Unique bioactive polyphenolic profile of guava (Psidium guajava']java) budding leaf tea is related to plant biochemistry of budding leaves in early dawn

BACKGROUND: Guava leaf tea (GLT), exhibiting a diversity of medicinal bioactivities, has become a popularly consumed daily beverage. To improve the product quality, a new process was recommended to the Ser-Tou Farmers' Association (SFA), who began field production in 2005. The new process comprised simplified steps: one budtwo leaves were plucked at 3:006:00 am, in the early dawn period, followed by withering at ambient temperature (2528 degrees C), rolling at 50 degrees C for 5070 min, with or without fermentation, then drying at 4550 degrees C for 7090 min, and finally sorted. RESULTS: The product manufactured by this new process (named herein GLTSF) exhibited higher contents (in mg g1, based on dry ethyl acetate fraction/methanolic extract) of polyphenolics (417.9 +/- 12.3) and flavonoids (452.5 +/- 32.3) containing a compositional profile much simpler than previously found: total quercetins (190.3 +/- 9.1), total myricetin (3.3 +/- 0.9), total catechins (36.4 +/- 5.3), gallic acid (8.8 +/- 0.6), ellagic acid (39.1 +/- 6.4) and tannins (2.5 +/- 9.1). CONCLUSION: We have successfully developed a new process for manufacturing GLTSF with a unique polyphenolic profile. Such characteristic compositional distribution can be ascribed to the right harvesting hour in the early dawn and appropriate treatment process at low temperature, avoiding direct sunlight. (c) 2012 Society of Chemical Industry