Bioactive components of Rhoicissus tridentate : a pregnancy-related traditional medicine : research letter

Abstract

Rhoicissus tridentatal/Ig subsp. cuneifolia , or wild grape (Vitaceae), is one of the most commonly selected plant species for South African traditional medicines used during pregnancy and childbirth. Twenty compounds novel to the species were isolated from the plant, which has received little prior chemical investigation. Most of these compounds have documented health-promoting properties. Water extracts of roots show notable in vitrol/Ig activity on isolated rat uterine smooth muscle tissue. Extracts exhibiting the highest activity were found to contain proanthocyanidin monomers: (-)-epigallocatechin, (+)-gallocatechin, (+)-catechin hydrate, (+)-mollisacacidin, (+)-epicatechin, (-)-fisetinidol and epicatechin-3-lIgOl/Ig-gallate; and dimers: procyanidin B3, procyanidin B4, fisetinidol-(4a -8)catechin and fisetinidol-(4b -8)catechin, as well as gallic acid and 74% polymeric proanthocyanidins. The relative amounts of proanthocyanidins, determined colorimetrically, were higher in summer than in winter, and roots harvested in summer also produced greater uterine activity. Glucose, and a partially identified hydrogel of glucose which also greatly stimulated uterine muscle contraction, were isolated in addition. Sitosterol and sitosterolin exhibited only slight oestrogenic activity. Oleanolic acid was isolated from a chloroform extract, and two further triterpenoids, 20(29)-lupen- 3-one and 20-epi-y -taraxastananol, and a sterol, g -sitosterol, were identified by gas chromatography-mass spectrometry. The plant growth hormone, triacontanol, was purified from an extract of young branches. The reported paralysis of the central nervous system attributed to Rhoicissus tridentatal/Ig preparations is possibly linked to the action of sitosterol, sitosterolin and proanthocyanidins present in extracts.