartar formation determined on cervical partion of lower incisors

In a second study, PURACAL was incorporated in toothpaste at a concentration of 7%. After three months, it was found that the calculus scores of the group that had used the toothpaste containing PURACAL were significantly reduced in comparison with the control group. This tartar-reducing action is comparable with pyrophosphates (26-48%), which are widely used as anti-tartar agents.

	Baseline	3 Months	Reduction
Control +PURACAL +PURACAL/SLS	1.56 ± 2.50 1.12 ± 1.99 1.19 ± 1.56	1.33 ± 2.15 0.75 ± 0.99 0.72 ± 0.83	15 33 39

Tartar formation determined on lingual of the lower incisors

Aluminum lactate (PURAMEX AL) and zinc lactate (PURAMEX ZN) can be used in oral care formulations such as toothpastes and mouthwashes. The astringent properties of PURAMEX AL have a positive effect on gums and mucous membranes in the mouth.

Zinc salts are often added to oral care products because zinc ions help to prevent the formulation of tartar, oral malodor and gingivitis. PURAMEX ZN is very suitable for this purpose because it has good solubility, a mild taste and is considered a pharmaceutically acceptable zinc source.

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