**7. Discussion**

Our experiments demonstrated that the interaction of carotenoids with lipids could result in the formation of their complexes, which were thermodynamically

#### *Carotenoids in Thermal Adaptation of Plants and Animals DOI: http://dx.doi.org/10.5772/intechopen.104537*

more favourable than when these two groups of molecules were separate. As a result of this, carotenoids were better able to absorb the light energy in the longer wavelength of the red part of the spectrum.

The physical properties of lipids in these complexes were also changed due to a possible reduction in their cohesiveness between these molecules. For oil droplets or fat globules, this resulted in a reduction of their surface tension and, consequently, facilitated their fusion or enlargement. The larger the lipid droplets are, the less energy they have. Therefore, carotenoids can create complexes with lipids, which trigger their transition into a thermodynamically more favourable and stable phase. The fact that a single molecule of the carotenoid can affect the behaviour of 10,000 or 100,000 molecules of lipids may imply the possibility that the released energy, after formation of this type of complex, can dissipate beyond its physical location and cause a long-range transition of the lipid matrix, with consequent physical changes of its properties.

Lipid droplets with increased size would have less friction between each other, and the oils and fats became less viscous. Whether the reduction in the viscosity was a result of blending carotenoids in existing oil or fat products, or their incorporation into *de novo* assembled lipid structures, the effect in principle was the same. This was confirmed in the clinical trial, when the increase in lycopene concentration in the skin sebum resulted in the reduction of the viscosity of its droplets (**Figure 2**). These changes in sebum quality were similar to the observations on the supplementation of volunteers with other carotenoids such as lutein (results not presented here) and astaxanthin [6].

A significantly higher response in changes of the viscosity of plant lipids, over animal ones, could probably be either a result of their stronger interaction with carotenoids or easier spreadability of conformational changes in the plant lipids than in the animal fats. Or this can be a combination of both of these factors. Animals cannot synthesise carotenoids but plants can, and this is probably why the affinity to these molecules to other plant molecules, lipids, is higher than to animal ones.

The increased surface area of enlarged oil droplets or fat globules would have more surface-to-surface contacts with each other, which would facilitate the transfer of changing temperature between these particles. Whether there is a thawing of frozen liquid hydrocarbons, or melting of solid lipids, or their heating, the incorporation of carotenoids into these molecules accelerated temperature energy transfer within them.

Since one molecule of a carotenoid was able to facilitate temperature changes in 10,000, or 100,000 or more molecules of lipids, it is unclear whether this was due to changes in lipid molecule thermoconductivity, or carotenoids, in their complex with lipids, may work as 'thermal antennas', which could dissipate and distribute thermal radiation/energy far beyond the physical location of carotenoid-lipid complex.

The ability of carotenoids to increase the accumulation of thermal energy and its distribution was significantly higher for the plant lipids than for the fish oil, which, in turn, responded better than the mammalian fats. The reason for this effect of carotenoids on heat absorption gradient in different lipids could be the fact that plants are exposed to much broader variations in environmental temperature changes than ectotherms/poikilotherms like fish, when the body temperature of endotherms like mammals is constant.

The viscosity of lipids is the essential parameter, which controls cellular membrane permeability to electrolytes and nutrients, energy synthesis, cell growth and proliferation. One of the main factors determining the viscosity of lipids, and their ability to conduct the heat or the cool, is a lipid composition, a ratio of triglyceride saturated and unsaturated fatty acids, their length, other incorporated lipids, etc.

Our experiments indicate that carotenoids could have a new biological role not only to control viscosity of lipids but their thermal energy absorption, retention and conductivity too. If this is the case, this could be a much more efficient pathway to control these parameters. For a plant cell, to synthesise one molecule of a carotenoid, which can change the viscosity of 10,000 or even 100,000 molecules of lipids, would be much faster and more economic than to activate a lipid replacement process, which would involve a few hundred or thousand more new lipid molecules to be synthesised.

This possible new role of carotenoids as a factor facilitating adaptation to environmental, and in particular, temperature variation stresses, may explain a number of observations, which do not have clear explanations. What is the role of carotenoids, which are not involved in photosynthesis whether in a plant or in a light harvesting microorganism? What is the role of these molecules in parts of the plant where photosynthesis is not happening at all, like fruits or roots?

Since plants, or microorganisms such as algae, have exposure to much higher day-night, seasonal or other environmental temperature variability than animals, it is not surprising that the level of carotenoids in their tissue is 103 –106 higher than in animals [8, 9]. Within animals, ectotherms, which do not have their own mechanism to control their temperature, rely more on the accumulation of ingested carotenoids than endotherms, which can maintain their thermal homeostasis. It is not surprising that in tissues of fish or reptiles, carotenoid concentration could be from 10- to 100 fold higher than in mammalians [10, 11].

The ability of carotenoids to work as antennas facilitating transmission and distribution of the thermal energy within lipid matrixes may find its practical applications in different industries. This carotenoid property may improve the performance of lipids, and possibly other hydrocarbons, when they are used for the production of greases, lubricants, liquid crystal devices, nanotubes, thermal energy storage, biodiesel and some other products, oils and fuels.

For example, carotenoids can accelerate the heating of oil or lipid-in-oil emulsions in general (**Figure 4f**), or when they used for cooking purposes in particular. This can shorten the time of the cooking process, save fuel, which is used to generate heating energy, and preserve more thermo-sensitive vitamins and micronutrients in the finished cooked meal (**Figure 5**). The correlation between the rate of acceleration of the heating of the cooking meal, in oils with different carotenoids, and the level of preserved thermo-sensitive vitamins was not always observed. This was probably due to additional antioxidant properties of carotenoids, which could contribute to preservation of these vitamins in the cooking process.

Another useful application of the ability of carotenoids to disrupt lipid folding would be to increase the size and reduce the viscosity of oil droplets and fat globules in food products. We demonstrated that the ingestion of dairy butter, vegetable oils and chocolate with enlarged lipid particles resulted not only in the reduction of the postprandial lipidaemia but also, if these products were regularly consumed, in the reduction of elevated fasting blood lipids. This means than carotenoids can be used to convert edible oils and fats into lipid lowering and weight management food products.

Perhaps, the culinary practice of cooking in oils/fats with lycopene-rich tomato sauce is a contributing factor as to why Italians are one of the slimiest nations in Europe and the USA [12, 13].

In our *in vitro* and *ex vivo* experiments, on the effect of lycopene and lutein of formation and dissolution of cholesterol crystals, we used a range of the ratio *Carotenoids in Thermal Adaptation of Plants and Animals DOI: http://dx.doi.org/10.5772/intechopen.104537*

between these molecules the same as is present in humans from 1:4000 to 1:1000. The observed ability of carotenoids to interact with cholesterol molecules, to reduce the rate of its crystallisation, may be used for the prevention or control of the growth of cholesterol crystals and/or for the treatment by facilitating the disassembly of the already formed crystals, which are responsible for the rupture of atherosclerotic plaques leading to heart attack or ischaemic stroke [14, 15].

To assess the industrial, nutritional and medical applicability of using carotenoids to affect lipid properties, to create new materials, food and health care products would require more work and expertise in different fields.

In conclusion, it should be said that the main objective of the presentation of the data in this paper is to illustrate the new phenomenon, its potential biological role and practical applicability. The main body of the backing/supporting experiments on different carotenoids, lipids, doses, conditions, products, clinical trial participants, etc., would be a subject of future separate publications.

## **Acknowledgements**

The author is grateful to his colleagues for conducting experiments results of which are presented in this paper: Dr Alexandre Loktionov Jr., Dr Alexey Petyaev, Professor, Pavel Dovgalevsky, Professor Viktor Klochkov, Dr Natalya Chalyk, Dr Dmitry Pristenskiy, Dr Marina Chernyshova, Dr Alexandre Loktionov, Dr Tatyana Bandaletova, Nigel Kyle, Marina Lozbiakova. A special thank you to Mr. William George for his personal supporting this project, Professor Yuriy Bashmakov for stimulating discussions in the filed, and Mrs. Anne George for editing this manuscript.

## **Conflict of interest**

The author is a founder and director of Lycotec Ltd, the company that research and develop carotenoid based technologies.

*Carotenoids - New Perspectives and Application*
