New ketosteroids from the red alga Hypnea musciformis

The dichloromethane/methanol extract from the red alga Hypnea musciformis exhibited PPE elastase inhibition. A diketosteroid, the 20-hydroxy-5α-cholest-22-ene-3,6-dione was responsible for this activity. Two new steroids were isolated, 2 was assigned as the 6α-hydroxy-cholest-4-ene-3-one and 3 as the 6α-hydroxy-cholest-4,22-diene-3-one. The structures were assigned mainly on the basis of 1H and 13C NMR experiments.