Suitable compounds: (1) have the general formula shown in formula 1 where R2 is a hydroxy group, R8 is an oxygen function comprising a 16 alpha hydroxy group or a keto group (=0), R1, and R9-R11 are hydroxy groups or nonreactive hydrogen groups and R7 is a methyl group; or (2) have the general formula shown in formula 2 where R2 is a hydroxy group and R1 and R9-R11 are hydroxy groups or nonreactiv