Biotransformation of pentacyclic terpene isolated from Alstonia scholaris (R.BR.)

Abstract

Betulin (1) a pentacyclic triterpene was isolated from medicinal plant Alstonia scholaris (R.BR.) and its structural modification by five filamentous fungi was investigated using flask shake and stirred bioreactor methods. Screening-scale and preparative-scale biotransformation with a standard two-stage protocol yielded betulinic acid (2). Out of five fungal strains (Microsporum canis, Trichophyton tonsurans, Aspergillus niger, A. niger NIAB-280 and Penicillium spp.) only two strains, M. canis and T. tonsurans, showed significant yield of (2). Samples withdrawn from fermentation medium were extracted with ethyl acetate and purified using column chromatography. Compound 2 was extracted from fermentation medium after 5–10 days. Flasks and the bioreactor were stirred at 250 rpm and 28°C. The yield of (2) gradually increased with incubation time. A stirred bioreactor was found to be convenient and simple for compound 1 oxidation. A validated analytical HPLC method was employed to confirm the biotransformation of compound 1 to 2.

Keywords::

• Pentacyclic triterpene
• betulin biotransformation
• Alstonia scholaris (R.BR.)
• microsporum canis
• trichophyton tonsurans
• betulinic acid
• stirred bioreactor

Declaration of interest: The authors report no declarations of interest. The authors alone are responsible for the content and writing of the paper.