Antibiotic Potential of Endophytic Actinomycetes of Medicinal Herbs Against Human Pathogenic Bacteria

Abstract

Endophytic actinomycetes were isolated from six medicinal herbs viz., Abrus precatorius L., Aloe vera (L.) Burm. f., Asparagus racemoses Willd., Adhatoda vasica Nees, Catharanthus roseus (L.) G. Don. and Plumbago zeylanica L. which are known for their ethno botanical properties. A total of 34 endophytic actinomycetes were isolated through surface sterilization procedures. In the present study, procedure I for sterilization was effective for isolation of endophytic actinomycetes. All the medicinal herbs were positive for the endophytic actinomycetes. Maximum number of isolates of endophytic actinomycetes were obtained from Aloe vera (L.) Burm. f. The isolates obtained from roots (55.88 %) dominated over leaf (32.35 %) and stem (11.76 %). All these isolates were assessed for their antibacterial activity against human pathogenic bacteria. Thirteen actinobacterial isolates exhibited antagonistic activity through cross streak assay. The isolates, Streptomyces chromofuscus (Ck-S3) from stem and Streptomyces anulatus (Ck-L2) from leaf portion of Plumbago zeylanica L., showed significant antagonistic activity against all the tested human pathogenic bacteria. Out of 13 isolates, six (46.15 %) isolates obtained from root portion of Aloe vera (L.) Burm. f. and Abrus precatorius L. exhibited antibacterial activity against at least one of the tested pathogenic bacteria in agar well diffusion method.