Hydroxylation and Glucosidation of ent-16β-Hydroxybeyeran-19-oic Acid by Bacillus megaterium and Aspergillus niger

Abstract

ent-16β-Hydroxybeyeran-19-oic acid (1) has potential antihypertensive activity. To obtain novel and more-effective compounds, 1 was incubated with Bacillus megaterium ATCC 14 581 and Aspergillus niger CCRC 32 720. The structures of the metabolites were determined by HR-FAB-MS, 1D- and 2D-NMR spectral data, and enzymatic hydrolysis. Bacillus megaterium hydroxylated and glucosidated 1 to yield ent-7α,16β-dihydroxybeyeran-19-oic acid (2), ent-16β-hydroxybeyeran-19-oic acid α-D-glucopyranosyl ester (3), and ent-7α,16β-dihydroxybeyeran-19-oic acid α-D-glucopyranosyl ester (4). Aspergillus niger hydroxylated 1 to yield ent-1β,7α,16β-trihydroxybeyeran-19-oic acid (5) and ent-1β,7α-dihydroxy-16-oxobeyeran-19-oic acid (6). Metabolites 3 - 5 were characterized as new compounds. In addition, 2, 3, 5, and 6 were tested for antihypertensive effects, and we found that 5 and 6 were more potent than the parent compound 1.

Key words

Microbial hydroxylation - glucosidation - ent-16β-hydroxybeyeran-19-oic acid - diterpenoids - antihypertensive testing

References

• 1 Ali H S, Hanson J R, de Oliveira B H. The biotransformation of some ent-beyeran-19-oic acids by Gibberella fujikuroi .  Phytochemistry. 1992;  31 507-10
• 2 Hou C C. Studies on the active components from Bacopa monniera, Lactuca indica, and Stevia rebaudiana .  Ph. D. Dissertation. College of Pharmacy, Taipei Medical University Taiwan; 2003: pp. 126-30
• 3 Lee C N, Wong K L, Liu J C, Chen Y J, Cheng J T, Chan P. Inhibitory effect of stevioside on calcium influx to produce antihypertension.  Planta Med. 2001;  67 796-9
• 4 Fuganti C, Minut J, Fantoni P, Servi S. On the microbial transformation of α,β-unsaturated aryl ketones by the fungus Beauveria bassiana .  J Mol Catal B: Enzym. 1998;  4 47-52
• 5 Adam W, Luckacs Z, Kahle C, Saha-Möller C R, Schreier P. Biocatalytic asymmetric hydroxylation of hydrocarbons by free and immobilized Bacillus megaterium cells.  J Mol Catal B: Enzym. 2001;  11 377-85
• 6 Hsu F L, Hou C J, Yang L M, Cheng J T, Liu P C, Lin S J. Microbial transformations of isosteviol.  J Nat Prod. 2002;  65 273-7
• 7 de Oliveira B H, dos Santos M C, Leal P C. Biotransformation of the diterpenoid, isosteviol, by Aspergillus niger, Penicillium chrysogenum and Rhizopus arrhizus .  Phytochemistry. 1999;  51 737-41
• 8 Cheng J T, Hsu F L, Chen H F. Antihypertensive principles from the leaves of Melastoma candidum .  Planta Med. 1993;  59 405-7
• 9 Chatterjee P, Pezzuto J M, Kouzi S A. Glucosidation of betulinic acid by Cunninghamella species.  J Nat Prod. 1999;  62 761-3
• 10 Hammer E, Schoefer L, Schäfer A, Hundt K, Schauer F. Formation of glucoside conjugates during biotransformation of dibenzofuran by Penicillium canescens SBUG-M 1139.  Appl Microbiol Biotechnol. 2001;  57 390-4
• 11 Kirkman S K. Zhang MY, Horwatt PM, Scatina J. Isolation and identification of bromfenac glucoside from rat bile.  Drug Metab Dispo. 1998;  26 720-3
• 12 Kouzi S A, Chatterjee P, Pezzuto J M, Hamann M T. Microbial transformations of the antimelanoma agent betulinic acid.  J Nat Prod. 2000;  63 1653-7 and references cited therein