Forsythiae Fructus: A Review on its Phytochemistry, Quality Control, Pharmacology and Pharmacokinetics

Forsythiae Fructus, as a traditional Chinese medicine, has been widely used both as a single herb and in compound prescriptions in Asia, mainly due to its heat-clearing and detoxifying effects. Modern pharmacology has proved Forsythiae Fructus possesses various therapeutic effects, both in vitro and in vivo, such as anti-inflammatory, antibacterial and antiviral activities. Up to now, three hundred and twenty-one compounds have been identified and sensitive analytical methods have been established for its quality control. Recently, the pharmacokinetics of Forsythiae Fructus and its bioactive compounds have been reported, providing valuable information for its clinical application. Therefore, this systematic review focused on the newest scientific reports on Forsythiae Fructus and extensively summarizes its phytochemistry, pharmacology, pharmacokinetics and standardization procedures, especially the difference between the two applied types—unripe Forsythiae Fructus and ripe Forsythiae Fructus—in the hope of providing a helpful reference and guide for its clinical applications and further studies.


Introduction
Forsythiae Fructus, the dried fruit of Forsythia suspensa (family Oleaceae), known as lianqiao in China, was first recorded in Shennong Bencao Jing, a prestigious monograph on traditional Chinese medicine (TCM) [1], and subsequently listed in the pharmacopoeias of the People's Republic of China, Japan and Korea [2][3][4]. It has been used as a heat-clearing and detoxifying TCM for the treatment of infectious diseases, such as acute nephritis, erysipelas and ulcers, for over 2000 years [5,6]. Modern pharmacological studies have confirmed that Forsythiae Fructus possesses anti-inflammatory, antioxidant, antiviral, antivomiting and antitumor activities, as well as hepatoprotective, neuroprotective and cardiovascular protective effects [7][8][9][10][11][12]. Nowadays, more than forty Chinese medicinal preparations containing Forsythiae Fructus are included in the Chinese Pharmacopoeia, Volume I [2]. For example, Forsythiae Fructus is used as a principal drug in Yinqiao Jiedu tablet exerting effects of expelling wind, relieving the exterior, clearing heat and detoxifying [2].
In the clinic two types of Forsythiae Fructus are used, namely the unripe Forsythiae Fructus (Qing qiao, UFF) and ripe Forsythiae Fructus (Lao qiao, RFF). Due to the different harvest times, they are distinguished as UFF and RFF collected at early September and October, respectively [6]. Although both of them have been listed as Forsythiae Fructus in the Chinese Pharmacopoeia, previous studies have found that the harvest time could affect the qualitative profile and relative contents of compounds in Forsythiae Fructus, which might further influence its pharmacological activities. For instance, Jia et al. [6] found a higher antioxidant activity for UFF than for RFF, but no significant difference in antibacterial activities was shown, indicating the differences between UFF and RFF should be considered for their clinical efficacies.
Up to now, a large number of studies focusing on the chemical compounds, pharmacology and quantitative analysis of Forsythiae Fructus have been published. In 2012, a mini review [13] naming chemical constituents of plants from the genus Forsythia reported only one hundred and twenty-one chemical constituents in Forsythiae Fructus, which was much less than those we summarize herein (three hundred and twenty-one compounds). New pharmacological activities and quality control methods have been discovered, so a systematic and updated review is very necessary, as well as a comprehensive comparison between UFF and RFF. Therefore, this review aims to extensively summarize the phytochemistry, quality control data, pharmacology and pharmacokinetics of Forsythiae Fructus, thus providing evidence for further research and clinical applications of this plant.

Phytochemistry
With the analysis technologies of nuclear magnetic resonance (NMR), liquid chromatography-mass spectrometry (LC-MS), gas chromatography-mass spectrometry (GC-MS) and infrared spectroscopy (IR), a total of three hundred and twenty-one compounds were identified from Forsythiae Fructus, including fifty-one phenylethanoid glycosides, fifty lignans, nineteen aliphatic alcohols with the C6-C2 skeleton, two iridoids, nineteen diterpenoids, twenty-seven triterpenoids, six sterols, nineteen flavonoids, fifty-two volatiles, seven alkaloids, twenty-eight organic acids, six amino acids, nine sugar derivatives, two allylbenzene glycosides and twenty-four others. Most of them were not mentioned whether obtained from UFF or RFF. The detailed information for these compounds is summarized in Table 1.

Lignans
The lignans are another major bioactive constituents in Forsythiae Fructus and their structures are shown in Figure 2.

Alkaloids
Alkaloids represent a relatively small class of compounds in Forsythiae Fructus. To date, seven alkaloids, namely rutaecarpine (246)

Alkaloids
Alkaloids represent a relatively small class of compounds in Forsythiae Fructus. To date, seven alkaloids, namely rutaecarpine (246)

Alkaloids
Alkaloids represent a relatively small class of compounds in Forsythiae Fructus. To date, seven alkaloids, namely rutaecarpine (246)
[88]  Moreover, total contents of flavonoids in the UFF were higher than in the RFF, while those of phenolic acids were on the contrary. Contents of the aliphatic acids and terpenoids were not significantly different between the UFF and the RFF. [58] α-pinene, Camphene, β-Pinene, Myrcene, p-Cymene, Limonene α-Terpineol

Pharmacology
Forsythiae Fructus has long been used in China, Korea, Japan and other Southeast Asian countries because of its various pharmacological effects. The bioactivities of the active constituents of Forsythiae Fructus, including phenylethanoid glycosides, lignans and flavonoids, have been studied, but these constituents also exhibit new pharmacological activities. The pharmacological effects of this herb are listed in Table 3. Table 3. Pharmacological effects of Forsythiae Fructus.

LPS-induced liver injury in rats Ethanol extract
The extract inhibited generation of ROS, MDA, TNF-α, IL-1β and IL-6 in serum and liver via activation of Nrf2-mediated antioxidation and inhibition of NF-κB-mediated inflammatory response. [92] LPS-stimulated RAW 264.7 cells Ethyl acetate fraction of the ethanol extract The extract at 12.5-200 µg/mL inhibited expression of COX-2, thus decreasing the levels of ROS, NO and PGE 2 does-dependently. [93]

LPS-stimulated BV-2 microglial cells Aqueous extract Forsythin
The extract at 1 µg/mL inhibited the MAPK pathway and down-regulated NO biosynthesis-related genes. Forsythin at 50-200 µg/mL significantly suppressed the production of NO and decreased iNOS and TRL4 protein expression in a dose dependent manner. [94,95] Soybean β-conglycinin-stimulated weaned piglets Methanol extract The methanol extract (100 mg/kg) reduced the levels of anaphylactic antibodies, mast cell degranulation, histamine release, T lymphocyte proliferation and IL-4 synthesis and improved intestinal microbial flora. Further study revealed that forsythoside A, phillyrin, pinoresinol and phylligenin may be the active constituents for the therapy of atopic dermatitis. [97] Carrageenan-induced rats Ethanol extract The extract (5 g/kg) alleviated carrageenan-induced paw edema in rats, probably by increasing the production of COX-2 and decreasing the expression of PGE 2 , PGD 2 , 6-keto-PGF1α and TXB 2 . [98] Xylene-stimulated mice Acetic acid-stimulated mice Carrageenan-induced rats Oleic acid-stimulated rats

Volatiles
Volatiles inhibited the ear-swelling induced by xylene at 0.12 and 0.24 mL/kg, withstood the hyperfunction of celiac capillary permeability induced by acetic acid at 0.24 mL/kg, alleviated rats paw edema induced by carrageenan at 0.12 and 0.24 mL/kg, inhibited pleuritis induced by carrageenan at 0.24 mL/kg and decreased acute lung injury induced by oleic acid at 0.12 and 0.24 mL/kg.

Antibacterial Activity
Escherichia coli (E. coli) Staphylococcus aureus (S. aureus) Essential oil The essential oil changed the permeability and integrity of the cell membrane, leading to leakage of nucleic acids and proteins with MIC values of 3.13 and 1.56 mg/mL for E. coli and S. aureus, respectively. [112] Pneumococcus, Escherichia coli (E. coli), S. aureus, Haemophilus influenza, a beta-group Streptococcus, Yersinia enterocxolitica, Klebsiella pneumonia, F's dysentery bacillus, Salmonella typhi, Pseudomonas aeruginosa

Essential oil
The essential oil showed antibacterial activity against these ten bacteria. Particularly, β-pinene and the oil after chromatography showed a better inhibitory effect on the other bacteria, except Yersinia enterocolitica and Klebsiella pneumonia. IBV-infected primary chicken embryo kidney cells Forsythoside A Forsythoside A pretreatment at a dose of 0.64 mM had a direct virucidal effect on IBV, but it had no effect on IBV-infected cells. [121]  Peroxynitrite-treated LLC-PK1 cell Phillygenin 8-Hydroxypinoresinol Phillygenin and 8-hydroxypinoresinol significantly decreased the leakage of lactate dehydrogenase (LDH) at 10 µM and even reverse the LDH release induced by 3-morpholinosydnonimine, an ONOO − generator, at 50 µM. [126] High-density lipoprotein Pinoresinol, Phillygenin, 8-Hydroxypinoresinol, 7 -Epi-8-Hydroxypinoresinol, Lariciresinol, Isolariciresinol, Olivil, Cedrusin The lignans inhibited the generation of thiobarbituric acid-reactive substances in a dose-dependent manner with IC 50 values from 8.5 to 18.7 µM and thermo-labile radical initiator-induced lipid peroxidation with IC 50 values from 12.1 to 51.1 µM. Among them, pinoresinol and lariciresinol also exerted an inhibitory effect against Cu 2 +-induced lipid peroxidation of HDL at a concentration of 3 µM. [32]

D-galactose induced aging mice Phillyrin
A decrease in weight gain rate, spleen index, SOD, GSH-Px and T-AOC activities in serum and liver tissue and an increase in the content of MDA and MAO-B activities in brain tissue were observed after injection of 15 or 45 mg/kg phillyrin. [127]

Weaned piglets Ethanol extract
Dietary supplementation (100 mg/kg) of Forsythiae Fructus ethanol extracts after fourteen days significantly increased glutathione peroxidase activities and serum complement 4 concentration and lowered serum endotoxin and MDA concentration. The oxidative injury disappeared after twenty-eight days. [128] Corticosterone-treated broilers Methanol extract Dietary supplementation (100 mg/kg) of Forsythiae Fructus methanol extract attenuated the decrease of the total antioxidant capacity and SOD activity and increase of serum MDA. [129] Arbor Acres broilers under high stocking density Methanol extract Treatment with Forsythiae Fructus methanol extract (100 mg/kg) increased serum T-AOC and SOD activity and reduced MDA expression. However, no significant differences were found in serum GSH-Px activity. Forsythoside A (60, 120 and 240 mg/kg) increased the activity of SOD, ChAT, and GSH-PX inordinately and decreased the content of MDA and NO by varying degrees in a dose-dependent manner. [132] SAMP8 mice Forsythoside A Oral administration of forsythoside A (60, 120 and 240 mg/kg) decreased the levels of IL-1β, NO, MDA and NE and increased the T-SOD and GSH-Px activities and the production of GLU and Ach. [133] Scopolamine-induced learning and memory impairment in mice Forsythoside A Forsythoside A (200 mg/kg) ameliorated scopolamine-induced learning and memory impairment by modulating AchE activity, cAMP expression and p-ERK production and protecting against oxidation. [134] Gerbils with transient cerebral global ischemia Forsythoside A Oral administration of forsythoside A (10 mg/kg) significantly increased the number of viable neurons and decreased degenerating neurons, activated glial cells and the expression of IL-1β and TNF-α, indicating the involvement of anti-inflammatory activities. [135] Aβ 25-35 oligomer-stimulated HT22 cells Forsythoside A Forsythoside A (25 µg/mL) significantly decreased production of NO to improve neuroinflammation in Aβ 25-35 oligomer-stimulated HT22 cells. [136]

Anti-tumor Activity
The murine melanoma B16-F10 cell line and C57BL/6 mice bearing melanoma Aqueous extract The aqueous extract inhibited proliferation and angiogenesis of cancer cells, which were closely related to the antioxidant and anti-inflammatory activities via the MAPKs/Nrf2/HO-1 pathway. [7] HeLa cells Aqueous extract  Phillyrin (5 and 10 g/kg) significantly inhibited the tumor size and tumor tissue density dose-dependently by decreasing the expression of VEGF and increasing the expression of endostatin. [142] Anti-tumor Activity

CCl 4 -induced toxicity in rats Phillygenin
Phillygenin at 0.15 and 0.5 mg/kg significantly decreased the levels of ALT, AST, total bilirubin, TNF-α and IL-8 in serum and the content of MDA in liver tissue. Meanwhile, it increased the activities of SOD, GSH-Px and GSH. [10] Bovine serum albumin-induced hepatic fibrosis in rats Forsythoside A Forsythoside A alleviated hepatic fibrosis at 0.1, 0.3 and 1.0 mg/kg by decreasing the hydroxyproline content and the levels of layer fibronectin, hyaluronic acid, IV-collagen and procollagen III. [144] Human normal liver cell lines LO2 Forsythin Forsythin reversed nuclear condensation and nuclear fragmentation and decreased expression of apoptosis related proteins (PARP and caspase 3) to prevent alcoholic liver injury does-dependently. [145] Rats with severe acute pancreatitis Aqueous extract The aqueous extract (1.25, 2.5 and 5 g/kg) significantly reduced the serum levels of amylase, ALT and TNF-α in a dose dependent manner and expression of NF-κB mRNA and Foxp3 mRNA in liver tissue. [146]

Cardiovascular Protective Effect
Streptozotocin-induced diabetic mice Ethyl acetate extract Oral administration of the extract (50, 100 and 200 mg/kg) after four weeks significantly decreased the levels of blood glucose, triglyceride, creatinine and so on and increased body weight, insulin secretion and glucose tolerance, which were related to inhibition of glucokinase, phosphorenolpyruvate carboxykinase, insulin-1, insulin-2 and duodenal homeobox factor-1, thus exhibiting antidiabetic and antihyperlipidemic activities. [147] SD rats with atherosclerosis Phillyrin Phillyrin (150 mg/kg) reduced the area of AS plaques and the contents of ICAM-1, VACM-1, IL-1, IL-6 and MDA and increased the contents of NO and SOD, probably by decreaseing expression of sodium hydrogen exchange protein 1 (NHE-1). [12] Rat aortic rings Forsythoside A Forsythoside A inhibited norepinephrine-stimulated vasocontraction by decreasing calcium influx from the extracellular space. [148]  Cisplatin-treated mice Aqueous decoction The aqueous decoction reduced the contents of serum gastrin and promoted gastrointestinal movement at 3, 6 and 12 g/kg, indicating its anti-vomiting activity. [9] HepG2 cells Phillyrin Phillyrin at the concentration of 1, 2.5 and 5 µM induced phosphorylation of LKB1 and activated AMPK, thus reducing expression of SREBP-1c and fatty acid synthase and avoiding accumulation of lipid. [149] TNF-α-stimulated 3T3-L1 adipocytes Phillyrin Phillyrin (40 µM) suppressed activation of I kappaB kinase and N-terminal kinase to attenuate TNF-α-mediated insulin resistance and lipolytic acceleration. [150] Obese C57BL/6J mice Phillyrin Treatment with phillyrin (15 and 45 mg/kg) significantly decreased body weight, the serum levels of TNF-α and leptin and increased expression of PPAR-β/δ, ANGPTL4 and p-AMPK-α. [151] Dihydrotestosterone-stimulated mice Forsythoside A Forsythoside A suppressed apoptosis of hair cells by reducing expression of caspase-9 by 40%, caspase-3 by 53% and increasing the Bcl-2/Bax ratio by 60%. It also retarded the entry into the catagen phase and reduced the expression of TGF-β2 by 75%. [152] Mice with endotoxemia Forsythoside A Forsythoside A (80 mg/kg) enhanced the immune function of mice with endotoxemia, which may be associated with the inhibition of TNF-α and IL-10 secretion and the gene expression of Foxp3. [153] Yeast-stimulated C57BL/6 mice Forsythoside A Forsythoside A (4 and 8 mg/kg) significantly decreased the temperature of mice by up-regulating expression of TRPA 1 in the paraventricular nuclei (PN), supraoptic nucleus (SO) and dorsal root ganglion (DRG). [154] Caco-2 cells Forsythoside A Forsythoside A inhibited P-gp ATPase activity to influence the efflux of drugs. [155]

Neuroprotective Effect
The neuroprotective effect is a newly established research direction for Forsythiae Fructus. Zhang et al. [131] found that the Forsythiae Fructus ethanol extract reduced rotenone toxicity and protected PC12 cells. Further in vivo study demonstrated that Forsythiae Fructus (50 and 200 mg/kg) exhibited a protective effect in rotenone-stimulated rats through down-regulating inflammatory and oxidation factors. Forsythoside A (1) was the main compound with neuroprotective effects reported in Forsythiae Fructus. It ameliorated the physiology of senescence-accelerated mouse prone (SAMP8) mice and scopolamine-induced memory deficit mice, with significant increase in total superoxide dismutase (T-SOD), choline acetyl transferase (ChAT) and GSH-Px activities; significant decrease in MDA and NO levels; inhibition of AchE activity and increase of p-ERK expression, indicating that its mechanism might be to regulate the cholinergic system and antioxygenation [132][133][134]. Furthermore, cognitive functions of gerbils with transient cerebral global ischemia were ameliorated after treatment with forsythoside A (1) at 10 mg/kg due to the inhibition of activated microglia and astrocytes [135]. In vitro, forsythoside A (1) significantly inhibited the cell apoptosis induced by Aβ [25][26][27][28][29][30][31][32][33][34][35] in PC12 and HT22 cells, which are closely related to Alzheimer's disease [136,137]. Moreover, phillyrin (60) protected SH-SY5Y neuroblastoma cells against MPP + [138], while forsythoneoside B (191) and forsythoneoside D (193) at 0.1 µM significantly inhibited PC12 cell damage induced by rotenone and increased cell viability [11], indicating their potential toward Parkinson's disease.

Hepatoprotective Effect
The active compound phillygenin (59) in Forsythiae Fructus has been shown to exhibit a protective effect against acute liver injury induced by CCl 4 in rats at the dosages of 0.05, 0.15, 0.5 mg/kg. It increased the activities of SOD, GSH-Px and GSH; decreased MDA and reduced the levels of TNF-α and IL-8 in liver tissue [10]. Wang et al. [144] reported that Lian qiao gan yuan (phillygenin) protected against hepatic fibrosis induced by bovine serum albumin in rats. However, the author considered forsythoside A (1) to be Lian qiao gan yuan in Chinese. Forsythin (60) showed a protective capability against alcohol-induced liver injury by suppressing expression of apoptosis factors (PARP and caspase 3) [145]. Moreover, the aqueous extract of Forsythiae Fructus excerted a hepatoprotective effect in liver injured rats with acute pancreatitis at three dosages of 1.25, 2.5 and 5.0 g/kg. This was associated with inhibition of mRNA expression of NF-κB and Foxp3, subsequently reducing activation of the NF-κB signaling pathway, which plays an important role in the pathogenesis of severe acute pancreatitis [146].

Cardiovascular Protective Effect
The cardiovascular protective activity of Forsythiae Fructus and its compounds has been reported in recent years. In an in vivo study, oral administration of ethyl acetate extract at dosages of 50, 100 and 200 mg/kg improved pathological damage and increased the serum level of insulin as well as expression of pancreatic function genes (PDX-1, INS-1 and INS-2) in streptozotocin-induced diabetic mice, indicating its potency as an antihyperglycemic and antihyperlipidemic agent [147]. Treatment with 150 mg/kg phillyrin (60) for ten weeks in an atherosclerosis (AS) model noticeably reduced the area of AS plaques, improved the function of arterial condensation and inhibited expression of sodium hydrogen exchange protein 1 (NHE-1), intercellular cell adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VACM-1), IL-1 and IL-6 [12]. Moreover, forsythoside A (1) exhibited a vasorelaxant effect against norepinephrine-stimulated vasocontraction in rats by decreasing calcium influx from the extracellular space [148].

Others
The aqueous extract of Forsythiae Fructus reduced the serum gastrin content and promoted gastrointestinal movement, demonstrating an anti-vomiting effect in mice exposed to chemotherapy [9]. Phillyrin (60) was shown to exert a remarkable antiobesity effect in high glucose-induced lipid accumulation in HepG2 cells and 3T3-L1 adipocytes, as well as in obese mice [149][150][151]. The mechanism of action was possibly due to inducing the liver kinase B1 (LKB1) phosphorylation and activating AMP-activated protein kinase (AMPK), thus reducing expression of sterol regulatory element-binding protein-1c (SREBP-1c) and fatty acid synthase. Interestingly, forsythoside A (1) exhibited antiandrogenic alopecia activity in dihydrotestosterone-stimulated mice by suppressing the apoptosis of hair cells [152]. Forsythoside A (1) also exhibited an immune regulation effect in endotoxemia mice by down-regulating mRNA expression of Foxp3 and decreasing the secretion of IL-10 and TNF-α [153]. Moreover, in yeast-stimulated pyrexia mice, forsythoside A (1) increased the expression of temperature-sensitive transient receptor potential A1 (TRPA1), thereby taking antipyretic effect [154]. Furthermore, a study demonstrated that forsythoside A inhibited P-gp ATPase activity, thus influencing the efflux of drugs [155].

Pharmacokinetics
Pharmacokinetic studies have provided a scientific basis for the clinical application of Forsythiae Fructus and the data were presented in Table 4. When Sprague Dawley (SD) rats were orally administrated UFF and RFF extract, the main active compounds of forsythoside A (1), phillyrin (60), rutin (175), quercetin (177) and isorhamnetin (180) showed very different pharmacokinetic parameters, including C max , AUC 0-24 h and T max . Generally, the AUC 0-24 h and C max were much higher in the UFF group than in the RFF group. The absorption was faster after oral administration of UFF, as reflected by T max , whereas quercetin (177) and isorhamnetin (180) couldn't be detected after RFF treatment. The pharmacokinetic properties after multiple-dose treatment had significantly increased than those after single-dose treatment, indicating that the harvest times affected the contents and bioavailability of active compounds in Forsythiae Fructus [59]. Liu et al. [31] developed an HPLC-ESI-MS/MS method for the quantification of matairesinol-4 -O-glucoside (58), phillygenin (59), phillyrin (60), (+)-pinoresinol-β-D-glucoside (69) and hyperin (182) in rat bile after oral administration of 75% methanol extract of Forsythiae Fructus, revealing that bile was the major pathway for the excretion of lignans in Forsythiae Fructus. Forsythoside A (1), phillygenin (59) and phillyrin (60) were the three most studied compounds in Forsythiae Fructus for pharmacokinetics. After oral administration of forsythoside A, the absorption was fast with a T max of 20 min, but the bioavailability was only 0.5% [158]. Furthermore, Chen et al. [159] revealed that most of forsythoside A (1) was excreted through bile due to the bile-to-blood distribution ratio was 0.32 ± 0.06 after intravenous administration. Phillyrin (60) was absorbed into plasma through passive diffusion and could be influenced by P-gp, thus exhibiting a low bioavailability [160]. After oral administration, a total of thirty-four metabolites of phillyrin (60) were found in rat bile, urine and feces by UPLC-Q-TOF-MS, providing a basis for the pharmacological activities of phillyrin in vivo, and the results also revealed that deglucosidation was the main metabolic reaction for phillyrin [161]. Absorption of phillygenin (59) was linear at three dosages of 1.4, 2.8, and 5.6 mg/kg, but it showed a rapid elimination rate of approximately 6 min [162]. In addition, forsythoside A induced the activities of CYP1A2 and CYP2C11, while phillyrin induced the activities of CYP1A2 and CYP2D1, which provided very useful information about interactions in the combination drug therapy [163].  The average percentages of (+)-pinoresinol-β-D-glucoside, matairesinol-4 -O-glucoside, hyperin, phillyrin and hillygenin excreted in the bile over the dose administered (12 mL/kg body weight) were 0.002%, 0.234%, 0.116%, 0.288%, and 12.700%, respectively. Hyperin was found in plasma, urine and excrement of rat while the others were detected only in bile, indicating lignans of Forsythiae Fructus were excreted mainly via bile. [31] Forsythoside A LC-MS/MS Forsythoside A was rapidly absorbed into the blood with a T max of 20.0 min after oral (100 mg/kg) administration, but the C max was only 122.2 ± 45.4 ng/mL, indicating a quite low absolute bioavailability with a value of 0.5%. [158] Forsythoside A Microdialysis coupled with HPLC Forsythoside A went through hepatobiliary excretion and the bile-to-blood distribution ratio (AUC bile /AUC blood ) was 0.32 ± 0.06 after the intravenous administration of 50 mg/kg. [159] Phillyrin UPLC-Q-TOF-MS A total of thirty-four metabolites of phillyrin were detected in rat bile, urine and feces and M26 was the major one. Phillyrin mainly went through hydrolysis, oxidation and sulfation to transform into the effective forms in vivo. [161] Phillygenin HPLC The elimination half-time (t 1/2z ) of phillygenin after intravenous administration of 1.4, 2.8 and 5.6 mg/kg were 6.02 ± 1.66, 5.62 ± 0.35 and 5.79 ± 0.81 min, respectively and the AUC (0-∞) were 166.29 ± 18.01, 242.40 ± 7.12 and 332.48 ± 23.98 mg/L min, respectively. All these results suggested the pharmacokinetics of phillygenin followed first-order kinetics. [162] Phillyrin and Forsythoside A UHPLC-MS-MS

Conclusions
In Asia, Forsythiae Fructus is widely used in the clinic as a single drug or compound prescription. Modern pharmacology showed that it has a variety of bioactivities, including anti-inflammatory, antibacterial, antiviral, antioxidant, antitumor, antidiabetic, antihyperlipidemic, antiandrogenic alopecia, antivomiting, antiaging and anti-obesity activities, as well as neuroprotective, hepatoprotective and vasorelaxant effects. In the past few years, many sensitive analysis technologies have been used for research of this herb. Three hundred and twenty-one compounds have been identified, including fifty-one phenylethanoid glycosides, fifty lignans, nineteen aliphatic alcohols with the C6-C2 skeleton, two iridoids, nineteen diterpenoids, twenty-seven triterpenoids, six sterols, nineteen flavonoids, fifty-two volatiles, seven alkaloids, twenty-eight organic acids, six amino acids, nine sugar derivatives, two allylbenzene glycosides and twenty-four others. Among them, forty-five were from the UFF, twenty-two were from the RFF, twenty-one were from the UFF and RFF and the remaining compounds have not been mentioned from UFF or RFF.
Moreover, phenylethanoid glycosides (forsythoside A), lignans (phillyrin, arctiin) and flavonoids (rutin, forsythoneoside D) are the major constituents and exerted various bioactivities, such as anti-inflammatory, antiviral, and neuroprotective effects. Additionally, the different harvest times not only affected the contents but also the bioavailabilities of the active compounds, especially forsythoside A and phillyrin. However, few studies have reported the difference in pharmacological activities between UFF and RFF. Altogether, this review extensively summarized the phytochemistry, quality control, pharmacology and pharmacokinetics of Forsythiae Fructus, especially the UFF and RFF, and provided evidence for its further research and clinical applications.