Streptomycete endophytes from anti-diabetic medicinal plants of the Western Ghats inhibit alpha-amylase and promote glucose uptake

alpha-amylase inhibitor retards the liberation of glucose from dietary complex carbohydrates and delays the absorption of glucose. The purpose of the study was to isolate and select alpha-amylase inhibitor-producing endophytic actinomycetes from the leaves and stems of Leucas ciliata and Rauwolfia densiflora, two of the well-known medicinal plants used in the treatment for diabetes. Sterilized plant samples were inoculated on the actinomycete isolation agar medium containing 50ppm cycloheximide and incubated for 4-8weeks at room temperature. The actinomycetes were isolated on agar medium and identified on the basis of 16S rRNA sequences, the isolates exhibiting >99% similarities were submitted to NCBI, and gene accession numbers were obtained. They were inoculated to International Streptomyces Project 1 medium (ISP 1) for fermentation. The extracts obtained were tested for the anti-diabetic potential by the inhibition of alpha-amylase by colorimetric assay and glucose uptake in the porcine hemidiaphragm. Streptomyces longisporoflavus () isolated from the stem fragments of L.ciliata exhibited alpha-amylase inhibitory activity (IC50 values=162 center dot 3 +/- 1 center dot 05 mu gml(-1)) in comparison with the standard Acarbose (TM) (IC50 value=73 center dot 1 +/- 1 center dot 12 mu gml(-1)). Extract of Streptomyces sp. () from R.densiflora indicated glucose uptake in the porcine hemidiaphragm. Results indicate for the first time the potential of endophytic streptomycete extracts with anti-diabetic activity. Significance and Impact of the Study Endophytic actinomycetes were isolated from two medicinal species of the Western Ghats, a biodiversity 'hotspot' in southern India and screened for the anti-diabetic potential for inhibition of alpha-amylase and improved glucose uptake in the porcine hemidiaphragm. Results indicate the inhibition of alpha-amylase by Streptomyces longisporoflavus extract with IC50 values of 162 center dot 3 +/- 1 center dot 05 mu gml(-1) in comparison with the standard inhibitor Acarbose (TM) with IC50 value 73 center dot 1 +/- 1 center dot 12 mu gml(-1). Further, extract from Streptomyces sp. showed increased glucose uptake by hemidiaphragm. The present investigation implicates the potential of endophytic actinomycetes as sources of anti-diabetic agents.