Identification of the Composition of Isomeric Canthaxanthin Sample by NMR, HPLC, and Mass Spectrometry

Green synthesis of silver nanoparticles using canthaxanthin from Dietzia maris AURCCBT01 and their cytotoxic properties against human keratinocyte cell line

AIM

Nano-biotechnologically synthesizing silver nanoparticles via canthaxanthin pigment extracted from Dietzia maris AURCCBT01 and assessing their cytotoxic therapeutic potential against human keratinocyte cell line (HaCaT) were the key objectives of this study.

METHODS AND RESULTS

The pigment extracted from D. maris AURCCBT01 was identified as canthaxanthin using UV-VIS spectroscopy, FTIR, NMR (¹ H NMR and ¹³ C NMR) and MS. Canthaxanthin, treated with silver nitrate solution, produced canthaxanthin-mediated silver nanoparticles and they were characterized by UV-VIS spectroscopy, FTIR, XRD, FESEM-EDX and TEM-SAED techniques. UV-VIS spectroscopy pointed out an absorption band at 420 nm, relating to the surface plasmon resonance of silver nanoparticles. FTIR findings suggested that the diverse functional groups of canthaxanthin bio-molecules played a significant task in capping the silver nanoparticles. XRD analysis exhibited 40·20 nm for the crystal size of nanoparticles. FESEM and TEM exhibited that the biosynthesized silver nanoparticles were spherical in shape with crystalline nature and the particle size was 40-50 nm. Moreover, the cytotoxicity assessment of the synthesized nanoparticles in HaCaT revealed significant cytotoxicity in the cultured cells with an IC₅₀ value of 43 µg ml^-1 .

CONCLUSION

Stable silver nanoparticles synthesized using canthaxanthin from D. maris AURCCBT01 were found effective for application in wound healing activity.

SIGNIFICANCE AND IMPACT OF THE STUDY

Biosynthesized silver nanoparticles via canthaxanthin bacterial pigment exhibited their cytotoxicity effect in HaCaT and testified their eventual therapeutic potential in the wound healing activity with no side effects in a cost effective and eco-friendly process.

Canthaxanthin, a Red-Hot Carotenoid: Applications, Synthesis, and Biosynthetic Evolution

Carotenoids are a class of pigments with a biological role in light capture and antioxidant activities. High value ketocarotenoids, such as astaxanthin and canthaxanthin, are highly appealing for applications in human nutraceutical, cosmetic, and animal feed industries due to their color- and health-related properties. In this review, recent advances in metabolic engineering and synthetic biology towards the production of ketocarotenoids, in particular the red-orange canthaxanthin, are highlighted. Also reviewed and discussed are the properties of canthaxanthin, its natural producers, and various strategies for its chemical synthesis. We review the de novo synthesis of canthaxanthin and the functional β-carotene ketolase enzyme across organisms, supported by a protein-sequence-based phylogenetic analysis. Various possible modifications of the carotenoid biosynthesis pathway and the present sustainable cost-effective alternative platforms for ketocarotenoids biosynthesis are also discussed.

Two-dimensional liquid chromatography analysis of all-trans-, 9-cis-, and 13-cis-astaxanthin in raw extracts from Phaffia rhodozyma

An effective two-dimensional liquid chromatography method has been established for the analysis of all-trans-astaxanthin and its geometric isomers from Phaffia rhodozyma employing a C18 column at the first dimension and a C30 column in the second dimension, connected by a 10-port valve using the photo-diode array detector. The regression equation of astaxanthin calibration curve was established, and the precision and accuracy values were found to be in the range of 0.32-1.14% and 98.21-106.13%, respectively. By using two-dimensional liquid chromatography, it was found that day light, ultrasonic treatment, and heat treatment have significant influence on the content of all-trans-astaxanthin in the extract from P. rhodozyma due to the transformation of all-trans-astaxanthin to cis-astaxanthin. The day light and ultrasonic treatments more likely transform all-trans-astaxanthin to 9-cis-astaxanthin, and the thermal treatment transforms all-trans-astaxanthin to 13-cis-astaxanthin. These results indicate that the two-dimensional liquid chromatography method can facilitate monitoring astaxanthin isomerization in the raw extract from P. rhodozyma. In addition, the study will provide a general reference for monitoring other medicals and bioactive chemicals with geometric isomers.

Kinetic and Thermodynamic Study of the Thermally Induced (E/Z)-Isomerization of the retro-Carotenoid Rhodoxanthin

The hitherto scarcely investigated retro-carotenoid rhodoxanthin possesses high potential for coloration in the food and beverage industry using technofunctional formulations prepared thereof. Hence, we studied (E/Z)-isomerization pathways of rhodoxanthin, including seven (E/Z)-isomers comprising (Z)-configured double bonds at unusual exocyclic and inner polyene chain positions. A mathematical approach was developed to deduce kinetic and thermodynamic parameters of six parallel equilibrium reactions interconnecting (all-E)-rhodoxanthin with mono-, di-, and tri-(Z)-isomers using multiresponse modeling. At 40-70 °C in ethyl acetate, reaction rate constants regarding the rotation from (all-E)- to (6Z)-rhodoxanthin were 11-14 times higher than those of the common (E/Z)-isomerization reaction at C-13,14 of the non-retro-structured carotenoid canthaxanthin. Moreover, the equilibrium reaction between (all-E)- and (6Z)-rhodoxanthin was strongly product favored as indicated by negative Gibbs energies (-1.6 to -2.2 kJ mol^-1), which is unusual for carotenoids within the studied temperatures. Overall, this study provides novel insights into structure-related dependencies of (E/Z)-isomerization reaction kinetics and thermodynamics of polyenes.

Carotenoids from UV-resistant Antarctic Microbacterium sp. LEMMJ01

The Microbacterium sp. LEMMJ01 isolated from Antarctic soil does not belong to any of the nearest species identified in the RDP database. Under UV radiation (A, B and C wavebands) the survival fractions of Microbacterium sp. cells were much higher compared with wild-type E. coli K12A15. Especially remarkable for an Antarctic bacterium, an expressive resistance against high UV-B doses was observed. The increased survival of DNA repair-proficient E. coli grown overnight added of 0.1 mg/ml or 1 mg/ml of the whole pigment extract produced by Microbacterium sp. revealed that part of the resistance of Microbacterium sp. against UV-B radiation seems to be connected with photoprotection by its pigments. Scanning electron microscopy revealed that UV-A and UV-B ensued membrane alterations only in E. coli. The APCI-MS fingerprints revealed the diagnostic ions for neurosporene (m/z 580, 566, 522, 538, and 524) synergism for the first time in this bacterium by HPLC-MS/MS analysis. Carotenoids also were devoid of phototoxicity and cytotoxicity effects in mouse cells and in human keratinocytes and fibroblasts.