Analysis on the Main Components of Selenium-Enriched Premna microphylla Leaves and Processed Tofu

Premna microphylla is a medicinal plant species distributed in Southeast Asia and China. P. microphylla leaves have been widely used for processing edible gels called Chai tofu, which have many medicinal values, such as clearing heat and detoxifying. However, the main functional components of P. microphylla leaves and Chai tofu are still unknown. In this study, selenium-enriched cultivation of P. microphylla was conducted, and the main compositions of pectins, flavonoids, total phenolics, carotenoids, chlorophylls, and proteins were separated and comparatively analyzed. The results are that kaempferol was the main composition of flavonoids, with the average contents of 5.19% DW (dried weight) in leaves and 3.83% DW in Chai tofu; the composition of the Chai tofu pectin included glucose, fructose, and mannose. Contents of phenolics, kaempferol, chlorophyll, and carotenoids were significantly increased by the selenium enrichment cultivation in a concentration-dependent manner (R2 = 0.989, 0.994, 0.94, 0.948). Moreover, selenium enrichment produced selenized pectins with Se-O bonds. Selenium-enriched P. microphylla is an important plant source for functional foods. Related processing and extraction techniques deserve further research.