Abstract
Bryophyllum pinnatum has been used since the 1970s to prevent premature
labour, first in anthroposophic hospitals and, more recently, also in the main
Swiss perinatal centres. However, it is not known which compounds in B.
pinnatum leaves contribute to the tocolytic effect. Here we studied the
effects of a flavonoid-enriched fraction, the corresponding flavonoid aglycon
mixture, a bufadienolide-enriched fraction, and B. pinnatum leaf press
juice on human myometrial contractility in vitro. The strength (area
under the curve and amplitude) and frequency of contractions were recorded using
strips of human myometrium mounted in an organ bath system. Cell viability
assays were performed with the human myometrium hTERT-C3 and PHM1 – 41 cell
lines. Repeated addition of the flavonoid-enriched fraction, flavonoid aglycon
mixture, bufadienolide-enriched fraction, or B. pinnatum leaf press juice
led to a progressive decrease of contraction strength, without jeopardising the
vitality of myometrium strips. The bufadienolide-enriched fraction was the most
active, since 1 µg/mL of the bufadienolide-enriched fraction lowered the area
under the curve to 40.1 ± 11.8% of the initial value, whereas 150 µg/mL of the
flavonoid-enriched fraction, 6.2 µg/mL of the flavonoid aglycon mixture, and
10 mg/mL of the B. pinnatum leaf press juice were required to achieve
comparable inhibition. A progressive increase of contraction frequency was
observed, except in the case of the flavonoid aglycon mixture, which did not
affect frequency. None of the test substances decreased myometrial cell
viability, even at concentrations of 500 µg/mL of the flavonoid-enriched
fraction, 40 µg/mL of the flavonoid aglycon mixture, 3.8 µg/mL of the
bufadienolide-enriched fraction, and 75 mg/mL of the B. pinnatum leaf
press juice, i.e., higher than those used in the myometrium experiments. Given
the concentrations of flavonoids in the flavonoid-enriched fraction and B.
pinnatum leaf press juice, and of bufadienolides in the
bufadienolide-enriched fraction and B. pinnatum leaf press juice, it
appears that bufadienolides may be mainly responsible for the relaxant
effect.
Key words
Bryophyllum pinnatum
- Crassulaceae - myometrium - flavonoids - bufadienolides - toxicity
