Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
(A) Example chromatograms of birch bark extract (red line) and reference compounds (green line): 1 (betulinic acid), 2 (oleanolic acid), 3 (ursolic acid), 4 (betulin). Over the chromatograms the spectra of identified and reference compounds. (B,C); The spectro-chromatograms of extract and reference compounds, respectively. RP18e LiChro-spher, acetonitrile–water—phosphoric acid aqueous solution at concentration of 1% (75:25:0.5, v/v/v), flow rate 1.0 mL/min at 10 °C.
