Condition - Nature's antixoidant: astaxanthin
Throughout history, man has worshipped, and nature has harnessed, the power of the sun, providing us with photosynthesised energy and a plethora of nutrients such as vitamin D and powerful antioxidants like astaxanthin.
Astaxanthin is a bright red pigment, classified as a xanthophyll carotenoid. It is related to other colourful members of the carotenoid family such as b-carotene, lutein, zeaxanthin and lycopene, thus sharing many of their metabolic, physiological and antioxidant functions, as well as being lipid-soluble (lipophilic). Although its molecular structure is most similar to b-carotene, astaxanthin will not convert to pro-oxidant vitamin A (retinol) in the body. Compared with other carotenoids, astaxanthin contains additional oxygenated groups on each ring structure, i.e. hydroxyl and keto endings on each ionone ring, (Fig. 1) with a more polar configuration, resulting in enhanced antioxidant properties(1) without any negative pro-oxidant qualities. This has been confirmed by a number of studies(2,3,4).
Sources of astaxanthin
As with all carotenoids, animals cannot synthesise astaxanthin, so it has to be provided in the diet(5). Haematococcus pluvialis, a green micro-alga, is one of the richest sources of natural astaxanthin. When joined to certain proteins, astaxanthin can appear green, yellow, blue or brown. With the application of heat, the proteins change their structure and the bright red colour of the astaxanthin is exposed. This alga is consumed by aquatic species such as salmonids, trout, krill and other crustaceans, like prawns, lobster and shrimp; as well as non-aquatic species, such as the flamingo. The astaxanthin accumulates rapidly in their tissues, muscles and feathers, giving them their distinctive pink colouring.
Synthetic astaxanthin is currently manufactured from petrochemicals. Although it has the same chemical formula as natural astaxanthin, it has a different molecular shape/stereo-chemical orientation. The difference in the geometrical configuration of atoms between natural and synthetic astaxanthin confers different biological and pharmacokinetic qualities.
Like all lipophilic carotenoids, astaxanthin is emulsified and solubilised into mixed-lipid micelles in the intestines(6). Within the enterocytes, the micelles are incorporated into triglyceride-rich lipoproteins called chylomicrons, which enter the lymphatic system before passively diffusing into the blood(7). Once in the circulation, chylomicrons are transferred to lipoproteins and transported through the blood(8).
The presence of the hydroxyl and keto endings on each ionone ring (Fig. 1) reflects astaxanthin’s ability to be esterified or complex with other molecules and thus to increase its stability(1). In nature, it is found either conjugated to proteins such as in salmon muscle and lobster exoskeleton or esterified with one or two fatty acids(9). Synthetic astaxanthin is in the free (un-conjugated) form, which may render it considerably less stable and particularly sensitive to oxidation.
Esterification of natural astaxanthin also makes it significantly more fat-soluble than the synthetic, free form. Several studies on the kinetics of dietary astaxanthin uptake have demonstrated increased oral bioavailability of natural astaxanthin esters when mixed with various lipid formulations(10,11).
Natural astaxanthin can also be found in combination with additional carotenoids; b-carotene, canthaxanthin and lutein(9), which work synergistically, enhancing each others’ effects.
The stereoisomers (isomers/compounds with the same structural bonds but differing geometrical positioning of atoms and functional groups in space) of natural astaxanthin, found in fish and Haematococcus pluvialis, are the most studied and researched form of astaxanthin. So, although synthetic isomers of astaxanthin may not be harmful, no significant biological effect has been established.
Astaxanthin’s potent antioxidant qualities, combined with its unique ability to span through the fatty bi-layer of every cell membrane, allow it to extend its protection throughout the body and even penetrate the blood- brain and the blood-retinal barriers in the central nervous system and eyes, respectively. A characteristic that is not seen with all carotenoids or antioxidants.
Astaxanthin’s ability to support whole-body health and wellbeing has been the subject of growing medical research all over the world in the past few years. There are currently over 300 publications; including in-vitro experiments, in-vivo pre-clinical studies and several human clinical trials; supporting the use of astaxanthin, either on its own or in conjunction with other components, as an essential dietary supplement.
Key areas of research and applications
Immunity, inflammation and exercise
Inflammation is inextricably linked to the immune system, as it is a type of non-specific immune response.
M. Kurashige was the first researcher to discover the anti-inflammatory effects of astaxanthin in 1990, when he demonstrated its ability to inhibit oxidative injury to cell membranes(2). Research into gastric inflammatory conditions has shown that astaxanthin may help alleviate symptoms associated with indigestion and gastric ulceration, while demonstrating a positive effect against Helicobacter pylori(12) and inflammatory irritation of gastric mucosa(13).
Antioxidants have been shown to be important in preventing deterioration of immune function, especially in the elderly(14). Astaxanthin may reduce or prevent this decline by enhancing immunoglobulin production in response to T-dependent stimuli and antigens(15). Astaxanthin has also exhibited immune-modulating potential by inhibiting the production of inflammatory mediators associated with immune imbalances(16).
Strenuous exercise, with increased energy production and breathing rate, exposes our body to excessive oxidation and inflammation. Studies show that astaxanthin’s potent antioxidant properties may protect muscle tissue against free radical damage, thereby inhibiting secondary inflammatory responses and protecting the mitochondria, while supporting muscle strength, endurance and repair during exercise(17,18).
Since the carotenoids are exclusively transported by lipoproteins, various studies have demonstrated astaxanthin’s ability to protect LDL (low density lipoprotein) cholesterol from oxidation(19) and may, thus, reduce the incidence of atheroma and arteriosclerosis(20). As well as inhibiting inflammatory activation associated with atherosclerotic lesions(21) and increasing HDL cholesterol levels(22), astaxanthin has also been found to support healthy blood pressure(23).
Neurological and ocular health
Astaxanthin is one of a select few antioxidants that may penetrate the blood-brain and blood-retinal barriers in the central nervous system and eyes. As such, it may protect against oxidative stress associated with neurodegenerative disorders in these areas. A 2001 study found that astaxanthin could improve poor memory and prevent age-related memory loss(24). Meanwhile, a growing number of recent studies, regarding astaxanthin’s effects on ocular health, suggest it may help improve age-related maculopathy(25) and help alleviate eye fatigue(26, 27).
Astaxanthin has proved to be superior to other commonly-used antioxidants in its ability to protect skin cells against damage from reactive oxygen species (ROS) generated by sunburn and UVA light damage(28, 29), as well as suppressing hyperpigmentation(30), inhibiting melanin synthesis and photo-ageing(31). Positive results in skin hydration, elasticity and wrinkle reduction have also been achieved through a combination of astaxanthin and tocotrienol supplementation(32, 33).
Astaxanthin has also been shown to be effective in limiting diabetic nephropathy(34) and improving semen quality and health(35).
To date, there have been no toxicity reports with H. pluvialis astaxanthin supplementation(36).
So, as summer illuminates warm, long days filled with colours and bright smiles, we are reminded of the magnificence of the sun as it embraces us with another wonderful gift: Astaxanthin!
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