The alkaloids vincarine, herbadine, and herbamine isolated from the herbage of Vinca herbacea Waldstet. et Kit. are pharmacologically active. A method for their quantitative determination in plant raw material is proposed, which consists in obtaining combined alkaloids, separating them by TLC (using KSK No. 2 silica gel and ethyl acetate-methanol (95:5) system), eluting with chloroform, and determining the alkaloids in the eluates by spectrophotometry on an SF-26 instrument. The method includes steps such as extracting alkaloids from 25 g of comminuted air-dry raw material with a 2% aqueous solution of sulfuric acid, obtaining amorphous combined alkaloids, dissolving them in chloroform, depositing the solution on a TLC plate, performing ascending chromatography, staining the marker band with cerium ammonium sulfate in 85% orthophosphoric acid, extracting the corresponding sorbent sections with chloroform, evaporating the extract, dissolving the residue in methanol, and calculating the amounts using optical density and a formula. Results show the amounts of vincarine (0.064%), herbadine (0.081%), and herbamine (0.077%) in the raw material on an absolutely dry weight basis. Additionally, it is known that the oxygen radical anion (O2•−) is formed in the autooxidation of phenols in alkaline media; Renard et al. suggest it plays an active part in the oxidation of lignin by a radical chain mechanism, but there are no experimental proofs of its formation in the oxidation of lignin and its model compounds in the literature.