A review of research on coumarins from Radix Glehniae

Lili Wang ,Zhong Yuan

a Medical and Nursing Branch,Panjin Vocational and Technical College,Panjin 124000,PR China;

b School of Traditional Chinese Materia Medica,Shenyang Pharmaceutical University,Shenyang 110016,PR China

Abstract Radix Glehniae,witha wide range of chemical components of various pharmacological effects,is widely used in the prevention and treatment of various diseases in clinical practice.It has a broad prospect of development and application.Coumarin,as one of its major active components,also displays good biological activities for analgesia and sedation,antibacteria,antivirus,anti HIV,anti-inflammation,anti-tumor,anti mutation,tyrosinase inhibition,vasodilation and blood pressure reduction.The aim of the present review is to discuss the studies on coumarin components,content determination,pharmacological activities,processing methods and provide a guide for the further development and utilization of Radix Glehniae.

Key words:Radix Glehniae; coumarin; content determination; pharmacological activity; processing method

1 Introduction

Radix Glehniaeis the dry root ofGlehnia littoralisfr.SchmidtexMiq,a plant ofUmbelliferae.It is mainly produced in Shandong,Hebei,Liaoning,and Inner Mongolia.Laiyang in Shandong Province is its main producing area,so it is also called Laiyangshen.Radix Glehniaeis sweet,slightly bitter,and slightly cold,with meridian tropism in lung and stomach.It has the function of nourishing Yin,moistening the lung,benefiting the stomach and promoting body fluid.It is used for treating lung heat,cough,hemoptysis,thermal burn and thirst [1].

There are many kinds of chemical components inRadix Glehniae,such as coumarins,polyacetylenes,lignans,flavonoids,polysaccharides and so on.As one of the main effective components,coumarins were reported to display many biological activities,in modern pharmacological research,for analgesia and sedation,antibacteria,antivirus,anti HIV,anti-inflammation,anti-tumor,anti mutation and many others [2].The present study reviewed studies on the chemical components,content determination,pharmacological activities and processing methods,in order to provide reference for the quality control and further development and utilization ofRadix Glehniae.

2 Chemical components

Coumarins refer to theO-hydroxycinnamic acid lactones with the basic skeleton of benzoα-pyranone parent nucleus,some of which have sweet smell.They are widely found in higher plants such asUmbelliferaeandLeguminosae.There are various kinds of coumarins extracted fromRadix Glehniae,whose parent nucleus structure is mainly 6,7-position acyclic coumarin and 6,7-position cyclized linear coumarin.Coumarin glycosides are mainly glucoside and gentian diglucoside.

Up to now,there are 38 kinds of coumarins and coumarin glycosides isolated and extracted fromRadix Glehniae[3-7],they are psoralen (1),bergapten (2),isoimperatorin (3),imperatorin (4),bergaptin (5),xanthotoxin (6),8-geranyloxypsoralen(7),cnidilin (8),xanthotoxol (9),alloisoimperatorin(10),8-(1,1-dimethylallyl)-5-hydroxypsorolen (11),bergaptol 5-O-β-D-glucopyranoside (12),xanthotoxol 8-O-β-D-glucopyranoside (13),bergaptolO-β-D-glucopyranoside(14),isopimpinellin (15),8-[(2E)-6-oxo-3,7-dimethyloct-2-enyloxy]psoralen (16),scopoletin (17),6-(3,3-dimethylallyl)-7-hydroxy-coumarin (18),7-O-(3,3-dimethylallyl)-scopoletin (19),esculetin(20),umbelliferone (21),(R)-peucedanol-3'-O-β-D-glucopyranoside (22),(S)-peucedanol-3’-O-β-Dglucopyranoside (23),(S)-peucedanol-3’-O-β-Dapiofuranosyl-(1-6)-β-D-glucopyranoside (24),(S)-7-O-methypeucedanol-3’-O-β-D-glucopyranoside(25),(S)-7-O-methypeucedanol-3’-O-β-Dapiofuranosyl-(1-6)-β-D-glucopyranoside (26),(S)-peucedanol-7-O-β-D-glucopyranoside (27),marmesin (28),marmesinin (29),marmesinin 4’-Oβ-D-apiofuranosyl-(1-6)-β-D-glucopyranoside (30),oxymarmesin 5’-β-D-glucopyranosid (31),4”-hydroxyimperatorin 4”-β-D-glucopyranoside (32),5”-hydroxyimperatorin5”-β-D-glucopyranoside(33),8-[(2E,5E)-7-hydroxy-3,7-dimethylocta-2,5-dinyloxyl]psoralen (34),(3’R)-hydroxymarmesin 4’-O-β-D-glucopyranoside (35),osthenol7-β-D-glucopyranoside (36),umbelliferone 7-β-Dglucopyranoside (37),and bergaptol 5-O-β-D-gentiobioside (38).The structures of these compounds are listed in Table 1.

Continued table 1

3 Content determination

Although the content determination method ofRadix Glehniaeis not recorded inChinese Pharmacopoeia2015,it has developed in recent years.At present,the content determination methods include High Performance Liquid Chromatography(HPLC),ultraviolet spectrophotometry (US),etc.,and the content of imperatorin,isoimperatorin and psoralen inRadix Glehniaehas become an important index for scholars to evaluate the quality ofRadix Glehniae.

3.1 High performance liquid chromatography

Li et al.determined six coumarin components of psoralen,zanthoxylin,bergamot lactone,imperatorin,cnidilin and isoimperatorin fromRadix Glehniaeby HPLC [8].The results showed that the recovery rate of each component was between 92.8%and 99.2%,and theRSDvalue was less than 3.3%.Feng et al.used the same method to determine the four coumarin components of psoralen,zanthoxylin,imperatorin and isoimperatorin fromRadix Glehniae[9].The results showed that there were significant differences in the content of our coumarins inRadix Glehniaefrom different habitats.The content of psoralen and isoimperatorin from Liaoning was the highest,while the content of zanthoxylin and imperatorin produced in Chifeng was the highest,0.02153 mg/g and 0.02079 mg/g respectively.Liu et al.determined the content of coralline,imperatorin and isoimperatorin in the fruits,leaves and roots,peeled roots and root skins [10].The content of the three components in the fruit was the highest,0.6364 mg/g,and that in the peeled root was the lowest,only 0.0081 mg/g.The total content of coumarin,psoralen,imperatorin and isoimperatorin in the root decreased by 87.7%,100%,82.76% and 85.25%,respectively.Zhang et al.used HPLC method to determine the content of imperatorin and isoimperatorin inRadix Glehniaeof different years from Shandong Province [11].The average recovery of the two components was 98.23% and 96.94%,and theRSDvalue was 1.36%and 0.98%,respectively.In 2009,the highest content of imperatorin and isoimperatorin in the samples was 0.0212% and 0.01425% respectively,and the average content of the two coumarins was 0.03477%.The coumarins in different batches ofRadix Glehniaeshowed good quality stability.

3.2 Other methods

In addition to high performance liquid chromatography,Su et al.used ultraviolet spectrophotometry to determine the content of total coumarins with psoralen as the control group at the wavelength of 290 nm [12].The results showed that the concentration of psoralen in the range of 3.07-13.31μg/mL had a good linear relationship with the absorbance.The average recovery rate was 99.35%,and theRSDvalue was 1.59%.The content of coumarins in 22 batches ofRadix Glehniaesamples ranged from 1.18 mg/g to 2.73 mg/g.Liu et al.used micellar electrokinetic capillary electrophoresis to determine five coumarin components inRadix Glehniae,including psoralen,zanthoxylin,isoanisolactone,bergamot lactone and scopolactone [13].The results showed that the five components were separated within 7 min.The linear range was 9.91-82.6,37.2-162,2.23-18.6,2.73-22.3,2.89-20.1 mg/L,the average recovery was 98.9%,98.4%,101.3%,99.1%,98.0%respectively,and the total content of the five active compounds from Hebei was significantly higher than that from other origins.

4 Pharmacological activities

Radix Glehniaehas a wide range of pharmacological activities,including antitussive,expectorant,immune,anti-cancer,anti-mutation,and anti-oxidation [14].As one of its active ingredients,coumarins also have good biological activities.

4.1 Analgesia and sedation activities

As early as the end of the last century,Okuyama et al.found that the coumarin components in JapaneseRadix Glehniae,such as scopolamine,imperatorin,isoimperatorin,zanthoxylin,psoralen and bergamot lactone,had significant analgesic effect [15].When the dose of furacoumarin was 10 mg/kg body weight,it effectively prolonged the sleep time of mice.Wang et al.used hot plate method and acetic acid writhing method to study the analgesic effect of four coumarins inAngelica Dahurica,i.e.eugenol,isoimperatorin,oxyimperatorin hydrate and angelica sinensis [16].The results showed that the four coumarins could significantly reduce the writhing time of mice caused by acetic acid,imperatorin and isoimperatorin could significantly delay the emergence of writhing,imperatorin and isoimperatorin significantly inhibited the pain of mice caused by hot plate method,and the effect of imperatorin was significantly stronger than that of isoimperatorin.

4.2 Antibacterial,antiviral and anti HIV effects

Ban et al.found that imperatorin could inhibit not only the production of prostaglandins in peritoneal macrophages of rats,but also the production of cyclooxygenase-2 and prostaglandin E synthetase (mpees) [17].Lechner et al.found that imperatorin had antibacterial effect [18].Roselli et al.found that imperatorin had strong inhibitory activity on Gram-positive and Gram-negativebacteria(the minimum inhibitory concentration is 32-128 mg/mL) [19].Tsass et al.found that imperatorin had significant antiviral activity [20].Sancho et al.found that imperatorin could also inhibit the infection of T cells and HeLa cells with human immunodeficiency virus type I (HIV-1) encapsulated by vesicular stomatitis virus pseudotype or glycoprotein gpl60 [21].

4.3 Anti inflammatory effects

Lee et al.found that coumarin compounds inRadix Glehniaecould inhibit the production of NO in RAW 264.7 macrophages stimulated by lipopolysaccharide [22].Huang et al.found thatRadix Glehniaecould block the expression of inducible nitric oxide synthetase (iNOS)and cyclooxygenase-2 (COX-2) in RAW 264.7 macrophages [23].It could enhance the activities of catalase (CAT),superoxide dismutase (SOD)and glutathione peroxidase (GPX)in vivoand reduce the levels of NO,tumor necrosis factor and prostaglandin E2 in tissues,displaying significant anti-inflammatory activity.

4.4 Antitumor and antimutagenic effects

Kenney et al.found that isoimperatorin had obvious inhibitory effect on human central nervous system tumor cell line XF 498,human ovarian cancer cell line SK-OV-3 and human lung cancer cell line A 549 through the anti-tumor experimentin vitro[24].Dong et al.showed that Bergamot lactone inRadix Glehniaehad obvious inhibitory effect on hepatoma mother cellline [25].The inhibitory effect of bergamot lactone was compromised with the decrease of bergamot lactone concentration.When the concentration was 100.00 mg/L,bergamot lactone had a significant inhibitory effect on human gastric cancer cell line.Tan et al.showed that psoralen hada significant inhibitory effect on human breast cancer cell line MCF-7 (P＜ 0.05),and the half inhibitory concentration (IC50) was 15.160μg/mL [26],Sha et al.used MCF-7/ ADR as a model to screen breast cancer stem cells [27].The results showed that psoralen could block the proliferation of breast cancer stem cells and had a certain toxic effect on breast cancer stem cells.It could improve the expression of Topo IIα protein and mRNA in breast cancer stem cells,and increase the target of chemotherapy drugs.

4.5 Tyrosinase inhibitory activities

Tyrosinase is a key enzyme in melanin synthesis,and its overexpression can lead to the production of pigmentation diseases in human body [28].Duan et al.extracted tyrosinase inhibition fromRadix Glehniaewith hollow fiber immobilized enzyme method [29],and identified three coumarin components with known reference materials,namely psoralen,zanthoxylin and oxypreadolin.The tyrosine inhibitory activity of three coumarins was analyzed by microplate spectrophotometry.The inhibitory rate of psoralen,zanthoxylin and oxypreadolin increased with the increase of concentration,reaching nearly 50% at the concentration of 100μg/mL.

4.6 Vasodilation activities

Li et al.found that imperatorin and isoimperatorin had vasodilative effectsin vitrothrough rataortic ring model [30].Nie et al.found that imperatorin and isoimperatorin could dilate blood vessels in a dose-dependent manner,and the vasodilative effect of imperatorin was 4 times of that of isoimperatorin [31].Kong et al.measured the vasodilative effect of osthol,imperatorin and isoimperatorinin vitro[32].The results showed that the three components had vasodilative effect on KCl preshrinkingin vitrothoracic aortic rings,which was dose-dependent.

4.7 Antiallergic activities

Lin et al.found that imperatorin had antiallergic effect on asthmatic mice [33].Imperatorin inhibited the proliferation of activated Th2 cells and stimulated dendritic cells to induce and regulate the production of IL-10 by T cells.Xian et al.established a passive cutaneous anaphylaxis(PCA) model in rats [34].The results showed that imperatorin might inhibit histamine release and calcium influx in mast cells through PI3K/ Akt and NF -κ B signaling pathway,reduce the release level of TNF -α,IL-6 and other inflammatory factors,and block the activation of mast cells,so as to play an antiallergic role.

4.8 Effects on the nervous system

Research showed that imperatorin had certain effects on nervous system diseases,and it had certain therapeutic effects on neurodegenerative diseases such as Alzheimer’s disease,Parkinson’s disease,depression,anxiety and other neuropsychiatric disorders [35].Xiang et al.found that imperatorin might protect the nerves of Alzheimer’s disease (AD)rats induced by β amyloid protein (a β) and improve the cognitive impairment by inhibiting the apoptosis of mitochondria and the expression of p53,Bcl-2,Bax protein downstream and reducing oxidative stress damage of neurons in hippocampus [36].Zheng et al.showed that imperatorin could significantly reduce Chowdhury,the depressionlike behavior of offspring of SD rats induced by prenatal stress [37].Et et al.found that imperatorin could improve the memory impairment induced by lipopolysaccharide (LPS) in the hippocampus and cortex of adult male mice [38].He attributed this effect in part to the anti-inflammatory effect of imperatorin and the ability to reduce proinflammatory cytokines.

4.9 Treatment of osteoporosis

According to Jia et al.,imperatorin stimulated the activity of Saos-2 in osteoblasts through estrogen receptor pathway [39].Yan found that imperatorin activated Akt/ GSK3 β/ β -Catenin in bone marrow-derived mesenchymal stem cells [40].The signal pathway promoted osteogenesis and inhibited osteoclasts.The osteoporosis model was established by removing bilateral ovaries of rats.Oral administration of imperatorin showed that imperatorin promoted osteogenesis and inhibited osteoclasts.Tan et al.also showed that imperatorin restored the osteogenic ability of endogenous bone marrow mesenchymal stem cells by improving autophagy level and treating estrogen deficiency osteoporosis in rats [41].These results suggested that imperatorin might be a potential drug for the treatment of osteoporosis.

4.10 Photosensitization

Gao pointed out that under the ultraviolet light,imperatorin reacted with proteins to generate new substances [42].The possible mechanism of protein denaturation caused by the light was that the increase of the activity of imperatorin induced by the light made it react with the acid groups in the protein,resulting in the change of the protein structure and the phenomenon of peeling.It was proved that the carboxyl group would participate in the photosensitization of imperatorin reaction.Feng further found that imperatorin produced 4-hydroxy-2,4-diene-1-valeric acid,5-methyl-4-hydroxydihydrofuran and their dimer hydrate,imperatorin C11 [43].A new compound,8-benzoa-pyranone-2'-S-cysteine ethyl ether,was synthesized by the addition of alkene bond to isopentane derivatives and 8-hydroxy-benzopyranfurothiadimer.Under the catalysis of UV light,the new compound,8-benzo-a-pyranone-2’-S-cysteine ethyl ether,was obtained.

5 Processing method

According toChinese Pharmacopoeia2015,Radix Glehniaeis processed by being boiled in water,peeled and dried,or being washed and dryeddirectly [1].According to the literature,the content of coumarins inRadix Glehniaeis significantly reduced in the peeling process.Li et al.determined the content of three coumarins in different parts ofRadix Glehniaewith HPLC at the same time [44].The content of psoralen,imperatorin,isoimperatorin and the total content of the three coumarins were the highest in the cork,and the lowest in the xylem.The total content of three coumarins was 76 times that in the boiled and peeled.Xin et al.studied the change of coumarin content in the peeled and unpeeledRadix Glehniaein the same period [45].The results showed that the total content of coumarin decreased sharply after being boiled and peeled.Compared with the unpeeled root,the total content of coumarin,psoralen,imperatorin and isoimperatorin in the peeled root decreased by 87.7%,100%,82.76% and 85.25% respectively,resulting in a serious loss of coumarin content.Peeling had a greater impact on the chemical composition of the root.The loss of some effective components also made the quality control ofRadix Glehniaemore difficult [46].Niu fumigatedRadix Glehniaewith sulfur,and determined the content of five coumarins in fumigated and non-fumigatedRadix Glehniaewith HPLC [47].The results showed that the content of coumarins inRadix Glehniaewas significantly reduced after sulfur fumigation.When the author studied the chemical composition of the skin ofRadix Glehniaein 2009,the results also showed that the content of coumarins in the skin ofRadix Glehniaewas rich.The results aroused reflection on the traditional processing method,and justified the fact that the skin should be developed and utilized [48].

6 Conclusion

Radix Glehniaeis a traditional Chinese herbal medicine with abundant plant resources.Coumarin,as one of its main active components,has good biological and pharmacological activities.However,due to the low content of coumarins inRadix Glehniae,no content determination method with evaluation significance has been established.In order to improve the clinical application value ofRadix Glehniae,effective content determination methods should be established.In addition,the processing method in the origin ofRadix Glehniaeremains to be further studied.Based on the investigation of the main effective components,the optimal processing technology should be found to realize the rational utilization of the resources.