Benefits
A concentrated plant source of rutin
The dried flower buds are rich in rutin, a flavonoid that is quercetin bound to a sugar. In one analysis, buds held about 19 to 31% rutin by weight depending on the drying method, because an enzyme in the bud breaks rutin down to quercetin during slow drying. Rutin content can therefore vary between products.
Leg vein comfort, studied with rutin-derived rutosides
A large review of placebo-controlled trials in people with leg vein problems found that vein products (phlebotonics) as a group slightly reduced lower-leg swelling and ankle size but made little or no difference to quality of life. Half of the 56 trials tested rutosides, made from rutin. No similar trials have tested Sophora bud extract itself.
Leg swelling during long standing or long flights
In 12 healthy young men, hydroxyethylrutosides at 1,000 mg/day reduced the leg swelling caused by an hour of standing still. In 151 healthy travelers on 8 to 9 hour flights, 2 g/day for 3 days was linked to lower ankle swelling scores than placebo. Both studies used a rutin derivative, not a bud extract.
Traditional bowel comfort use, tested in one formula trial
The flowers and buds have a long history of use in Chinese medicine. In a placebo-controlled trial of a Sophora flower formula in patients with symptomatic hemorrhoids, symptoms improved in both groups and the difference was not statistically significant. The formula was well tolerated.
Skin and antioxidant measures in a four-plant blend
In 100 women working outdoors in a polluted city, 250 mg/day of a blend of rosemary, olive leaf, lemon verbena and Sophora extracts for 12 weeks improved saliva antioxidant capacity, skin moisture, elasticity and dark spots versus placebo. The study was part-funded by the blend's maker, and Sophora's own share of the effect is unknown.
Mechanism of action
Rutin is absorbed as quercetin
In healthy volunteers, no intact rutin was found in blood after rutin was swallowed; it appeared as quercetin and its conjugates. Overall absorption was similar to plain quercetin, but blood levels peaked later (about 6.5 to 7.5 hours) and varied widely between people.
Raw material for semi-synthetic rutosides
Troxerutin and oxerutins are mixtures of hydroxyethylrutosides made by chemically modifying rutin. The controlled leg vein trials described on this page used these derivatives rather than natural rutin. Because they are different molecules, their trial results describe the derivatives rather than the natural rutin in a bud extract.
Flavonoid activity in laboratory and animal studies
Flavonoids and isoflavonoids isolated from Sophora japonica show antioxidant, anti-inflammatory and hemostatic (blood-clotting) effects in cell and animal studies. These findings explain the traditional uses but have not been confirmed as effects in people taking the extract.
Clinical trials
Prospective, double-blind, randomized, placebo-controlled preliminary trial of a traditional Chinese Sophora flower formula. (Man et al. 2013, Afr J Tradit Complement Altern Med)
Patients with symptomatic hemorrhoids; group sizes are not reported in the abstract.
After 7 days, major symptoms improved in 87.0% on the formula and 81.8% on placebo. After 14 days, 78.2% on the formula were symptom-free, while 40.9% on placebo still had symptoms. The difference was not statistically significant, and symptoms improved in both groups as bowel habits improved and patients took sitz baths. The formula was reported as safe.
Randomized, double-blind, placebo-controlled, parallel-group study of a blend of rosemary, olive leaf, lemon verbena and Sophora japonica extracts (Sophora standardized to quercetin), 250 mg/day for 12 weeks; part-funded by the ingredient maker Monteloeder, which employs two authors. (Nobile et al. 2021, Food Nutr Res)
100 women (50 Asian, 50 Caucasian) working outdoors in Milan, Italy.
Compared with placebo, the blend improved saliva antioxidant capacity, skin lipid oxidation, moisture, water loss, elasticity, wrinkle depth and dark spots, some from week 2. No adverse reactions occurred. Sophora was one of four extracts, so its own contribution cannot be separated.
Cochrane systematic review and meta-analysis of randomized, double-blind, placebo-controlled trials of oral phlebotonics. (Martinez-Zapata et al. 2020, Cochrane Database Syst Rev)
56 trials with usable data (7,690 participants, mean age 50) with chronic venous insufficiency; 28 of the trials tested rutosides.
Phlebotonics as a group probably reduced lower-leg edema slightly (risk ratio 0.70) and ankle circumference (by about 4.3 mm), but made little or no difference to quality of life. Adverse events were slightly more common than on placebo, mostly digestive. The authors said results for specific product groups were limited.
Randomized trial of two maintenance doses of O-(beta-hydroxyethyl)-rutosides versus placebo after a 1-week placebo run-in and 3 weeks at 1,000 mg/day. The first author's listed affiliation is the company Zyma GmbH (Munich). (Rehn et al. 1993, Arzneimittelforschung)
12 healthy young men; leg volume increase after standing still for 1 hour, measured by water displacement.
Three weeks at 1,000 mg/day reduced the standing-induced swelling slightly (from about 87.8 to 85.2 units). After randomization, the effect faded on placebo within 5 to 6 weeks, held steady on 500 mg/day and kept improving on 1,000 mg/day (to 79.1 units). Both doses beat placebo. Very small study of a rutin derivative.
Randomized, placebo-controlled trial of Venoruton (hydroxyethylrutosides) 1 g twice daily for 3 days, starting 2 days before an 8 to 9 hour economy flight. (Belcaro et al. 2003, Clin Appl Thromb Hemost)
164 healthy travelers randomized; 151 completed.
After the flight, the composite swelling score averaged 6.7 in the placebo group and about 3 with rutosides, and clear swelling was seen in only 8% of the rutoside group. The trial tested a rutin derivative, not a Sophora extract.
Double-blind, randomized comparison of two rutin-derived products, 900 mg/day for 12 weeks plus 4 weeks of follow-up; no placebo arm. The first author's listed affiliation is the company Zyma GmbH (Munich). (Rehn et al. 1993, Arzneimittelforschung)
12 postmenopausal women with grade II chronic venous insufficiency.
Both products reduced leg volume and improved self-rated symptoms. The volume reduction was larger with oxerutins than with troxerutin (about 261 vs 73 ml x week), a significant difference. With 12 patients and no placebo, this shows that different rutin derivatives do not perform alike rather than proving either works.