5-HYDROXYALOESAPONARIN-II, A MINOR BLUE PIGMENT IN AN ACTINORHODIN-NEGATIVE MUTANT OF STREPTOMYCES-COELICOLOR A3(2)

Blue pigmentation in Streptomyces coelicolor A3(2) is attributed to sy nthesis of the polyketide actinorhodin and its lactone derivative gamm a-actinorhodin, Therefore, actinorhodin-negative mutants show pigmenta tion other than blue, When the BZZ mutant of S.coelicolor A3(2) [defec tive in the actVI-ORFI gene coding for a putative keto(= oxo)reductase ] was examined for its secondary metabolite content, the presence of a loe-saponarin II (3,8-dihydroxy-1-methyl-9,10-anthraquinone) as the ma jor pigment was confirmed, However, a substantial fraction of a red/bl ue (acid/alkaline) pigment was detected after separation on HPLC, MS a nd NMR analysis revealed its structure as 3,5,8-trihydroxy-1-methyl-9, 10-anthraquinone. To our knowledge, this anthraquinone has not previou sly been reported in biological material, A possible route for biosynt hesis of this compound is discussed.