Papaya (Carica papaya L.) is widely cultivated in tropical and subtropical countries. While ripe fruit is a popular food item globally, the unripe fruit are only consumed in some Asian countries. To promote the utilization of unripe papaya based on the compositional changes of biological active metabolites, we performed liquid chromatography-Orbitrap-mass spectrometry-based analysis to reveal the comprehensive metabolite profile of the peel and pulp of unripe and ripe papaya fruit. The number of peaks annotated as phenolics and aminocarboxylic acids increased in the pulp and peel of ripe fruit, respectively. Putative carpaine derivatives, known alkaloids with cardiovascular effects, decreased, while carpamic acid derivatives increased in the peel of ripe fruit. Furthermore, the functionality of unripe fruit, the benzyl glucosinolate content, total polyphenol content, and proteolytic activity were detectable after heating and powder processing treatments, suggested a potential utilization in powdered form as functional material.
A material with a wide energy gap, 3,4-di(9H-carbazol-9-yl)benzonitrile (2CzBN), was synthesized and applied in organic light-emitting diodes (OLEDs). Pure blue electroluminescence with a peak wavelength of 436 nm and Commission Internationale de l'Èclairage (CIE) coordinate of (0.160, 0.084) were obtained for an OLED containing 2CzBN as an emitter, although its external emission efficiency was limited to around 1% because of the lack of thermally activated delayed fluorescence (TADF) activity. In contrast, a highly efficient TADF-based OLED was obtained when 2CzBN was used as a host instead of an emitter by taking advantage of the high triplet energy (2.92 eV) and unexpected electron transport capability of 2CzBN.
Lotus japonicus is a model legume, that accumulates 8-hydroxyflavonol derivatives such as gossypetin (8-hydroxyquercetin) 3-O-glycoside, which confer the yellow color to its petals. An enzyme, flavonoid 8-hydroxylase (LjF8H), is assumed to be involved in the biosynthesis, but the specific gene is yet to be identified. The LjF8H cDNA was isolated as an FAD-binding monooxygenase-like protein using flower buds and flower specific EST data of L. japonicus. LjF8H is a single copy gene on chromosome III consisting of six exons. The conserved FAD- and NAD(P)H-dependent oxidase motifs were found in LjF8H. Phylogenetic analysis suggested that LjF8H is a member of the flavin monooxygenase group, but distinctly different from other known flavonoid oxygenases. Analysis of recombinant yeast microsome expressing LjF8H revealed that the enzyme catalyzed the 8-hydroxylation of quercetin. Other flavonoids, such as naringenin, eriodictyol, apigenin, luteolin, taxifolin, and kaempferol also acted as substrates of LjF8H. This broad substrate acceptance was unlike known F8Hs in other plants. Interestingly, flavanone and flavanonol, which have saturated C-C bond at positions 2 and 3 of the flavonoid C-ring, produced 6-hyroxylflavonoids as a by-product of the enzymatic reaction. Furthermore, LjF8H only accepted the 2S-isomer of naringenin, suggesting the conformational state of the substrates might affect product specificity. The overexpression of LjF8H in Arabidopsis thaliana and Petunia hybrida synthesized gossypetin and 8-hydroxykaempferol, respectively, indicating that LjF8H was functional in plant cells. In conclusion, this study represents the first instance of cloning and identification of F8Hs responsible for gossypetin biosynthesis.
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