Ding Gong Teng

Three patients poisoned by Erycibe henryi, sold under the same drug name Ting Kung Teng, all presented with vomiting, diarrhoea, salivation, diaphoresis, lacrimation and rhinorrhoea; two also had miosis, hypothermia, bradycardia, hypotension and ventricular tachyarrhythmias. Laboratory findings included leucocytosis, hyperglycaemia, hyperamylasaemia, hypocalcaemia and transient rises in liver enzymes, creatinine and creatine phosphokinase. The authors attribute the syndrome to the cholinergic tropane alkaloids of the genus and note that Erycibe can be mistaken for Tripterygium wilfordii, the cholinergic features being the distinguishing sign. The species studied was Erycibe henryi, not the pharmacopoeial Erycibe obtusifolia, but the alkaloid class is shared across the genus.

A 73-year-old man drank a decoction of Erycibe taken for arthritis and rapidly developed dizziness, diaphoresis, chills, lacrimation, salivation, rhinorrhoea, nausea and vomiting with hypothermia and hypotension. Serum cholinesterase was normal, which locates the mechanism at the muscarinic receptor rather than at the enzyme, and blood urea nitrogen, creatinine and glucose rose transiently. The authors identify the tropane alkaloids of the herb as cholinergic rather than anticholinergic, the opposite of the tropane drugs of the Solanaceae.

Forty per cent ethanolic extracts of Erycibe obtusifolia, Erycibe schmidtii and Erycibe ellipptimba were compared, with the more toxic Erycibe ellipptimba taken forward for detailed study because of its higher baogongteng C content. An HPLC-MS method quantified baogongteng C within the total alkaloid fraction. Baogongteng A and baogongteng C were identified as the major toxic compounds of the species tested, the total alkaloid extract behaved cholinergically, and a subacute study implicated liver and kidney as the target organs at high dose.

Stem extract of Erycibe obtusifolia was given to mice orally and intraperitoneally at 10, 20 and 30 mg/kg. Mice died immediately after intraperitoneal injection of 10 mg/kg, whereas no deaths followed oral dosing at any of the three doses over at least two weeks of observation. Oral dosing nevertheless raised serum transaminases and blood urea nitrogen and lowered haematocrit at six hours, without a clear dose-response relationship. The route dependence is stark and the liver and kidney signal matches the later genus-wide toxicology work.

An HPLC method compared scopoletin, scopolin and chlorogenic acid across the pharmacopoeial Erycibe species and the market substitute Porana sinensis. All three forty per cent ethanolic extracts were essentially non-toxic at 5 g/kg acutely, reduced xylene-induced ear oedema and formalin-induced inflammation, suppressed prostaglandin E2 synthesis in the carrageenan air pouch, and inhibited acetic acid writhing and the second phase of the formalin response; naloxone did not reverse the analgesia, so the effect is not opioid-mediated. The authors conclude the substitution of Porana sinensis is supportable on these markers, which notably do not include the tropane alkaloids.

Scopolin at 50 and 100 mg/kg intraperitoneally for ten days from the onset of the secondary response inhibited both inoculated and non-inoculated paw swelling and articular index scores in rat adjuvant-induced arthritis. High-dose animals kept a near-normal joint histology and showed fewer new synovial vessels, with reduced IL-6, VEGF and FGF-2 expression in synovial tissue. This is the mechanistic basis usually cited for the traditional wind-damp indication, though the route is parenteral and the dose far above ordinary decoction exposure.

Scopoletin, the pharmacopoeial marker of the drug, reduced arthritis severity in rats and the effect tracked with reduced angiogenesis in the synovium rather than with direct analgesia. Together with the companion scopolin study this makes the coumarin fraction, not the alkaloid fraction, the plausible carrier of the anti-rheumatic effect.

Baogongteng A and a series of its derivatives were assayed as muscarinic agonists and a quantitative structure-activity relationship was derived. The work establishes the tropane alkaloid of Erycibe obtusifolia as a genuine muscarinic pharmacophore and underpins the Chinese medicinal chemistry programme that produced the synthetic analogue satropane.

Satropane, a synthetic tropane analogue developed from the Erycibe alkaloid line, activated iris muscarinic receptors and lowered intraocular pressure with marked stereoselectivity between enantiomers. The study is on a synthetic derivative rather than the herb, but it demonstrates that the ocular hypotensive action of this chemical series is receptor-mediated and enantiospecific.

An early Chinese-language clinical report of glaucoma treated with an alkaloid preparation from Erycibe obtusifolia, the work that put the herb's tropane alkaloid on the ophthalmic map in China. The report is preliminary, is not a controlled trial, and its full text is available only in Chinese; it is cited here as the origin of the glaucoma indication rather than as evidence of efficacy.