[Chemical constituents from hypoglycemic active part of Plantaginis Semen]

Iridoids isolated from Viticis Fructus inhibit paclitaxel-induced mechanical allodynia in mice

Chemotherapy-induced peripheral neuropathy (CIPN) manifests as mechanical allodynia and hyperalgesia, and is one of the main adverse effects of chemotherapeutic agents. Currently available therapeutic drugs are not sufficiently effective for the management of this adverse effect in the clinic. Therefore, the development of novel therapeutic agents for treating CIPN is necessary. Our previous study suggested the potential of aucubin and pedicularis-lactone (1) as active compounds responsible for the anti-allodynic property of Plantaginis Semen. However, the activity of purified 1 has not been evaluated due to its low content in Plantaginis Semen. In the present study, 1 was isolated from Viticis Fructus, as well as viteoid I (2) and viteoid II (3) during the process of isolation. The purities of isolated 1, 2, and 3 were determined as 67.15%, 92.12%, and 86.72%, respectively, by quantitative ¹H-NMR, using DSS-d₆ as an internal standard. Repeated daily oral administration of these three iridoids at a dose of 15 mg/kg significantly inhibited the PTX-induced mechanical allodynia in mice, suggesting the anti-allodynic activities of 1, 2, and 3. This study provides confirmatory evidence for the anti-allodynic activity of purified 1 and also reveals two additional active iridoids from Viticis Fructus. These three iridoids could be potential candidates for the treatment of CIPN.

Search of anti-allodynic compounds from Plantaginis Semen, a crude drug ingredient of Kampo formula "Goshajinkigan"

Chemotherapy-induced peripheral neuropathy (CIPN) is one of the dose-limiting side effects of cancer chemotherapy. Although the control of CIPN is important, it is difficult to manage with currently available therapeutic drugs. Therefore, there is a need for novel therapeutic agents for treating CIPN. Goshajinkigan (GJG) is a Kampo formula composed of ten crude drugs. While GJG has been used for the treatment of CIPN, the active constituents of GJG and their underlying mechanisms of pharmacological effects are still unknown. Our previous study revealed that repetitive oral administration of the water extract of Plantaginis Semen, a crude drug ingredient of GJG, inhibited the mechanical allodynia induced by an intraperitoneal injection of paclitaxel in mice. To elucidate the active compounds of Plantaginis Semen, activity-guided separation of the water extract of Plantaginis Semen was performed. From the active fraction, four iridoids (1-4) were identified. Repetitive oral administration of aucubin (1) at 100 or 30 mg/kg and 100 mg/kg of the fraction crude 3 [primarily comprised of pedicularis-lactone (3)], showed anti-allodynic activity, suggesting 1 and 3 could be some of the active compounds responsible for the anti-allodynic property of Plantaginis Semen and GJG. Our study establishes that oral administration of 1 has potent anti-allodynic effect in addition to the activity of intraperitoneally administered 1 reported previously. Identification of active anti-allodynic compounds found in Kampo formulations will support the development of novel therapies for the management of CIPN in cancer patients.

Plantago asiatica Seed Extracts Alleviated Blood Pressure in Phase I⁻Spontaneous Hypertension Rats

Arterial pressure of each new breeding spontaneous Phase-1 hypertension (P1-HT) rat was recorded for 5 min by intravascular femoral artery catheter that served as a reference value prior to treatment. In the acute antihypertensive test, 0.36 g/kg Bwt of Plantago asiatica seed extract (PSE) was administered, via gavage feeding, to P1-HT rats, and the arterial pressures were continuously recorded for 1 h. The acute antihypertensive effects of PSE on P1-HT rats appeared within 15 min after PSE administration and lasted over 1 h with systolic pressure decreased 31.5 mmHg and diastolic pressure decreased 18.5 mmHg. The systolic pressure decreased 28 mmHg and diastolic pressure decreased 16 mmHg in P1-HT rats when simultaneously compared with verapamil hydrochloride (reference drug), whereas there were no significant differences in the pretreated reference values of acute PSE treatment and the untreated control. In the chronic test, P1-HT rats received 0.36 g/kg Bwt day of PSE or equal volume of water for 4 weeks via oral gavage, and the lower blood pressure tendencies of chronic PSE treatment were also found when compared with the controls. The antihypertensive values of PSE were also confirmed in spontaneously hypertensive rats (SHRs). Oral administration with PSE can effectively moderate blood pressure within an hour, while taking PSE daily can control the severity of hypertension, suggesting PSE is a potentially antihypertensive herb.