Eucommia ulmoides (Tochu) and its extract geniposidic acid reduced blood pressure and improved renal hemodynamics

Tochu (Eucommia ulmoide) is a popular tree in Japan. Tochu tea is praised for its many health benefits and has been used in traditional medicine since ancient times. Extract from its leaves is consumed as tea and its hypotensive effect has also been described. In a study, it’s been found that another extract from its bark can also be used as antihypertensive. The Tochu leave is rich in important naturally occurring Iridoids such as (genisposidic acid, gensiposide, asperulosidic acid, diacetyl asperulosidic acid and asperuloside) and phenols (pyrogallol, protocathechuic acid and p-trans-coumaric acid).

Genisposide is a major iridoid in Gardenia jasminoides. It possesses anti-inflammatory and hypoglycemialc properties by stimulating the secretion of choleretic fluid. Its anti-inflammatory effect appears to mirror that of apocynin which is an extract from Picroria kuroria.

To this account, Professor Akihiro Tojo from the department of Nephrology and Hypertension, Dokkyo Medical University in Japan showed earlier the hypotensive effect of apocynin and its reduction of oxidative stress-induced renal damage in Kidney International 2005. Recently, the mechanism of antihypertensive effect of Tochu extracts was shown to be due to the inhibitory effect on NADPH oxidase and increased NO bioavailability. The original research article by Akira Ishimitsu, MD, PhD, Akihiro Tojo, MD, PhD, Hiroshi Satonaka, MD, PhD, and Toshihiko Ishimitsu, MD, PhD is now published in Journal Biomedicine & Pharmacotherapy.

In animal models of hypertension, it is believed that hypertension related renal damage is due to increased renal NADPH oxidase expression and reduced NO bioavailability. In the light of this, the researchers investigated if genisposidic acid could suppress the expression NADPH oxidase and improve the production of NO thereby resulting in prevention of hypertension and hypertensive renal damage in Dahl salt-sensitive rats.

The 4 week-old Dahl salt-sensitive (DS) rats were fed with 1% salt drinking water. After 5 weeks, they all developed hypertension (DSHS rat). One group were selected and treated with Tochu tea extract (DSHS+T) with 1% salt drinking water. Another group was treated with geniposidic acid (DSHS+G) with 1% salt drinking water. A third group continued to receive 1% salt drinking water alone. Age related DS rats that received tap water were also used as control (DSLS).

After 4 weeks, 24 hr, the authors collected urine and blood samples for renal hemodynamic studies and they removed kidneys from the various groups for PCR analysis and morphological studies. Blood pressures were measured and they found out that blood pressures were higher in DSHS rats than DSLS group. However, following treatment with genisposidic acid they noticed a singificant reduction in blood pressure in both in DSHS+T and DSHS+G groups. Importantly, renal plasma flow was significantly increased and renal fibrosis was markedly inhibited in both DSHS+T and DSHS+G groups. These effects of Tochu extract and its major component geniposidic acid were explained by inhibition of superoxide anion produced by NADPH oxidase and increased NO production via eNOS compared to those in DSHS rats. The increased NO bioavailabilities helps to reduce resistance of renal afferent arteriole which in turn increases renal blood flow and shows renoprotective effects by inhibiting profibrotic cytokines. It is important to notice that small rodent studies results might not translate to similar effects in humans. Therefore, such animal study results reported by the authors might not be relevant to the effect of the tochu extract in humans.

In a nutshell, the research team elucidated the mechanism of how Tochu extract and its major component geniposidic acid exert its beneficial healthy effects, including reduction of blood pressure, increase in renal blood flow and inhibition of renal fibrosis. Their study suggested the beneficial effect is due to inhibiting NADPH oxidase and increasing NO bioavailability.

Although Tochu extract has been used in traditional Chinese medicine for centuries with limited reports of side effects. However, one therapeutic trial of Tochu extract documented possible concerns including moderately severe headache, dizziness, edema, and the onset of a cold. Indeed, little is known about the safety of long-term or regular use of eucommia. There are no documented drug interactions, but people taking the following medications should not use eucommia unless under doctor supervision: Diabetes medications, High blood pressure medications, Anticoagulants, Antiplatelets, Thrombolytics. Currently there is little scientific evidence to support its use in the treatment or prevention of any disease. While preliminary research shows promise such as the current rodent study, more clinical trials are needed before it can be recommended.