A polyketide or glycosylated polyketide which has the formula: ##STR1##

wherein R* is methyl or ethyl;

each of R¹-R⁶ is methyl;

X¹ is OH or H; and/or

X² is=O, OH or H;

X³ is OH or H;

X⁴ is OH or H;

a pi bond is present at positions 10-11, 8-9, 4-5 and/or 2-3; and wherein at least one of the following characteristics is present:

X¹ is H;

X² is OH or H;

X³ is H;

X⁴ is H; or

a pi bond is present at positions 10-11, 8-9, 4-5 and/or 2-3.