Separation of targeted ganoderic acids from Ganoderma lucidum by reversed phase liquid chromatography with ultraviolet and mass spectrometry detections

Ganoderic acids are valuable bioactive secondary metabolites produced by a traditional medicinal mushroom Ganoderma lucidum (“Ling-zhi” in Chinese and “Reishi” in Japanese). In this work, a fast and efficient method for the recovery and purification of ganoderic acid T (GA-T) and ganoderic acid Me (GA-Me) from triterpene-enriched extracts of G. lucidum mycelia was developed by using reversed phase HPLC (RP-HPLC) on a C₁₈ column with an acidified methanol–water mobile phase in combination with ultraviolet (UV) detection and electrospray ionization mass spectrometry (ESI-MS). The presence of each targeted GA (GA-T and GA-Me) in its corresponding peak was easily identified and confirmed by UV and MS. The chemical structures of the purified GA-T and GA-Me were further confirmed by ¹H NMR. The retention behaviors of the two GAs over a temperature range of 15–55 °C were also investigated. From the retention time data, van’t Hoff plots were obtained. The estimated enthalpy (ΔH) and entropy (ΔS) data suggest that the retention time difference between GA-T and GA-Me might be driven by an enthalpy difference. Furthermore, a semi-preparative HPLC purification was achieved on a semi-preparative C₁₈ column using the conditions optimized for the analytical column. The method presented in this work can be a valuable tool for the rapid semi-preparative purification of targeted GAs, and it may also be applicable to some other natural products.