Abstract
This research aims to study the release, in vivo anti-aging activity against Caenorhabditis elegans and stability of astaxanthins in a crude acetone extract of Haematococcus pluvialis from electrospun cellulose acetate (CA) nanofibers. The content and 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) radical scavenging activity of astaxanthins in the crude extract were also determined. The content of astaxanthins was reported in terms of total carotenoid content (TCC) and found to be 10.75 ± 0.16 mg gcE−1. IC50 of DPPH radical scavenging activity for astaxanthins was 233.33 ± 4.18 μg mL−1. It has been well known that astaxanthins are very unstable under environmental conditions, so the electrospinning technique was used to enhance their stability. In order to fabricate CA nanofibers containing a crude acetone extract of H. pluvialis, various solvent systems and percent loading of the crude acetone extract were studied. The optimal solvent system for fabrication of CA nanofibers was the acetone/dimethylformamide (DMF) system (2 : 1 v/v) with incorporation of 0.25% v/v Tween80, resulting in good morphology of CA nanofibers with av. 420 nm diameter. The loading efficiency (%) of the crude astaxanthins extract was 5% w/w of CA. With regard to the results of the in vivo oxidative stress assay, C. elegans pre-treated with 200 μg mL−1 of the crude extract had a survival percent of 56 after administration of 250 mM of paraquat for 8 h. Under phosphate-buffered saline (pH 7.4) containing 10% v/v acetone, the release of astaxanthins from the CA nanofibers loaded with the crude extract exhibited a prolonged profile. The stability of astaxanthins in electrospun CA nanofibers was examined using the freeze–thaw cycle testing through a DPPH radical scavenging assay. It was found that their stability was significantly different (P < 0.05) after the 12th freeze–thaw cycle compared with the crude extract.
Highlights
Astaxanthin and its esters are naturally occurring and blood-red carotenoid pigments
It was found that their stability was significantly different (P < 0.05) after the 12th freeze–thaw cycle compared with the crude extract
The crude astaxanthin extract was puri ed by column chromatography resulting in 4.22 Æ 2.05% (w/w) of astaxanthin derivatives and accounted for 0.91 Æ 0.15% (w/w) of dry biomass. 1H-MNR and 13C-NMR spectroscopic techniques were used to characterize and identify as astaxanthin esters; mainly astaxanthin monoesters of fatty acids (Fig. S1–S3 in Electronic supplementary information (ESI)†)
Summary
Astaxanthin and its esters are naturally occurring and blood-red carotenoid pigments. Astaxanthin is considered as a natural super anti-oxidant as compared with the naturally occurring carotenoids.[3] For examples, astaxanthin exhibited 10 times more antioxidant activity than zeaxanthin, lutein, Most structures of natural astaxanthin have been found in the form of mono- and diesters; 70% monoesters of astaxanthins, 10% diesters, 5% free astaxanthin and the remaining 15% contains a mixture of b-carotene, canthaxanthin, lutein and other carotenoids Because of their structure containing high multiple bonds, they are oxidized and unstable upon exposure to heat, light and oxygen, which result in the decrease in their biological activities.[7] One simple and versatile technique for helping the astaxanthin stability is encapsulation with chitosan, cyclodextrin, calcium alginate, etc.[8,9,10] the encapsulation technique is limited with difficulty of handling, low loading of bioactive compounds and upscaling for mass production.[10] A new technique for delivery of bioactive compounds is electrospinning technique, which produced continuous nano to submicro bers using electrostatic forces.[11,12,13] The characteristic advantages of encapsulation
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