The Identification and Quantitative Analysis of Unusual Keto-Carotenoids in Ripe Fruits of Maclura tricuspidate and Its Potential as a Valuable Source of Cryptocapsin

Ripe fruits of Maclura tricuspidata (MT) are used as food material and a natural colorant in Korea. Although MT fruits have a deep red color due to carotenoid-like pigments, their chemical nature has not been explored in detail so far. The present study aimed at elucidating the chemical structures and composition of carotenoids in MT fruits and changes at different maturity stages. Two carotenoids from saponified MT fruit extract were isolated using repeated silica gel column chromatography. Based on interpretations of spectroscopic data, these compounds were determined as keto-carotenoids, i.e., capsanthin (3,3'-dihydroxy-β,κ-caroten-6'-one) and cryptocapsin (3'-hydroxy-β,κ-caroten-6'-one), and the contents of individual carotenoids were quantified with HPLC based on calibration curves obtained from authentic standards. The contents of capsanthin and cryptocapsin in the sample of saponified MT fruits were 57.65 ± 1.97 µg/g and 171.66 ± 4.85 μg/g as dry weight base (dw). The majority of these keto-carotenoids in the MT fruits were present in esterified forms with lauric, myristic or palmitic acid rather than in their free forms. The results also showed that esterification of these compounds occurred starting from early stage (yellow-brownish stage) of maturation. Considering the high cryptocapsin content, MT fruits can be applied as a potentially valuable source of cryptocapsin for food and medicinal application as well as a source of provitamin A.

Oxo-Carotenoids as Efficient Superoxide Radical Scavengers

Oxo-carotenoids containing conjugated carbonyl groups in their chains were designed to be more efficient superoxide radical scavengers than natural carotenoids, β-carotene and canthaxanthin. A practical chain-extension method for polyene dials (e.g., crocetin dial) was also proposed based on Horner–Wadsworth–Emmons olefination. Double aldol condensation between polyene dials and acetophenones with ring substituents produced oxo-carotenoids with substituted benzene rings. The antioxidant activity of oxo-carotenoids was measured using DPPH (radical) and ABTS (cationic radical) scavenging assays and compared with the analysis with the superoxide (anionic radical) probe. An effective conjugation length by carbon–carbon double bonds is important to provide superior antioxidant activity for oxo-carotenoids, regardless of the type of radical probe used in the assay. Increasing electron density is favorable to strong antioxidant activity in DPPH, and the phenol group is favored in ABTS, whereas electron deficient oxo-carotenoids are very potent in the superoxide radical assay. All oxo-carotenoids exhibited 105~151% better superoxide radical scavenging activity compared to beta-carotene (100%), whereas 38~155% in DPPH and 16~96% in ABTS radical scavenging activities were observed.

Excited state characterization of carbonyl containing carotenoids: a comparison between single and multireference descriptions

Carotenoids can play multiple roles in biological photoreceptors thanks to their rich photophysics. In the present work, we have investigated six of the most common carbonyl containing carotenoids: echinenone, canthaxanthin, astaxanthin, fucoxanthin, capsanthin and capsorubin. Their excitation properties are investigated by means of a hybrid density functional theory (DFT) and multireference configuration interaction (MRCI) approach to elucidate the role of the carbonyl group: the bright transition is of ππ* character, as expected, but the presence of a C[double bond, length as m-dash]O moiety reduces the energy of nπ* transitions which may become closer to the ππ* transition, in particular as the conjugation chain decreases. This can be related to the presence of a low-lying charge transfer state typical of short carbonyl-containing carotenoids. The DFT/MRCI results are finally used to benchmark single-reference time-dependent DFT-based methods: among the investigated functionals, the meta-GGA (and in particular M11L and MN12L) functionals show to perform the best for all six investigated systems.

Capsanthin Inhibits both Adipogenesis in 3T3-L1 Preadipocytes and Weight Gain in High-Fat Diet-Induced Obese Mice

Adipogenesis in murine preadipocyte 3T3L-1 has been used as a model system to study anti-obese bioactive molecules. During adipogenesis in 3T3-L1 preadipocytes, we found that capsanthin inhibited adipogenesis (IC₅₀; 2.5 μM) and also showed lipolytic activity in differentiated adipocytes from the preadipocytes (ED₅₀; 872 nM). We identified that the pharmacological activity of capsanthin on adipogenesis in 3T3-L1 was mainly due to its adrenoceptor-β₂-agonistic activity. In high-fat diet animal model study, capsanthin significantly enhanced spontaneous locomotive activities together with progressive weight-loss. The capsanthin-induced activation of kinetic behavior in mice was associated with the excessive production of ATP initiated by both the enhanced lipolytic activity together with accelerated oxidation of fatty acids due to the adrenoceptor β₂-agonistic activity of capsanthin. Capsanthin also dose-dependently increased adiponectin and p-AMPK activity in high fat diet animals, suggesting that capsanthin has both anti-obesity and insulin sensitizing activities.

Total synthesis of capsanthin and capsorubin using Lewis acid-promoted regio- and stereoselective rearrangement of tetrasubsutituted epoxides

The synthesis of capsanthin 1 and capsorubin 2 was accomplished via the C(15)-cyclopentyl ketone 6 prepared by Lewis acid-promoted regio- and stereoselective rearrangement of the epoxy dienal 5.

Structure of new carotenoids with the 6-oxo-kappa end group from the fruits of paprika, Capsicum annuum

New carotenoids 1 and 2 were isolated as minor components from the ripe fruits of paprika (Capsicum annuum). The structures of 1 and 2 were determined to be (3R,5'R)-3-hydroxy-beta,kappa-caroten-6'-one and (5'R)-3,4-didehydro-beta,kappa-caroten-6'-one, respectively, from UV-vis, NMR, CD, HRFABMS, and FABMS/MS spectra.

Total synthesis of capsanthin using lewis acid-promoted regio- and stereoselective rearrangement of tetrasubstituted epoxide

The synthesis of capsanthin 1 was accomplished via the C15-cyclopentyl ketone 13 prepared by Lewis acid-promoted regio- and stereoselective rearrangement of the epoxide 12.

Cancer chemopreventive activity of carotenoids in the fruits of red paprika Capsicum annuum L

Capsanthin and related carotenoids isolated from the fruits of red paprika Capsicum annuum L. showed potent in vitro anti-tumor-promoting activity with inhibitory effects on Epstein-Barr virus early antigen (EBV-EA) activation induced by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). Among them, capsanthin diester and capsorbin diester showed strong inhibitory effects. Furthermore, capsanthin , capsanthin 3'-ester and capsanthin 3,3'-diester , major carotenoids in paprika, exhibited potent anti-tumor-promoting activity in an in vivo mouse skin two-stage carcinogenesis assay using 7, 12-dimethylbenz[a]anthracene as an initiator and TPA as a promoter.

Selective hydroboration of alkenes and alkynes in the presence of aldehydes and ketones

The reactions of terminal alkenes in the presence of ketones or aldehydes with a variety of borane reagents have been investigated. It was found that the selective hydroboration of a terminal alkene in the presence of a ketone or an aldehyde is most efficient when dicyclohexylborane is used as the hydroborating agent. The hydroboration of olefinic ketones and olefinic aldehydes with dicyclohexylborane generates the corresponding hydroxyaldehydes and hydroxyketones in good yields after oxidation with sodium perborate. The hydroboration of alkynyl ketones and alkynyl aldehydes with dicyclohexylborane yields the corresponding olefinic carbonyl compounds after protonation, or dicarbonyl compounds after oxidation.Key words: hydroboration, reduction, dicyclohexylborane, hydroxyaldehyde, hydroxyketone.