A phenanthrene constituent in Eulophia macrobulbon (E.C.Parish & Rchb.f.) Hook.f., 1-(4'-hydroxybenzyl)-4,8- dimethoxyphenanthrene-2,7-diol (1) was previously reported as a phosphodiesterase 5 inhibitor. A simple and rapid thin layer chromatographic (TLC)-image analysis method was developed to quantify this compound in plant samples. Chromatographic separation of the phenanthrene was completed on silica gel TLC using dichloromethane–methanol (96:4, v/v) as a mobile phase. Image analysis of the scanned TLC plate was performed by Photoshop CS6 to quantify the amount of phenanthrenes. The area under the spot corresponding to 1 was integrated and used for quantification. The method was validated by the detection limit, calibration curve, repeatability, reproducibility, and recovery. The results showed that our digital imaging method was applicable for quantification of 1 on TLC. The method was convenient, efficient, and moderately accurate for the quantitative analysis of 1 in plant samples.
