DPPH‐Scavenging and Antimicrobial Activities of Asteraceae Medicinal Plants on Uropathogenic Bacteria

Abstract

Asteraceae species were widely applied in traditional medicines in Asian countries as sources of natural antioxidants and antimicrobial agents. This study aimed to evaluate DPPH-scavenging capacities and antimicrobial activities of nine Asteraceae species collected from Southern Vietnam. Antioxidant and antimicrobial activities were determined by standard protocols. Essential oils from <i>Ageratum conyzoides, Helianthus annuus,</i> and <i>Artemisia vulgaris</i> indicated significant inhibitory effects on <i>Staphylococcus aureus</i> and <i>Candida</i> spp. Crude extracts and fractions from <i>Taraxacum officinale, Chrysanthemum morifolium</i>, <i>A. conyzoides,</i> and <i>Tagetes erecta</i> showed inhibitory ability on at least one testing bacterial strains including <i>S. aureus</i>, <i>Escherichia coli</i>, <i>Klebsiella pneumoniae</i>, and <i>Pseudomonas aeruginosa</i>. In a study on clinical isolates, ethyl acetate fraction from <i>A. conyzoides</i> flower displayed the most potent effect on uropathogenic <i>E. coli</i> and <i>K. pneumoniae</i> with MIC at 1.25-10 mg/ml and 5-12.5 mg/ml, respectively. DPPH-scavenging assay indicated that <i>T. erecta</i> extract had the lowest IC₅₀ (17.280 <i>μ</i>g/ml) and is 2.4 times higher than vitamin C (7.321 <i>μ</i>g/ml). This study revealed that <i>A. conyzoides</i> has good potential against uropathogenic <i>E. coli</i> and <i>K. pneumoniae,</i> and therefore could be applied for prophylactic treatment of urinary infection.