Antioxidant Activity, Polyphenolic Profiles and Antibacterial Properties of Leaf Extract of Various Paulownia spp. Clones

Abstract

Paulownia spp. are widely distributed ornamental trees with leaves abundant in secondary metabolites of high medicinal potential. Eighteen breeding clones of Paulownia spp. were tested in terms of their antioxidant activity and total polyphenolic contents. The 50% ethanolic extracts (2 g/30 mL) of leaves and petioles were compared in the screening step. Eight paulownia clones were selected for detailed analyses including HPTLC polyphenolic profile, verbascoside content and antibacterial activity against five bacteria species (S. aureus, B. cereus, E. coli, Y. enterocolitica, S. enterica). The species-specific differences in terms of antioxidant activity correlated with phenolic compounds were found mainly in the case of leaf blade extracts, the highest for P. tomentosa × P. fortunei and the lowest for P. elongata × P. fortunei clones. The P. tomentosa clones varied greatly in this regard. In the HPTLC polyphenolic profile, the occurrence of some polyphenols was proved and the specific verbascoside content was quantified (70 to 225 mg/g DW). The P. tomentosa × P. fortunei hybrids had the highest inhibitory activity, mainly against Gram-positive bacteria, whereas only slight inhibition of S. aureus growth was observed for P. elongata × P. fortunei clones. The obtained results indicate diverse suitability of paulownia clones as a source of active ingredients.