In vitro screen of antiStaphylococcus aureus activity of 20 kinds of heatclearing and toxicityremoving Chinese herbal medicines

Abstract:

ObjectiveTo determine antimicrobial activity of 80% ethanol extracts of 20 kinds of heatclearing and toxicityremoving Chinese herbal medicines(CHM) against Staphylococcus aureus(SA) and methicillinresistant Staphylococcus aureus (MRSA),so as to screen medicines with strong bacterial inhibition.MethodsEthanol extracts of 20 kinds of CHM were prepared, in vitro antimicrobial activity against SA and MRSA (MRSA 82, MRSA 92, MRSA 111,MRSA 135,and MRSA 144) were determined by agardiffusion method, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined by doubledilution method.ResultsThe extraction rate of ethanol extracts of 20 kinds of CHM ranged 5.33%-15.89%, Flos Carthami had the highest extraction rate(15.89%),followed by Solanum nigrum (12.64%), Cuscuta chinensis Lam had the lowest extraction rate (5.33%), 16 kinds of ethanol extracts showed different inhibitory effect on SA and MRSA, 4 kinds of extracts had high antimicrobial activity (inhibition zone diameter ［IZD］≥16 mm, including Mahonia bealei［Fort.］,Prunella vulgaris,Herba moslae, and Geranium wilfordii Maxim), 9 extracts had moderate antimicrobal activity (IZD［>10 mm，<16 mm］, including Herba Verbenae,Potentilla discolor,Oxanlis corniculata L.,Solidago decurrens Lour,Viola philippica Car,Herba artemisiae Scopariae,Plantago asiaticaL&Plantago depressa Willd, Lysima chiachristinae Hance, and Leucas ciliata Benth), 3 extracts had low antimicrobial activity (IZD ≤10mm, including Pulsatilla chinensis ［Bunge］ Regel,Campsis grandiflora, and Allium tuberosum Rottler). IZD of most extracts for MRSA were larger than that of standard strain. MIC and MBC of 13 kinds of extracts with better antimicrobial activity against standard and drugresistant strains were 64-1 024 μg/mL and 128-2 048 μg/mL respectively.ConclusionEthanol extracts of Mahonia bealei(Fort.), Prunella vulgaris, Herba moslae, and Geranium wilfordii Maxim have strong antimicrobial activity against MRSA.