Benefits
Traditional use as a diuretic herb
Cleavers infusions are used in herbal practice as a diuretic and tonic, and the herb has also been used for bloating, lymph swellings and wounds. No published study measuring urine output or fluid balance in people taking cleavers was found, so the diuretic reputation rests on tradition, not trial data.
Lymphocyte activity in laboratory tests
A cleavers infusion, its fractions and ethanol extracts increased the transformation (activation) of lymphocytes, a type of white blood cell, in test tubes. Activating cells in a dish is not the same as lymph flow or lymphatic drainage, and no study has tested an immune outcome in people taking cleavers.
Immune measures in mice given injected extract
In mice whose immune systems were suppressed with the drug cyclophosphamide, a cleavers water extract injected into the abdomen (intraperitoneally) once daily for 3 days, with three mice per group, raised spleen weight, spleen cell proliferation and natural killer cell activity. The extract was injected, not swallowed, and this has not been tested in people.
Liver markers in a rat acetaminophen model
Rats fed cleavers extract (250 or 500 mg/kg) for 5 days before a toxic dose of acetaminophen had less liver tissue damage and lower ALT, AST and bilirubin than rats given acetaminophen alone. This is one animal study of an overdose model and does not show a liver benefit in people.
Mechanism of action
Iridoid glycosides
Iridoids are a main compound group in cleavers: asperulosidic acid was the most abundant compound in Estonian cleavers herb, and infusions are rich in monotropein and desacetylasperulosidic acid. In mouse macrophage cells, asperuloside and asperulosidic acid from another Rubiaceae herb lowered nitric oxide, TNF-α and IL-6 by suppressing NF-κB and MAPK signaling.
Asperuloside in preclinical research
A systematic review of asperuloside, an iridoid common in the Rubiaceae family, describes anti-inflammatory, antioxidant and anti-obesity effects in cell and animal models but found no clinical trial in people. None of the studies cited here measured how much asperuloside a cleavers tea supplies.
Phenolic acids and flavonoids
Cleavers contains caffeoylquinic (chlorogenic) acids and flavonoids such as rutin and quercetin glycosides. In chemical assays, radical scavenging tracked phenolic and flavonoid content, but absorption and effects of these compounds after drinking cleavers were not measured in any study cited here.
Clinical trials
Animal study: Wistar rats received cleavers extract by mouth at 250 or 500 mg/kg body weight for 5 days, then a toxic oral dose of acetaminophen (1500 mg/kg) on day 6; liver blood tests, liver tissue and behavior were assessed. (Sahin et al. 2022, Chem Biol Interact)
Wistar rats; no human participants.
Pretreated rats had less liver necrosis and lower ALT, AST and bilirubin than rats given acetaminophen alone, and showed an anxiolytic-like effect in behavior tests; short-term memory did not change in any group. The authors judged the effect on hepatic encephalopathy limited. Not tested in people.
Animal study: male BALB/c mice received one injection of cyclophosphamide, then a cleavers water extract (5, 50 or 500 micrograms per mouse) injected into the abdomen (intraperitoneally) once daily for 3 days; three mice per group. (Lee et al. 2024, Nutrients)
Male BALB/c mice, three per group in five groups (15 total); no human participants.
Extract groups showed dose-related increases in spleen weight and spleen cell proliferation, higher natural killer cell activity at the two higher doses, and higher IL-6, TNF-α and IFN-γ from stimulated spleen cells compared with cyclophosphamide alone. The extract was injected, not given by mouth, and the groups were very small; the authors named administration by injection rather than longer-term administration as the main limitation.
Laboratory study: a raw cleavers infusion and its polyphenol, polysaccharide and pectin fractions were profiled by UHPLC-MS and tested in the lymphocyte blast transformation test and in chemical radical-scavenging assays. (Ilina et al. 2020, Molecules)
No human or animal participants; isolated lymphocytes and chemical assays.
The infusion and its fractions significantly stimulated lymphocyte transformation and scavenged DPPH, nitric oxide and hydrogen peroxide; stimulation was lower at the highest concentration tested (500 µg/mL). The main iridoids were monotropein and desacetylasperulosidic acid. The authors linked the results to topical use for skin infections and wounds, not to oral use.
Laboratory study: a hydroalcoholic whole-plant extract was fingerprinted by HPTLC and tested for antibacterial and antioxidant activity, cell toxicity and scratch-wound closure. (Beirami et al. 2024, BMC Complement Med Ther)
No human or animal participants; human umbilical vein endothelial cells, normal human dermal fibroblasts and bacterial cultures.
The extract was not toxic to either cell line, increased cell viability with dose, and improved cell migration and closure in the scratch assay. S. aureus was more susceptible than E. coli or S. epidermidis, and DPPH antioxidant activity was comparable to ascorbic acid. The authors called for animal studies as the next step.