| Haematococcus pluvialis, a unicellular green alga has the ability to accumulation the largeamount of astaxanthin once exposed environmental stresses and was considered as the bestbioresource of astaxanthin at present. Astaxanthin is a kind of keto-carotenoids. It has stronganti-oxidative ability and can scavenge ROS effectively. Therefore, it has a broad applicationprospect in nutraceutical, aquaculture, cosmetics, food and feeding nutrition industry.Haematococcus pluvialis has various morphological types in its life cycle and has differentantioxidative mechanisms in each cell type. Study on Haematococcus pluvialis in China beganin the middle of 20th century, and industrialization have not been carried out. Therefore, it isvery important that the qualitity safety assessment be carried out before the powder used as thematerial of food and function food.The Haematococcus pluvialis strain was used to study the antioxidation of astaxanthin andquality safety toxicological assessment. According to the morphological characteristics of H.pluvialis cell, the different cell types were obtained by exposing the cells to different stressenvironments. And then the mechanisms of antioxidation in different cell types were discussed.On the other hand, synergistic effect of DPA, an astaxanthin synthesis inhibitor, and other stressfactors was analyzed. Finally, the assessment on hygiene safety and toxicology were carried out,which provided the directed information for study on astaxanthin antioxidation in animal andhuman further.The main results were as follows:(1)Sequence of antioxidation abilities in the three cell types was: red cell>brown cell>green cell.(2)When additional ROS was absent, ROS content in red cell was the most, and the brownwas the second, the green cell was the lest. Once cell exposed to additional ROS, quantum ofROS and MDA content increased rapidly in the green cell but had no significant changes in redcell.(3)In H. pluvialis cell, there were two antioxidation mechanisms, the one was antioxidativeenzyme system and the other was astaxanthin. The antioxidation mechanisms were various indifferent cell types. In the green cell, protective enzyme system was the main antioxidationmechanism. On the contrary, it was astaxanthin in the red cell. Compared with the twomechanisms, astaxanthin acted more quickly and powerfully against ROS than the enzyme did.(4)There was temporal and special sequence in the two antioxidation mechanisms, andastaxanthin took its role firstly. Only when astaxanthin was absent or very low content (such asin green cell), the protective enzymes would take the leading to fighting ROS. In enzymesystem, SOD traps O2ˉ first, then POD quenches H2O2, which is the by-product by SOD, and atlast APX and CAT scavenge excessive ROS. In green cell, SOD was the first defensive line andthe key enzyme of quenching ROS.(5) CAT and APX were the enzymes of quenching H2O2 in chloroplast, howerever, theresults showed that protective role of APX against ROS was more important than that of CATin Haematococcus pluvialis cell. Therefore it was concluded that APX was the key enzyme butnot CAT to quench ROS in the green cell chloroplast.(6)Oxidative stress induced the increase of SOD isoenzyme activity, and made theisoenzyme bands brighter. However, it induced the new bands of POD(Rf=0.29) in the greencell.(7) Antioxidative abilities increased with DPA addition in high light stress, but decreasedin high light and N absence stress.Results of assessment of quality safety and toxicology experiment showed that hygienemicroorganism and heavy metal content were in accord with General standard for health(functional) foods. Acute toxicology and 30 feeding experiments were carried out, not anyevident poisoning symptom with mouse and pathological changes with rats were found. Theresults showed that the Haematococcus pluvialis powder was safe used as the raw materials offood and health food.
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