Chemical Composition and Nutraceutical Functions of Edible Bird’s Nest: Development of Quality Control Parameters and Health Food Products

摘要

Edible bird's nest (EBN) is a glue-like substance secreted by the specific swiftlets, including Aerodramus fuciphagus and Aerodromus maximus, which is a valuable Chinese esteemed food. Despite long history of human consumption, the detailed chemical compositions and biological functions of EBN are largely unknown. Here, a comprehensive research on EBN, including chemical composition and functional evaluation, were carried out, aiming to develop quality control parameters and health products. Although protein is the main component of EBN, the exact identities of EBN proteins are still not well understood, despite the difficulties of extraction, purification and identification. By using EBN proteins as antigens, 31 monoclonal antibodies specifically against the proteins were generated. By immunochemical analysis, the antibodies recognized proteins derived from EBN products but not the fake products. In parallel, the monoclonal antibodies were used to immunoprecipitate proteins from EBN extract, and AMCase-like protein was the highest frequency of being precipitated by the antibodies. Besides, we developed a quality control method using HPLC peptide fingerprints deriving from EBN being digested with simulated gastric fluid (SGF). The characteristic peptide peaks, corresponding to the protein fragments of acidic mammalian chitinase-like, lysyl oxidase and mucin-5AC-like were identified and quantified. With the development of anti-EBN monoclonal antibodies and peptide fingerprint, comprehensive information for the quality evaluation of EBN was revealed. The major proteins of EBN are in large molecular size (>100kDa) and the dominant active ingredients, NANA is in conjugate form combing with glycans. However, both are not being easily absorbed by human being. Within 48 hours digestion with SGF, the major proteins were completely digested, and the free NANA was fully released in White EBN and Yellow EBN. The release of free NANA was highly efficient in acid hydrolysis. Red EBN was found difficult to be digested, as compared to that of White EBN and Yellow EBN. In addition, edible materials with reasonable price were selected for health product development. Having a full digestion of EBN, we can develop an advanced formulation of low molecular weight EBN peptide with high amount of NANA in free form: this digested product ensures rapid absorption in a single step. From Chinese medicine theory, the conditions of skin and hair depend on "Lung". Traditionally, EBN is able to reinforce "Lung" and improve the digestive system. Women are the major groups in consuming EBN but there is insufficient scientific proof in its nourishing functions for women interest. In present study, the skincare functions of EBN extract and digest were examined in different aspects. Overall, the skin whitening, osteogenic effect and absorption efficiency of EBN digest are better than extract, while EBN extract exhibited better effect in wound healing assay and anti-oxidant. A significant difference was not observed in immune-modulatory and estrogenic activity among EBN samples with/without digestion. Higher activities in skin whitening and osteogenic were observed in White EBN and Yellow EBN, whereas Red EBN showed stronger immune-modulatory effect. From our findings, White EBN digest could be an excellent source in commercialization and health product development in consideration of supply, cost and bio-functions. The red color of EBN remains a mystery over hundreds of years. Here, different analytical methods were employed to identify the color origin of EBN. The treatment of White EBN with NaNO2/HCl turned that into red color. In SGF digested EBN, the HPLC chromatogram, NMR spectrum, circular dichroism spectrum and Raman spectrum of a NaNO2-treated White EBN closely resembled with that of authentic Red EBN. From the HPLC chromatogram of SGF-digested EBN, the peptides associated with red color were identified in Red EBN and NaNO2-treated White EBN. Several li