Psoralea is a large widely distributed genus of herbs throughout tropical and subtropical regions, in which Psoralea corylifolia L. has long been used in traditional Chinese and Ayurvedic medicine. From ancient times to the present, there are countless descriptions about its appearance in herbal books. P. corylifolia L. is an annual upright herb, with a height of 60−150 cm (Fig. 1A). The branches are hard, fully covered with white villi. The leaf blade is broadly ovate with black glandular spots on both sides, and sparsely hairy or nearly glabrous. The pericarp is black and its surface is irregular reticulate. Its dried ripe fruits, Psoraleae Fructus (Bu Gu Zhi in Chinese) are flat and fragrant (Fig. 1B). The whole plant has crucial medicinal properties for the treatment of various diseases, such as leukoderma, menstruation disorder, uterine hemorrhage and lumbago. PF and its pharmaceutical preparations are also widely used to treat bone and skin diseases in China. The main constituents dominate its bioactivities, such as antitumor, anti-inflammatory, anti-oxidant, and osteoblastic effects (Table 1).
No. Bioactivities Representative compounds Reference 1 Anticancer Psoralen, isopsoralen and psoralidin [4-7] 2 Osteoblastic effct Psoralen, bavachin, isobavachin,
corylin and bakuchiol
[8-10] 3 Anti-oxidation Psoralen, isopsoralen, psoralidin, bavachinin, isobavachin, corylifol A, isobavachalcone, and bakuchiol [11, 12] 4 Anti-inflammation Isopsoralen, psoralidin, bavachin, bavachinin, corylin, corylifol A, bavachalcone, isobavachalcone, and bakuchiol [13-15] 5 Antimicrobial effect Psoralen, isopsoralen, psoralidin, bavachin, bavachinin, bavachalcone, isobavachalcone, corylifol B, and bakuchiol [16, 17] 6 Estrogenic effect Psoralen, isopsoralen, psoralidin, bavachin, corylifol A, isobavachalcone, and bakuchiol [18, 19] 7 Antidepression Psoralen, isopsoralen, and psoralidin [20, 21] 8 Improving aging-related diseases Bavachin and bavachinin,
bavachalcone and isobavachalcone
 9 Neuroprotection Bavachin and bavachinin,
bavachalcone and isobavachalcone
 10 Improving cardiovascular function Bakuchicin 
Table 1. The bioactivities and related representative compounds of Psoralea corylifolia L
More than 200 compounds were isolated and identified from PF, including coumarins, flavones, meroterpenes, lipids, and volatile oil [44, 45]. Many constituents and metabolites have significant bioactivities, but some of them demonstrate potential toxicity. These potential toxic compounds have been explored from different perspectives. In the study, they are categorized based on their chemical structures and their toxic characteristics are summarized in Table 2.
Constituents Structural types Organs Experimental models Mechanisms Related targets Reference Psoralen Coumarin The liver Rats Inducing the bile acid transporters CYP7A1, BSEP, MRP2, SULT2A1, FXR and MRP3  Liver microsome of mice Inducing th activity and expression of CYP450 enzymes CYP3A11 and CYP2E1  HuH-7 and HepaRG cells Inducing the activity of CYP450 enzymes CYP3A4  HepG2 cells Inducing hepatocyte apoptosis by the endoplasmic reticulum stress Grp78, PERK, eIF2α, ATF4 and ATF6  The kidneys Male mice Affecting renal organic ion transporters OCT1, OCT2, OCTN1, OCTN2, OAT1, OAT3, URAT1, GLUT9 and MRP4  The reproductive system Female rats Accelerating estrogen metabolism UGT1A6 and CYP1A1 [49, 50] Embryonic development Zebrafish Inducing oxidative stress, apoptosis and lipid metabolism pathways Keap1, Nrf2, Mn-sod, Cu/Zn-sod, p53, Puma, Bax, Bcl-2, Apaf-1, Caspase-9, Caspase-3, Hmgcra, Pparα and Fas  Isopsoralen Coumarin The liver Rats
Inducing the bile acid transports
CYP7A1, BSEP, MRP2, MRP3, SULT2A1 and FXR; NTCP, MDR1, ABCG5, ABCG8, and OSTα [46, 52] Liver microsome of mice Inducing the activity and expression of CYP450 enzymes CYP3A11 and CYP2E1  Zebrafish Reducing the antioxidant capacity of the liver LFABP, GSTP2 and SODL  HepG2 cells Inducing the bile acid transports MRP2 and MRP3  The kidneys Male mice Affecting renal organic ion transporters OCT1, OCT2, OCTN1, OCTN2, OAT1, OAT3, URAT1, GLUT9 and MRP4  Psoralidin Coumarin The liver Female mice Inducing idiosyncratic liver injury by activating the inflammasome NLRP3, IL-1β, TNF-α, Caspase-1 and ROS  Bavachin Flavonoid The liver Human UGT1A1 enzyme Inhibiting bilirubin metabolism UGT1A1  HepG2 cells Inducing the mitochondrial damage by endoplasmic reticulum stress ROS, Mfn2, Akt, ATF4, CHOP and XBP1s  Bavachinin Flavonoid The liver Human UGT1A1 enzyme Inhibiting bilirubin metabolism UGT1A1  HepaRG cells Inducing oxidative stress P38, p-P38, JNK, p-JNK and ROS  Isobavachalcone Flavonoid The liver Human UGT1A1 enzyme Inhibiting bilirubin metabolism UGT1A1  Bakuchiol Monoterpene phenol The kidneys HK-2 cells With obvious cytotoxicity  The liver Mice Altering the bile acid transport receptor NTCP  Rats Inducing lipid metabolism disorder CYP7A1, HMG-CoA, BSEP, PPARα and SREBP-2 
Table 2. Characterization of the potential toxic compounds of PF
Jois et al. isolated and identified psoralen and isopsoralen from PF, which are considered as two main active components of PF [60, 61]. According to Chinese Pharmacopeia, their minimum total content in decoction pieces is 0.7% . Modern pharmacological studies have shown that the coumarins of PF play a double role in pharmacological action and toxicity. XIA et al. found that the possible toxic substances were mainly rich in the ethyl acetate extract and the n-butanol extract, which are highly associated with the content of coumarins . Moreover, other studies suggested that psoralen and isopsoralen had certain hepatotoxicity in zebrafish, mice and rats [63, 64]. The median lethal dose (LD50) of psoralen and isopsoralen in mice was 638.69 and 351.72 mg·kg−1, respectively . On the other hand, two benzofuran glycosides of PF had potential hepatotoxicity. Psoralenoside and isopsoralenoside were rich in aqueous extract of PF and quickly absorbed into the circulation system, before being metabolized into excessive psoralen and isopsoralen in the gastrointestinal microenvironment, leading to liver injury .
Several flavonoids in PF exhibited stronger in vitro toxicity than coumarins, such as bavachin, bavachinin and isobavachalcone. Bavachin induced a significant increase in the production of reactive oxygen species (ROS), aggravating mitochondrial damage in HepG2 cells . Bavachinin had strong cytotoxic effect on HepaRG cells, and the underlying mechanism was associated with oxidative damage via the p38/JNK MAPK pathways .
It was found that bakuchiol induced nephrotoxicity and hepatotoxicity . Bakuchiol exhibited obvious toxicity to HK-2 cells, and its combination with psoralen aggravated cell damage . With regard to hepatotoxicity, after treatment with bakuchiol at 52.5 mg·kg−1·d−1 for six weeks, the transaminase activities of rats were enahnced, and the expression of bile acid transporter-related proteins significantly changed . Bakuchiol also inhibited the growth of HepG2 cells, with the half maximal inhibitory concentration (IC50) of 41.3 μmol·L−1 .
Compatibility is one of the most classical principles in TCM theories, with synergistic effect and detoxification compatibility. There are many PF-related prescriptions compatible with other herbs that have been recorded in TCM books and widely used in clinical applications. Common compatible herbs with PF include Myristicae Semen (MS), Juglandis Semen (JS), Eucommiae Cortex (EC), and Cistanches Herba (CH), etc. We summarized the combination effects and possible mechanisms involved (Table 3). The underlying detoxification mechanisms and profound connotation of classical prescriptions require further studies, which will help to reveal the key point of safe use of herbal combination.
No. PF-herbal medicine Experimental model Dose of FP (raw drug) Duration Combination effect Mechanism Reference 1 PF-Rehmanniae Radix Rats 4.05 g·kg−1 28 d Reducing hepatotoxicity Regulating body temperature and ATPase activity  2 PF-Epimedii Folium Rats 0.22 g·kg−1 1 d Increasing hepatotoxicity Inducing idiosyncratic hepatotoxicity under immunological stress conditions  3 PF-Paeoniae Radix Rubra Rats 3.75 g·kg−1 1 d Reducing hepatotoxicity Regulating arachidonic acid
metabolism and glycerophospholipid metabolism pathways
 4 PF-Glycyrrhizae Radix et Rhizoma Rats 40 g·kg−1 1 d Increasing renal toxicity The absorbance of bakuchiol increased, and its clearance was prolonged.  5 PF-Eucommiae Cortex Rats 0.68 g·kg−1 6 w Increasing bioactivity during treatment
Exerting the greatest estrogen-like effects  6 PF-Eucommiae Cortex Zebrafish 200 μmol·L−1 6 dpf Reducing toxicity The gene expression of immune activation and toxicity decreased.  7 PF-Cnidiic Fructus Mice 3.6 g·kg−1 6 w The inhibitory effect on mammary cancer metastasis to bone was enhanced Regulating OPG/RANKEL secretion ratio 
Table 3. The compatibility effects with PF and possible mechanisms
The metabolic process of main ingredients of PF changes, during combined use with other medicines, while the pharmacokinetics parameters of some compositions also change (Table 4). TANG et al. simultaneously determined the multiple compounds of Xianling Gubao Capsules in a reversed pharmacodynamic-pharmacokinetics study, and found that coumarins and prenylated flavonoids from PF had high exposure and profiled the pharmacokinetic features of representative substances . ZHAO et al. investigated the compatibility from the perspective of pharmacokinetics and drug metabolism, and found that glycyrrhetinic acid, one of the main components of Glycyrrhiza uralensis Fisch., might increase renal toxicity by inhibiting the metabolism of PF by CYP450 enzyme . In addition, some studies focused on formula decomposition and toxicity comparison, and some representative components of PF were selected to preliminarily screen out the crucial compatible herbs and identify its composition and to explore the detoxification mechanism. NING et al. utilized an effective and high-sensitive model of zebrafish to screen the detoxification compatible medicines with PF, and found that EC exhibited the stronest effects on attenuating the toxicity of PF. Further studies revealed that the aucubin of EC reduced the hepatoxicity induced by psoralen, which were associated with the HIF-1 pathway, chemical carcinogenic pathway and glutathione metabolic pathway .
Oral medicines t1/2 (h) Tmax (h) Cmax (mg·L−1) AUC0-t (mg·h·L−1) CL (h·L−1·kg−1) Reference PF extract Psoralen 2.67 ± 0.65 9.00 ± 1.67 3,970 ± 1.26 41,140 ± 16.20 0.02 ± 0.01  Isopsoralen 2.97 ± 0.87 10.00 ±1.27 2,130 ± 0.82 25,310 ± 9.40 0.02 ± 0.01  Psoralenoside 3.49 ± 0.45 2.58 ± 0.59 1,460 ± 0.24 12,010 ± 2.47 4.38 ± 1.02  Isopsoralenoside 5.64 ± 3.13 2.58 ± 0.59 2,580 ± 1.60 16,820 ± 6.45 2.56 ± 0.88  Psoralidin 25.15 ± 2.08 1.08 ± 0.88 1.09 ± 0.34 35.61 ± 1.31 191.33 ± 7.61  Bavachin 24.89 ± 4.73 1.00 ± 0.61 2.71 ± 0.83 100.59 ± 28.66 74.15 ± 23.08  Isobavachalcone 22.21 ± 6.15 2.00 ± 0.00 2.35 ± 0.44 75.96 ± 10.16 136.69 ± 35.11  Neobavaisoflavone 8.88 ± 5.15 24.00 ± 0.00 3.63 ± 1.23 88.46 ± 18.40 140.67 ± 21.90  Bakuchiol 10.22 ± 5.54 2.8 ± 1.10 395.73 ± 107.45 4,516 ± 516 7.18 ± 1.54  PF combinated with other herbal medicines Psoralen (compatibility with Semen myristicae) 9.22 ± 2.44 9.33 ± 2.73 7.91 ± 1.34 130.92 ± 18.72 139.03 ± 25.96  Psoralen (Sishen Wan) 4.28 ± 0.68 8.25 ± 0.71 7.85 ± 0.78 99.49 ± 16.58 200.42 ± 33.46  Isopsoralen (compatibility with Semen myristicae) 11.40 ± 6.60 9.33 ± 2.73 3.89 ± 0.54 69.49 ± 9.05 25.85 ± 58.57  Isopsoralen (Sishen Wan) 4.97 ± 1.25 8.25 ± 0.71 3.53 ± 0.62 49.23 ± 8.50 400.91 ± 82.75  Bakuchiol (compatibility with Glycyrrhizae Radix et Rhizoma) 8.65 ± 4.24 3.6 ± 0.89 575.16 ± 148.90 6,067.24 ± 416.01 5.50 ± 1.03 
Table 4. Pharmacokinetic parameters of compounds in PF
Processing is an equivalently important method to attenuate the toxicity of herbs, according to TCM theories. There are two traditional processing methods of PF, which were recorded in medical books and have been widely used nowadays, namely the alcohol soaking and water rinsing method and the salt processing method. The former originated from Lei’s Treatise on Processing of Drugs and is the oldest detoxification method of PF. Modern studies have found that the content of some ingredients decrease when they are soaked in alcohol, including psoralen, isopsoralen, psoralenoside and isopsoralenoside, while psoralenoside and isopsoralenoside are transformed into psoralen and isopsoralen when being steamed. About 50% of the toxic components can be reduced by this method, and more potential toxics of PF may be alcohol-soluble . Recently, SONG et al. has used 3D cultured human liver organoids combined with high connotation imaging to evaluate the detoxification of PF processed products, and verified that the hepatoxicity of PF decreased by the alcohol soaking and water rinsing method . With regard to the salt processing method, XIA et al. found that it obviously alleviated liver injury induced by PF . It is also listed in Chinese Pharmacopoeia due to the enhanced efficacy of PF.
A systematic review on the safety of Psoraleae Fructus: potential risks, toxic characteristics, underlying mechanisms and detoxification methods
- Received Date: 2022-04-02
- Available Online: 2022-11-20
Abstract: Psoraleae Fructus (PF) is an important traditional herbal medicine with a long history of clinical application. It is widely used to treat various diseases, such as osteoporosis, leucoderma and diarrhea. As a traditional nontoxic herb, it has aroused worldwide concern about the potential risks due to increasing adverse reaction events. This article reviews the botany, ancient records of medical uses, adverse reactions, toxicological research advance and detoxification methods of PF. According to clinical studies, liver injury is the most predominant in PF-related adverse reactions. The underlying mechanisms include bile acid metabolism and transport disorders, oxidative stress, mitochondrial damage, inhibition of liver cell regeneration and inflammatory reactions. Furthermore, the potential toxins of PF are summarized. Traditional methods of processing and compatibility will provide reference for reducing the toxicity of PF, which requires further research. In sum, this work systematically summarizes the reserach progress on the safety of PF, which will provide comprehensive insights into the toxicity of PF and facilitate its safe use and future development.