Phytochemical constituents from the roots and lignotubers of Rhoicissus tridentata and their in vitro uterotonic activity

Rhoicissus tridentata is one of the most frequently used plants in preparing Isihlambezo, a herbal drink consumed by many South African women to induce labour and tone the uterus in pregnancy. This study aimed to identify the uteroactive compounds in this plant. Chromatographic purification of the methanol and water extracts from the roots yielded eight compounds, i.e. morin 3-O-α-L-rhamnopyranoside, trans-resveratrol 3-O-β-glucopyranoside, a mixture of asiatic and arjunolic acids, quercetin 3-O-rhamnopyranoside, catechin, β-sitosterol, and linoleic acid. All compounds were evaluated for their uterotonic effects using uterine smooth muscle isolated from stilboestrol-primed Sprague-Dawley rats. The mixture of asiatic and arjunolic acids showed the highest activity with EC₅₀ of 0.02129 μg/mL for amplitude. These results validate the use of R. tridentata in ethnomedicine to facilitate labour in childbirth. Morin 3-O-α-L-rhamnopyranoside and trans-resveratrol 3-O-β-glucopyranoside caused a relaxation of the uterine muscle, which suggests that some compounds in R. tridentata possess opposing activities.