Investigation of bacterial replicative DNA polymerase inhibitors and antioxidant properties of Paeonia daurica Andrews subsp. Macrophylla plant extract fractions

The methanolic extracts from fruit, leaf, stem and roots of Paeonia daurica subsp. macrophylla were investigated for inhibitory effects on replicative bacterial and viral DNA polymerases by primer extension assay. While all plant parts showed inhibition effect on bacterial and viral DNA polymerases, roots of the plant was focused to purify inhibitory compounds. The chemical structures of compounds were completely elucidated using a combination of NMR, MS and FT-IR analyses. Five molecules with paeoniflorin, paeoniflorigenone, benzoyl paeoniflorin, and benzoic acid with its derivate 2,4,6 trihydroxy-1-methyl benzoate were purified and identified. Both DNA-dependent and RNA-dependent polymerase activity of MMLV-RT was strongly inhibited by these five molecules. On the other hand, bacterial polymerases PolC and DnaE were strongly inhibited by only paeoniflorigenone. Molecular modeling result suggested that paeoniflorigenone interacts with the important residues at active site of three polymerases which support our experimental result. SPME and hydrodistilled essential oil of the fresh root, scape, fruit and fruit bark of Paeonia daurica was investigated by using GC-MS and the major constituents of the essential oil were salicylaldehyde, myrtanal, palmitic acid, methyl salicylate and myrtenal. Furthermore, the essential oils of P. daurica were evaluated for their inhibition on MMLV-RT. All essential oil extracts have shown strong inhibition effect on viral transcriptase. Ethyl acetate fraction of root had smallest SC50 value against DPPH and ABTS radicals. It showed also higher scavenging activity than quercetin, trolox and ascorbic acid since its quite high total phenolic content. We proposed that the parts of P. daurica might be used to find new antimicrobial agents and generate supplementary material for foods.