title: Streptomycete endophytes from anti-diabetic medicinal plants of the Western Ghats inhibit alpha-amylase and promote glucose uptake.
abstract: α-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 α-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 50 ppm cycloheximide and incubated for 4-8 weeks 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 (JX965948) isolated from the stem fragments of L. ciliata exhibited alpha-amylase inhibitory activity (IC50 values = 162.3 ± 1.05 μg ml⁻¹) in comparison with the standard Acarbose™ (IC50 value = 73.1 ± 1.12 μg ml⁻¹). Extract of Streptomyces sp. (JQ926174) 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.
  
  
  CONCLUSIONS
  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 α-amylase and improved glucose uptake in the porcine hemidiaphragm. Results indicate the inhibition of α-amylase by Streptomyces longisporoflavus extract with IC50 values of 162.3 ± 1.05 μg ml⁻¹ in comparison with the standard inhibitor Acarbose™ with IC50 value 73.1 ± 1.12 μg ml⁻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.
authors: Department of Studies in Botany, University of Mysore, Mysore, Karnataka, India.
authors: V J
authors: VJ
authors: Akshatha
authors: M S
authors: MS
authors: Nalini
authors: C
authors: C
authors: D'Souza
authors: H S
authors: HS
authors: Prakash
mesh_terms: D000818:Animals; D001681:Biological Assay; D060026:Endophytes / Q000737:chemistry* / Q000145:classification; D007004:Hypoglycemic Agents / Q000302:isolation & purification*; D007194:India; D008969:Molecular Sequence Data; D010936:Plant Extracts; D018515:Plant Leaves / Q000382:microbiology*; D018547:Plant Stems / Q000382:microbiology; D010946:Plants, Medicinal / Q000382:microbiology*; D013302:Streptomyces / Q000145:classification / Q000235:genetics / Q000254:growth & development / Q000302:isolation & purification*; D013552:Swine; D000516:alpha-Amylases / Q000037:antagonists & inhibitors
chemical_list: D007004:Hypoglycemic Agents; D010936:Plant Extracts; D000516:alpha-Amylases
keywords: Western Ghats; endophytic actinomycetes; glucose uptake; medicinal plants; molecular characterization; α-amylase inhibition