4. Conclusions
EBN has been consumed for several hundred years in China and other Southeast Asian countries. In the descriptions
of ancient Chinese literatures, EBN was often used to treat respiratory disorder. The most famous record
about EBN usage, as the form of “bird’s nest congee”, can be found in “Dream of the Red Chamber”, or called
that as “The Story of the Stone”, a masterpiece of Chinese literature written in 18th century and is generally acknowledged
to be the pinnacle of Chinese fiction. Until now, EBN is a popular food supplement for skin lightening.
The trend of EBN consumption is growing [17] but stopped by the safety incident of nitrite in 2011 [11].
Although EBN has a long historical consumption record and strong belief in its skincare functions by the general
public in Asia is reported, no scientific evidence has shown any relationship between EBN and skin healthiness.
Here, we demonstrated the skin lightening functions of different types of EBN. On top of this, we discovered
that NANA was the major ingredient of EBN responsible for the skincare functions after systematic fractionation
by LC-MS/MS.
From our previous finding, the content of free NANA varied with the grading of EBN [6]. Coincidently, EBN
with higher grade showed stronger skin lightening. NANA should be one of the major compounds responsible
for the skin lightening function of EBN. However, NANA should not be the only compound within EBN, which
is responsible for skin lightening function. The IC50 of NANA on human tyrosinase inhibition is 0.10 mM which
is coherent to our previous study on over a hundred batches of EBNs. The maximum content of free NANA was
around 1000 ppm (i.e. about 3 mM). Certainly, the inhibition of EBN on tyrosinase activity may also involve the