From the HMBC spectrum, the proton at H-19 showed correlations to carbons at δ 43.0 (C-17), 45.4 (C-18), 31.2 (C-21), 181.6 (C-28); these correlations infer the presence of a lactone group. The HMBC spectrum also showed that the lactone system is in the ring E, between the 19-hydroxyl and 28-carbonyl group