Medicinal herb research: serum pharmacological method and plasma pharmacological method

Serum pharmacological method has generally been used in herb studies. However, preparation of test serum for ex vivo experiment is an intricate process: besides pretreatment (heat or chemicals), it involves the proteolytic cascades of coagulation along with fibrinolysis, complement and kinin systems, as well as platelet and leukocyte activation resulting in release reactions. These processes deviate serum sample components away from the original in vivo state, and possibly also have effects on the absorbed herbal components and their downstream effectors in blood. The conclusions drawn from serum pharmacological method are at least partially uncertain in its validity. These processes can be avoided by anticoagulation. Compared to those of the serum, constituents of plasma are better reflectors of the in vivo physiological/pathological state and medicinal herb-induced changes. Therefore, we have advocated the adoption of plasma pharmacological method in ex vivo experiments of herb studies. Recent studies including our work demonstrated that the constituents and biological activities are partially different between absorbed medicinal herbs in plasma and serum. This review summarizes the experimental evidence supporting the feasibility of plasma pharmacological method and discusses the reasons and facts that flaw the serum pharmacological method. But serum pharmacological method can be used if anticoagulants interfere with experiments. It should be emphasized that the domination between plasma and serum pharmacological methods is different depending on the usage. Indeed, the pros and cons of both methods as well as the appropriate choices of coagulants in different ex vivo experimental settings remain to be further elucidated.