1 Antioxidant , Cytotoxic , and Antimicrobial Activities 2 of Glycyrrhiza glabra , Paeonia lactiflora , and 3 Eriobotrya japonica Extracts 4

Abstract: Background: The phytochemical composition, antioxidant, cytotoxic, and antimicrobial 11 activities of a methanol extract from Glycyrrhiza glabra (Ge), a 50% ethanol (in water) extract from 12 Paeonia lactiflora (Pe) and a 96% ethanol extract from Eriobotrya japonica (Ue) were investigated. 13 Methods: The phytochemical profiles of the extracts were analysed by LC-MS/MS. Antioxidant 14 activity was evaluated by scavenging DPPH and ABTS radicals and reducing ferric complexes, and 15 the total phenolic content was tested with the Folin-Ciocalteu method. Cytotoxicity was determined 16 with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay in murine 17 macrophage RAW 264.7 cells. Antimicrobial activity of the three plant extracts was investigated 18 against six bacterial strains with the broth microdilution method. Results: Only the extract of Paeonia 19 lactiflora showed high antioxidant activities compared to the positive controls ascorbic acid and (−)20 epigallocatechin gallate (EGCG) in DPPH assay, and generally the antioxidant activity order was 21 ascorbic acid or EGCG > Pe > Ue > Ge. The three plant extracts didn’t show strong cytotoxicity 22 against RAW 264.7 cells after 24 h treatment with IC50 values above 60.53 ± 4.03 μg/mL. Eriobotrya 23 japonica extract was not toxic against the six tested bacterial strains at all, with minimal inhibitory 24 concentration (MIC) values above 5 mg/mL. The Glycyrrhiza glabra extract showed medium 25 antibacterial activity against some bacterial strains, with MICs between 0.31 and 1.25 mg/mL. 26 Paeonia lactiflora extract inhibited the growth of Acinetobacter bohemicus, Micrococcus luteus, and 27 Bacillus megaterium at a MIC of 0.08 mg/mL. Conclusions: In this study, extract of Paeonia lactiflora 28 showed high antioxidant activities compared to ascorbic acid and EGCG in DPPH assay. The three 29 plant extracts only showed a weak cytotoxicity against RAW 264.7 cells. The microdilution method 30 showed that the extract of Eriobotrya japonica was not toxic against the six tested bacteria strains. 31 Glycyrrhiza glabra extract showed weak antibacterial activity against five bacteria strains, but Paeonia 32 lactiflora extract significantly inhibited Acinetobacter bohemicus, Micrococcus luteus, and Bacillus 33 megaterium. This study may help to evaluate the phytotherapeutic value of the three plants, which 34 are used in Traditional Chinese Medicine. 35