has functional parent avermectin B1b 22,23-dihydroavermectin B1b A macrocyclic lactone that is avermectin B<small>_1b</small> in which the double bond present in the spirocyclic ring system has been reduced to a single bond. It is the minor component of ivermectin. dihydroavermectin B1b avermectin H2B1b H2B1b ivermectin B1b ivermectin component b1b CHEBI:63943 chebi_ontology macrocyclic lactone spiroketal