Complex sentence: Hydroxocobalamin (OHCbl, or B 12a) is a natural form, or vitamer, of vitamin B 12, a basic member of the cobalamin family of compounds.
Split into simpler sentences: Hydroxocobalamin (OHCbl, or B 12a) is a natural form, or vitamer, of vitamin B 12. It is a member of the cobalamin family of compounds.