Detection of unusual carotenoid esters in fresh mango (Mangifera indica L. cv. 'Kent')

The carotenoid pattern of mango cv. 'Kent' was investigated by LC-(APcI)MS analyses. In solvent extracts from the mesocarp an unusual carotenoid ester was identified as violaxanthin dibutyrate. For unequivocal identification of butyric acid by an independent method, total lipids were isolated by solvent extraction from the fruit flesh and analyzed by GC after saponification and subsequent methylation. Thus, evidence of butyric acid (1.6 area%) was provided. To the best of our knowledge, this is the first report on a xanthophyll dibutyrate in plants. Additionally, further carotenoid peaks were tentatively assigned to 9-cis-violaxanthin and neochrom or luteoxanthin, respectively, by their UV/vis and MS data of the saponified extracts.     

Human hemoglobin-derived peptides exhibit antimicrobial activity: a class of host defense peptides

Hemoglobin is a known source of biologically active peptides with various functions. In the present study, we report for the first time the existence of natural processed hemoglobin fragments exhibiting antimicrobial activity in humans. Two antimicrobial hemoglobin-derived peptides were purified from a human placental peptide library by consecutive chromatographic steps tracking the maximum growth inhibitory activity against Escherichia coli BL21. These peptides, consisting of 17 and 36 amino acid residues, were identified as being C-terminal fragments of gamma-hemoglobin and beta-hemoglobin, respectively. The antimicrobial beta-hemoglobin fragment was also purified from lysed erythrocytes, demonstrating that proteolytic degradation of hemoglobin into small bioactive peptides already starts inside erythrocytes. The identified peptides inhibit the growth of Gram-positive and Gram-negative bacteria and yeasts in micromolar concentrations. Moreover, by LPS-binding, the beta-hemoglobin fragment reduces biological activity of endotoxins. In contrast, even at high concentrations, the identified antimicrobial hemoglobin peptides do not exhibit toxic activity on human primary blood cells. We conclude that antimicrobial hemoglobin-derived peptides could be important effectors of the innate immune response killing microbial invaders.     

Enzymatic hydrolysis of carotenoid fatty acid esters of red pepper (Capsicum annuum L.) by a lipase from Candida rugosa

Analyses of red pepper extracts which had been pretreated with lipase type VII (EC 3.1.1.3.) from Candida rugosa showed for the first time pepper carotenoid esters to be substrates of this enzyme. However, the extent of enzymatic hydrolysis depends on the respective carotenoid and was not quantitative compared to chemical saponification. After enzymatic cleavage, 67-89% of total capsanthin, 61-65% of total zeaxanthin, 70-81% of total beta-cryptoxanthin and 70-86% of total violaxanthin were detected in free form. Nevertheless, the method described here offers the possibility to cleave in part several carotenoid esters originating from red pepper quickly and under comparatively mild reaction conditions. Replacement of the generally performed alkaline hydrolysis by enzymatic cleavage allows the resulting product to be used in food industry as "natural" coloring agent e.g. to colour cheese and jellies.     

On the subunit structure of crotoxin: hydrodynamic and shape properties of crotoxin, phospholipase A and crotapotin.

This paper reports physical-chemical properties of the subunit structure of crotoxin, phospholipase A and crotapotin. The native crotoxin has a sedimentation coefficient of 3S and a radius of gyration of R_g = 16.5 Å and a molecular weight of 30,900. Dissociation of the 3S particle results in two proteins of unequal size with sedimentation coefficients of 1.5 S (crotapotin) and 1S (phospholipase A). These dissociated species and the reconstituted complex were investigated by means of hydrodynamic methods including small angle X-ray scattering. The actual frictional ratios were obtained indicating that crotoxin is a sphere with a Stokes' radius of R_o = 22.5 Å and an axial ratio of 1:3, whereas phospholipase A, depending on the degree of association, has a radius of gyration of R_g = 32.4 Å and a high axial ratio of 1:14 for the monomer. Crotapotin has a radius of gyration of R_g = 12.4 Å, indicating an oblate ellipsoid of revolution of an axial ratio of 1:4. Evidently, the crotoxin complex consists of one highly asymmetric molecule (phospholipase A) and an oblate ellipsoid (crotapotin), which reconstitutes to a spherical 3S-particle (crotoxin).