Antimicrobial effects of plant extracts on Streptococcus mutans, Candida albicans, Trichophyton rubrum and other micro-organisms


*Biology Department, Pennsylvania State University, Schuylkill Haven, Pennsylvania 17972, USA.


Extracts of 54 plant species were tested for ability to inhibit bacteria and fungi, especially Candida albicans, Trichophyton rubrum and Streptococcus mutans. The latter three species cause common dermal, mucosal, or oral infections in humans that are difficult to control effectively. Fifteen plant extracts produced detectable antimicrobial activity. The most active included Celastrus scandens root bark, Juglans nigra fruit husks, Kalmia latifolia leaves, Pelargonium xhortorum leaves, and Rhus glabra root bark. Five plant species inhibited Strep. mutans, four inhibited T. rubrum, and two inhibited C. albicans. Lindera benzoin, a common temperate zone shrub, showed evidence of selective toxicity. Extract of L. benzoin bark strongly inhibited C. albicans and T. rubrum, but did not affect any of the other microorganisms tested.