Activity of SDH, QDH, and PAL in species, accumulating different types of tannins

The biosynthesis of different classes of tannins in plants is a complex process that remains insufficiently studied. This study aimed to evaluate the activity of shikimate dehydrogenase (SDH), quinate dehydrogenase (QDH), and phenylalanine ammonia-lyase (PAL), and their influence on the accumulation of proanthocyanidins (PA) and/or hydrolyzable tannins (HT) in medicinal plants. The leaves of Hippophae rhamnoides and Cornus sericea (accumulating HT), Astilbe chinensis (accumulating PA), and Agrimonia pilosa and Agrimonia asiatica (accumulating both HT and PA) were used in the present study. The highest PA levels were found in A. chinensis, while the highest HT content was observed in H. rhamnoides. Water-soluble PA predominated in all species. The highest SDH activitiy were detected in the leaves of the HT-rich species C. sericea and H. rhamnoides, while QDH activity was comparatively low. Activity of PAL was the highest in the leaves of H. rhamnoides, and the lowest – in A. chinensis. Correlation analysis revealed a positive relationship between SDH activity and HT levels. No significant correlation was found between QDH or PAL activity and tannin content. These findings add valuable information into the enzymatic regulation of tannin biosynthesis in medicinal plants that accumulate different types of tannins.