Determination of Vitamin B₁₂ in Chinese Black Tea Leaves

Abstract

We determined vitamin B 12 content of Chinese black tea leaves using a microbiological assay based on Lactobacillus delbrueckii ATCC 7830. Trace levels (0.25 - 0.69 μg/100g dry weight) of vitamin B 12 were detected in Pu’er, Fu, and Brick tea leaves. However, vitamin B 12 content (0.06 - 1.37 μg/100g dry weight) of Ryubao tea leaves significantly varied. To determine whether Chinese black tea leaves contain vitamin B 12 or other corrinoid compounds that are inactive in humans, corrinoid compounds were purified from Ryubao tea by an immunoaffinity column chromatography and vitamin B 12 was identified by liquid chromatography-electrospray ionization/tandem mass spectrometry. Vitamin B 12 content in the tea drink prepared from Ryubao tea leaves was very low (0.8 ng/100mL). Our results indicate that Chinese black tea is usually not a good source of B 12 , although Ryubao tea leaves with the highest B 12 content may be utilized as a source of this vitamin for vegerarians.