bao gong teng A

Description

Obtuseleaf Erycibe Stem (Ding Gong Teng) is one of the Chinese herbal medicines recorded by the Pharmacopoeia of the People’s Republic of China (2015). It is a dried rattan from the plants of Convolvulaceae Erycibe obtusifolia Benth. or Erycibe schmidtii Craib. and can be harvested all year. The indications of Ding Gong Teng included rheumatoid arthritis, hemiplegia, swelling, and pain. So Ding Gong Teng is used as a folk medicine to relieve the symptoms of rheumatism in Guangdong and Guangxi provinces.
Erycibe alkaloid II belongs to scopolamine alkaloids, whose chemical structure is different from other known cholinomimetic drugs. It has remarkable effects in the treatment of glaucoma by contracting the pupils, reducing the intraocular pressure, and improving the aqueous humor coefficient. It has rare adverse reactions and mild side effects. So erycibe alkaloid II is an ideal drug for the treatment of glaucoma.
The content of erycibe alkaloid II is only about one-hundred-thousandth of the original plant. Therefore, efficient synthesis of erycibe alkaloid II is very important for the further research.

Physical properties

Appearance: white sticky substance. Its benzoate is a white fine acicular crystal. = - °( = ) D C , CHCl 20 3 5.56 0.90 . Melting point: 159–160 °C .

History

ing Gong Teng, as a folk herbal medicine for sweating and defervescence, is commonly known as “Zhu Mu Jiao” in Lufeng County of Guangdong province. Because of its serious side effects, Ding Gong Teng was once only applied to those patients with strong physical constitution. However, in the 1970s, pharmacological studies indicated that the water decoction of Ding Gong Teng showed a strong pupil contraction that was rare for other Chinese medicinal herbs. In that period of time, the source of pilocarpine and physostigmine used for pupil contraction was lacking in China, so a plenty of chemical and pharmacological research has been done in order to develop a new miotic for the treatment of glaucoma.
There were few studies reported on the chemical composition of Obtuseleaf Erycibe Stem. In 1967, Sasorith, Souvan K. did some work about the chemical composition of Erycibe elliptilimba originated from Laos. That study reported that there were flavonoids in its leaves and tannin in its xylem, respectively, and its stems are not poisonous. Chinese scientists extracted two monomer compounds from the stem of Erycibe obtusifolia Benth. collected from Lufeng County, named as Baogongteng A (erycibe alkaloid II) and Baogongteng B. In the 1980s, the pharmacological studies of glaucoma treatment and the synthesis studies of erycibe alkaloid II were carried out promptly.

Pharmacology

Erycibe alkaloid II can reduce the intraocular pressure in normal rabbit and the experimental high intraocular pressure induced by water overload. Its effect is stronger than that of pilocarpine, which is not suitable for long-term use. Local infusion of erycibe alkaloid II has no effect on systemic blood pressure in rabbit, and intravenous administration can lower blood pressure without affecting intraocular pressure.
Erycibe alkaloid II is a cholinergic drug while has no inhibitory effect on cholinesterase. It shows muscarinic effect via direct interaction with M-cholinergic receptor . Through the M3 receptor on cell membrane, erycibe alkaloid II can trigger to increase the Ca2+ concentration in the human eye ciliary muscle cells. Then it takes on the pupil contraction effect and the intraocular pressure reduction effect mediated by the M3 receptor subtype . The mechanism of erycibe alkaloid II is coupled with the cyclic nucleotide system .
Moreover, the animal experiments indicate that erycibe alkaloid II may improve cardiac function via slowing heart rate, enhancing cardiac contractility, reducing oxygen consumption, strengthening full oxidation of acidic metabolites and sodium pump activity, etc. .

Clinical Use

The miotic effect, intraocular pressure reduction, and improvement of the coefficient of aqueous outflow are similar between erycibe alkaloid II eye drop and pilocarpine. Furthermore, it has strong myotic effect than pilocarpine without obvious side effects. So it is suitable for long-term application.
Erycibe alkaloid II has been shown a good dose-dependent response in both the miosis and the intraocular pressure reduction. The intraocular pressure reduction effects of 0.01% and 0.05% erycibe alkaloid II are similar to that of 1% pilocarpine, and 0.25% erycibe alkaloid II has stronger activity than 1% pilocarpine. The miotic effects of 0.01%, 0.05%, and 0.25% erycibe alkaloid II are similar to that of 1% pilocarpine. There is no significant difference in the intraocular pressure reduction response between 0.05% erycibe alkaloid α and l% pilocarpine after chronic administration (1 month). Both erycibe alkaloid II and pilocarpine are able to improve significantly the coefficient of aqueous outflow without the obvious side effects .
Overdose of oral administration or injection of erycibe alkaloid II will cause poisoning, mainly shown as sweating, salivation, asthma, abdominal pain, diarrhea, limb numbness, miosis, blood pressure reduction, bradycardia, etc. It should be paid attention. Local application of erycibe alkaloid II may cause different degrees of blurred vision, conjunctival congestion, and foreign body sensation .