Forsythia

Scientific Name(s): Forsythia suspensa (Thunb.) Vahl. Family: Oleaceae (olives)

Common Name(s): Forsythia , golden bells , lian qiao , weeping forsythia

Uses

Forsythia has been used for treatment of bacterial infections and upper respiratory tract infections, although the clinical evidence supporting its use is limited.

Dosing

There are no recent clinical studies of forsythia to provide a basis for dosage recommendations.

Contraindications

Contraindications have not yet been identified.

Pregnancy/Lactation

Documented adverse effects. Uterine stimulant, emmenagogue. Avoid use.

Interactions

None well documented.

Adverse Reactions

Forsythia is contraindicated in pregnancy.

Toxicology

Forsythia has minimal potential for toxicity.

Botany

F. suspensa is an attractive deciduous shrub native to China. It is often grown ornamentally in the United States for its bright yellow flowers that appear in early spring. There are numerous horticultural varieties that are vegetatively propagated. The Chinese drug is obtained in the fall from the ripe fruits of the cultivated plant. The related species F. viridissima and F. koreana also are used medicinally.

History

Forsythia fruits are widely used in Chinese traditional medicine for antipyretic and anti-inflammatory activity in the treatment of bacterial infections and upper respiratory ailments. They are commonly combined with honeysuckle flower ( Lonicera ) and other ingredients. Forsythia fruits are also reputedly used as a diuretic and as a cardiovascular tonic.

Chemistry

Lignans, such as phylligenin and pinoresinol, and their glucosides are major constituents of F. suspensa fruits, while the other species contain related compounds. 1 Caffeic acid glycosides with variation in the number of sugars include forsythiaside, 2 suspensaside, 3 and a number of forsythosides. 4 The reduced cyclohexylethane derivatives rengyol, rengyoxide, and rengyolone 5 and their glycosides (rengyosides A-C, 6 and forsythensides A and B 7 ) have been reported. The distribution of various phenolics among 7 different species of forsythia in leaves and fruits has been studied. 8 , 9 Rutin is the major flavonoid of all 7 forsythia species. 9 Caffeic ester glycosides from related genera of the Oleaceae have been compared. 10 Several triterpenes have been isolated from the fruits as well. 11 An HPLC assay for major forsythia phenolics has been published. 12 The essential oil composition of the fruits has been studied. 13

Uses and Pharmacology

Treatment of bacterial and upper respiratory tract infections
Animal data

The caffeic acid glycosides forsythoside A, C (=suspensaside), and D have been found to have antibiotic activity against Staphylococcus aureus , 3 , 4 , 14 although the activity was relatively weak. The anti-inflammatory activity of the extract in 1 study 15 was tracked to a dammarane triterpene; 11 however, other studies have found the caffeoyl glycosides to inhibit arachidonate metabolism in leukocytes. 16 Similarly, the structure-activity relations for the ability of caffeoyl glycosides to inhibit formyl-methionyl-leucyl-phenylalanine stimulated leukocytes in an antioxidant model have been delineated. 17 The ability of the butanol extract of F. koreana to inhibit nitric oxide production in a murine macrophage cell line also may be a related phenomenon. 18

The bioactivity of the lignan constituents also may play an important role. Pinoresinol and its glucoside were shown to inhibit cyclic adenosine monophosphate phosphodiesterase, while phillyrin and phillygenin were inactive. 1 However, phillygenin was found in a separate study to inhibit platelet-activating factor binding at low micromolar concentrations. 19 Several tetrahydrofuran lignans from forsythia were recently shown to be active inhibitors of LDL oxidation. 20

Clinical data

A clinical evaluation of a multiherbal mixture containing forsythia fruits in the treatment of respiratory infections was published. The herbal extract was administered IV in cases of severe disease, with the authors claiming efficacy equivalent to standard antibiotic treatment. 21

Other uses

The flavonoid rutin was found to be the active anti-emetic constituent of forsythia fruits using an experimental chicken model of emesis. 22

Dosage

There are no recent clinical studies of forsythia to provide a basis for dosage recommendations.

Pregnancy/Lactation

Documented adverse effects. Uterine stimulant, emmenagogue. Avoid use. 23

Interactions

None well documented.

Adverse Reactions

Use during pregnancy is strictly contraindicated because of its emmenagogue/uterine stimulant properties.

Toxicology

F. suspensa extracts were not mutagenic in Ames tests; however, the incidence of chromosomal aberrations and micronucleated polychromatic erythrocytes in bone marrow of treated mice were somewhat elevated. 24

Bibliography

1. Nikaido T, et al. Inhibition of cyclic AMP phosphodiesterase by lignans. Chem Pharm Bull . 1981;29:3586.
2. Nishibe S, et al. The structure of forsythiaside isolated from Forsythia suspensa . Chem Pharm Bull . 1982;30:1048.
3. Nishibe S, et al. Studies on the Chinese crude drug “Forsythiae Fructus.” VI. The structure and antibacterial activity of suspensaside isolated from Forsythia suspensa . Chem Pharm Bull . 1982;30:4548.
4. Endo K, et al. Validity of Oriental medicine, part 44. Structures of forsythoside C and D, antibacterial principles of Forsythia suspensa fruits. Heterocycles . 1982;19:2033.
5. Endo K, et al. Structures of rengyol, rengyoxide and rengyolone, new cyclohexylethane derivatives from Forsythia suspensa . Can J Chem . 1984;62:2011.
6. Seya K, et al. Structures of rengyosides A, B and C, three glucosides of Forsythia suspensa fruits. Phytochemistry . 1989;28:1495.
7. Ming D, et al. New quinoid glycosides from Forsythia suspensa . J Nat Prod . 1998;61:377.
8. Kitagawa S, et al. Phenolic compounds from forsythia leaves. Phytochemistry . 1984;23:1635.
9. Kitagawa S, et al. Phenolic compounds from forsythia leaves II. Chem Pharm Bull . 1988;36:3667.
10. Andary C, et al. Caffeic glycoside esters from Jasminum nudiflorum and some related species. Phytochemistry . 1992;31:885.
11. Ozaki Y, et al. Antiinflammatory effect of Forsythia suspensa Vahl. and its active principle. Biol Pharm Bull . 2000;23:365.
12. Cui Y, et al. [HPLC analysis of the active ingredients of Forsythia suspensa ]. Yao Hsueh Hsueh Pao . 1992;27:603.
13. Xu Z, et al. Analysis of constituents of essential oil from the Forsythia suspensa (Thunb.) Vahl. Natural Product Res & Dev . 1994;6:14.
14. Endo K, et al. Structure of forsythoside A, an antibacterial principle of Forsythia suspensa leaves. Heterocycles . 1981;16:1311.
15. Ozaki Y, et al. Antiinflammatory effect of Forsythia suspensa Vahl. and its active fraction. Biol Pharm Bull . 1997;20:861.
16. Kimura Y, et al. Effects of caffeoylglycosides on arachidonate metabolism in leukocytes. Planta Med . 1987;53:148.
17. Heilmann J, et al. Radical scavenger activity of phenylethanoid glycosides in FMLP stimulated human polymorphonuclear leukocytes: Structure-activity relationships. Planta Med . 2000;66:746.
18. Kim N, et al. Inhibitory effects of butanol fraction of the aqueous extract of Forsythia koreana on the nitric oxide production by murine macrophage-like RAW 264.7 cells. J Ethnopharmacol . 2000;73:323.
19. Iwakami S, et al. Platelet activating factor (PAF) antagonists contained in medicinal plants: lignans and sesquiterpenes. Chem Pharm Bull . 1992;40:1196.
20. Chen C, et al. Inhibition of low density lipoprotein oxidation by tetrahydrofurofuran lignans from Forsythia suspensa and Magnolia coco . Planta Med . 1999;65:709.
21. Houghton P, et al. A clinical evaluation of the Chinese herbal mixture `Aden-I' for treating respiratory infections. Phytotherapy Res . 1993;7:384.
22. Yang Y, et al. Novel experimental model using free radical-induced emesis for surveying anti-emetic compounds from natural sources. Planta Med 1999;65:574.
23. McGuffin M, Hobbs C, Upton R, Goldberg A, eds. American Herbal Products Association's Botanical Safety Handbook . Boca Raton, FL: CRC Press;1997.
24. Yin X, et al. A study on the mutagenicity of 102 raw pharmaceuticals used in Chinese traditional medicine. Mutat Res . 1991;260:73.

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