The researcher would like to express her deepest thanks to the Thailand Research Fund
(RSA 4870011) for providing the funding for this work. Thanks also go to Ms. Oraphan
Anurukvorakun, the research assistant, and the Royal Golden Jubilee Ph.D. program for her
support (PHD/0179/2547). Prof. Wolfgang Buchberger, Institute of Analytical Chemistry,
Johannes Kepler University of Linz, Austria was acknowledged for his advice on the mass
spectrometry experiments as well as his technical assistance.