Rhodoxanthin synthase from honeysuckle; a membrane diiron enzyme catalyzes the multistep conversation of β-carotene to rhodoxanthin

Stabilization of β-Carotene Liposomes with Chitosan-Lactoferrin Coating System: Vesicle Properties and Anti-Inflammatory In Vitro Studies

Liposomes serve as an effective delivery system capable of encapsulating a variety of bioactive substances. However, their structural integrity is susceptible to damage from various environmental factors, which can result in the leakage of the encapsulated bioactive agents. Consequently, identifying effective strategies to enhance the stability of liposomes has become a central focus of contemporary liposome research. Surface modification, achieved by introducing a protective layer on the liposome surface, effectively reduces liposome aggregation and enhances their stability. To this end, we designed a surface modification and constructed liposomes loaded with β-carotene through co-modification with chitosan and lactoferrin, resulting in enhanced stability. This improvement was evident in terms of storage stability, light stability, and in vitro digestion stability. The study investigated the morphology, structure, and physicochemical properties of liposomes with varying degrees of modification. CS-LF co-modified liposomes exhibited significant structural changes, with particle size increasing from 257.9 ± 6.2 nm to 580.5 ± 21.5 nm, and zeta potential shifting from negative to +48.9 ± 1.3 mV. Chitosan and lactoferrin were modified on the liposome surface through electrostatic interactions and hydrogen bonding, forming a dense protective barrier on the lipid membrane. Physicochemical analysis indicated that chitosan-lactoferrin co-modification led to a more ordered arrangement of the phospholipid bilayer, reduced membrane fluidity, and increased membrane rigidity. The interactions between chitosan, lactoferrin, and phospholipids were enhanced through hydrogen bonding, resulting in a denser surface membrane structure. This structural integrity reduced membrane permeability and improved the stability of liposomes under storage conditions, UV irradiation, and in vitro digestion. Additionally, co-modified chitosan-lactoferrin liposomes effectively alleviated lipopolysaccharide-induced inflammatory damage in mouse microglial cells by increasing cellular uptake capacity, thereby enhancing the bioavailability of β-carotene. The results of this study demonstrate that chitosan-lactoferrin co-modification significantly enhances the stability of liposomes and the bioavailability of β-carotene. These findings may contribute to the development of multi-substance co-modified liposome systems, providing a more stable transport mechanism for various compounds.

Haskap Berry Leaves (Lonicera caerulea L.)—The Favorable Potential of Medical Use

The presented research evaluates the medical use potential of Lonicera caerulea leaves, which are waste plants in cultivating berries. The study’s screening activity included the leaves of five varieties of Lonicera caerulea: Atut, Duet, Wojtek, Zojka, and Jugana. The microbiological analysis confirmed the safety of using Lonicera caerulea leaves without significant stabilization. Lonicera caerulea leaves standardization was carried out based on the results of the chromatographic analysis, and it showed differences in the contents of active compounds (loganic, chlorogenic and caffeic acids, and rutin), which are attributed to biological activity. For the Lonicera caerulea leaves varieties tested, the differences in the content of total polyphenol content, chlorophylls, and carotenoids were also confirmed. The screening of biological activity of five Lonicera caerulea leaf varieties was carried out concerning the possibility of inhibiting the activity of α-glucosidase, lipase, and hyaluronidase as well, and the antioxidant potential was determined. The defined profile of the biological activity of Lonicera caerulea leaves makes it possible to indicate this raw material as an essential material supporting the prevention and treatment of type II diabetes. However, this research showed that tested enzymes were strongly inhibited by the variety Jugana. The health-promoting potential of Lonicera caerulea leaves was correlated with the highest chlorogenic acid and rutin content in the variety Jugana.

Atmospheric pressure chemical ionization mass spectrometry of retro-carotenoids

RATIONALE

The single and double bonds of the polyene chain of the studied retro-carotenoids are located at the neighboring positions compared to those of regular carotenoids. Our mass spectrometry approach targeted at facilitating the characterization of retro-carotenoids as their structural diversity in nature is not yet fully elucidated. Moreover, extended π-electron systems endow several retro-carotenoids with exceptional colors from golden-orange to vibrant red that stimulate the food industry's interest.

METHODS

Atmospheric pressure chemical ionization-quadrupole time-of-flight-high-resolution mass spectrometry (APCI-QTOF-HRMS) experiments of the three structurally related retro-carotenoids rhodoxanthin, eschscholtzxanthone, and eschscholtzxanthin were performed to elucidate the formation of specific ion species compared to those of the common carotenoids lutein and zeaxanthin. Mass fragmentations of the aforementioned retro-carotenoids were unraveled using APCI-tandem mass spectrometry (MS/MS) in the negative and positive ion modes.

RESULTS

Abundant in-source fragment ions [M + H - H₂ O]⁺ of eschscholtzxanthin and eschscholtzxanthone were formed in the positive ion mode owing to the loss of water at the hydroxylated ε-rings. Eliminations of the ε-rings at the characteristic exocyclic double bonds at C-6,7 and C-6',7' were observed after the resonance-stabilized loss of water. Distinct product ions were yielded for all retro-carotenoids assessed because of the cleavage at their typical central single bond at C-15,15'.

CONCLUSIONS

Detailed APCI-QTOF-HRMS analyses enabled a highly accurate detection of the most abundant ion species and respective signal intensity ratios of retro-carotenoids, facilitating their further screening and reliable identification in natural sources. Mass fragmentations of the studied retro-carotenoids were found to be substantially impacted by the extraordinary configuration of their polyene backbone.

Promiscuous activity of β-carotene hydroxylase CrtZ on epoxycarotenoids leads to the formation of rare carotenoids with 6-hydroxy-3-keto-ε-ends

Carotenoids with rare 6-hydroxy-3-keto-ε-end groups, such as piprixanthin, vitixanthin or cochloxanthin, found in manakin birds or plants, are rare carotenoids with high antioxidant activity. The same chemical structure is found in abscisic acid or blumenol, apocarotenoids found in plants or fungi. In this study, we serendipitously discovered that the promiscuous activity of the β-carotene hydroxylase CrtZ, a diiron-containing membrane protein, can catalyze the formation of 6-hydroxy-3-keto-ε-end by using epoxycarotenoids antheraxanthin or violaxanthin as substrate. We suggest that the reaction mechanism is similar to that of a rhodoxanthin biosynthetic enzyme. Our results provide further understanding of the reaction mechanism of diiron-containing β-carotene hydroxylases, as well as insight into the biosynthesis of natural compounds with 6-hydroxy-3-keto-ε-end carotenoid derivatives.

Carotenoid profiles of red- and yellow-colored arils of cultivars of Taxus baccata L. and Taxus × media Rehder

The botanical delimitation of Taxus species and cultivars may be facilitated by characterizing the pigment profiles of their red- and yellow-fleshed arils. Therefore, we determined genuine carotenoid profiles of differently colored arils of seven defined cultivars of Taxus baccata L. and Taxus × media Rehder. In-depth HPLC-DAD-ESI/APCI-MSⁿ analyses revealed the presence of 43 carotenoids. Exceptional retro-carotenoids dominated the profiles of all samples assessed. Rhodoxanthin (E/Z)-isomers were predominant in the red-colored arils, resulting in a rather unusual abundance of carotenoid isomers as expressed by ratios of up to 1.3:2.0:0.9 between (all-E)-, (6Z)-, and (6Z,6'Z)-rhodoxanthin, respectively. By contrast, the uncommon yellow arils of Taxus baccata L. 'Lutea' mainly contained eschscholtzxanthin (E/Z)-isomers and esters. Total carotenoid concentrations ranged from 17.00 to 58.78 μg/g fresh weight across all samples assessed. Highest total rhodoxanthin concentrations of 51.33 ± 0.46 μg/g fresh weight were obtained from the red arils of Taxus × media Rehder 'Hicksii'. Overall, Taxus arils represent a promising source of carotenoids and, in particular, of retro-carotenoids with exceptional molecular structures and extraordinary absorption properties.