SUSTAINABILITY
phases. These revolutionary solvents are not only easy to produce and handle, but they are also unreactive to air and moisture which are key prerequisites for their use as extraction and/or formulation fluids for the cosmetics sector. Mechanistically speaking, combinations
are formed between DES components, rearranging the molecular lattice by increasing the void volume.3
DES behave
like a sliding puzzle: molecules can only move if there is space (void) next to them that is big enough for the molecule in question. For example the packing of molecules in a solid A is too compact to allow for movement, meaning that the void between molecules is very low (Fig. 2). This packing can be weakened by introducing new molecules – for instance B – that will associate with A, thus disrupting the crystalline structures to generate a less ordered system. By doing so, cavities are created in the vicinity of both molecules, allowing them to move. Introducing more void into the system, makes molecules more diffusible – hence the mixture becomes liquid. The recipe to prepare DES is relatively
easy: mix an asymmetric quaternary ammonium (a powder) with a hydrogen- bond donor (powder or viscous liquid) in various molar ratios (1:1, 1:2, 1:3), apply moderate heat, then select the mixture that stays stable, clear and limpid at room temperature. Not all combinations form a melt, much less a stable one. Making DES is both an art and a science and knowing the theoretical background of eutectics – hole theory for instance – makes it possible to prepare less viscous and more stable mixtures, all the while fine-tuning their solvation properties. Accordingly, a lot of hydrogen-bond donors available in nature have been tested to date, such as amides, amines, acids, alcohols, and so on.4 The wide range of available natural hydrogen-bond donors, along with the multiple methods for combining them with quaternary ammoniums, means that this novel class of liquids is almost infinitely tunable: myriad DES can be created, thus opening an avenue for their use in industry.
Do plant cells contain liquids other than water and lipids? The story about deep eutectic solvents took an unexpected turn when suspicions began to grow that nature had been using them long before the advent of green chemistry. Considering the data which has been collected in the last decades using metabolomics, it is indeed worth asking why a few very simple compounds are always present in considerable amounts in all plant cells.5
Such molecules include 46 PERSONAL CARE February 2016
Radiance & whitening* Anti-wrinkle* Photo-ageing* Regenerating* Antioxidant Hair shine Hair repair
Radiance & whitening* Energising Antioxidant Anti-ageing Hair shine Hair repair
Anti-wrinkle* Regenerating* Firming*
Photoprotection* Aftersun Antioxidant Hair shine Hair repair
Calming* Antioxidant* Regenerating Hair shine Hair repair
Radiance & whitening* Antioxidant
Dermo-purifying Hair shine Hair repair
Figure 3: The first series of the Eutectys collection (*
sugars, amino acids, quaternary ammoniums, polyols, and certain organic acids. With the exception of sugars, which may serve as cell energy providers, the other compounds are present in such large amounts that it does not make sense to consider them as mere intermediates in metabolic pathways. These compounds must serve an ignored but crucial basic function in living organisms. Robert Verpoorte and his collaborators
from the Universities of Leiden and Delf started considering the problem from a new perspective. The first hint came from the experimental observation that these primary metabolites were able to form deep eutectic mixtures. The second hint – which
a
4.0 3.8 3.6 3.4 3.2 3.0 2.8 2.6 2.4 2.2 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0
–0.2 –0.4
5 6 7 8 9 10 11 12 13 14 15 Acquisition time (mn) b
80 60 40 20 0
*** x5 **
n Dexamethasone 10 µM n Horsetail GlyH2 n Horsetail GlyH2
n Horsetail EutectysTM n Horsetail EutectysTM
16 17 18 19 20 21 22
Antioxidant* Calming
Dermo-purifying Photoprotection Hair shine Hair repair
in vitro proven benefits).
led to the epiphany – was the realisation that drought tolerance in plants is often accompanied with the accumulation of sugars, amino-acids, quaternary ammonium and organic acids, all perfect candidates for constituting eutectics. They soon realised that under extreme environmental conditions such as drought, salt stress, and high or low temperatures, living cells may survive by forming deep eutectic liquids in which the membranes, enzymes and metabolites remain stable, and wherein, the last molecules of water are strongly retained, and freezing is prohibited by the very low melting point of the eutectic mixture.5 To understand such a breakthrough
Phelonic acids concentration: +18%
O 0.01% O 0.1%
BLA 0.01% BLA 0.1%
**p<0.01, ***p<0.001 TNFα inhibition
Figure 4: Horsetail Eutectys: a) augmented phytoactive content [LC/UV chromatogram of Horsetail Eutectys BLA (red) compared to a standard horsetail glycerine extract (blue) at 280 nm]; and b) enhanced biological property [Horsetail Eutectys BLA showed soothing properties at 0.1% by inhibiting the release of TNF-αin HaCaT keratinocyte cells].
Protective gain (%)
Response units (x102
)
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76
