Forsythia suspensa is a broad spectrum antibiotic, inhibiting many gram-positive and gram-negative bacteria. The MIC of the herb decoction against the following organisms in vitro were: Staphlococcus aureus 1:320, Diplococcus pneumoniae 1:160, alpha and beta hemolytic Streptococci 1:80. Shigella shigae, Shigella schmitziii, Pasteurella pestis and Mycobacterium tuberculosis var. hominis 1:640, Salmonella typhi and Vibrion cholerae 1:320, Salmonella partyphi 1:160, Shigella flexneri, Escherichia coli, Proteus vulgaris, and Corynebacterium diptheriae 1:180.

The chief antibacterial principle was reported to be forsythol: its MIC against Staphylococcus aureus and Shigella shigae in vitro were 1:5120 and 1:1280, respectively.

The alcohol extract of the herb at the concentration of 7.8 mg/ml was also lethal against leptospirae. In vitro experiments on chicken embryos proved that the herb inhibited Asian influenza type A and rhinovirus type 17. The MIC of the volatile oil of F.suspensa seed against Asian influenza virus type A Jingke 68-1 strain was 1:65,536. The aqueous extract of the herb also inhibited Nocardia asteroides.

In experiments on granulation cysts in rats it was shown that intraperitoneal injection of the 10% alcohol extract of the herb at the dose of 20ml/kg had a very marked anti exudation action and reducing action on capillary fragility at the inflammatory site.

A prominent anti-inflammatory action was exhibited by the compound F. suspensa injection including lowering of capillary permeability, reduction in induced paw swelling in rats and mice. It also enhanced the phagocytic function of the inflammatory cells in exudates of mice therefore enhancing resistance. F. suspensa has exhibited the actions of promoting formation of specific antibodies, increasing the phagocytic function of inflammatory cells and antagonism of histamine-induced inflammation.

The compound F. suspensa injection at the dose of 4g crude drug/kg had a marked antipyretic action: abating the typhoid vaccine-induced fever in rabbits and lowering the normal body onload="highlight();" temperature of rabbits.

Intravenous injection of the 100% F. suspensa injection at the dose of 0.25g/kg to anesthetized dogs produced an excellent diuretic action.

In adult cats with hypotensive shock caused by typhoid vaccine, the intravenous injection of 300% F.suspensa injection at 10g/kg produced initially a transient reduction of blood pressure, which was then followed by a marked rise. The range of elevation was 30-40mmHg and the action lasted for two hours. The antiendotoxic shock effect of F. suspensa may be related to vasodilation, increase in cardiac output and improvement in the microcirculation.

The injection produced a pressor action and stabilizing effect on the blood pressure: a mean rise of as high as 44mmHg was achieved. Continued elevation of blood pressure was achieved by further medication and fluid replenishment. The effect of the injection on blood pressure was probably due to its dual actions vasodilation which improved microcirculation, and vasoconstriction which maintained vascular tone and blood pressure. In cats with endotoxic shock, the injection improved myocardial contractility, increased cardiac output and venous return, thus correcting the low stroke volume and high peripheral resistance.

Experiments showed that the 1:1 herb decoction significantly alleviated hepatic degeneration and necrosis induced by carbon tetrachloride. It facilitated the recovery of the hepatocellular glycogen and RNA to almost normal levels and a reduction of SGPT.

From its applications to infectious conditions, F. suspensa is considered to be an effective bactericide. It has been ascertained that the decoction exhibits bactericidal effect on Bacillus typhi, B. paratyphi, Escherichia coli, B. diphtheria, B. cholerae, Staphylococci, Streptococci, and B. Tuberculosis. Extracts of the fruit Forsythia inhibited Staphylococcus flavus as a result of the bacterial properties of the forsythosides.

It has been reported that Fructus Forsythia exhibits antiviral actions for influenza.

The syrup of 1:1 F.suspensa fruit decoction 10ml three times daily by mouth for course of one month was reportedly effective lowering serum transaminase in acute viral hepatitis.

F. Suspensa decocted over low heat into 150 ml was given to 8 cases with edema, hypertension, the presence of albumin, granular casts, and red and white blood cells in the urine. After medication, complete subsidence of edema in 6 cases, marked improvement in 2 cases with obvious reduction of blood pressure, negative urinalysis in 6 cases and improvement in 2 cases.

Two cases of retinal hemorrhage in the macular region were treated with 30-35 g of the herb decocted over low heat, taken in 3 doses before meals. Marked absorption of the blood and some improvement of vision were achieved after 20-27 days of medication.

In another report, 1 case of thrombocytopenic purpura and 2 cases of anaphylactoid purpura were treated with 30g of the herb taken as a decoction for 2-7 days. The purpuric skin lesions completely disappeared, in addition, oral administration of the herb decoction suppressed vomiting due to drug reaction.

Except those noted, all references come from Weng Weiliang, et al., Clinical Chinese materia medica, Henan Science & Technology Press, 1998