Natural products and traditional medicines are of great importance. Such forms of medicine as traditional Chinese medicine, Ayurveda, Kampo, traditional Korean medicine, and Unani have been practiced in some areas of the world and have blossomed into orderly-regulated systems of medicine. This study aims to review the literature on the relationship among natural products, traditional medicines, and modern medicine, and to explore the possible concepts and methodologies from natural products and traditional medicines to further develop drug discovery. The unique characteristics of theory, application, current role or status, and modern research of eight kinds of traditional medicine systems are summarized in this study. Although only a tiny fraction of the existing plant species have been scientifically researched for bioactivities since 1805, when the first pharmacologically-active compound morphine was isolated from opium, natural products and traditional medicines have already made fruitful contributions for modern medicine. When used to develop new drugs, natural products and traditional medicines have their incomparable advantages, such as abundant clinical experiences, and their unique diversity of chemical structures and biological activities.

Many prescriptions of traditional medicines (TMs), whose efficacy has been tested in clinical practice, have great therapeutic value and represent an excellent resource for drug discovery. Research into single compounds of TMs, such as artemisinin from Artemisia annua L., has achieved great success; however, it has become evident that a TM prescription (which frequently contains various herbs or other components) has a synergistic effect in effecting a cure or reducing toxicity. Network pharmacology targets biological networks and analyzes the links among drugs, targets, and diseases in those networks. Comprehensive, systematic research into network pharmacology is consistent with the perspective of holisticity, which is a main characteristic of many TMs. By means of network pharmacology, research has demonstrated that many a TM show a synergistic effect by acting at different levels on multiple targets and pathways. This approach effectively bridges the gap between modern medicine and TM, and it greatly facilitates studies into the synergistic actions of TMs. There are different kinds of synergistic effects with TMs, such as synergy among herbs, effective parts, and pure compounds; however, for various reasons, new drug discovery should at present focus on synergy among pure compounds.

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In this study, we investigated the effects of a petroleum ether fraction of Artemisia sacrorum Ledeb. (Compositae) (PEASL) on glucose production through AMP-activated protein kinase (AMPK) activation in human HepG2 cells. PEASL significantly inhibited glucose production in a concentration-dependent manner, and this effect was reversed in the presence of compound C, a selective AMPK inhibitor. PEASL markedly induced the phosphorylation of AMPK and downstream acetyl-CoA carboxylase (ACC) in a time- and concentration-dependent manner. In addition, it markedly increased the phosphorylations of glycogen synthase kinase 3β (GSK3β) in a concentration-dependent manner. In contrast, cAMP response element binding protein (CREB), a key transcription factor for gluconeogenic enzyme phosphorylation, decreased in a concentration-dependent manner. PEASL downregulated the gluconeogenesis gene expression of peroxisome proliferation activated receptor-γ coactivator-1α (PGC-1α), phosphoenolpyruvate carboxykinase (PEPCK), and glucose-6-phosphatase (G6Pase) in a concentration-dependent manner. In addition, the gene expression of orphan nuclear receptor small heterodimer partner (SHP) increased, also in a concentration-dependent manner. These effects were also abolished by pretreatment with compound C, an AMPK inhibitor. This indicates that PEASL inhibited glucose production via the AMPK-GSK-CREB pathway in HepG2 cells, and these effects appeared to be capable of revealing anti-diabetic mechanism of PEASL in HepG2 cells.

Artemisia sacrorum Ledeb., a Compositae forage plant in China, has been found to have an inhibitory effect on lipid accumulation. We selected 12 flavonoids, which we had isolated from A. sacrorum and had the potential to inhibit lipid accumulation in the literature or in our preliminary experiments, and grouped them into 11 compound combinations; we investigated their synergistic inhibitory effects on lipid accumulation in 3T3-L1 cells. In screening experiments, Oil-Red O staining, triglyceride levels, and lipid accumulation levels all indicated that combined acacetin and apigenin displayed a significant synergistic inhibitory effect and the best repeatability. Subsequent research showed that this combination could synergistically promote the phosphorylations of AMPK and ACC. Furthermore, to a different extent, that combination had significant synergistic inhibitory effects on various genes or proteins related to adipogenesis and lipogenesis. Thus, that combination could significantly reduce triglyceride levels and lipid accumulation compared with acacetin or apigenin acting alone.