Benzaldehyde is a precursor of phenylpropylamino alkaloids as revealed by targeted metabolic profiling and comparative biochemical analyses in Ephedra spp

• Published in: Phytochemistry (Oxford) Vol. 81; pp. 71 - 79
• Main Authors: Krizevski, Raz, Bar, Einat, Shalit, O.r, Levy, Asaf, Hagel, Jillian M., Kilpatrick, Korey, Marsolais, Frédéric, Facchini, Peter J., Ben-Shabat, Shimon, Sitrit, Yaron, Lewinsohn, Efraim
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.09.2012
• Subjects: (S)-Cathinone reductase, (1R,2S)-norephedrine N-methyltransferase; Acetone - analogs & derivatives; Acetone - metabolism; Alcohol Oxidoreductases - metabolism; alkaloids; Alkaloids - metabolism; benzaldehyde; Benzaldehyde carboxyligase; Benzaldehydes - metabolism; biosynthesis; Enzyme Activation; enzyme activity; enzymes; Ephedra - enzymology; Ephedra - metabolism; Ephedra foeminea; Ephedra sinica; Ephedra sinica Stapf; ephedrine; Ephedrine - metabolism; Ephedrine alkaloids; magnesium; medicinal plants; medicine; Metabolic pathway elucidation; Metabolome; metabolomics; microextraction; Plant Proteins - metabolism; Plant Stems - metabolism; Propylamines; proteins; pseudoephedrine; Pyruvic Acid - metabolism; Solid Phase Microextraction; Solubility; Species Specificity; stems; thiamin; Ephedra sinica Stapf; Benzaldehyde carboxyligase; Ephedra foeminea; Ephedrine alkaloids; (S)-Cathinone reductase, (1R,2S)-norephedrine N-methyltransferase; Metabolic pathway elucidation
• ISSN: 0031-9422; 1873-3700
• DOI: 10.1016/j.phytochem.2012.05.018

Ephedra species that vary in ephedrine alkaloid content were chemically and biochemically compared. Our results indicate that benzaldehyde is a metabolic precursor of ephedrine alkaloids, and that described benzaldehydecarboxyligase activity and (S)-cathinone reductase limit alkaloid production in Ephedra spp. [Display omitted] ► The metabolic pathway to ephedrine alkaloids was explored in Ephedra spp. ► Benzaldehyde is seemingly a metabolic precursor to ephedrine alkaloids in Ephedra. ► Benzaldehyde carboxyligase and cathinone reductase are key in ephedrine formation. Ephedrine and pseudoephedrine are phenylpropylamino alkaloids widely used in modern medicine. Some Ephedra species such as E. sinica Stapf (Ephedraceae), a widely used Chinese medicinal plant (Chinese name: Ma Huang), accumulate ephedrine alkaloids as active constituents. Other Ephedra species, such as E. foeminea Forssk. (syn. E. campylopoda C.A. Mey) lack ephedrine alkaloids and their postulated metabolic precursors 1-phenylpropane-1,2-dione and (S)-cathinone. Solid-phase microextraction analysis of freshly picked young E. sinica and E. foeminea stems revealed the presence of increased benzaldehyde levels in E. foeminea, whereas 1-phenylpropane-1,2-dione was detected only in E. sinica. Soluble protein preparations from E. sinica and E. foeminea stems catalyzed the conversion of benzaldehyde and pyruvate to (R)-phenylacetylcarbinol, (S)-phenylacetylcarbinol, (R)-2-hydroxypropiophenone (S)-2-hydroxypropiophenone and 1-phenylpropane-1,2-dione. The activity, termed benzaldehyde carboxyligase (BCL) required the presence of magnesium and thiamine pyrophosphate and was 40 times higher in E. sinica as compared to E. foeminea. The distribution patterns of BCL activity in E. sinica tissues correlates well with the distribution pattern of the ephedrine alkaloids. (S)-Cathinone reductase enzymatic activities generating (1R,2S)-norephedrine and (1S,1R)-norephedrine were significantly higher in E. sinica relative to the levels displayed by E. foeminea. Surprisingly, (1R,2S)-norephedrine N-methyltransferase activity which is a downstream enzyme in ephedrine biosynthesis was significantly higher in E. foeminea than in E. sinica. Our studies further support that benzaldehyde is the metabolic precursor to phenylpropylamino alkaloids in E. sinica.