A molecular species produced by living systems of biological origin when it is composed of two parts of different origins, e.g. a conjugate of a xenobiotic with some groups, e.g. glutathione, sulfate or glucuronic acid, to make it soluble in water or compartmentalized within the cell.
Source:
PAC, 1997, 69, 1251. 'Glossary of terms used in bioinorganic chemistry (IUPAC Recommendations 1997)' on page 1260 (https://doi.org/10.1351/pac199769061251)