The study of α-glucosidase inhibitor of endophytic actinomycetes isolated from brotowali (Tinospora crispa).

Abstract

An α-glucosidase inhibitor is one of the compounds for the treatment of diabetes. This inhibitor can retard the liberation of glucose from dietary complex carbohydrates and delay glucose absorption, resulting in reduced postprandial plasma glucose levels and suppress postprandial hyperglycaemia. Diabetic medicinal plants are potencial sources of α-glucosidase inhibitor-producing endophytic microorganisms. Actinomycetes has been known as a source of various bioactive compounds that have been used in human health. The purpose of this study were to isolate and to select α-glucosidase inhibitor-producing endophytic actinomycetes from Tinospora crispa and to characterize the selected isolated and their α-glucosidase inhibitor. Endophytic actinomycetes were isolated from the roots, leaves and stems of T. crispa. Sterilized plant samples were inoculated on the HV Agar medium containing 50 ppm cycloheximide and 30 ppm nalidixic acid and were incubated for 2-3 weeks at room temperature. All actinomycetes isolates were tested for their ability to inhibit the α-glucosidase. Identification for the selected isolates was based on 16S rDNA sequences. The inhibitor activity to α-glucosidase was determined spectrophotometrically at 400 nm using p-nitrophenyl-α-D-glucopyranoside as a substrate, and acarbose as a positive control. Characterization and identification of inhibitor component was based on thin layer chromatography, column chromatography, phytochemicals, UV-Vis spectrophotometer and FTIR analyses.The results showed that endophytic actinomycetes isolated from T. crispa produced various inhibition activities. The highest inhibition activity to α-glucosidase was shown by BWA65 found from T. crispa. Production of α-glucosidase inhibitor compounds in this plant largely related with the contribution of its actinomycetes endophytes. The identification based on 16S rDNA sequence revealed that the isolate has 98% similarity to Streptomyces diastaticus. Separation of bioactive components by column chromatography obtained active fraction (F6), which has a low IC50 and high inhibitory activity. Based on phytochemicals, UV-Vis spectrophotometer and FTIR analyses, the active compound F6 is an auron group of flavonoid.

Pengobatan diabetes secara tradisional pada umumnya adalah dengan memanfaatkan berbagai jenis tanaman yang memiliki kandungan bahan aktif yang dapat menurunkan kadar gula dalam darah, diantaranya adalah senyawa yang dapat menghambat enzim α-glukosidas. Eksplorasi mikrob endofit diharapkan dapat menghasilkan metabolit sekunder penting yang memiliki khasiat sama dengan metabolit yang dihasilkan tanaman inangnya. Tanaman obat diabetes merupakan sumber mikrob potensial pengahsil inhibitor α-glukosidase. Isolat potensial dari tanaman obat tersebut diharapkan dapat digunakan untuk memproduksi senyawa inhibitor α-glukosidase secara mikrobiologis.