Determination of ganoderic acids in triterpenoid constituents of Ganoderma tsugae

Ganoderma product has the highest sale volume in the health food market in Taiwan. The most widely-used raw material is the species of G. tsuage. Nine triterpenoids were isolated from the fruiting body of G. tsugae and their structures were identified, using H-1 NMR and FT-IR, as ganoderic acid A (1), B (2), C (3), D (4), E (5), C5 (6), C6 (7), G (8) and ganoderenic acid D (9). A reverse-phase HPLC method was also established for the determination of these nine triterpenoids. Among these compounds, ganoderic acid E, C5, C6, G and ganoderenic acid D were analyzed for the first time by reverse-phase HPLC. The separation was carried out on a C18 reverse-phase column with a gradient elution of acetonitrile and 2% acetic acid (1/4 and 1/2, v/v) as mobile phase at a flow-rate of 0.8 mL/min and detection at 252 nm. Regression equation revealed the linear relationship (correlation coefficient: 0.9990similar to0.9999) between the peak-area ratios and concentrations of ganoderic acids. The recoveries of nine ganoderic acids were between 96.85similar to105.09%. The relative standard deviations of nine ganoderic acids range from 0.8similar to4.8% (intraday) and 0.7similar to5.1% (interday). The total contents of the nine ganoderic acids in eight Ganoderma samples were between 0.28similar to2.20%.