Keisuke Ohsawa

Metabolites of orally administered Magnolia officinalis extract in rats and man and its antidepressant‐like effects in mice

As a part of our search for the active metabolite from the bark of Magnolia officinalis (Magnoliaceae), the aqueous extract was orally administered to rats, and metabolites in the urine were analysed by a high‐performance liquid chromatograph equipped with a photodiode array detector. When the extract was given to rats, five metabolites (sinapic acid‐4‐O‐sulfate (1), sinapic acid‐4‐O‐β‐glucuronide (2), sinapic acid (3), 3‐[2′,6‐dihydroxy‐5′‐(2‐propenyl)[1,1′‐biphenyl]‐3‐yl]‐(E)‐2‐propenoic acid (4), and an unchanged form, magnolol (5)) were detected in the urine. It was revealed that metabolites 1–3 and 4 were respectively derived from syringin and magnolol contained in the extract. In a human urine sample, metabolites 3–5 and dihydroxydihydromagnolol (6) were detected. These structures were identified by a combination of spectral methods and/or by comparison with authentic compounds obtained by synthesis. Among these free form metabolites (3–6), acute treatments with magnolol and dihydroxydihydromagnolol (50–100 mg kg−1, i.p.) attenuated the forced swim‐induced experimental depression in mice. The results indicated that magnolol and dihydroxydihydromagnolol were the antidepressant constituents of Magnolia officinalis.

Determination of synephrine from Chinese medicinal drugs originating from Citrus species by ion-pair high-performance liquid chromatography

Abstract A simple and precise method was established for the determnation of synephrine in Chinese crude drugs from Citrus plants using high-performance liquid chromatography with sodium dodecyl sulphate (SDS) as ion-pair reagent. Synephrine is known as a sympathomimetic drug contained in Chinese crude drugs from Citrus plants, namely Aurantii nobilis Pericarpium (Japanese name “Chinpi”), Aurantii fructus Immaturus (“Kijitsu”), “Kikoku” and “Seihi”. The optimum conditions for extracting synephrine from these Chinese crude drugs was a 15-min reflux with water—acetonitrile—SDS—H3PO1 (65:35:0.5:0.1) as the mobile phase. Synephrine was eluted within 13 rain without interference from co-existing components using an ODS column and SDS as an ion-pair reagent. The results revealed that synephrine was present at levels of 0.174-0.566% in the Chinese crude drugs, which were 1.3–2.2 times higher than those reported previously.

Inhibitory effects of urinary metabolites on platelet aggregation after orally administering Shimotsu‐To, a traditional Chinese medicine, to rats

Shimotsu‐To, which consists of four herbal extracts, has been used clinically for improving abnormal blood coagulation, fibrinolysis, atherosclerosis and chronic inflammation in Japan and China. We have investigated the pharmacological relationship between the effects and chemical components of Shimotsu‐To after oral administration to rats. The urinary constituents were separated and identified by three dimensional (3D‐) HPLC equipped with a photodiode array detector as a new tool and the chemical structures were determined by spectroscopic methods to be trans‐ferulic acid‐3‐O‐sulfate (1), vanillic acid (2), m‐hydroxyphenylpropionic acid (3), trans‐ferulic acid (4) and cis‐ferulic acid (5). Of these compounds, 2–5 strongly inhibited platelet aggregation induced by ADP and arachidonic acid. Compound 1, the sulfate conjugate of 4, did not show any inhibitory effect, which suggested that the inhibitory effect on platelet aggregation was inactivated by sulfate conjugation. These results indicated that compounds 2–5 partly contributed to the anti‐Oketsu effect of Shimotsu‐To through the inhibition of platelet aggregation.

[Determination of synephrine in oriental pharmaceutical decoctions containing evodiae fructus by ion-pair high-performance liquid chromatography].

A simple and precise method was established for the determination of synephrine in oriental pharmaceutical decoctions containing Evodiae Fructus using high-performance liquid chromatography with sodium dodecyl sulfate (SDS) as an ion-pair reagent. Synephrine was eluted within 25 min without interference from co-existing components using an ODS column and a mixture of water-acetonitrile-SDS-phosphoric acid (70:30:0.5:0.1, v/v/w/v) as a mobile phase.