Traditional Chinese medicines (TCMs) usually have complex chemical composition, and unknown effective components. Meanwhile, some of their bioactive compounds suffered from poor bioavailability. These have been major hurdles for the modernization of TCM. Herein, we integrated chemical investigation, in vivo metabolism, and bioactivity evaluation to systematically elucidate the effective components of licorice. We then used biocatalytic approaches to improve the pharmacological properties of these compounds.
Firstly, 311 compounds were detected in licorice by using comprehensive 2DLC/MS. In total 257 compounds were isolated from three medicinal Glycyrrhiza plants (G. uralensis, G. glabra, G. inflata), including 44 new compounds. Chemical difference among the three species was revealed by quantifying 151 secondary metabolites in 95 samples using LC/MS/MS. Successively, 247 compounds were screened using 11 cell- and enzyme-based bioassays. A number of isoprenylated phenols were found as bioactive compounds for the first time. Furthermore, the in vivo metabolites of licorice were analyzed, where 90 metabolites were detected and 55 were monitored by multi-component pharmacokinetic analysis. Finally, compounds with potent bioactivity and high plasma exposure were confirmed for their bioactivities using animal models. For example, glycycoumarin showed hepatoprotective effect to chronic and acute alcoholic liver injuries, and isoangustone A induced apoptosis in colorectal cancer cells principally by inducing mitochondrial outer membrane permeabilization.
Biocatalytic approaches were then used to modify the structures of effective components. MhGT1, a glycosyltransferase from Mucor hiemalis, catalyzed the regio- and stereo- specific glycosylation of isoprenylated flavonoids. YjiC, a glycosyltransferase from Bacillus subtilis, catalyzed the 3-O-glycosylation of glycyrrhetinic acid. These modifications improved the bioavailability of the bioactive components.
The study established the chemical−bioactivity correlation for the popular herbal medicine licorice, and found a number of bioactive compounds related to its clinical application. It set a good example for the discovery of bioactive natural products, and for the modernization of TCM.