Determination of vegetable tannins from plants in China

Abstract Tannin is a chemical compound found in plants such as tea, with yellow or brown as a characteristic color. Tannin is present in any plant species’ wood, stems, barks, leaves, roots, and fruits. However, the tannin contents in those plants are not the same and plants rich in tannin are the most used raw material for industrial‐level tannin extraction, such as chestnut. The central purpose of this article was to identify the tannin content of vegetables. In this study, tannins were extracted from 72 plants in China. The contents and purities of tannins, non‐tannins and insoluble substances in those studied plants were determined. A gravimetric approach, using hider powder as a precipitate to bind tannins, has been developed to quantify total tannins in plants. The results showed that high contents of tannins (>20%) were found in Pltycarya strobilacea fruit, Quercus acutissima shell, Quercus variabilis shell, Acacia mearnsii bark, Albizia kalkora bark, Camellia oleifera wood, Rosa cymosa root, Rosa laevigata root, Rhus chinensis gallnut, Bruguiera sexangular bark, Kandelia candel bark, Ceriops tagal bark, Lumnitzera racemose bark and Dioscorea cirrhosa tuber. The purity of tannins was more than 70% in some plants: Larix gmelimi bark, Causuarina equisetifolia bark, P. strobilacea fruit, Castanopsis tibetana wood, Quercus aliena shell, Quercus chenii shell and bark, A. mearnsii bark, A. kalkora bark, Bruguiera gymnorrhiza bark, C. tagal bark, K. candel bark and D. cirrhosa tubers . These plants are excellent resources for vegetable tannins in China. © 2023 Society of Industrial Chemistry and John Wiley & Sons Ltd.