Enzymatic extraction of cobalamin from monoclonal antibody captured haptocorrin and transcobalamin

Response surface methodology for ultrasound-assisted extraction of astaxanthin from Haematococcus pluvialis

Astaxanthin is a novel carotenoid nutraceutical occurring in many crustaceans and red yeasts. It has exhibited various biological activities including prevention or amelioration of cardiovascular disease, gastric ulcer, hypertension, and diabetic nephropathy. In this study, ultrasound-assisted extraction was developed for the effective extraction of astaxanthin from Haematococcus pluvialis. Some parameters such as extraction solvent, liquid-to-solid ratio, extraction temperature, and extraction time were optimized by single-factor experiment and response surface methodology. The optimal extraction conditions were 48.0% ethanol in ethyl acetate, the liquid-to-solid ratio was 20:1 (mL/g), and extraction for 16.0 min at 41.1 °C under ultrasound irradiation of 200 W. Under optimal conditions, the yield of astaxanthin was 27.58 ± 0.40 mg/g. The results obtained are beneficial for the full utilization of Haematococcus pluvialis, which also indicated that ultrasound-assisted extraction is a very useful method for extracting astaxanthin from marine life.

Cobalamin analogues in humans: a study on maternal and cord blood

BACKGROUND

Haptocorrin (HC) carries cobalamin analogues (CorA), but whether CorA are produced in the body is unknown. All cobalamins (Cbl) to the foetus are delivered by the Cbl-specific protein transcobalamin (TC), and therefore analysis of cord serum for CorA may help to clarify the origin of CorA.

METHODS

HC-CorA were quantified in paired samples of cord serum from newborns and serum from mothers (n = 69).

RESULTS

The CorA-concentration was higher in cord serum (median = 380, range: 41-780 pmol/L) than in serum from the mothers (median = 160, range: 64-330 pmol/L), (p<0.0001). HPLC-analysis showed CorA-peaks with retention times of 13.5, 14,5 and 16.5 min in samples from both the mother and cord serum. The peak with retention time 16.5 min constituted 24% (mother) and 45% (cord serum) of the total amount CorA, and eluted as does dicyanocobinamide.

CONCLUSION

Our results support that CorA in the human body are derived from Cbl.

Optimization of ultrasound-assisted extraction of anthocyanins from mulberry, using response surface methodology

Mulberry is one of the most widely used traditional Chinese medicines. Anthocyanins are the main bioactive components of mulberry, and possess important biological activities, such as antimicrobial, anti-inflammatory and antioxidant activities. This study investigated the ultrasound-assisted extraction (UAE) of anthocyanins from mulberry by using response surface methodology (RSM). The extraction conditions associated with anthocyanin yield, including extraction solvent, liquid-to-solid rate, temperature and extraction time, are discussed. The optimal conditions obtained by RSM for UAE from mulberry include 63.8% methanol contains 1% (v/v) trifluoroacetic acid (TFA), 43.2 °C temperature, 23.8 (v/w) liquid-to-solid ratio, and 40 min time for the maximum yield (64.70 ± 0.45 mg/g). The results indicated that the UAE can be an effective method for the extraction of some active components from plant materials.

Assessment of vitamin B(12) absorption based on the accumulation of orally administered cyanocobalamin on transcobalamin

BACKGROUND

Vitamin B(12), or cobalamin (Cbl), is absorbed in the intestine and transported to the cells bound to transcobalamin (TC). We hypothesize that cyanocobalamin (CNCbl) is absorbed unchanged, thereby allowing measurement of the complex of CNCbl bound to TC (TC-CNCbl) to be used for studying the absorption of the vitamin.

METHODS

TC was immunoprecipitated from serum samples obtained from healthy donors at baseline and at 24 h after oral administration of three 9-microg CNCbl doses over 1 day. Cbl was released by treatment with subtilisin Carlsberg. The different forms of Cbl were isolated by HPLC and subsequently quantified with an ELISA-based Cbl assay.

RESULTS

At baseline, the median TC-CNCbl concentration was 1 pmol/L (range, 0-10 pmol/L); the intraindividual variation (SD) was 1.6 pmol/L (n = 31). After CNCbl administration, the TC-CNCbl concentration increased significantly (P = 0.0003, paired t-test), whereas no major changes were observed in any of the other Cbl forms bound to TC (n = 10). Only a moderate additional increase in TC-CNCbl was observed with prolonged (5 days) CNCbl administration (n = 10). We designed an absorption test based on measuring TC-CNCbl at baseline and 24 h after CNCbl intake and established a reference interval for the increase in TC-CNCbl (n = 78). The median absolute increase was 23 pmol/L (range, 6-64 pmol/L), and the relative increase was >3-fold.

CONCLUSIONS

Our data demonstrate that CNCbl is absorbed unchanged and accumulates on circulating TC. We suggest that measuring TC-CNCbl will improve the assessment of vitamin B(12) absorption.

High concentrations of haptocorrin interfere with routine measurement of cobalamins in human serum and milk. A problem and its solution

BACKGROUND

Human milk and occasional serum samples contain high concentrations of unsaturated haptocorrin, which influence accurate measurement of cobalamins.

METHODS

Cobalamins in serum samples spiked with increasing amounts of unsaturated haptocorrin were measured employing the Centaur, Cobas and Architect analysers. Cobinamide-coated EAH sepharose was employed for pretreatment of the samples. Human milk samples were collected from 24 healthy mothers. Haptocorrin was measured by ELISA.

RESULTS

The measured concentration of cobalamins either increased (Centaur analyser) or decreased (Architect, Cobas analysers) significantly for haptocorrin >10 nM, and was 220%, 52% or 45% of the expected values in a serum sample containing 50 nM haptocorrin. Following pretreatment with cobinamide-sepharose, the expected cobalamin concentration was obtained (Centaur). The milk samples contained 4.5-180 nM haptocorrin. In samples containing >10 nM haptocorrin (n=19), the median concentration of cobalamins decreased from 1.3 nM to 0.67 nM after pretreatment with cobinamide-sepharose.

CONCLUSIONS

Haptocorrin in concentrations above 10 nM influences measurement of cobalamins giving rise to falsely elevated or decreased results. Removal of unsaturated haptocorrin by pretreatment with cobinamide-sepharose solves the problem.

A New Principle for Measurement of Cobalamin and Corrinoids, Used for Studies of Cobalamin Analogs on Serum Haptocorrin

Background: Transcobalamin (TC) and haptocorrin (HC) are serum corrinoid–binding proteins. We developed new methods for measurement of the corrinoids bound to HC and TC.

Methods: TC (n = 10) or HC (n = 138) was immunoprecipitated, and corrinoids were released by enzymatic degradation [subtilisin Carlsberg (EC 3.4.21.62)] of the binding proteins. Binding of the released corrinoids to added unsaturated TC (apoTC) or HC (apoHC) created holoTC (as measure of cobalamins) and holoHC (as measure of corrinoids). holoTC and holoHC were measured by use of ELISA. The amounts of analogs were calculated as the difference between corrinoids and cobalamins. Corrinoids extracted from HC were separated with HPLC after addition of potassium cyanide (n = 3).

Results: The corrinoid- and cobalamin-specific assays had a positive linear relation between analyte concentration and assay signal, detection limits of 8 and 4 pmol/L, and imprecision values (CV) of ≤10% and ≤13% for concentrations between 45–200 and 12–115 pmol/L, respectively. No analogs were bound to serum TC, whereas the mean (95% reference range) for analogs present on HC was 245 (100–380) pmol/L. On HPLC a substantial amount of the analogs showed elution patterns similar to those of dicyanocobinamide.

Conclusions: Our methods for measurement of unmodified corrinoids in serum demonstrate that HC carries cobalamin analogs not recognized by TC, and that on HPLC a substantial part of these analogs elute similarly to cobinamide.