Correlation between Polyphenol Contents and Antioxidant Activities in Different Echinacea Purpurea Varieties.

OBJECTIVE: Polyphenols are complex compounds containing multiple phenolic hydroxyl groups. They are widely distributed in plants and have antioxidant activities. Whether the antioxidant activities of the cultivated varieties of Echinacea are similar to or better than those of the wild ones and the relationship between the accumulation of polyphenols and their antioxidant activities are still not clear. METHODS: Folin-Ciocalteu method, high performance liquid chromatography (HPLC), 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay, ferric ion reducing antioxidant power (FRAP) assay, 2,2'-azino-bis(3-ethylbenzothiazoline-6)-sulfonic acid (ABTS) radical scavenging assay, and Fe2+ chelating ability assay were used, respectively, to detect the total polyphenols and 5 kinds of caffeic acid derivatives (chicoric acid, caffeic acid, caftaric acid, chlorogenic acid, and 1,5-dicaffeoylquinic acid) in the roots, stems, leaves, and flowers, and the antioxidant activities of 3 varieties of Echinacea: E. purpurea L., cultivar E. purpurea 'Aloha', and E. purpurea 'White Swan'. RESULTS: E. purpurea L. had the highest contents of total polyphenols, 5 caffeic acid derivatives and antioxidant activities, followed by E. purpurea 'White Swan' and E. purpurea 'Aloha', respectively. E. purpurea 'White Swan' had the strongest ability to remove the DPPH, ABTS•+ and free radicals, and to chelate Fe2+; E. purpurea L. had the strongest ability to reduce FRAP. The correlation analyses revealed that the contents of total polyphenols and caffeic acid derivatives of E. purpurea L. and E. purpurea 'White Swan' were correlated with their antioxidant activities. CONCLUSION: E. purpurea L. was the most appropriate material for the development of medicinal plants. E. purpurea 'White Swan' could be used as a substitute for E. purpurea L. in terms of its antioxidant activity.

Suitability of yeast- and Escherichia coli-expressed hepatitis B virus core antigen derivatives for detection of anti-HBc antibodies in human sera.

Antibody to hepatitis B virus core antigen (anti-HBc) is one of the most important serological markers during hepatitis B virus (HBV) infection. The quality of the hepatitis B virus core antigen (HBcAg; diagnostic antigen) is crucial to the accuracy of anti-HBc detection. In an attempt to explore the suitability of recombinant HBcAg (rHBcAg) for diagnostic purposes, HBcAg was expressed in Escherichia coli (E. coli) and Pichia pastoris (P. pastoris) and evaluated for the detection of anti-HBc. The expression level of the recombinant protein satisfied the criteria for large-scale biologic production. P. pastoris- and E. coli-derived rHBcAg were purified with gel filtration followed by sucrose gradient (reagents A and C) or with a monoclonal anti-HBc antibody binding (reagents B and D) and were utilized to detect anti-HBc in competitive inhibition enzyme-linked immunosorbent assay (ELISA) format. The ELISA using P. pastoris-derived rHBcAg had a higher specificity and sensitivity than that using E.coli-derived rHBcAg to detect the anti-HBc standard panel. Serum specimens were collected from HBV-infected patients and healthy individuals (voluntary blood donors). Anti-HBc was detected in those specimens using P. pastoris- and E. coli-derived rHBcAg. The positive rate of anti-HBc detection in HBV-infected patients' sera was 100% with reagents A and B, 96.4% with reagent C, and 93.6% with reagent D. The negative rate in healthy control sera was 100% with reagents A and B, 97.0% with reagent C, and 99.7% with reagent D. These data indicate that P. pastoris-derived rHBcAg is superior to E.coli-derived rHBcAg for the detection of anti-HBc using the diagnostic ELISA.