The pharmacological actitvity of Rhoicissus tridentata subsp cuneifolia in relation to parturition
Date
2014-04-29
Authors
Katsoulis, Lynn Coleen
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Abstract
Decoctions and infusions of Rhoicissus tridentata subsp. cuneifolia (Vitaceae)
roots and Hgnotubers are widely used as traditional medicine by South African
women during pregnancy and childbirth. Pharmacological studies using isolated rat
uterus and ileum were done to determine whether there is any pharmacological
grounding for the use of the remedies to induce labour. Initial studies showed a large
variation in the contractile activity of the extracts, so investigations were done to
determine whether the contractile activity varied according to the season in which
plant material was harvested, the location in which the plant grew, or the length of
storage of harvested plant material.
Plant material harvested from Umlazi (KwaZulu-Natal) and the Suikerbos Nature
Reserve (Gauteng) was used for studies on the mechanism of contractile activity.
Seasonal variation was investigated by harvested three plants from Suikerbosrand
for two years at approximately three monthly intervals. The distributional effect was
done using material harvested from around South Africa. Material from
Suikerbosrand was stored for either three months or a year to determine whether
storage altered the contractile activity. After each harvesting, the different parts of the
plants were separated, dried, milled and boiled for approximately an hour. The
solutions were allowed to settle overnight at 4°C, after which the supernatant was
siphoned off, then frozen and lyophilised. All lyophilised end products were kept
frozen until use.
Oestrogenized virgin Sprague-Dawley rats euthanazed with CO2. Uterine and ileal
tissue was dissected out and mounted in 50 ml organ baths containing Tyrode
solution, aerated with 5% CO2 in O2. After a resting period the organs were
challenged with cumulative doses of reference agonist or herbal extract, or
pretreated with the herbal extract before adding the reference drugs.
The pharmacological action of an aqueous extract of R. tridentata subsp.
cuneifolia was investigated using isolated rat uterus and ileum. The results
showed that the extract directly stimulates concentration dependent contractions
of uterus and ileum. Preincubation of the organs with the plant extract had no
effect on the maximal uterine response to the cumulative addition of acetylcholine
or oxytocin, and slightly depressed the response to serotonin and noradrenaline.
The maximal ileal response to acetylcholine was depressed where the response to
maximal concentrations of serotonin was unchanged. Pretreatment with atropine
and indomethacin both blocked the initial response to the Rhoicissus extract which
indicates that the muscarinic receptors and prostaglandin synthesis could be
involved in the contractile response to the extract. Methysergide and prazosin had
no effect on the direct action of the extract which infers that serotonin receptors
and a-adrenoceptors do not play a role in mediating the smooth muscle response
to the plant extract.
Cellular toxicity of R. tridentata extracts from Umlazi and Suikerbosrand was
determined using M Tf assays, and enzyme immunoassays were used to determine
the effect of the extracts on cellular prostaglandin E2 production.
Results from the pharmacological studies indicate that the contractions of isolated rat
uterus and ileum seem to be mediated by muscarinic receptors and the synthesis of
cyclooxygenase products. The contractility of the plant extract appears to be
mediated predominantly by muscarinic M4 receptors. The other muscarinic receptor
subtypes play less of a role. The contractions seem to be devoid of serotonergic,
adrenergic, histaminergic or nicotinic activity.
Studies on the variation in contractile activity suggest that the activity of the extract
does vary according to the season or location of material harvesting. The extracts
form material harvested during summer or autumn was more active than material
harvested during winter or spring. The lignotubers yielded the most active extracts.
Extracts of plants from most geographic areas stimulated contractions although
the response varied in magnitude, however, the extract of a plant from Mondeor,
acted in an opposite manner, inhibiting acetylcholine induced contractions. Storing
dried plant material did not alter the activity of the extracts.
The plant extracts, up tv a concentration of 1 mg/ml, appear not to be toxic to
human kidney epithelial ns>H, human hepatoma cells, human histiocytoma cells or
mouse leydig cells. The production of PGE2 by human histiocytoma cells was
stimulated by 1 mg/ml R. tridentata extract confirming that contractions are
possible mediated by the synthesis of cyclooxygenase products.